Fermentation doi: 10.3390/fermentation12080376

Authors: Georgios Chrysochoou Socratis Thomaidis Maria Antoniadou Theodoros Varzakas

Fermented foods contain diverse microorganisms that may influence oral microbial ecology and contribute to oral health. This narrative review aimed to examine the current evidence regarding microorganisms present in fermented foods and their role in oral health promotion. Twenty relevant clinical, experimental, observational, and review studies published between 2016 and 2026 were identified through a structured literature search and critically synthesized according to major thematic areas, including oral microbiota modulation, dental caries prevention, periodontal health, probiotic delivery systems, and evidence from review articles. The findings appear to indicate that fermented food-derived microorganisms may reduce cariogenic and periodontal pathogens, modulate oral biofilms, improve gingival health, and promote microbial homeostasis. Yogurt, kefir, fermented dairy products, and kimchi-derived microorganisms were the most frequently investigated sources. Emerging evidence further suggests that the benefits of these microorganisms are linked to ecological regulation of the oral microbiome and host–microbe interactions rather than direct antimicrobial activity alone. Microorganisms associated with fermented foods may therefore represent promising functional dietary components for supporting oral health and complementing preventive oral healthcare strategies. Further well-designed clinical studies are needed to establish strain-specific recommendations and explore the potential of postbiotic applications in dentistry.

Fermentation doi: 10.3390/fermentation12080375

Authors: Xiaoying Zhang Yujie Zhang Zhaoyi Duan Zhouying Liu Bowen Xu Ruixi Wang Jishi Zhang

Huangshui (HS) is rich in organic matter from Baijiu production. Anaerobic digestion (AD) of HS offers a hopeful strategy for efficient waste utilization and energy recovery. However, high organic load often causes low methane (CH4) yield and process instability. The aim of this study was to explore the mechanism of Saccharomyces cerevisiae (S. cerevisiae) to favor AD systems for more CH4. And the results revealed that with an inoculation at 8% (v/v) addition of S. cerevisiae, CH4 yield was 219.7 mL/g COD, representing a 20% increase compared to the control without S. cerevisiae. The main manifestation of augmentation was the increased bioavailability of dissolved organic compounds. In addition, the ethanol produced by S. cerevisiae under anaerobic conditions served as an electron donor to supply metabolic intermediates supporting methanogenesis, enriching Bacteroidetes_vadinHA17, Longilinea and Methanosaeta. This strategy promoted organic matter degradation and increased CH4 yield, favoring the efforts of the industry to reduce pollution and carbon emissions.

Fermentation doi: 10.3390/fermentation12080374

Authors: Sijia Chen Lei Dong Jia Guo Runmei Zhang Jun Cai

This study investigated the changes in flavor and texture of duck meat during co-fermentation with Saccharomyces cerevisiae and Lactobacillus plantarum. Characteristic flavor compounds of duck meat, including hexanal, nonanal, octanal, (E)-2-octenal, and 1-octen-3-ol, were detected. With the extension of fermentation time, the variety and contents of alcohols, ketones, and esters increased. The contents of 1-hexanol, ethanol and 3-hydroxy-2-butanone increased from 0.24 ng/g, 0 ng/g and 0 ng/g prior to fermentation to 11.25 ng/g, 8.93 ng/g and 1.94 ng/g after fermentation. Respectively these compounds endow duck meat with intense fruity, alcoholic and creamy aromas. Meanwhile, the contents of compounds that produce a peculiar smell in duck meat, such as hexanal, heptanal, pentanal, and 1-octen-3-ol, decreased significantly. After fermentation, the hexanal content declined from 11.2 ng/g (before fermentation) to 2.7 ng/g, and the 1-octen-3-ol content decreased from 2.21 ng/g to 1.51 ng/g. Furthermore, under the interaction of S. cerevisiae and L. plantarum, the hardness of duck meat decreased from 1186.44 N to 561.48 N, and the chewiness decreased from 633.63 g to 167.16 g. These results demonstrate that co-fermentation with S. cerevisiae and L. plantarum is an effective approach to improve the flavor and quality of duck meat. This study provides a new strategy for the application of microbial fermentation in processing duck meat to enhance its flavor and quality.

Fermentation doi: 10.3390/fermentation12080373

Authors: Xiaomeng Fu Liangzi Zhang Yong Wang Jingru Zhou Jingjing Xu Kunqiang Hong

Baker’s yeast with high freeze tolerance is essential for frozen-dough technology. The CYR1 gene, which encodes adenylate cyclase, is a central element of the cyclic adenosine monophosphate (cAMP) signaling pathway that regulates cellular stress tolerance. In this study, we aimed to enhance the freeze tolerance by modulating the expression level of CYR1. A series of diploid strains (BY14-30, BY14-60, BY14-90, and BY14-120) were constructed via a two-step integration method, in which the CYR1 promoter was truncated by 30, 60, 90, and 120 base pairs, respectively. Compared with the parent strain, strains BY14-30 and BY14-60 exhibited 4.3- and 4.2-fold higher survival rates after freezing, 60.0% and 40.0% increases in post-thaw dough-leavening ability, 88.9% and 64.6% increases in trehalose content, and 60.0% and 82.5% increases in proline levels, respectively. Collectively, our results demonstrate a novel strategy for regulating freeze tolerance in baker’s yeast, leading to improved cell viability and fermentation activity after freezing.

Fermentation doi: 10.3390/fermentation12080372

Authors: Khalil Abid

Spent green tea residues are an abundant lignocellulosic by-product that poses environmental disposal concerns, while its use in ruminant nutrition is constrained by low ruminal degradability associated with high fiber and phenolic contents. This study investigated the effects of gamma irradiation and solid-state fermentation using Saccharomyces cerevisiae, and their combination, on chemical composition and ruminal fermentation. Gamma irradiation reduced neutral detergent fiber (379 to 336 mg g−1 dry matter), acid detergent fiber (277 to 244 mg g−1 dry matter), and total phenolics (89 to 75 mg gallic acid equivalents g−1 dry matter) while increasing non-fiber carbohydrates (234 to 269 mg g−1 dry matter) and ash (32 to 44 mg g−1 dry matter). These modifications enhanced the gas production rate (3.26 to 3.37% h−1), neutral detergent fiber degradability (38.9 to 46.1%), and the acetate-to-propionate ratio (2.25 to 2.43) while reducing ammonia nitrogen (108 to 96 mg L−1), crude protein degradability (55.1 to 48.8%), and increasing rumen exoglycanase activity by 11% and xylanase activity by 15%. However, the methane proportion in total gas increased from 12.4 to 13.3% and methane yield per unit of degraded dry matter increased from 36.5 to 39.2 mL g−1 degraded dry matter. Solid-state fermentation using Saccharomyces cerevisiae alone did not change the chemical composition or ruminal fermentation of non-irradiated biomass. However, when applied to irradiated biomass, it increased the crude protein from 320 to 383 mg g−1 dry matter and ether extract from 31 to 49 mg g−1 dry matter, improved dry matter degradability (53.3 to 63.1%), organic matter degradability (55.3 to 64.3%), crude protein degradability (48.8 to 54.6%), total volatile fatty acids (49 to 57 mmol L−1), and net energy for lactation (2.43 to 3.02 MJ kg−1 dry matter), and maintained ammonia nitrogen at levels similar to the irradiated biomass. Although the combined treatment increased the methane yield per unit of incubated dry matter (19.2 to 23.4 mL g−1 dry matter), the methane yield per unit of degraded dry matter was lower than that of the irradiated biomass alone (37.0 vs. 39.2 mL g−1 dry matter degraded) and comparable to the untreated control (36.5 mL g−1 dry matter degraded). Overall, the integration of gamma irradiation as a pretreatment followed by solid-state fermentation with Saccharomyces cerevisiae enhances the nutritional value of spent green tea residues, supporting its valorization as a sustainable alternative ruminant feed resource.

Fermentation doi: 10.3390/fermentation12080371

Authors: Anara Yeleussizova Modestas Ruzauskas Gulnur Aliyeva Saniya Tyshtykbayeva Rita Šiugždinienė Vytaute Starkute Yablochkova Gulmira Elena Bartkiene Nurlan Kaumenov

This study aimed to select lactic acid bacteria (LAB) strains based on their antagonistic activity and mycotoxin mitigation capacity, develop a biocompatible multistrain consortium, and evaluate its application for the fermentation of extruded wheat bran. The selected strains were assessed for biocompatibility, and a four-strain consortium comprising Lacticaseibacillus casei, Levilactobacillus brevis, Pediococcus acidilactici, and Latilactobacillus curvatus was established. The consortium was propagated in supplemented sour whey and subsequently applied to wheat bran fermentation. Compared with the two-strain formulations, the four-strain consortium reduced the total bacterial count by 1.6-fold and the yeast and mold count by 1.75-fold after 36 h of fermentation. The consortium also produced the most pronounced acidification of the substrate, reducing the pH from 5.65 to 3.82 and increasing titratable acidity from 0.20 to 4.40 °N (22.0-fold). In contrast, fermentation with the two-strain formulations reduced the pH to 4.02 ± 0.01, while titratable acidity increased by 20.5–20.6-fold. After 36 h of fermentation, the viable LAB count in the substrate fermented with the four-strain consortium reached 7.23 ± 0.11 log10 CFU/g, compared with 6.23 ± 0.02 and 6.42 ± 0.01 log10 CFU/g in the substrates fermented with the two-strain formulations. These findings indicate that the developed four-strain consortium represents a promising starter culture for wheat bran fermentation and highlight its potential for the valorization of cereal by-products into value-added feed material through LAB fermentation. All experiments were conducted in vitro, and the effectiveness of the proposed approach under animal feeding conditions requires further experimental validation.

Fermentation doi: 10.3390/fermentation12080370

Authors: Han Cheng Xiangwei Li Salma Tabassum Hongbo Liu

Early warning has been widely proven to be reliable in lowering the risk of instability for biological processes. However, it is very difficult for the warning systems used currently to achieve satisfactory accuracy, timeliness and universality simultaneously. This study developed a novel early warning system for instability in food waste anaerobic digestion (FWAD) by bioimitating the human disease screening paradigm. It consists of single, comprehensive and microbiological indicators. Findings showed that single-factor early warning systems resembled acute patient diagnosis, having high accuracy but low timeliness and poor universality. Each of the chosen single indicators showed distinct early warning performances and clear preferences for diverse inhibitions concerning the instabilities of high organic load rate, high ammonia, and high fat in FWAD. Then, a new comprehensive indicator was developed using the entropy weights of several indicators. Confirmatory tests revealed that the comprehensive indicator-based early warning system was analogue to the resident sub-health diagnostic regarding superior foresight and good operability but poor targeting. Therefore, an early warning system based on microbial changes was proposed for potential instability in FWAD by bioimitating human periodic physical examination. The sensitive bacteria were identified as norank_o_ norank_c_Dojkabacteria and Rikenellaceae_RC9_gut_group. Enlarged tests showed that the developed system could be used for emergent, indistinct and potential early warnings simultaneously while avoiding the shortcomings of existing systems. More preciously, this study provided a paradigm for developing early warning systems of FWAD, which is also suitable to be applied to the intelligent systems that rely on automated machine learning.

Fermentation doi: 10.3390/fermentation12080369

Authors: Jianghua Chen Yujue Wang Qiang Wang Zhiming Rao Xian Zhang

Trehalose is a functional disaccharide widely used in the food, pharmaceutical, and cosmetic industries. It is industrially produced via a dual-enzyme process involving maltoligosaccharide trehalose synthase (MTSase) and maltoligosaccharide trehalose hydrolase (MTHase), with Escherichia coli (E. coli) serving as the expression host. Bacillus subtilis (B. subtilis) is an ideal host for industrial trehalose production due to its generally recognized as safe (GRAS) status and low phage susceptibility. However, engineered B. subtilis strains often exhibit slow growth, low heterologous protein expression, and high fermentation costs, thereby limiting their industrial application. To address these challenges, this study employed a synergistic strategy that combined chassis modification, expression element optimization, and knockout of substrate-competition pathways. First, a tryptophan-independent strain was constructed by reverting the trpC2 mutation to shorten the growth cycle. Next, knockout of flgD, yueB, and integration of E. coli-derived glutamate dehydrogenase (gdhA) significantly enhanced biomass accumulation. Expression of MTSase and MTHase was markedly improved through tandem strong promoters (PHpaII-P36) and ribosome-binding site (RBS) optimization (RBS1), achieving a 10.87-fold and 4.22-fold increase in enzyme activity, respectively. Finally, disruption of the amyE gene reduced non-specific substrate degradation. Using maltodextrin as substrate, the final trehalose conversion rate reached 76%. This study constructed B. subtilis chassis cells that highly express MTHase and MTSase respectively, laying a foundation for subsequent industrial trehalose production.

Fermentation doi: 10.3390/fermentation12080368

Authors: Nyan Minn Paing Witsaponr Jorsungnoen Sumittra Thaingoea Shankar Neupane Do Quyen Nguyen Nattaya Konsue

Jackfruit seeds (JFSs) are an underutilized agro-industrial by-product with considerable nutritional and functional potential for sustainable food fermentation. This study evaluated the feasibility of using jackfruit seed flour as a partial malt substitute in beer brewing at replacement levels of 0%, 25%, 50%, and 75% (w/w). Fresh jackfruit seeds were processed into flour, gelatinized, and mashed with pale ale malt in the presence of α-amylase before fermentation with Saccharomyces cerevisiae, Lutra kveik ale yeast. The physicochemical properties of the raw materials, starch hydrolysis during mashing, beer quality attributes, and volatile aroma compounds were investigated. Compared with pale ale malt, JFS contained higher crude protein (13.22%), total phenolic content (476.66 mg GAE/100 g), and antioxidant activity. HPLC-IR analysis demonstrated the formation of fermentable sugars during mashing, although starch conversion from JFS remained incomplete at higher substitution levels. Increasing JFS substitution significantly enhanced beer foamability (up to 142.22%) and foam stability (112.84 s), which was attributed to the higher protein content of the seeds. However, beers containing higher proportions of JFS exhibited darker color and increased turbidity, reaching 680 NTU at 75% substitution. HS-SPME-GC-MS analysis revealed changes in alcohols, esters, and ketones with increasing JFS substitution. These findings demonstrate that jackfruit seed flour can serve as a sustainable malt adjunct for beer production, improving selected quality attributes while valorizing agricultural by-products. The study highlights the potential of jackfruit seeds as a functional brewing ingredient that supports the development of sustainable and next-generation fermented beverages.

Fermentation doi: 10.3390/fermentation12080367

Authors: Lorena Celador-Lera Rosana Chiva Ana Jiménez-López Fernando Sánchez-Juanes José Antonio Uña Raúl Rivas María Ángeles Santos Encarna Velázquez Mercedes Tamame

Lactic acid bacteria (LAB) are Gram-positive cocci or rods from different genera and species that synergistically coexist with yeasts in cereal sourdoughs. Although the production and consumption of sourdough breads have increased in the last decade, there are still few studies that identify the LABs present in sourdoughs of different origins. In this study, we identified LAB strains isolated from wheat sourdoughs sourced from bakeries in north-western Spain and from experimental sourdoughs developed by a baker with four different cereal flours: wheat, rye, spelt, and tritordeum. Through a combination of MALDI-TOF and pheS gene sequence analyses, we identified Lactiplantibacillus plantarum and Levilactobacillus brevis in all analysed sourdoughs. Moreover, Lactiplantibacillus paraplantarum, Lacticaseibacillus paracasei, Lactococcus lactis, Pediococcus pentosaceus, and Weissella paramesenteroides were identified in different sourdoughs. These species were also isolated from sourdoughs obtained in other European countries, although we did not identify the other LAB genera identified in some of them. Our results demonstrate the need to identify the LAB species from sourdoughs of different origins prior to designing suitable starters for inoculated sourdoughs, particularly those produced with innovative flours. To our knowledge, this is the first report on the identity of LABs present in tritordeum sourdoughs in Spain.

Fermentation doi: 10.3390/fermentation12080366

Authors: Yanjie Jia Wanting Yang Lulu Zhang Xinkang Hu Huanhuan Zhang Bo Zhang

Xylitol is a five-carbon sugar alcohol widely used in the food, pharmaceutical, oral healthcare, and personal care industries because of its low caloric value, low glycaemic index, and non-cariogenic properties. Industrial production is mainly based on catalytic hydrogenation of xylose, which provides high conversion efficiency but requires intensive energy input, costly catalysts, and complex purification processes. Microbial fermentation has emerged as a sustainable alternative for producing xylitol from renewable lignocellulosic biomass. This review summarizes recent advances in xylitol production, with a particular focus on microbial biomanufacturing. Key developments in lignocellulosic biomass utilization, metabolic engineering, cofactor balancing, oxygen regulation, and fermentation optimization are discussed. Chemical and biological production routes are critically compared in terms of efficiency, sustainability, and industrial applicability. Recent progress in downstream purification and biorefinery integration is also highlighted. Despite substantial advances, challenges including inhibitor toxicity, limited microbial robustness, low fermentation productivity, and high purification costs continue to hinder large-scale commercialization. Future research should focus on feedstock valorization, systems metabolic engineering, process intensification, and sustainable separation technologies to improve the economic and environmental sustainability of bio-based xylitol production.

Fermentation doi: 10.3390/fermentation12080365

Authors: Tongxin Xue Jiahao Zhang Yapeng Song Ahmed Mahdy Wei Qiao

Acidogenic fermentation offers a promising approach to convert chicken manure into carbon-rich liquid products for various practical applications. However, the high nitrogen content in chicken manure hinders acidogenesis and limits product utilization due to ammonium accumulation. To address this, a 320-day fermentation experiment was conducted in a two-stage operation (Stage I: uncontrolled pH; Stage II: pH controlled at 5.0). pH adjustment was conducted by adding HCl. The continuously stirred tank fermentation reactor was operated at 37 °C and manually fed daily. Results showed that pH adjustment shifted the metabolic pathway from volatile fatty acid (VFA)-dominated production to lactic acid-enriched production: lactic acid increased from 12.6 to 35.7 g-COD/L, total VFAs decreased by 58%, while acetic acid remained at a relatively high level of chemical oxygen demand (COD) of 17.6 gCOD/L. Total ammonia nitrogen (TAN) decreased from 7.0 to 3.1 g/L, increasing the ratio of soluble COD (SCOD) to TAN from 19:1 to 38:1. The ammonium reduction was primarily due to selective inhibition of uric acid degradation under low pH, while protein hydrolysis remained largely unaffected. These findings demonstrate the potential of pH-regulated chicken manure fermentation liquor as a high-value product.

Fermentation doi: 10.3390/fermentation12080364

Authors: Viola Galli Damiano Barbato Eleonora Mari Giacomo Buscioni Silvia Mangani Lisa Granchi Simona Guerrini

The principal critical issue in the production of Vin Santo passito wine is the high likelihood of fermentation arrests or sluggish fermentation, resulting in low sensory quality. A potential solution is to select indigenous yeasts from well-conducted spontaneous fermentations. In this study, a novel mixed starter culture consisting of two indigenous strains, Saccharomyces cerevisiae Ris III and Zygosaccharomyces rouxii Zr186, was evaluated. After selecting the strains and testing their compatibility, the mixed culture was used as a starter in the winemaking process of dried grapes, which was conducted in barrels of various sizes. The fermentations were monitored microbiologically for a period of 100 days to verify the ability of the inoculated strains to dominate and thus facilitate the fermentation process. Both strains dominated the fermentations: S. cerevisiae showed a 100% isolation rate immediately, while Z. rouxii achieved dominance within a month. The mixed starter demonstrated a 25% improvement in fermentation purity for the same barrel size. Sensory analyses revealed that the wines produced with the mixed starter were very consistent with one another, contrasting with those obtained through spontaneous fermentations, and received the highest scores for gustatory descriptors. In conclusion, this mixed culture represents an effective strategy for standardizing fermentation and improving the sensory quality of Vin Santo.

Fermentation doi: 10.3390/fermentation12080363

Authors: Murat Er Bekir Tosun Derya Merve Karagöz Muhammad Shazaib Ramay Anas Tahir Syed Umer Akhter Ifrah Raza Eren Kuter Umair Ahsan

This study evaluates the effect of homofermentative and heterofermentative inoculants used independently or in combination on the quality of fermentation, chemical composition, fiber digestion, and nutritional value of silage made from four wheat varieties (Bayraktar 2000, Kızıltan 91, Bezostaja 1, and Tosun bey). Four treatments were applied within each variety: an untreated control group; a homofermentative inoculant (HMF group; Lactiplantibacillus plantarum, formerly Lactobacillus plantarum, and Enterococcus faecium, applied at 1.0 × 105 cfu/g fresh weight); a heterofermentative inoculant (HTF group; Lentilactobacillus buchneri, formerly Lactobacillus buchneri, applied at 5.0 × 104 cfu/g fresh weight); and their combination (HMF+HTF; group 1.5 × 105 cfu/g fresh weight). The whole-crop wheat silage collected at the dough stage was allowed to ferment for 120 days using a 4 × 2 × 2 factorial design having four replications. Statistically significant differences between varieties and inoculation treatments were seen in most of the recorded characteristics (p < 0.001), demonstrating that inoculant responses were significantly impacted by genotype. In Kızıltan 91, dry matter (DM) did not differ significantly among treatments (p > 0.05). In Bayraktar 2000, DM was reduced only by HTF applied alone (36.56% vs. 43.23% in the control), while HMF and HMF+HTF did not differ from the control. In Bezostaja 1, both HTF and HMF+HTF decreased DM relative to the control, whereas HMF alone had no effect. In Tosun bey, all LAB treatments increased DM relative to the control, with the homofermentative inoculant producing the greatest increase. Homofermentative inoculants demonstrated improved fermentation characteristics by lowering silage pH and ammonia-nitrogen concentrations and enhancing physical traits, while Heterofermentative inoculants reduced butyrate accumulation and raised acetic acid concentration, which reached 3.50 g/kg DM in Kızıltan 91 during combined inoculation. According to genotype, the application of inoculants varied the amount of fiber and digestibility. In vitro dry matter and organic matter digestibility, net energy of lactation, total digestible nutrient, and relative feed value (RFV) were frequently reduced by the combination HMF+HTF treatment. In Bayraktar 2000, RFV was found to have decreased the most, from 166.79 to 106.51. Conversely, Bezostaja 1 showed comparatively constant levels of energy content and digestibility regardless of the treatment, suggesting greater adaptability to the effects of microbial inoculants. In general, wheat genotype was the main factor influencing the nutritional value and quality of silage, and varietal characteristics had a significant impact on the efficacy of microbial inoculation. These results show how essential it is to choose inoculant methods according to variety in order to maximize fermentation quality and maintain feeding value in the production of wheat silage.

Fermentation doi: 10.3390/fermentation12080362

Authors: Angel Benjamin Fernandez Canchos José Antonio Reyes Rodríguez Ricardo Giancarlo Gamarra Condori Giovanni Martín Champin Luy Berlan Rodríguez Pérez Reinier Jiménez Borges Yoisdel Castillo Alvarez

The management of organic waste in high-altitude mining poses a distinctive circularity challenge: waste is generated at sites decoupled from agricultural systems, while the same operations are legally required to revegetate the land they disturb. This study provides, to the best of our knowledge, the first primary-data environmental characterization of a real system that valorizes dining-facility organic waste from a high-altitude mining unit in northern Peru into a solid biofertilizer and a liquid biol, both applied in situ for land reclamation. Unlike methanogenic digesters, the system operates under a lactic (acidogenic) fermentation regime inoculated with effective microorganisms and does not recover biogas. A cradle-to-gate life cycle assessment (ISO 14040/14044) with Monte Carlo uncertainty propagation was combined with a well-established family of five circular economy indicators, adapted to the non-energy-recovery case by redefining the Energy Self-Sufficiency Ratio (ESSR) and the Decarbonization Circularity Indicator (DCI). The principal contribution is methodological: the framework is extended to a circularity archetype that previous, biogas-centered formulations could not represent, showing that a system can close its material and nutrient loops robustly (WVI = 0.97) while the energy loop is absent by design (ESSR = 0). The climate result is conditional and is a first-order greenhouse-gas (GHG) screening balance, not a physical carbon-sequestration claim: under the upper-bound assumption of full fertilizer substitution, the avoided fertilizer credit outweighs non-methane process emissions only below a narrow fugitive-methane threshold (≈0.32 kg CH4 per ton), a margin that narrows further once agronomic equivalence is discounted. The measured product acidity suggests that this condition is plausible, but, because methane was not measured directly, the low-emission interpretation is presented as a hypothesis requiring confirmation rather than as a demonstrated result. The environmental burden is driven by material and electricity inputs—chiefly the polypropylene containers and grid electricity—rather than by the biological process, which broadens the set of improvement priorities beyond methane management to include capital-good reuse and electricity decarbonization, without implying that methane can be neglected.

Fermentation doi: 10.3390/fermentation12080361

Authors: Yunhao Liu Wenbo Zhang Mengqi Shen Xu Xu Jing Geng Weiliang Dong Xiayuan Wu

The emission of odorous gases has become a critical environmental challenge in livestock and poultry farming, organic solid waste treatment, and wastewater and sludge management, with typical pollutants including NH3, H2S, and various volatile organic compounds (VOCs). Conventional physicochemical deodorization methods are limited by complex equipment, high energy consumption, and secondary pollution, whereas microbial deodorization has attracted increasing attention because of its low energy demand, environmental friendliness, and environmentally safe end products. At present, comprehensive reviews of microbial deodorization technology remain limited, particularly those addressing the differences in microbial removal mechanisms for odorous gases and their components originating from different sources. The major components, characteristics, and emission patterns of odorous gases from different sources are summarized in this paper. Recent advances in the screening and consortium construction of highly efficient deodorizing microorganisms, together with their practical applications in odor treatment, are further summarized. Furthermore, emerging metabolic engineering strategies based on genetic modification, enzyme regulation, and metabolic pathway reconstruction are discussed, highlighting their potential for enhancing microbial degradation capacity and facilitating the rational design of next-generation deodorization systems. Future research directions are also proposed to address existing challenges, thereby providing insights for the rational design and engineering application of microbial deodorization systems.

Fermentation doi: 10.3390/fermentation12080360

Authors: Aditi David Tanvi Govil Dipayan Samanta Anjali Thapliyal Nidhi Kapatia Abhilash Kumar Tripathi Shailabh Rauniyar Sudhir Kumar Sachin Kumar Rajesh K Sani

In this study, thermophilic anaerobic digestion (TAD, 60 °C) was evaluated as a downstream waste-to-energy step within a cascading thermophilic biorefinery using four interrelated substrates—primary cafeteria wastes (pCFWs) and primary corn stover wastes (pCSWs) were evaluated without physicochemical pretreatment. Their corresponding secondary substrates, secondary cafeteria waste (sCFW) and secondary corn stover wastes (sCSWs), were residual solids generated after thermophilic bioethanol production and exopolysaccharide production, respectively. To our knowledge, this is the first study to demonstrate sequential thermophilic valorization in which primary wastes are untreated and the remaining biotreated secondary residues are subsequently converted into biomethane, adding each step to bioeconomy. Biomethane potential was quantified to determine how substrate composition and upstream bioprocessing influence methane yield and biodegradability. In the batch, pCFW achieved the highest biodegradability (84% VS reduction) but suffered rapid acidification at higher loadings, whereas pCSW was hydrolysis-limited by lignocellulosic recalcitrance. Upstream bioprocessing (biological pretreatment) improved digestibility, with sCSW exhibiting a 1.8-fold increase in methane yield (300 L CH4 kg−1 VS) relative to pCSW. All co-digestion treatments outperformed monodigestion, with the best-performing (among the tested) sCFW:sCSW ratio of 3:1 delivering the highest methane yield (413 L CH4 kg−1 VS) and VS reduction (95.8%). Scale-up in a 40 L fed-batch reactor achieved methane productivities of 49–142 L CH4 kg−1 VS per feeding cycle, reaching stable operation after two cycles, with cumulative methane production of ~800 L CH4 kg−1 VS for secondary wastes compared to ~550 L CH4 kg−1 VS for primary wastes. Microbial analysis revealed dominance of syntrophic acetate-oxidizing bacteria (Acetomicrobium, 22.6%) and hydrogenotrophic methanogens (Methanothermobacter, 72.3%). Therefore, biologically pretreated wastes enabled higher methane recovery and improved solids destruction under thermophilic conditions and demonstrates circular conversion of wastes into renewable biomethane.

Fermentation doi: 10.3390/fermentation12080359

Authors: Yukun Zhang Amina Moss Weilong Wang

This Editorial concludes the Special Issue “Fermentation Strategies to Enhance Feed Nutritional Value and Optimize Industry Resources” [...]

Fermentation doi: 10.3390/fermentation12080358

Authors: Jiawei Hu Jie Wu Jinsong Liang Xin Yin Yongli Wang Shaogang Hu

Calcium hypochlorite (CH) is a strong oxidant that can be utilized to enhance sludge hydrolysis and anaerobic digestion (AD) performance; however, its suppressive effect on methanogens restricts the development of CH treatment technologies. This laboratory-scale study introduced zero-valent iron (ZVI) into a CH-treated sludge AD system to alleviate the adverse effect, thereby synergistically enhancing biomethane production, and the correlation between methane yield and the two key treatment parameters (ZVI and CH dosages) was explored. The experimental results revealed that the best conditions for the ZVI + CH method were 5 g/L of ZVI plus 0.12 g/g of volatile suspended solids (VSSs) of CH, under which the maximum biomethane yield of 275.8 mL/g VSS was achieved, representing increases of 81.5%, 43.2%, and 28.2% over the control, solo ZVI, and solo CH conditions, respectively. More organic matter in the sludge was found to be degraded during AD by the ZVI + CH treatment compared with the control, solo ZVI, or solo CH conditions. An enzyme activity analysis illustrated that the ZVI + CH treatment not only enhanced the bioactivity of anaerobes but also eliminated the suppression of methanogens by CH. A microbial analysis demonstrated that all functional microbes responsible for sludge AD were enriched by the ZVI + CH treatment, with total abundances of 8.41% and 20.58% in the control and ZVI + CH-treated reactors, respectively.

Fermentation doi: 10.3390/fermentation12080357

Authors: İlker Atik Azize Atik Gökhan Akarca

This study evaluated the effects of milk type, UV-C treatment condition and refrigerated storage on selected quality characteristics of ayran. Cow and buffalo milk was standardised to 1.5% fat and subjected to UV-C treatment at flow rates of 20 or 40 mL/min, corresponding to calculated nominal doses of 54 and 27 J/mL, respectively. Conventionally pasteurised milks were used as controls. During ayran production, all samples were subsequently heated at 90 °C for 5 min, fermented to pH 4.30 and stored at 4 °C for 14 days. Physicochemical, instrumental textural, colour, starter culture and organic acid characteristics were evaluated during storage. The measured responses varied according to milk matrix, UV-C treatment condition and storage duration, and no single treatment was consistently favourable for all parameters. At day 14, C20 showed the highest dry matter content (5.12%), firmness (15.43 g), consistency (292.32 g·s) and Lactobacillus delbrueckii subsp. bulgaricus count (7.52 log CFU/mL). In contrast, B40 showed the highest Streptococcus thermophilus count (8.14 log CFU/mL), lactic acid concentration (15,092.95 mg/kg) and concentrations of most of the other organic acids evaluated, whereas C20 showed the highest acetic acid concentration (1122.14 mg/kg). During storage, pH, dry matter, citric acid, ascorbic acid and starter culture counts generally decreased, while most other organic acids increased. Instrumental colour parameters also changed according to treatment group and storage duration. These findings provide preliminary laboratory-scale evidence that UV-C pretreatment can influence selected quality characteristics of ayran. However, because UV-C-treated samples subsequently underwent thermal processing, the results represent a combined UV-C and thermal processing sequence rather than an exclusively non-thermal process. Sensory acceptability, pathogenic and spoilage microorganisms, oxidative stability, extended shelf life, and scale-up performance should be evaluated before practical application is considered.

Fermentation doi: 10.3390/fermentation12080356

Authors: Cansu Yay Bilgen Özsoy Onur Güneşer Özlem Aslan Emine Aytunga Arık Kibar Müge İşleten Hoşoğlu

Fermentation has significant potential for valorizing de-oiled sunflower meal (DSM) protein for human consumption. Here, DSM extracts were fermented for 48 h with Lactobacillus helveticus B-4526 and Bacillus subtilis B-3387, and their nutritional, bioactive, and techno-functional properties were evaluated. DSM extract supported the growth of both organisms, with cell numbers increasing by >1.5 log CFU/mL for B. subtilis and approximately 1 log CFU/mL for L. helveticus. During fermentation, B. subtilis degraded protein bands in the 23–46 kDa range, whereas L. helveticus promoted protein aggregation due to acidification, which may have reduced protein solubility. Antioxidant activities (DPPH, ABTS, and CUPRAC assays) and ACE-inhibitory activity increased in both fermentations, with B. subtilis showing the strongest effect. FTIR analysis indicated fermentation-induced alterations in the protein secondary structure. The total amino acid content decreased after B. subtilis fermentation but remained similar after L. helveticus fermentation. Phytic acid present in the meal decreased as a result of extraction/fermentation workflow. B. subtilis fermentation improved solubility at pH 4.0 but reduced foaming and emulsifying properties. Both fermentations decreased the oil-holding and water-holding capacities. Overall, this study underscores the need to match the fermenting microorganism to the desired outcome, as enhancements in one property often involve trade-offs with others.

Fermentation doi: 10.3390/fermentation12080355

Authors: Jingyi Li Shuyu Sun Xiaoming Wang Wenhao Zhu Qigui Niu

In conventional anaerobic digestion (AD) of livestock manure, temperature regulation faces an inherent paradox: thermophilic conditions facilitate pathogen inactivation but inhibit methanogenesis, whereas mesophilic conditions enable efficient methane production but are less effective at eliminating pathogens. This study systematically analyzed the methanogenic performance, microbial physiology, and the dynamics of biosafety factors during AD of chicken manure at 4 °C, 35 °C, and 55 °C. Additionally, a ceramic membrane (CM) coupled with ozone micro-nano bubbles (O3-MNBs) backwashing was configured for advanced digestate purification. Contrary to conventional understanding, mesophilic conditions (35 °C) simultaneously achieved optimal methanogenic efficiency (277.83 mL/gVS) and the efficient removal of viruses (66.65%) and antibiotic resistance genes (ARGs) (>77.11%), supported by a more diverse microbial community. While thermophilic conditions (55 °C) inactivated certain viruses, methanogenic efficiency was significantly inhibited by thermal stress. Moreover, the residual plasmid-borne ARGs were 3.04-fold higher than under mesophilic conditions. The integration of CM filtration with O3-MNBs backwashing effectively retained and inactivated pathogens while reducing the membrane fouling rate by 83.97%. The integration of mesophilic digestion, membrane filtration, and O3-MNBs processes synergistically achieved efficient energy recovery and robust pathogen control, providing technical support for the safe treatment and high-value resource utilization of manure.

Fermentation doi: 10.3390/fermentation12080354

Authors: Margareth Andrea Patiño Lagos Diana Carolina Tusso Pinzón Jorge Alejandro Cristancho Caviativa Mario Enrique Velásquez Lozano Boris Ugarte Stambuk

Xylitol is a sugar alcohol of interest in the food, pharmaceutical, and healthcare industries due to its applications as a food sweetener and sugar substitute. A wild-type Saccharomyces cerevisiae yeast strain designated 202-3 was isolated from a Colombian distillery located near sugarcane fields. This diploid 202-3 strain showed non-common, modest but noticeable xylose consumption and xylitol production in lignocellulosic hydrolysates. To enhance its natural xylose consumption ability, the strain was genetically engineered and submitted to adaptive laboratory evolution (ALE). Firstly, it was considered the deletion of the GAL80 gene to enable continuous expression of GAL genes, enhancing the uptake and assimilation of xylose. While the deletion of one copy of GAL80 (strain 202-3/∆) showed improved xylose consumption and xylitol production, better results were obtained when both copies of GAL80 were silenced (strain 202-3/∆∆). Subsequently, ALE experiments were conducted for these three strains in rich medium containing 20 g/L xylose. While the parental 202-3 strain consumed 2.46 g/L xylose and produced 0.42 g/L xylitol, the evolved 202-3/∆∆/ALE strain was able to consume 5.61 g/L xylose and produced 4.87 g/L xylitol, with a xylitol yield of 0.87 g xylitol/g xylose, and also the highest xylitol volumetric productivity (0.034 g xylitol/L/h) among the strains. Thus, our engineered and evolutionary experiments allowed a significant improvement in terms of xylose consumption, xylitol production and xylitol yield.

Fermentation doi: 10.3390/fermentation12080352

Authors: Itza Nallely Cordero-Soto María Angélica Martell-Nevárez María Gorety Contreras-Hernández Itzel Carolina Núñez-García Nicolás Oscar Soto-Cruz Jesús Bernardo Páez-Lerma Olga Miriam Rutiaga-Quiñones

This study evaluated the effects of nitrogen source, temperature, and agitation on fermentation performance and volatile compound formation in an agave juice-based beverage fermented with Saccharomyces cerevisiae. Agave juice contained a high concentration of reducing sugars (156.69 g/L), representing 83.16% of the total sugars, predominantly fructose, and a low assimilable nitrogen concentration (0.069 g/L), indicating nitrogen limitation. Fermentation assays were performed at 18 and 28 °C under static or agitated (100 rpm) conditions, with inorganic or organic nitrogen supplementation. At 28 °C, organic nitrogen supplementation under static conditions increased ethanol production to 72.26 g/L. At 18 °C, fermentation kinetics were markedly slower, but nitrogen supplementation increased ethanol production from 34.25 g/L in the control to 59.89 g/L with inorganic nitrogen, indicating that nitrogen supplementation had a greater relative effect under low-temperature fermentation. Volatile profiling revealed that under static fermentation at 18 °C, organic nitrogen supplementation increased the relative abundance of higher alcohols, particularly 2-phenylethanol, whereas ester formation varied according to both nitrogen source and fermentation temperature. Overall, nitrogen source, agitation and temperature strongly affected both fermentation efficiency and volatile formation, supporting the design of controlled processes to improve aromatic complexity and performance in agave-based fermented beverages.

Fermentation doi: 10.3390/fermentation12080353

Authors: Karla Ramírez-Frías Solmaría Mandi Pérez-Guzmán José Manuel Hernández-Martínez Roger Emmanuel Sales-Pérez Alejandro Alvarado-Lassman Juan Manuel Méndez-Contreras

Agro-industrial residues from livestock and sugarcane production—particularly abundant in regions such as Veracruz, Mexico, where both agro-industries co-occur in high density—constitute underutilized carbon and nitrogen streams with high potential for biotransformation within circular bioeconomy frameworks. This study aimed to evaluate whether inoculation with Lactobacillus delbrueckii subsp. bulgaricus SP96 at increasing levels (5, 10, and 15% v/v) achieves simultaneous stabilization, carbohydrate-to-lactic-acid conversion, and nutritional enrichment of a thermally pretreated bovine manure (BM)–agro-sugarcane waste (ASCW) mixture, and to describe the underlying growth kinetics using the Gompertz model. Thermal pretreatment reduced Salmonella spp. and fecal coliforms to levels compliant with NOM-004-SEMARNAT-2002 Class B biosolid standards, yielding a substrate with suitable fermentability (14.56 gL−1 carbohydrates, 0.44% total nitrogen, pH 6.52, and 90.43% volatile solids). Fermentation at 37 °C and 120 rpm for 72 h followed Gompertz kinetics (R2 = 0.92–0.97). The 15% inoculum achieved the highest conversion efficiency and product yield (lactic acid and carbohydrate consumption), whereas the 10% inoculum represented the most balanced operating condition (best kinetic fit, R2 = 0.97). However, differences in lactic acid concentration among treatments were not statistically significant (p > 0.05). The resulting biomass showed high organic matter (93.45%), increased crude protein (8.5%), a C/N ratio of 39.9, and enrichment in P2O5, MgO, Na2O, and B. These findings validate a low-cost, scalable platform for simultaneous waste stabilization and generation of value-added, protein-enriched biomass with potential application as a feed supplement and soil amendment, pending further safety and functional characterization, from agro-livestock residues.

Fermentation doi: 10.3390/fermentation12080351

Authors: Rajendran Poorniammal Somasundaram Prabhu Krishnakumar Rithikha Sharmi Subburamu Karthikeyan Laurent Dufossé

Agricultural biomass, comprising animal manure, food processing residues, lignocellulosic agricultural by-products, and other agro-industrial wastes, is generated in large quantities worldwide, particularly in developing countries. Although these residues pose significant environmental disposal challenges, they represent abundant renewable carbon resources that can be valorized into biofuels, contributing to sustainable waste management and circular bioeconomy initiatives. Biohythane, a gaseous fuel consisting of hydrogen and methane, is primarily produced through two-stage anaerobic digestion, in which dark fermentation generates hydrogen-rich intermediates that are subsequently converted into methane during methanogenesis. The separation of these stages enables independent optimization of hydrogen and methane production, resulting in improved substrate conversion efficiency and higher energy recovery than conventional single-stage anaerobic digestion. In addition, the presence of hydrogen enhances combustion characteristics while reducing greenhouse gas and nitrogen oxide emissions. This review critically evaluates recent advances in biohythane production from agricultural biomass through a structured assessment of peer-reviewed literature retrieved from major scientific databases. The selected studies were synthesized to examine biomass feedstocks, pretreatment technologies, microbial communities, metabolic pathways, reactor configurations, and process optimization strategies influencing biohythane production. The review further discusses the advantages and limitations of different agricultural residues, identifies current technological and economic challenges, and highlights emerging research opportunities to improve process efficiency and facilitate the sustainable commercialization of biohythane as a low-carbon renewable energy source.

Fermentation doi: 10.3390/fermentation12080350

Authors: Hongxin Ji Fei Li Xiqing Guo Pengbao Shi Hejing Yan

This study developed an ABTS-targeted sequential fermentation strategy for fermented apple beverages using Metschnikowia sp. Mp58 belonging to the M. pulcherrima clade (Mp) and Lactiplantibacillus plantarum Cro3-2 (Lp). Thirteen Metschnikowia isolates and ten Lactiplantibacillus isolates were initially screened according to their effects on ABTS radical-scavenging activity, after which Mp58 and Cro3-2 were selected for further investigation. Different fermentation strategies were compared, and sequential inoculation of Mp followed by Lp produced the highest ABTS radical-scavenging activity. Single-factor experiments, an orthogonal design, and response surface methodology were subsequently used to optimize the inoculation interval, fermentation temperature, and total fermentation time, with ABTS radical-scavenging activity as the sole response variable. The selected conditions consisted of Mp inoculation at 0 h, Lp inoculation after 25 h, and fermentation for a total of 46 h at 21.50 °C. The experimentally obtained ABTS radical-scavenging activity was 78.17 ± 0.49%, which was close to the model-predicted value. Under the selected conditions, Mp–Lp sequential fermentation significantly altered the physicochemical, bioactive, in vitro functional, and volatile characteristics of the apple beverage. Compared with the uninoculated control, total phenolic content, total flavonoid content, and ascorbic acid content increased by 73.08%, 32.97%, and 7.14%, respectively. These changes were accompanied by increases of 41.00%, 39.77%, and 37.86% in ABTS radical-scavenging activity, DPPH radical-scavenging activity, and ferric reducing antioxidant power, respectively. The Mp–Lp beverage also exhibited the highest α-glucosidase and α-amylase inhibitory activities, reaching 85.97% and 78.35%, respectively, as well as bile salt-binding capacities of 51.57% for sodium glycocholate and 54.97% for sodium taurocholate. Ethanol accumulation remained limited under the tested conditions, although concentrations below the measurement capability of the distillation–hydrometer method could not be excluded. A total of 95 volatile compounds were tentatively identified by HS-SPME-GC-MS. The sequentially fermented beverage contained a larger number of detected volatile compounds than the single-strain fermented beverages and showed treatment-associated changes in the relative distribution of esters, alcohols, and fatty acids. Exploratory PCA and OPLS-DA indicated differences in volatile composition among treatments, while nonanoic acid, ethyl hexanoate, n-decanoic acid, isophorone, and (E)-2-hexen-1-ol were identified as candidate compounds associated with group separation. These chemical changes should not be interpreted as direct evidence of improved aroma or sensory quality in the absence of sensory evaluation. Overall, Mp–Lp sequential fermentation represents a potentially useful bioprocessing strategy for modifying the bioactive properties, in vitro functional indicators, and volatile composition of fermented apple beverages.

Fermentation doi: 10.3390/fermentation12080349

Authors: Ziyan Wang Yumeng Yan Lingzhi Kong Yu Zhang Zhixian Zhao Kainan Xu Muyang Li Lei Zhao Fangfang Zhao Yanbing Li

This study evaluated a compound chemical additive (CA) composed of potassium sorbate, sodium benzoate, and sodium nitrite. Potassium sorbate is suitable for high-temperature ensiling, while sodium nitrite functions well under low-temperature conditions, and sodium benzoate inhibits bacterial energy metabolism. This compound theoretically provides stable antibacterial effects across variable storage temperatures. The effects of CA on fermentation quality, aerobic stability, and microbial communities of high-moisture corn (HMC) silage were investigated at 35 °C and 5 °C, including the control group (CON) and CA group. After 28 days of fermentation and 7 days of aerobic exposure, microbial communities were analyzed via high-throughput sequencing. CA significantly improved silage quality at both temperatures, increasing lactic acid and crude protein content, reducing pH, NH3-N and neutral detergent fiber, and suppressing yeasts and enterobacteria to enhance aerobic stability. Storage temperature dominated microbial community composition, while CA further optimized microbial structure. At 35 °C, CA eliminated spoilage yeast Nakaseomyces glabratus and enriched Levilactobacillus brevis and Aspergillus spp. with elevated relative abundance. At 5 °C, CA inhibited cold-resistant spoilage microbes, promoted the accumulation of Latilactobacillus curvatus, and restricted cyanobacteria growth. Metabolic prediction indicated that CA was correlated with pathways related to enhanced lactic acid synthesis and inhibited proteolysis and silage spoilage. In conclusion, CA effectively stabilizes HMC silage by regulating microbial and metabolic characteristics under different temperatures, serving as a promising temperature-adaptive preservative.

Fermentation doi: 10.3390/fermentation12080347

Authors: Qi Wang Can Yuan Liran Yang Bin Jiang Kunyi Liu

Traditional fermented sausages are widely consumed in China but often face quality and safety risks due to contamination by spoilage and pathogenic microorganisms during natural fermentation. This study investigated the effect of Litsea cubeba essential oil (LCEO) on the microbial community structure and volatile flavor compounds (VFCs) of fermented sausages using multi-omics approaches, including 16S/ITS amplicon sequencing and HS-SPME-GC-MS. The results showed that LCEO significantly altered the microbial community, increasing the relative abundance of Lactobacillus from 4.65% to 76.22% and Debaryomyces from 11.95% to 22.35%, while reducing Staphylococcus and Aspergillus by 47.01% to 4.55% and 37.28% to 17.09%, respectively. A total of 695 VFCs were identified, with terpenoids and hydrocarbons being the most abundant. A differential analysis revealed that LCEO enhanced the relative content of key aroma-active compounds, including ethyl esters and aldehydes, with odor activity values exceeding 1 for fruity-related compounds such as decanoic acid, ethyl ester and nonanoic acid, methyl ester. Strikingly, the elevated levels of these fruity esters translated into significantly higher sensory scores for odor (p < 0.05) in LCEO-treated sausages, as panelists consistently perceived a pronounced fruity and fresh aroma profile, ultimately leading to a superior overall acceptability compared to the control. A correlation analysis indicated strong positive associations between Lactobacillus, Debaryomyces, and major flavor-contributing esters. In conclusion, LCEO potentially reduces the microbial risks and improves the flavor profile of fermented sausages, making it a promising natural additive for meat fermentation.

Fermentation doi: 10.3390/fermentation12080348

Authors: Daolei Zhang Rongxin Zhang Yueming Lv Guang Yang Jian Zhao Xianqin Lu

In strong-flavor Baijiu brewing, surface spraying of recycled distillation tail liquor (TL) leads to volatile aroma loss, uneven substrate distribution and localized fermentation inhibition. A patented telescopic subsurface injector was adopted to deliver 0–30 kg TL per pit at a 50 cm depth on fermentation day 30, the critical transition point between acidogenesis and esterification. At the highest dosage (30 kg), total esters rose 14.8% (from 4.45 to 5.11 g/L), with ethyl hexanoate up 52.2% (to 1.72 g/L) and ethyl lactate up 69.8% (to 3.82 g/L). Fermentation temperature curves stayed unchanged, and grain-derived ethanol yield remained near 38.2% in all groups after correcting for the ethanol already present in the added TL. Subsurface injection of tail liquor-supplying ethanol and organic acid precursors-at the acidogenesis-to-esterification transition enhances ester synthesis without disrupting fermentation or reducing distillate yield. Acid profiles were also stable, suggesting that the added substrates were channeled into ester synthesis rather than acid accumulation. Targeted subsurface TL injection at this metabolic transition thus represents an industrially feasible strategy to boost ester biosynthesis, offering a recyclable TL valorization approach and verifying substrate-limited esterification in solid-state Baijiu fermentation.

Fermentation doi: 10.3390/fermentation12080346

Authors: Cennet Acar Deniz Koçan Fatma Şahmurat

Kefir is a self-carbonated fermented milk produced with kefir grains which is valued for its complex symbiotic microbiota and probiotic potential. Flavouring kefir is a recognised strategy to broaden consumer appeal, yet the moment at which a flavouring ingredient is introduced—before or after fermentation—may differentially affect the product. The present study evaluated the effect of the timing of instant coffee addition on the physicochemical, microbiological and sensory properties of kefir during 14 days of refrigerated storage (4 ± 1 °C). Three kefir samples were produced from UHT cow’s milk (3% fat) inoculated with 3% (w/v) kefir grains: a control without coffee (K), kefir with 0.5% (w/v) instant coffee added before fermentation (PreF_CK) and kefir with 0.5% (w/v) instant coffee added after fermentation and maturation (PostF_CK). Samples were analysed on days 1, 7 and 14. The coffee addition significantly increased the total dry matter (K = 10.72%; PreF_CK = 11.04%; PostF_CK = 11.00%; p < 0.01) and slightly modified the titratable acidity and pH (p < 0.05), whereas the ash content (expressed in terms of dry matter) did not differ among samples (p > 0.05). The titratable acidity increased and the pH decreased with storage in all samples (p < 0.05). Crucially, the coffee addition—irrespective of the timing—did not impair the viability of the kefir microbiota; the total mesophilic aerobic bacteria, Lactobacillus spp., mesophilic lactic cocci and yeast counts did not differ significantly among the samples (p > 0.05) and remained high throughout storage (lactic acid bacteria ≥8 log CFU/g; yeast ≥5.7 log CFU/g), exceeding the minimum thresholds of the standards for fermented milk products. Sensory evaluation showed that the control achieved the highest odour and taste scores (p < 0.001), while among the coffee-containing samples, the post-fermentation addition (PostF_CK) was generally scored at least as high as the pre-fermentation addition (PreF_CK); overall acceptability did not differ significantly among the samples (p > 0.05). These findings demonstrate that 0.5% instant coffee can be incorporated into kefir without compromising its characteristic microbiota or storage stability and that post-fermentation addition is a viable route for producing an acceptable coffee-flavoured kefir.

Fermentation doi: 10.3390/fermentation12080345

Authors: Yingjie Liang Weicheng Li Chuangye Liu Zhiyin Xie

Internal temperature distributions in black tea fermentation regulate enzymatic oxidation, heat accumulation and fermentation uniformity, but continuous three-dimensional measurements remain difficult in practical processing. We developed a CFD-prior-constrained physics-informed neural network (PINN + CFD) to reconstruct the three-dimensional thermal state of a 1.35 m × 0.96 m × 0.08 m fermentation bed under sparse sensing. Nine sensors at z = 0.04 m were used for training, and six held-out depth-wise sensors at z = 0.02 m and z = 0.06 m were reserved for depth-wise validation. The model integrated measured temperatures, transient heat-transfer physics, convective boundary conditions and a CFD-derived volumetric soft spatial prior, which guided spatial extrapolation rather than serving as ground-truth temperature data. Although the multilayer perceptron achieved the lowest fitting error at the instrumented z = 0.04 m plane, PINN + CFD showed better depth-wise extrapolation, with RMSEs of 0.128, 0.129 and 0.296 °C across the three stages. However, its advantage was stage- and validation-target-dependent: the baseline PINN was slightly better in part of the dynamic-stage validation, and standalone CFD had the lowest surface infrared error in the constant-temperature stage, indicating that PINN + CFD mainly improved spatial extrapolation rather than uniformly minimizing all error metrics. The inferred apparent process-level heat-source index Qreact(t) varied continuously, and its cumulative trajectory showed a descriptive association with cumulative polyphenol loss. These results indicate that PINN + CFD enables physically consistent thermal-state reconstruction within the tested sparsely instrumented black tea fermentation bed.

Fermentation doi: 10.3390/fermentation12080344

Authors: Daoguang Zhu Tingyao Tu Huanqing Niu Yuqin Tong Qingguo Liu Shijin Xue Yong Chen Hanjie Ying

Taiwanofungus camphoratus, an edible and medicinal fungus endemic to Taiwan, produces a distinctive and complex fragrance during mycelial growth, indicating its potential as a source of natural flavor compounds for food and cosmetic applications. However, few research efforts have focused on changes in its flavor-related metabolites and the related underlying molecular mechanisms remain largely unexplored. In this study, we found that the water extract of Cinnamomum camphora leaves (CC water extract) markedly stimulated T. camphoratus mycelial growth, increasing biomass by 29.7% in liquid fermentation. Integrated transcriptomics, UPLC-based metabolomics and HS-SPME-GC-MS analyses revealed that CC water extract could enhance metabolic fluxes through glycolysis, the pentose phosphate pathway, and galactose metabolism, thereby supporting mycelial growth and the accumulation of flavor-related metabolites. Specifically, CC water extract promoted the abundance of metabolites associated with mushroom-like, floral, and fruity aroma profiles, together with sweet taste-related metabolites. These findings provide new insights into optimizing the liquid fermentation processes and flavor profiles of T. camphoratus mycelia, providing a reference for better utilizing this valuable fungal resource.

Fermentation doi: 10.3390/fermentation12080343

Authors: Maria de Fátima Dantas Linhares Thatyane Vidal Fonteles Antônia Yvina Silva dos Santos Brenda Novais Santos Ana Lúcia Fernandes Pereira Sueli Rodrigues

This study evaluated the influence of sucrose addition on kombucha fermentation and the use of agro-industrial fruit residues (cashew apple bagasse, mango peels, and grape pomace) as natural flavoring agents. Processing parameters, including pH, total soluble solids (TSS), total titratable acidity (TTA), sugar consumption, and the evolution of organic acids, ethanol, and Total Phenolic Compounds (TPC), were monitored during a 9-day fermentation period and subsequent 30-day refrigerated storage period. Fermentation without added sucrose caused a significant reduction in TPC (p < 0.05), suggesting microbial biotransformation and enzymatic cleavage of bonded polyphenols into smaller, more reactive phenolic monomers. During refrigerated storage, the chemical profiles of the developed beverages remained relatively stable, and ethanol concentrations remained below the regulatory limit for non-alcoholic beverages (0.5% v/v or 4.0 g/L). In addition, four commercial kombucha samples were evaluated over the same storage period to compare ethanol stability and regulatory compliance. Sensory analysis showed that visual appearance and complex flavor profiles were mainly driven by fruit matrices, confirming their effectiveness as natural functional and flavoring agents. These findings demonstrate that initial sucrose can be excluded from kombucha brewing, as fruit residues supported late fermentation dynamics without inducing non-compliant ethanol accumulation.

Fermentation doi: 10.3390/fermentation12080342

Authors: Jia Tian Li’e Hou Yuanyuan Zhang Yuan Wan Siyuan Cheng Xin Li

As an eco-friendly strategy for improving intestinal health, production performance, and meat quality in livestock and poultry, live probiotic strains (Lactobacillus, Bifidobacterium, Bacillus), paraprobiotics and postbiotics have exhibited considerable application potential in monogastric livestock in animal husbandry. However, probiotic efficacy is commonly characterized by striking individual heterogeneity, and its intrinsic regulatory basis remains poorly understood. This review systematically summarizes the core mechanisms by which probiotics modulate meat quality, feed efficiency and small intestinal and cecal health in pigs and broilers via the gut–muscle axis, nutrient metabolic axis, and immune regulatory axis. We elucidate the heritable effects of host genetics on shaping the gut microbiome and the fundamental principles underlying genotype–probiotic (G×P) interactions, highlighting that host genetic background represents an important of differential responses to probiotics. Accordingly, we propose integrating microbial genome-wide association studies (mGWAS) and genomic selection to develop novel breeding programs targeting probiotic responsiveness, with the aim of establishing a precision breeding system for probiotic-friendly livestock and poultry. This review may facilitate the paradigm shift of probiotic applications from universal administration to precision intervention, and from single nutritional regulation to host–microbiome synergistic breeding, providing a conceptual framework and innovative strategies for the green, efficient, and sustainable development of animal husbandry.

Fermentation doi: 10.3390/fermentation12080341

Authors: Hajer Ammar Alexey Díaz-Reyes Ahmed E. Kholif Jihen Jemaï María-Luisa Tejido Halimeh Zoabi Soha Ghzayel Bassam Abu Aziz Seyed Morteza Vaghar Seyedin Moyosore J. Adegbeye Francisco Javier Giráldez Secundino López

This study evaluates the effects of plant part (leaves vs. stems), harvest season (spring vs. autumn), and irrigation on the chemical composition, in vitro ruminal fermentation kinetics, and digestibility of three Mediterranean leguminous shrubs: Acacia fimbriata, Medicago arborea and Anthyllis barba-jovis. Samples were collected under field conditions, analysed for chemical composition, and assessed for in vitro ruminal fermentation, including incubations with and without polyethylene glycol (PEG) to assess the biological activity of phenolic compounds. Crude protein and fibre fractions did not differ significantly among species; ash was highest (p < 0.05) in Ac. fimbriata. In vitro fermentation kinetics were similar among species; however, the response to PEG was higher (p < 0.05) for Ac. fimbriata than for M. arborea and An. barba-jovis. In vitro digestibility was superior (p < 0.05) in M. arborea and An. barba-jovis. Leaves contained higher ash and protein contents and less fibre than stems, resulting in greater gas production, fermentation rate, and digestibility (p < 0.05). Spring-harvested fodder showed higher digestibility than autumn samples. Irrigation had negligible effects, except for a marginal numerical but nonsignificant (p = 0.05) greater extent of degradation observed in browse prior to irrigation. Overall, M. arborea showed a better nutritional quality, whereas Ac. fimbriata was the species with the lowest nutritive value. Forage quality was strongly influenced by plant part and harvest season, with leaves and fodder in spring showing superior potential as a feedstuff for ruminants.

Fermentation doi: 10.3390/fermentation12070340

Authors: Jetsada Khamfu Jeeranan Situtha Phimphisa Thammawong Shankar Neupane Anh Dao Trinh Nattaya Konsue

The rising consumer demand for functional, low-alcohol beverages necessitates innovative brewing strategies. This study evaluated germinated Thai glutinous rice (Oryza sativa var. glutinosa, cv. Kheiw Ngu 8974) as a novel malt adjunct for non-alcoholic beer fermented with the probiotic yeast Saccharomyces boulardii. Formulations with germinated glutinous rice to barley malt ratios of 0:100, 40:60, 60:40 and 80:20, designated as R0, R40, R60, and R80, respectively, were systematically analyzed for their fermentation properties, physicochemical properties, bioactive enrichment, volatile compounds, and sensory attributes. Results showed that the high substitution levels in glutinous rice restricted enzymatic saccharification, successfully limiting ethanol accumulation in R60 and R80 to below the 0.5% v/v regulatory threshold. The final ethanol values for R0, R40, R60, and R80 were 1.34 ± 0.04%, 0.65 ± 0.04%, 0.4 ± 0.04%, and 0.13 ± 0.04% v/v, respectively. Although the control formulation (R0) exhibited the highest initial total phenolic content (TPC), antioxidant capacity, and gamma-aminobutyric acid (GABA) levels, S. boulardii fermentation significantly enriched these functional compounds across all adjunct-substituted formulations. Furthermore, gas chromatography–mass spectrometry (HS-SPME-GC/MS) analysis revealed a distinct shift in the volatile profile, with increasing levels of rice substitution resulting in a reduction in fermentation-derived aliphatic esters and a greater relative abundance of hop-derived terpenes and terpenoids. Sensory evaluations indicated that while extreme substitution (R80) negatively impacted color and aroma balance, the 40% and 60% formulations maintained highly acceptable organoleptic profiles. The overall liking scores for R0, R40, R60, R80, and the commercial product were 6.71 ± 1.66, 5.42 ± 1.65, 5.68 ± 1.80, 5.03 ± 1.92, and 6.45 ± 1.65, respectively. In conclusion, integrating a 60% substitution of germinated Thai glutinous rice provides the most balanced formulation among those tested, producing compliant, sensory-acceptable non-alcoholic beer with enhanced bioactive functionality.

Fermentation doi: 10.3390/fermentation12070339

Authors: Shuzhen Li Qi Wang Xiaoping Du Bo He Jun Zhang

To investigate the influence of single fungi fermentation on dark tea, Aspergillus chevalieri and Aspergillus cristatus were isolated from Fu-brick tea in this study. Both strains were used for solid-state fermentation of Fu-brick tea to analyze volatile compounds, while A. cristatus was used for liquid-state fermentation to analyze metabolite changes. Solid-state fermentation with Aspergillus chevalieri and Aspergillus cristatus yielded 56 and 63 volatile compounds, respectively, with alcohols, aldehydes, and ketones as the predominant classes. Notably, A. cristatus biotransformation resulted in the highest total volatile content, primarily characterized by trans-linalool oxide, cis-linalool oxide, and dihydroactinidiolide. Conversely, Aspergillus chevalieri fermentation produced fewer aroma compounds, mainly trans-linalool oxide and dihydroactinidiolide. Widely targeted metabolomics further revealed that flavonoids, amino acids and derivatives, phenolic acids, lipids, and tannins were significantly reduced in the liquid-state-fermented tea leaves, whereas most differential metabolites accumulated in the tea infusions. Flavonoid biosynthesis and amino acid metabolism were identified as the most significantly enriched pathways. These findings elucidate strain-dependent divergence in aroma composition and non-volatile metabolite transformation, offering a scientific basis for targeted strain selection and process optimization in the development of industrial fermented tea products.

Fermentation doi: 10.3390/fermentation12070338

Authors: Jun-Su Choi Su-Hyun Lee Sae-Byuk Lee

While sucrose chaptalization is commonly used in persimmon wine production to achieve adequate fermentable sugar levels, the fermentation suitability of a persimmon substrate modified by artificial botrytization has not been adequately investigated. In this study, persimmon must obtained from Botrytis cinerea-treated fruit and a sucrose-chaptalized control were fermented using the same yeast (Saccharomyces cerevisiae Fermivin) and temperature (20 °C) conditions. The noble rot-treated group displayed gradual changes in appearance during storage and faster alcohol production and reducing sugar depletion during fermentation compared with the control. Despite lower initial soluble solids (21.50 °Brix) compared with the control (23.00 °Brix), the noble rot-treated group achieved a higher final alcohol content (11.60% vs. 8.80%) within a shorter fermentation period (9 vs. 16 days). These findings suggest that artificial botrytization may serve as a distinct pre-fermentation treatment in persimmon wine production compared with simple sucrose chaptalization. However, further studies are needed to elucidate the compositional and metabolic factors underlying these differences.

Fermentation doi: 10.3390/fermentation12070337

Authors: José María Arroyo Manel Riahi Javier González María Dolores Carro

Including oilseeds in the diet is a widely studied strategy to reduce CH4 emissions in ruminants, but the effects on ruminal fermentation depend on oilseed composition. This study compared the effects of including three oilseeds (soybean, sunflower and cardoon) differing in fiber content and lignification on in vitro ruminal fermentation and CH4 production of dairy and fattening diets. Oilseeds were included to achieve two dietary lipid levels: low (3.5–4.0%) and high (5.5–6.0%). Diets were incubated in vitro with buffered ruminal fluid from sheep for 17 h. The high lipid level reduced microbial activity only in the fattening diet, particularly after 6 h of incubation, although this effect largely disappeared by 17 h. The most consistent differences among oilseeds were observed in NH3-N concentrations, with soybean yielding lower values than sunflower and cardoon, suggesting reduced protein degradation due to soybean processing. In the fattening diet, cardoon at the low lipid level reduced CH4 production compared with soybean and sunflower (44.9, 50.5 and 52.3 mL/g incubated dry matter) but also reduced total volatile fatty acid production and fermented organic matter, whereas no differences were detected for dairy diets. At equal lipid supply, sunflower and cardoon can replace soybean in dairy diets without negatively affecting ruminal fermentation, whereas cardoon may reduce CH4 production and fermentation in fattening diets at low lipid levels.

Fermentation doi: 10.3390/fermentation12070336

Authors: Mariama Alidu Symone L. M. Alexander

Bacterial cellulose (BC) is a high-purity biopolymer with significant potential for sustainable material applications. However, its production remains limited by the metabolic behavior and compositional complexity of available carbon substrates. Simple sugars such as fructose, glucose, and sucrose support BC synthesis but differ in their metabolic pathways and associated byproduct formation, which can influence medium pH and cellulose biosynthesis. Across refined substrates, fructose generally outperforms glucose, producing the most favorable balance between productivity and structure. Reported fructose-based yields range from 1.55 to 6.29 g/L depending on the composition. In media containing hexoses, such as fructose, and three-carbon compounds, such as glycerol and pyruvate, biosynthesis proceeds via the pentose phosphate pathway. Additionally, pyruvate can be further metabolized via gluconeogenesis coupled with the tricarboxylic acid cycle, producing more BC precursors. In contrast, glucose-based yields are limited primarily by oxidation to gluconic acid, and sucrose often shows slower or lower initial production due to delayed metabolism, depending on the medium’s composition. Interestingly, structural trends showed that yield and structural quality are not always coupled. Fructose-based BC can reach around 90% to 92% crystallinity index (CrI) and is associated with lower porosity and larger nanoribbon networks, while sucrose-based BC can reach up to a 95.2% CrI despite slower initial production. Dual sugar systems further reveal differences in metabolism. Glucose-containing carbon sources are often suppressive because glucose dominates metabolism and acidification, whereas fructose-containing systems more often show synergistic behavior and support higher yields. Structural outcomes in these systems depend more on biosynthesis rates and strain-specific behavior than on carbon sources only. Additionally, low-cost substrates derived from agro-industrial residues and lignocellulosic biomass offer economically viable feedstock but introduce variability due to inhibitory compounds such as organic acids and phenolics. This review examines how sugar type and substrate complexity affect BC production and its structural properties in acetic acid bacteria, particularly the genera Acetobacter, Gluconacetobacter, and Komagataeibacter, with emphasis on the relationship between BC yield and CrI. Our analysis of the reported fermentation and characterization data in this review reveals a recurring paradox between yield and structural quality, in which substrates that promote higher BC yields do not always produce materials with superior structural properties such as crystallinity or degree of polymerization. Comparative examination of the literature revealed that inhibitory compounds such as phenolic compounds may act as structural modulators rather than simple yield suppressors. Phenolic compounds are predicted to bind to BC through non-covalent interactions facilitated by the large surface area and porous structure of BC. These interactions may influence the self-assembly of BC nanofibers. These findings indicate that fructose often offers the best balance of yield and structure. While sucrose tends to favor structural order, glucose is susceptible to yield loss from acidification, and waste-derived substrates can provide economic, high-yield, and structural properties only when their inhibitory compounds are well controlled.

Fermentation doi: 10.3390/fermentation12070335

Authors: Melisa Puntillo Guillermo H. Peralta Josefina del Rio Dina L. Hernández Torres Soraya Bellini Juan Martín Oteiza Gabriel Vinderola María Florencia Zacarías

The growing demand for plant-based functional foods has encouraged the development of non-dairy fermented beverages able to deliver viable microorganisms and improve the technological and nutritional value of plant matrices. This study aimed to develop a prototype fermented peanut beverage using Lactiplantibacillus plantarum strains and to evaluate their technological performance, stability, and functional potential. Two plant derived strains, L. plantarum F1B and LpAv, and the commercial probiotic L. plantarum 299v were assessed in animal-free culture media and used to ferment peanut extract supplemented with sucrose and yeast extract. Fermented beverages were characterized through microbiological, physicochemical, rheological, peptide profile, refrigerated storage, and simulated gastrointestinal digestion. The selected formulation allowed all strains to reach pH ≤ 4.5 after 6.5 h, with LAB counts of 8.6–9.0 log CFU/mL. Lactic acid was the main fermentation product, and oxalic acid levels were significantly reduced. Fermentation increased peptide signals and improved rheological behavior, generating pseudoplastic beverages with higher viscosity than the control. LAB counts remained ≥8 log CFU/mL after 28 days at 4 °C, although gastrointestinal resistance after storage was strain-dependent. Taken together, L. plantarum strains showed promising technological and functional properties for developing fermented peanut-based beverages. The nutritional properties of peanut, together with the fact that it supports the growth and survival of LAB in a fermented beverage, positions peanuts as a candidate which deserves further studies in the space of fermented functional foods.

Fermentation doi: 10.3390/fermentation12070334

Authors: Chien-Hao Chen Sheng-Qi Cai Saeid Jafari Katarzyna Świąder Christelle Bou-Mitri Liviu Gaceu Chang-Wei Hsieh Kuan-Chen Cheng

Background: Premium table grapes are often underutilized for winemaking due to suboptimal sugar–acid balance and limited aroma complexity. This study evaluated the chemical and sensory characteristics of wine produced through mixed fermentation of yeasts and lactic acid bacteria (LAB) to valorize Kyoho grapes. Methods: Kyoho grapes were fermented using a sequential yeast inoculation (Hanseniaspora opuntiae followed by Saccharomyces cerevisiae, HO+SC), combined with either simultaneous (SIM-MLF) or sequential (SEQ-MLF) malolactic fermentation using Lactoplantibacillus plantarum. Volatile compounds were quantified via Gas Chromatography with Flame Ionization Detection (GC-FID), and consumer sensory evaluation was conducted. Results: The HO +SC fermentation increased total ester content 4.21-fold compared to the S. cerevisiae control (p < 0.05). SIM-MLF yielded significantly higher levels of ethyl lactate, diethyl succinate, and diacetyl than SEQ-MLF (p < 0.05), with total esters reaching 267.38 ± 17.71 mg/L. Both MLF treatments reduced titratable acidity and increased pH. Conclusions: Sensory evaluation confirmed that SIM-MLF achieved the highest overall acceptance (7.63/9), strongly associated with “floral,” “blackberry,” and “creamy” descriptors. Thus, SIM-MLF effectively enhances the sensory attributes of Kyoho wine, providing a practical valorization strategy for non-traditional grape varieties.

Fermentation doi: 10.3390/fermentation12070333

Authors: Bin Chi Penghui Huang Shenghua Zhang Heyong Zhang Jian Wu Ang Li

Aerobic composting of food waste (FW) is constrained by delayed temperature increase initially. This study evaluated the use of high-solid anaerobic digestion (HSAD) biogas residue as a composting initiator. In the co-composting treatment containing biogas residue and FW (C3), the temperature peaked at 69.8 °C on day 5. In comparison, the FW composting alone (C1) reached a lower peak temperature of 67.1 °C on day 8. Similarly, C3 sustained the thermophilic phase (>55 °C) for 10 days, comparable to the 11 days observed in C1. The incorporation of biogas residue adjusted the pH of FW toward neutrality, helping to reduce nitrogen loss. C3 also demonstrated a distinctive phytohormone profile, with salicylic acid (SA) content reaching 42.62 ng g−1, significantly exceeding that of C1 (31.54 ng g−1), suggesting enhanced bio-stimulatory potential. Compared with C1, N2O emissions in C3 were both reduced and delayed, while cumulative CH4 emissions were lower than those in the biogas-residue-alone composting (C2). Biogas residue addition introduced thermotolerant microbes, reduced acidification by suppressing acidophiles, and enhanced humification via cooperative networks. Metagenomics revealed that C3 developed a denitrification gene profile favoring net N2O consumption under high pH. These results demonstrate that HSAD biogas residue can serve as an effective initiator for FW composting.

Fermentation doi: 10.3390/fermentation12070332

Authors: Hailong Chen Wanlu Xu Fenbian Sun Xinxing Gao Wangshui Cai Long Xu Haiyun Rui Guanxing Zhu

Saccharomyces cerevisiae, widely used in industrial fermentation, still suffers from inherent problems in the efficient utilization of carbon sources. Here, a strategy for alleviating glucose effect and improving S-adenosyl-L-methionine (SAM) production by deleting Mig1 combined with introducing MetK1 from Leishmania infantum was applied in S. cerevisiae. The deletion of Mig1 improved glucose utilization by increasing the expression levels of genes related to glucose transport and glycolysis, thereby increasing the levels of glycolytic intermediates and increasing both the transcriptional levels of ACS1 and ALD6 and the activity of ADH2, which promotes the conversion of ethanol into acetyl-CoA. The deletion of Mig1 also upregulated the transcripts of genes involved in the metabolism of precursor amino acids of SAM and ultimately responsible for the improvement in SAM synthesis. Finally, MetK1 was introduced into yeast to redirect carbon flux toward SAM biosynthesis. As expected, the SAM production of the mutant YMig1ΔPMetK1 reached 8.91 g/L in a 10 L fermenter, which was 72.3% higher than that of the parent strain S. cerevisiae CGMCC 2842 (5.17 g/L) reported in our previous studies. This study revealed that the strategy of alleviating glucose effect and redirecting carbon flux to nonethanol products by Mig1 deletion combined with heterologous MetK1 introduction possesses great potential for improving SAM synthesis in yeast cells.

Fermentation doi: 10.3390/fermentation12070331

Authors: Bing Wang Jingyan Gao Furan Zhang Jian Luan

Possessing a high nitrogen content, low cost and stable supply, urea serves as a critical non-protein nitrogen (NPN) source that represents a promising alternative to conventional protein feedstocks for reducing production costs in microbial protein (MP) synthesis. This article systematically discusses the application potential of urea in MP production, the metabolic pathways governing microbial urea utilization, and the key factors influencing the conversion efficiency of urea to microbial protein. Herein, we summarize recent progress in urea modification technologies covering slow-release urea, extruded urea, and urea-based composite preparations and elucidate the complete metabolic mechanisms of urea assimilation in both rumen fermentation and in vitro cultivation, including transmembrane transport, urease-catalyzed hydrolysis, ammonia assimilation, and MP synthesis. Furthermore, we analyze the regulatory effects of dietary energy level, carbohydrate structure, protein concentration, forage quality, urea formulation type, and functional additives on nitrogen utilization efficiency. Current evidence indicates substantial knowledge gaps regarding urea transporter functionality, the coordinated regulation of UC and nitrogen assimilation pathways, microbial community interactions, and the stability control of industrial-scale production. The development of high-efficiency utilization technologies, feed safety evaluation systems, and precision feeding models for industrial applications remains incomplete. This article seeks to provide a thorough theoretical reference for the efficient utilization, mechanistic elucidation, and industrial promotion of urea-based nitrogen sources within MP production systems.

Fermentation doi: 10.3390/fermentation12070330

Authors: Jelena Vulić Sladjana Stajčić Olja Šovljanski Dragoljub Cvetković Sara Brunet Vesna Tumbas Šaponjac

Beetroot pomace is a valuable food-processing by-product that is rich in betalains and phenolic compounds, but the instability of these bioactives limits their direct use in functional foods. This study aimed to develop a pumpkin seed protein-based encapsulated ingredient from beetroot pomace extract and evaluate its preliminary application in yogurt fortification. Beetroot pomace contained 193.75 ± 3.83 mg GAE/100 g DW of total phenolics and 95.78 ± 1.27 mg/100 g DW of total betalains. Encapsulation was optimized using the response surface methodology, with the wall-to-core ratio, extract dilution, and mixing time as independent variables. The optimal encapsulate showed experimentally confirmed encapsulation efficiencies of 75.37% for phenolics and 84.02% for betalains, containing 196.62 ± 4.37 mg GAE/100 g total phenolics and 53.19 ± 0.90 mg/100 g total betalains. After simulated gastrointestinal digestion, betalains remained detectable at 43.15 ± 1.46 mg/100 g, while total phenolics increased to 726.56 ± 30.59 mg GAE/100 g and DPPH antioxidant activity reached 1472.76 ± 7.58 mg TE/100 g, indicating the improved extractability of phenolics from the protein matrix. The encapsulate showed low water activity and moisture content but high hygroscopicity and very poor flowability, indicating the need for further powder-handling optimization. Yogurt fortification with 3% encapsulate, selected as a preliminary technologically feasible level, improved the bioactive profile during storage at 4 °C for 7 days and −18 °C for 21 days. These results support pumpkin seed protein-encapsulated beetroot pomace bioactives as sustainable multifunctional ingredients for yogurt fortification, while further sensory validation and comparison with free extracts are required.

Fermentation doi: 10.3390/fermentation12070329

Authors: Ramon Akkharapreechanont Pipat Macharoen Wanilada Rungrassamee Awanwee Petchkongkaew

Water kefir is a non-dairy fermented beverage widely recognised for its health benefits. The supplementation of fruits can further diversify product offerings while enhancing nutritional and functional value. In this study, karanda juice, derived from a fruit native to Thailand and known for its beneficial health properties, was used as a substrate for water kefir production, with the aim of increasing both product diversity and the value of this raw material. The study aimed to investigate changes in microbial diversity and chemical characteristics during fermentation using this specific substrate. The results demonstrated that the fermentation process is driven by a consortium of microorganisms, with Lactobacillus spp. and Saccharomyces spp. identified as the dominant genera. Formic acid was the predominant organic acid produced, while propionic, isobutyric, and butyric acids were detected in trace amounts. Notably, valeric acid, an organic acid associated with potential health benefits, was identified in karanda juice kefir (KJK). Overall, the findings highlight dynamic changes in both microbial diversity and chemical composition throughout fermentation. These results demonstrate that karanda juice is a promising substrate for water kefir production, with the resulting beverage containing diverse beneficial microorganisms and bioactive organic acids with potential functional properties.

Fermentation doi: 10.3390/fermentation12070328

Authors: Do-Yun Bang Du-Yong Cho Min-Ju Ahn Hee-Yul Lee Jong-Bin Jeong Mu-Yeon Jang Da-Hyun Kim Hye-Rim Kim Ye-Rim Jeong Dea-Cheol Son Kye-Man Cho

Bitter melon (BM; Momordica charantia L.) is rich in phytochemicals and has been widely studied for its pharmacological effects. However, BM is mainly consumed as a tea, and its application in fermented foods remains limited. This study investigated changes in phenolic compounds, bioactive metabolites, antioxidant and enzyme inhibitory activities, and DNA-protective effects in mul-kimchi with bitter melon (MKBM). MKBM was prepared with different BM concentrations (0%, 10%, and 20%) and fermented for 0–12 days. The phenolic profile changed according to BM concentration and fermentation periods. Epicatechin and epigallocatechin gallate were detected from day 3 only in BM-treated groups (MKBM-10 and MKBM-20). On day 12, catechin was detected only in MKBM-20, reaching 64.42 μg/mL, whereas it was not detected in MKBM-0. MKBM-20 also showed the highest total phenolic and flavonoid contents on day 12. Antioxidant and digestive enzyme inhibitory activities increased during fermentation, and DNA protection against oxidative damage was enhanced by day 9. These results suggest that mul-kimchi fermentation can improve the functional potential of BM as a fermented food ingredient.

Fermentation doi: 10.3390/fermentation12070327

Authors: Tobias Hübner Lucie Moeller

Lactic acid fermentation (LAF) is a promising low-tech approach for the stabilization and hygienization of human feces from dry toilets. However, practical implementation remains limited due to a lack of application-relevant knowledge. This study systematically evaluated the influence of a series of practical process parameters on the performance of LAF under standardized laboratory conditions. Feces obtained from different types of dry toilets were physicochemically characterized and subsequently fermented under varying process conditions, using pH and lactic acid production as key indicators of fermentation performance. The results indicate that LAF is feasible across a broad range of process conditions, including temperatures between 8 and 30 °C, and is largely independent of carbon source type, air intrusion, and extended storage periods (>1 year), provided that a sufficient carbon supply is ensured. The investigated parameters exhibited varying degrees of influence on process performance, with carbon source dosage (≥10 w/w-% sugar beet molasses equivalent) and feces type emerging as the most influential factors. While ferrous iron addition (≤5 w/w-%) enhanced pH reduction, biochar, bentonite, and rock flour (≤10 w/w-%) showed negligible effects. Maximum lactic acid production was limited to ≤4.5 w/w-%, irrespective of carbon source dosage, resulting in minimum pH values ranging from 4.1 to 5.2. These values varied primarily with fecal type, suggesting a strong influence of intrinsic buffering capacity. Under conditions supporting stable LAF, i.e., rapid acidification followed by sustained low pH, E. coli was consistently reduced below the detection limit in the investigated samples. Overall, the findings suggest that LAF is a comparatively robust treatment approach and highlight operational parameters that are likely to be important for its practical implementation as a sanitation technology.

Fermentation doi: 10.3390/fermentation12070326

Authors: Zhi Li Qingjing Huang Liangju Li Bangmeng Zhou Xiao Zou Lixiu Yan Jiamin Zhang Jie Cheng

Amino alcohols are a class of compounds bearing both amino and hydroxyl groups, ubiquitous in natural products and extensively utilized as key structural motifs in pharmaceuticals and functional materials. Owing to their structural diversity, inherent chirality, and high reactivity, they exhibit significant application value in the pharmaceutical field, materials industry, and organic synthesis. Compared with chemical synthesis, which suffers from limitations such as insufficient enantioselectivity, dependence on precious metal catalysts, and environmental concerns, biosynthesis offers core advantages of high stereoselectivity, mild reaction conditions, and environmental sustainability. This review systematically delineates the diverse applications of amino alcohols in the pharmaceutical field (e.g., anti-HIV, antimalarial, and antitumor drugs), materials industry (e.g., polymer modification and metal corrosion protection), and organic synthesis (e.g., chiral ligands and catalysts). Particular emphasis is placed on the biosynthetic strategies and pathways of representative amino alcohols, including ethanolamine, (2S,3R)-2-amino-1,3,4-butanetriol, (R)-3-amino-1-butanol, sphingosine, and metaraminol, as well as the metabolic engineering design principles and downstream processing technologies for amino alcohol biosynthesis. Although current biosynthetic approaches still face bottlenecks in enzyme catalytic efficiency, substrate tolerance, cofactor regeneration, product toxicity, and thermodynamic equilibrium, substantial improvements in synthetic efficiency and stereoselectivity have been achieved through protein engineering, metabolic engineering, in situ product removal, and multi-enzyme cascade optimization. This review aims to provide systematic theoretical references and technical insights for the green and efficient biomanufacturing of amino alcohols.

Fermentation doi: 10.3390/fermentation12070325

Authors: Yinpeng Ma Xiaoyu Sun Jinbo Gao Liguo Wang Jianzhao Qi Likun Chen Yihong Bao

Traditional methods for screening high-melanin-yielding Auricularia heimuer strains are time-consuming and environmentally unfriendly. To address this issue, fifteen A. heimuer strains were used to determine the mycelial biomass, absorbance at 500 nm, CIE L*a*b* colorimetric values, and melanin yield of the fermentation broth. Pearson correlation analysis was performed to clarify the correlations among these indicators, and a regression equation was fitted to establish a rapid screening method. A total of 84 A. heimuer strains were used to verify this method, of which one high-melanin-yielding strain was obtained. The structural characterization and in vitro antioxidant activities of A. heimuer melanin (AHM) were determined. The results showed that the melanin yields of fifteen A. heimuer strains were extremely significantly positively correlated with absorbance at 500 nm (r = 0.880, p < 0.01). The fitted linear regression equation was Y = 0.0246X + 0.00094 (R2 = 0.8756, p < 0.01). When 84 tested strains were investigated with this method, 8 strains (53.33%) exhibited relative differences below 10%, which is consistent with the satisfactory accuracy of the absorbance-based screening method. Finally, a high-melanin-yielding strain HMCC50028 was obtained, with a melanin yield of 0.0540 g/100 mL. The results of UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) of AHM indicated that the melanin exhibited structural characteristics consistent with fungal melanins, belonging to the natural melanin family. In vitro assays demonstrated that AHM possessed excellent superoxide anion radical scavenging activity and ferric reducing power.

Fermentation doi: 10.3390/fermentation12070324

Authors: Daina Eglite-Antona Kristine Majore Inga Ciprovica

This study investigated lactic fermentation of green buckwheat beverages formulated at 8% (A, AA) and 10% (B, BB) solids using single- and multiple-strain cultures of Lactiplantibacillus plantarum, Lactobacillus acidophilus, Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus. Fermentation at 37 °C rapidly reduced pH from slightly alkaline values (7.44–7.57) to approximately 4.2–4.5 within 3–8 h, while viable counts increased from near-zero to 8–9 log10CFU mL−1, confirming efficient lactic acid bacteria (LAB) proliferation in all substrates. A general trend was observed in the sugar consumption strategy of studied LAB: sucrose (after hydrolysis) and glucose were almost completely depleted within 6–8 h, fructose was consumed more slowly, and raffinose remained largely unchanged, with the 10% substrate mainly accelerating early sugar turnover without altering final cell densities or the qualitative utilisation pattern. Dry matter changed little during fermentation, whereas total phenolic content (TPC) and total tannin content (TTC) were strongly affected in a matrix- and strain-dependent manner. At 8% solids, fermentation promoted substantial TTC reduction and, for several cultures, a net decrease in extractable phenolics. In contrast, 10% formulations, particularly those inoculated with L. acidophilus and L. paracasei (alone or in combination), partially preserved or increased TPC while achieving more moderate tannin losses. Overall, green buckwheat proved to be a promising substrate for developing fermented beverages in which solids level and starter composition can be tuned to combine rapid acidification and high LAB viability with tailored sugar depletion and favourable modulation of phenolic and tannin fractions.

Fermentation doi: 10.3390/fermentation12070323

Authors: Mariam Alimardanova Zhanagul Doumchariyeva Nurzhan Zhumakhan Kulzhan Togzhanova Dinara Tlevlessova

The present study aimed to develop and evaluate a predictive approach for modeling pH dynamics during ayran fermentation using kinetic analysis, multivariate statistics, and IoT-based monitoring. Ayran is a low-viscosity fermented dairy beverage characterized by rapid acidification and high sensitivity to formulation and processing parameters, which limits the effectiveness of conventional endpoint pH control. The effects of two types of functional additives were investigated at empirically selected concentration ranges: a multifunctional dry fortifier (1–3%, w/w) and a vitamin–mineral syrup (2–4%, w/w). The data were analyed within a grouped comparative exploratory framework; the primary objective was comparative kinetic modeling of the fermentation process and prediction of the technological pH endpoint rather than evaluation of strict dose–response relationships. Fermentation was conducted at 41.0 ± 0.5 °C until the target pH range of 4.30 ± 0.05 was reached. An IoT monitoring architecture was used to generate a structured time-series dataset consisting of 909 sequential time-series measurements obtained during nine fermentation experiments. The formulation-associated kinetic behavior was evaluated using ANOVA, Tukey’s test, correlation analysis, and principal component analysis (PCA). The additives significantly affected the final pH and fermentation duration (p < 0.05; η2 > 0.90). The application of additives reduced fermentation time by 1.6–1.8 h compared with the control. The first principal component explained 96.4% of the total variance, confirming that pH can serve as a sufficient proxy indicator for monitoring the overall fermentation system. A comparative analysis of four kinetic models (Gompertz, logistic, logarithmic, and linear) was performed over the full fermentation range (t = 0–10 h). The Gompertz model demonstrated the highest predictive accuracy (R2 = 0.994–0.996; MAE = 0.027–0.033 pH units), whereas the logarithmic model was inadequate for describing the sigmoidal acidification profile of ayran (R2 = 0.685–0.703). Numerical solution of the inverse problem enabled prediction of the time required to reach pH ≤ 4.35 in experimental groups with an accuracy of 0.90–1.93 h, providing a preliminary early warning signal suitable for operator decision support. For the control group, the asymptotic behavior of the Gompertz model during the stabilization stage limited the applicability of numerical prediction, indicating the necessity of direct pH sensor monitoring for this formulation. The proposed approach may serve as an exploratory basis for further development of predictive monitoring frameworks for fermented dairy production.

Fermentation doi: 10.3390/fermentation12070322

Authors: Alaa S. Alharbi Nahed M. Rashed Amal A. Matar

Sidr (Ziziphus spina-christi L.) is an underutilized fruit native to arid and semi-arid regions that possesses considerable nutritional and phytochemical value. However, its potential for controlled lactic fermentation and development into value-added fermented products has received limited scientific attention. This study investigated the effects of five brine formulations on the controlled fermentation of Sidr fruit pickles and monitored changes in physicochemical properties, bioactive compounds, microbial dynamics, texture, color, and sensory attributes during 90 days of storage at ambient temperature. The treatments consisted of 10% NaCl (control), NaCl supplemented with sodium sorbate, NaCl with sucrose and vinegar, NaCl with sucrose and Lactobacillus plantarum starter culture, and NaCl with sucrose, vinegar, and garlic. Brine formulation significantly influenced fermentation kinetics, microbial succession, and product quality throughout storage. The inoculated treatment containing L. plantarum exhibited the most rapid acidification, reaching a pH of 4.02 and titratable acidity of 0.24%, while maintaining the highest lactic acid bacteria population (>9 log CFU g−1) and enhanced microbiological stability. This treatment also showed superior retention of ascorbic acid, total phenolic compounds, antioxidant activity, and texture compared with the non-inoculated treatments. Pearson correlation analysis and principal component analysis (PCA) further demonstrated strong associations between starter-culture fermentation, bioactive compound preservation, and overall product quality. Sensory evaluation indicated that all treatments remained acceptable throughout storage; however, the inoculated samples consistently received the highest scores for taste, texture, and overall acceptability. Overall, the results indicate that controlled lactic fermentation using L. plantarum represents an effective approach for enhancing the quality, stability, and bioactive retention of fermented Sidr fruit products, supporting the valorization of this underexploited fruit resource for sustainable food applications.

Fermentation doi: 10.3390/fermentation12070321

Authors: Loredana Abbate Sara Amata Teresa Faddetta Carla Rizzo Francesco Mercati Giuseppe Gallo Antonio Palumbo Piccionello

Plant–microbe interactions can modulate the production of bioactive compounds involved in plant growth-promoting activity. This study investigates the metabolic reprogramming of the actinomycete model strain Streptomyces coelicolor M145 during co-cultivation with Citrus aurantium and Citrus limon seeds, used as defined plant-derived chemical inputs, under contrasting nutritional conditions with or without L-tryptophan (Trp) supplementation. Untargeted metabolome profiling revealed medium- and Citrus seed-dependent metabolic shifts in co-cultures compared with corresponding Citrus seed and S. coelicolor single cultures used as controls. Under R2YE production conditions, co-cultivation with C. limon resulted in 27 extracellular metabolites, compared with 11 detected in the TSB vegetative medium; similar trends were observed for C. aurantium. Multivariate analyses confirmed that growth medium, Citrus species, and Trp significantly shaped S. coelicolor extracellular metabolic profiles, mainly in quantitative terms. Production conditions, particularly with Trp supplementation, promoted metabolites associated with antimicrobial activity and iron acquisition, whereas vegetative conditions promoted primary metabolism and biotransformation of Citrus-derived compounds. Spent medium bioassays on Solanum lycopersicum showed that these metabolic differences were correlated with distinct biological responses. Overall, these findings demonstrate that defined plant-derived inputs modulate S. coelicolor specialized metabolism in a context-dependent manner, generating metabolomic signatures associated with differential plant growth responses compared to single cultures.

Fermentation doi: 10.3390/fermentation12070320

Authors: Nora Haring Milan Chňapek Blažena Drábová

The production of low- and non-alcoholic beer remains a major technological challenge due to the need to restrict ethanol formation while maintaining acceptable sensory quality and fermentation-derived complexity. Conventional approaches, including physical dealcoholization and arrested fermentation, often result in flavor imbalance, reduced aroma intensity, diminished mouthfeel, and persistent wort-like off-flavors. In this context, non-Saccharomyces yeasts have emerged as promising biological tools due to their species- and strain-dependent carbohydrate utilization, aroma production potential, and intrinsic metabolic constraints. This review provides a structured and mechanistically informed synthesis of current knowledge regarding the application of non-Saccharomyces yeasts in low- and non-alcoholic beer production, with emphasis on metabolic regulation, fermentation process control, and sensory implications. Particular attention is given to sugar transport limitations, glycolytic regulation, carbon redistribution, redox balance, and the role of controllable process variables, including wort fermentability, pitching rate, oxygen availability, and temperature. The available evidence indicates that fermentation outcomes depend strongly on interactions between strain-specific metabolic traits and process design. Collectively, this review proposes a brewery-oriented precision fermentation framework in which strain-specific physiological constraints are deliberately aligned with controllable process variables to support rational strain selection, more predictable ethanol control, and targeted sensory optimization in low- and non-alcoholic beer production.

Fermentation doi: 10.3390/fermentation12070319

Authors: Natalya Naumenko Irina Kalinina Rinat Fatkullin Anastasia Antonova Saveliy Grachev Vladislav Leonov Aleksandr Demidkin

The development of functional yogurt products enriched with plant-derived ingredients and biologically active compounds represents a promising strategy to improve the nutritional, probiotic, and antioxidant properties of fermented dairy foods. The aim of this study was to evaluate how plant-derived ingredients (whole-meal flour from sprouted wheat grain and a protein-rich functional ingredient derived from hemp press cake), used individually or in combination with curcumin- or ergosterol-enriched Saccharomyces cerevisiae biomass, influence the physicochemical, structural-mechanical, probiotic, antioxidant, and sensory characteristics of yogurt products. Two forms of yeast biomass were used as enrichment agents: one containing encapsulated curcumin and the other with a high ergosterol content. Milk mixtures were supplemented with yeast biomass containing 34.0 mg/g encapsulated curcumin or 10.55 mg/g ergosterol. Additionally, whole-meal flour from sprouted wheat grain or the hemp-derived protein ingredient was incorporated into the yogurt products at concentrations of 2–3%. These ingredients were tested both individually and in combination to identify optimal formulations that would confer novel properties to the final products. Based on the conducted studies, it was found that the addition of enriched yeast biomass and the protein ingredient resulted in a denser and more uniform structure in the yogurt products compared to those of the control. The titratable acidity of the experimental formulations ranged from 80.2 to 91.8 °T, while pH values ranged from 3.79 to 4.04. Compared with the control sample, these changes indicate enhanced lactic acid fermentation activity. The number of probiotic microorganisms in the experimental samples reached 1.6 × 107–6.4 × 107 MPN/g, exceeding those of the control by an order of magnitude. The type of plant ingredient used significantly determined the technological properties of the finished product. Compared with the control sample, yogurt products supplemented with the hemp press cake-derived protein ingredient exhibited higher protein content (33–34% on a dry matter basis), increased viscosity (2.5–2.6 Pa·s), and reduced syneresis (values of 16.1 mL). The whole-meal flour from sprouted wheat grain exhibited a more pronounced stimulating effect on the growth of probiotic microflora. Enrichment of yogurt products with yeast biomass also increased antioxidant activity: the AOA (DPPH) value increased to 69–84% compared to ~62% in the control. Biotesting using Paramecium caudatum, a sensitive protozoan model widely used for rapid assessment of biological compatibility, toxicity, and the relative biological value of food systems, demonstrated a statistically significant increase (p < 0.05) in protozoan growth to 104–106% compared with the control sample, suggesting the absence of toxic effects and the potential bioavailability of yogurt matrix components. This data confirm the potential of using enriched yeast biomass in combination with plant ingredients for creating probiotic yogurt products with improved structural and functional properties.

Fermentation doi: 10.3390/fermentation12070318

Authors: Nadya Armenova Lidia Tsigoriyna Penka Petrova Maria Gerginova Ekaterina Krumova Alexander Arsov Lyudmila Velkova Pavlina Dolashka Kaloyan Petrov

Botrytis cinerea, the causal agent of gray mold disease, is a major phytopathogen responsible for substantial losses in horticultural crops. In this study, cultivation conditions for Bacillus velezensis R22 were optimized to maximize overall antifungal activity against B. cinerea. A Plackett–Burman design was used to identify medium components affecting antifungal activity in flask cultures, followed by response surface methodology based on a central composite design (CCD) to optimize sucrose concentration, temperature, and agitation speed in a stirred bioreactor. Maximum antifungal activity was obtained at 17.45 g/L initial sucrose, 31.8 °C, and 293 rpm. The biological relevance of the optimized culture was confirmed in a tomato infection model, in which gray mold severity was reduced by 85.3% relative to the untreated control and by 59.9% relative to the non-optimized R22 culture. The same CCD approach was subsequently applied to determine cultivation conditions that maximize the concentration of R22 viable cells. The optimal parameters for 24-h growth (35.46 g/L sucrose, 36.5 °C, and 454 rpm) differed markedly from those identified for maximal antifungal activity. When evaluated on uninfected tomato plants, cultures produced under conditions favoring higher cell density showed enhanced plant growth-promoting activity compared to the non-optimized culture. Mass spectrometric analysis of lipopeptide extracts revealed that the enhanced antifungal activity was accompanied by an increased abundance of long-chain homologs across all major lipopeptide families, particularly surfactins. Thus, our results indicate that maximizing overall antifungal activity may be of greater practical significance than optimization of the individual fungicidal agent.

Fermentation doi: 10.3390/fermentation12070317

Authors: Yining Zhou Jinqiu Luo Xianping Li Junying Zhao Baoyu Yang Quansheng Zhu Weicang Qiao Lu Liu Lijun Chen

γ-aminobutyric acid (GABA) is crucial in neural inhibition and sleep regulation. This study screened lactic acid bacteria isolated from breast milk and infant fecal samples for their GABA-producing ability; their acid tolerance, bile salt resistance, and growth performance were evaluated. Based on TLC-HPLC analysis, Lactobacillus gasseri F002, Lactiplantibacillus plantarum R7, and Lacticaseibacillus rhamnosus B2-1 were identified as promising GABA-producing strains. L. gasseri F002 was selected for liquid-state fermentation of the Baihe Dihuang decoction. During fermentation, L. gasseri F002 utilized carbohydrates in the decoction matrix, increased GABA accumulation, with a peak of 0.063 mg/mL at 24 h, and reduced total saponin content, suggesting that lactic acid bacterial fermentation induced compositional shifts of major functional constituents in the Baihe Dihuang decoction. The sleep-promoting effect of the fermented decoction was assessed using a caffeine-induced zebrafish insomnia model. The fermented Baihe Dihuang decoction significantly prolonged sleep bout duration, while reducing wakefulness and total locomotor activity. Moreover, correlative changes altered sleep-related molecular and biochemical indicators in the zebrafish model. Correlative changes in the expression of gabra1, htr1aa, drd2a, dbh, and th, as well as in GABA, melatonin (MT), and monoamine oxidase (MAO) levels, suggest a potential association with the observed sleep-improving phenotypes. Therefore, fermentation with GABA-producing lactic acid bacteria may enhance the sleep-promoting potential of the Baihe Dihuang decoction and provide preliminary experimental support for the development of fermented medicinal–food homologous products aimed at improving sleep.

Fermentation doi: 10.3390/fermentation12070316

Authors: Samuel C. Oliveira Helenice O. Florentino

Few mathematical models describing the dynamics of cell growth, production formation and substrate consumption in batch and fed-batch bioprocesses have analytical solutions. In this study, analytical solutions for a mathematical model of a batch bioprocess of penicillin production based on the Logistic law for cell growth and on the Luedeking–Piret equation for antibiotic formation are obtained using classical methods of solving ordinary differential equations. The analytical solutions were validated by substitution into the differential equations themselves, as well as by comparison with numerical solutions obtained through the fourth-order Runge–Kutta–Gill integration method, using typical fungus inoculum concentrations (X0 = 0.25; 0.75% DW) and kinetic parameters (μm = 0.5 h−1, Xm = 3.7% DW, β = 0.02 U/(mL·h·% DW) and kh = 0.027 h−1). The novelty in relation to the few studies published on the subject, which deal with the production of different metabolites, including other antibiotics, is that in the present study, the hydrolysis of penicillin is considered simultaneously with its production in the description of the dynamics of product formation. The main finding demonstrates that the hydrolysis reaction acts as a stabilizing factor, resulting in a system with two equilibrium points: an unstable point with no penicillin production, and a stable point in which a certain amount of antibiotic is produced.

Fermentation doi: 10.3390/fermentation12070315

Authors: Renfeng He Wei Liu Xiaotong Shao Zejiang Zhu Keke Sun Yuwan Liu Huifeng Jiang Dingyu Liu

Microbial protein production from acetate represents a promising route for sustainable protein supply, yet its efficiency is constrained by limited understanding of carbon–nitrogen metabolic coordination. In this study, nitrogen availability was systematically varied to investigate its role in regulating biomass composition and protein biosynthesis in Yarrowia lipolytica. Nitrogen limitation markedly reduced cell growth and protein accumulation (19.56% of dry cell weight) while increasing lipid content (up to 34.16%), indicating a altered protein and lipid accumulation under different nitrogen conditions. Transcriptomic analysis revealed a global downregulation of anabolic pathways under nitrogen limitation, accompanied by a shift in nitrogen assimilation from the glutamate dehydrogenase (GDH) pathway to the glutamine synthetase/glutamate synthase (GS–GOGAT) pathway, as well as significant upregulation of genes related to ammonium and amino acid transport. Guided by these findings, metabolic engineering of key nitrogen assimilation pathways was performed. Strains harboring additional copies of GDH and GS expression cassettes showed increased protein content from 48.52% to 55.77% and improved amino acid composition, whereas strains with an additional copy of the GOGAT gene exhibited reduced growth and protein accumulation. These results demonstrate that nitrogen availability regulates biomass composition through coordinated control of nitrogen transport and assimilation, and that balanced upregulation of GDH and GS genes is an effective strategy to improve microbial protein production from acetate, supporting the development of efficient fermentation processes using low-cost carbon sources.

Fermentation doi: 10.3390/fermentation12070314

Authors: Susana C. Ribeiro Sofia P. M. Silva Vanessa Corvelo Pires Célia C. G. Silva

Six lactic acid bacteria isolated from São Jorge PDO cheese were characterised for technological, safety, antimicrobial, and probiotic properties. All isolates fermented a broad range of carbohydrates and lacked lipolytic activity, while SJC115 and SJC119 showed proteolysis. Safety profiling (γ-haemolysis, no DNase or gelatinase activity, and generally favourable antibiotic susceptibility) is promising, but tetracycline resistance warrants caution and genomic confirmation. L. paracasei and L. brevis isolates inhibited a wide range of foodborne pathogens (Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Bacillus spp.) and spoilage fungi (Penicillium and Aspergillus spp.). Notably, two isolates (SJC117 and SJC120) exhibited antibacterial activity in neutralized cell-free supernatants, indicating putative bacteriocin-like inhibitory substances (BLIS). The isolates survived intestinal conditions above the probiotic threshold, yet only SJC117 and SJC120 tolerated gastric acidity (pH 2.5, 1 h) with >5 log CFU/mL. Despite low hydrophobicity, strains showed good autoaggregation and pathogen coaggregation. All isolates produced exopolysaccharides (EPS) and angiotensin-converting enzyme (ACE) inhibitory peptides, whereas some exhibited moderate conjugated linoleic acid (CLA) production and glutamate decarboxylase (GAD) activity. L. paracasei SJC117 stood out by combining BLIS/antifungal activity, superior gastric tolerance, and an exceptional bioactive profile, making it a promising candidate for biopreservation and functional food applications that warrants further in vivo validation to confirm its efficacy and safety.

Fermentation doi: 10.3390/fermentation12070313

Authors: Diego Bernardo Petrignani Yolanda Paola Maturano Valeria Benegas Leandro Ruiz Simon Tornello María José Valera Francisco Carrau Maria Victoria Mestre Furlani

Sparkling wines are produced through a second fermentation of a base wine, whose composition strongly determines the final product quality. Yeast selection for primary fermentation is therefore crucial, as it influences both fermentation performance and sensory attributes. In this study, 156 yeasts were isolated from spontaneous fermentations of Vitis vinifera cv. Torrontés sanjuanino from Paraje de Hilario (1550 m.a.s.l., San Juan, Argentina), aiming to select autochthonous strains with oenological potential for sparkling base wine production. Isolates were phenotypically characterized and molecularly identified by sequencing the D1/D2 domain of the 26S rDNA. A total of 44 Saccharomyces cerevisiae and 60 non-conventional yeasts, mainly Hanseniaspora uvarum, were identified. Based on relevant oenological traits, two S. cerevisiae (M138M, F172M) and two H. uvarum (Mi14M, C135MJ) strains were selected. Laboratory and pilot-scale co-inoculation trials showed that the Mi14M/M138M (50:50) combination exhibited stable fermentation kinetics, low acetic acid production (0.44 g/L), high glycerol levels (7.1 g/L), and suitable pH (3.08) and ethanol content (11.2% v/v). Despite higher residual sugars than the control, no technological issues were observed. These findings support co-inoculation of autochthonous strains of S. cerevisiae and H. uvarum as a promising strategy to enhance wine quality and reinforce regional identity in sparkling base wines.

Fermentation doi: 10.3390/fermentation12070312

Authors: Javaria Bakhtawar Muhammad Zubair Ali Tri Handanyani Kurniati Iram Hafiz Muhammad Irfan Emmanuel Atta-Obeng

This study reports cellulase production by Bacillus paralicheniformis using Plumeria alba leaf powder under submerged fermentation with a focus on systematic bioprocess optimization. Physical parameters were first optimized using a one-factor-at-a-time (OFAT) approach, followed by optimization of yeast extract, MgSO4 and (NH4)2SO4 via a central composite design (CCD) and response surface methodology (RSM). An artificial neural network (ANN) with a 5:3:1 network trained by the Levenberg–Marquardt algorithm further improved prediction of carboxylmethylcellulase (CMCase) and filter paper cellulase (FPase) activities. This study is the first to exploit Plumeria alba leaf powder as an untapped, low-cost lignocellulosic substrate for cellulase production by B. paralicheniformis and uniquely benchmarks RSM against ANN-based modeling to identify superior predictive frameworks for bioprocess optimization. Under optimized conditions (24 h, 4% w/v substrate, 1% v/v inoculum), the maximum FPase and CMCase activities reached 60.53 IU/mL/min and 332.10 IU/mL/min respectively. Partial characterization showed optimum FPase and CMCase activities at 50 °C and 70 °C, respectively, at pH 7.5. Enzymes also showed activation by NaCl and some select solvents while tolerating a broad range of metal ions. The enzymatic hydrolysis of P. alba biomass released 59.42 mg/mL total reducing sugars after 8hr, confirming efficient saccharification from a low-cost feedstock. The ANN model (R2 = 97.59% for CMCase; 85.95% for FPase) outperformed RSM (R2 = 85.95% and 78.25%, respectively), while radial basis function optimization reached 99.99%. These findings highlight B. paralicheniforms cellulase as a promising biocatalyst for biorefinery applications and demonstrate the value of integrating RSM and ANN for process optimization.

Fermentation doi: 10.3390/fermentation12070311

Authors: Clarisse M. Lopes Luis F. Guido

Fermented foods are chemically complex systems in which substrate composition, microbial community dynamics, and physicochemical conditions interact to generate thousands of metabolites across diverse chemical classes. Conventional targeted analytical approaches quantify predefined compounds with high precision but operate within a restricted chemical space, systematically excluding emergent features central to product identity, safety, and sensory character. Untargeted metabolomics addresses this limitation by capturing global chemical fingerprints of fermented matrices, enabling discovery-driven investigation across a broad fraction of the metabolome. This review examines the application of untargeted metabolomics across key research areas in fermented food science, including fermentation monitoring, microbial interactions, flavour development, process optimisation, post-fermentation stability, and safety assessment. Across these domains, untargeted approaches reveal system-level metabolic relationships beyond the reach of targeted analyses, while also presenting interpretive challenges. A central limitation is the annotation bottleneck: despite high feature detection rates, only a small fraction of signals are structurally identified, constraining mechanistic interpretation and cross-study comparability. Additional challenges in data processing, statistical validation, and interlaboratory reproducibility further limit data interpretation. Addressing these constraints through improved spectral libraries, standardised workflows, and integration with complementary omics is essential for advancing untargeted metabolomics towards robust knowledge generation in fermented food systems.

Fermentation doi: 10.3390/fermentation12070310

Authors: Qunying Zhang Hongmei Sun Qi Wang Lianbin Cao Shujie Liu Yanfen Cheng Lizhuang Hao

The expansion of ruminant production has increased methane (CH4) emissions, highlighting the need for nutritional strategies that improve productivity while mitigating environmental impacts. Yaks, generally considered low CH4 producers, are increasingly raised under intensive winter-housed systems on the Qinghai–Xizang Plateau, highlighting the need to assess how dietary concentrate-to-forage (C:F) ratios affect both CH4 emissions and growth performance. This study investigated the effects of three dietary C:F ratios [L-C (48:52), M-C (60:40), H-C (72:28)] on growth performance, ruminal fermentation, microbial diversity (n = 6 per group) and CH4 emission (n = 3 per group) in winter-housed yaks. The results indicated that average daily gain (ADG) was significantly higher in M-C and H-C, while the feed-to-gain ratio (F/G) was significantly lower in M-C and H-C than in L-C (p < 0.05). Total CH4 production (g/day) did not differ among treatments (p > 0.05), while CH4 yield per unit body weight gain (CH4/BWG) was significantly reduced in M-C and H-C (p < 0.05). The protozoal count was significantly lower in H-C, and the proportions of isobutyrate and isovalerate were significantly higher in H-C and M-C compared with L-C (p < 0.05). 16S rRNA gene sequencing revealed that increasing the C:F ratio reduced the relative abundance of the archaeal genus Methanobrevibacter, while Thermogymnomonas exhibited a significant increase (p < 0.05). Collectively, these findings indicate that increasing the C:F ratio in winter-housed yaks improves growth efficiency and lowers CH4/kg BWG, with the M-C group showing the most favorable balance between productivity and environmental sustainability.

Fermentation doi: 10.3390/fermentation12070309

Authors: Yana Ilieva Maya Margaritova Zaharieva Alexander Kroumov Hristo Najdenski

The engineering, resource, and financial constraints in space and spacecraft so far have not allowed the incorporation of biological components into a closed-loop bioregenerative life support system (BLSS), despite decades of research. The expected increase in deep-space exploration and planetary bases with limited access to Earth-based resources necessitates the development of self-sustaining hybrid BLSS technology. The created physicochemical systems, together with photosynthetic organisms and bacteria, aim to revitalize the air, produce food, and recycle nutrients and water in mutually beneficial mini-ecosystems. While plants are best in the function of food production and bacteria in waste recycling, the incorporation of microalgae would add immense benefits in optimizing the life support system (LSS) and increasing the degree of closure. Microalgal photobioreactors (PBRs) could perform wastewater treatment (WWT), removing the nitrogen (N) and phosphorus (P) in the human-derived wastewater (WW), and couple it with converting carbon dioxide (CO2) from the cabin to oxygen (O2) and food production. As microalgal WWT on Earth is an emerging field with engineering hurdles, power, mass, volume, microgravity fluid dynamics, and other constraints have also prevented their operations in space. However, in space vehicles, there is no need for large upscaling of a laboratory prototype system, and the WW effluent is easier to predict, facilitating microalgal extraplanetary use in comparison to Earth treatment plants. These factors, combined with the qualities of microalgae such as surface-to-volume efficiency, fast growth rate, high yield, and tolerability to WW, etc., have led to many preliminary testbeds, prototypes, and ground demonstrations from space agencies, space centers, and academia, which show promising results. Microalgal participation in space WWT is beyond current operational practice; however, PBRs are on the space agenda, and the scientific community is elaborating the technologies that would allow their successful implementation.

Fermentation doi: 10.3390/fermentation12070308

Authors: Eva Gómez-Pérez Aida Zapico Silvia Arboleya Nuria Salazar Clara G. de los de los Reyes-Gavilán Sonia González Miguel Gueimonde

The intake of live microorganisms (LMOs) may contribute to modulating gut microbial ecology with an impact on health. In this study, we examined the intake of LMOs in adults and its association with gut microbiota composition, intestinal short-chain fatty acids (SCFAs), and health-related biochemical parameters. A total of 151 adults were analyzed across three age groups (18–50, 51–65, and 66–95 years). Dietary intake was assessed using a food frequency questionnaire (FFQ), and LMOs consumption was estimated with a previously developed database. The levels of some relevant intestinal microbial groups were measured using Quantitative Polymerase Chain Reaction (qPCR), SCFAs were determined using gas chromatography, and biochemical markers were assessed through standardized laboratory methods. LMOs intake was significantly higher in the two older age groups compared with younger adults, with yogurt identified as the primary dietary source of LMOs across all ages. In the middle-aged group, bacterial LMOs intake independently predicted higher abundances of Akkermansia and Bacteroides-related taxa, while fungal LMOs were positively associated with butyric acid levels. In the older age group, bacterial LMOs intake was directly associated with branched-chain fatty acids (BCFAs) while fungal LMOs intake was directly associated with circulating cholesterol and inversely with malondialdehyde (MDA). Overall, the findings suggest that LMOs consumption, mainly bacteria intake from fermented dairy products, increases with age and is linked to age-specific changes in gut microbiota, microbial metabolites, and biochemical health parameters.

Fermentation doi: 10.3390/fermentation12070307

Authors: Narjara de Medeiros Ribeiro Esther Pedroso Theisen Yuri Duarte Porto Maressa Caldeira Morzelle Juliana Aparecida Correia Bento

This scoping review maps and synthesizes scientific evidence on the use of non-Saccharomyces yeasts in wine fermentation, focusing on their contribution to ester formation and aroma modulation. The review followed the Joanna Briggs Institute (JBI) methodology and the PRISMA-ScR guidelines. A total of 71 original articles published between 2000 and 2025 were included, and evidence mapping was combined with an exploratory textual analysis of abstracts using Iramuteq® to characterize thematic trends, methodological approaches, and knowledge gaps. The textual analysis highlighted fermentation ecology, inoculation strategies, and aroma modulation as central themes, with ester formation emerging as a key topic. Torulaspora, Hanseniaspora, Lachancea, Metschnikowia, and Candida/Starmerella were the most frequently investigated genera, reflecting their potential to diversify wine sensory profiles beyond those typically associated with Saccharomyces cerevisiae fermentations. Non-Saccharomyces yeasts proved particularly relevant in the synthesis and modulation of ethyl and acetate esters linked to fruity and floral characteristics, especially in mixed fermentations. Key knowledge gaps include the limited transferability of laboratory-scale results to industrial conditions, insufficient understanding of interspecies interactions, and the need for stronger sensory validation of volatile compounds. These findings highlight the potential of non-Saccharomyces yeasts as tools for innovation, terroir expression, and enhanced sensory complexity in winemaking.

Fermentation doi: 10.3390/fermentation12070306

Authors: Ayşe Janseli Denizkara Gökhan Akarca Azize Atik İlker Atik

This study examined the physicochemical, microbiological, textural, organic acid, colour, and sensory aspects of cabbage pickles made with fermented dairy by-products as a brine medium. Yoghurt whey, whey, kefir whey, and buttermilk were used as brine media and compared with vinegar. Brine samples showed substantial changes in pH, Brix, colour, and rheology (p < 0.05). Yoghurt whey-based samples had the lowest brine pH (2.87) and Brix (10.04%), while buttermilk samples had the highest pH (3.26) and Brix (10.83%). Vinegar-based brine showed higher a* and b* values, whereas yoghurt whey-based brine had the highest L*. Yoghurt whey-based samples had lower consistency and a lower viscosity index. Pickle samples made with different brine types showed significant differences in physicochemical, microbiological, textural, and organic acid properties (p < 0.05). Pickle samples made with vinegar had the lowest pH (2.99), while samples made with buttermilk had the highest (3.31). Vinegar-based pickles had the highest dry matter (5.27%) and drained weight (64.15%). Yoghurt whey-based samples had the highest counts of Lactobacillus spp. (6.38 log CFU/g) and Lactococcus/Streptococcus (6.81 log CFU/g), while vinegar-based samples had the highest counts of acetic acid bacteria and total aerobic mesophilic bacteria. However, kefir whey-based samples had the highest yeast count (5.72 log CFU/g). The textural analysis showed that yoghurt whey-based samples had the highest hardness (471.72 N) and springiness, whereas buttermilk-based samples had higher adhesiveness and cohesiveness. Whey-based samples had the highest gumminess and chewiness. Yoghurt whey-based samples had the highest levels of lactic acid (14,569.39 mg/L) and citric acid, whereas vinegar-based samples had the highest levels of acetic acid (63,795.64 mg/L) and propionic acid. Kefir whey-based samples had the highest butyric acid content. Yoghurt whey-based pickles were the most popular with panellists, followed by whey and vinegar-based pickles. Buttermilk-based samples scored lowest in sensory rating. Finally, fermented dairy by-products can be used as a functional brine medium for cabbage pickle. Yoghurt whey has shown promise in improving microbiological quality, textural characteristics, and sensory acceptability. Using dairy industry by-products in pickle making is an innovative way to produce sustainable food and add value to by-products.

Fermentation doi: 10.3390/fermentation12070305

Authors: Siyu Lu Vanajah Liyinthan Gang Liao Qinghua Qiu Xianghui Zhao Yanjiao Li Kehui Ouyang

A three-factor completely randomized design was used to evaluate the effects of Lactococcus lactis, Bacillus subtilis, and Saccharomyces cerevisiae on the fermentation quality and nutritional composition of mixed silage prepared from navel orange pomace and rice straw. The addition of L. lactis increased lactic acid content and Flieg’s score of the mixed silage. The addition of B. subtilis decreased the pH value and increased the lactic acid content of the mixed silage. The addition of S. cerevisiae decreased the lactic acid content and Flieg’s score of the mixed silage. However, the interaction between the three strains significantly affected many parameters of the mixed silage. With respect to fermentation quality (Flieg’s score), adding 0.3 g kg−1 L. lactis and not adding S. cerevisiae achieved the best performance of the mixed silage. Under these conditions, increasing the level of B. subtilis resulted in a higher crude protein content of the mixed silage, whereas neutral detergent fiber and acid detergent fiber contents first decreased and then increased, and water-soluble carbohydrate content first increased and then decreased. Therefore, within the selected combination of adding 0.3 g kg−1 L. lactis and not adding S. cerevisiae, the addition of 0.8 g kg−1 B. subtilis gave the best nutritional quality.

Fermentation doi: 10.3390/fermentation12070304

Authors: Alexandra Cristina Blaga Irina Cârlescu Ioan Mămăligă Elena Niculina Drăgoi

Daunomycin (daunorubicin) is one of the most clinically significant anthracyclines used in chemotherapy, and its efficient production remains a major objective for biotechnological researchers. Industrial manufacturing relies on the fermentation of Streptomyces peucetius and Streptomyces coeruleorubidus, which produce daunomycin as a secondary metabolite under controlled conditions. This review will focus on the methods to enhance the total efficiency of biotechnological production, from upstream biosynthesis to downstream processing. Given the complexity of the daunomycin biosynthetic pathway in Streptomyces spp., substantial progress has been made in strain improvement to increase yield, metabolic robustness, and process stability. Advances in classical mutagenesis, pathway engineering, regulatory network modulation, and precursor supply optimization, along with rational medium design and advanced process control, have led to substantial increases in product titers and productivity. At the same time, innovations in downstream processes, such as extraction, purification and process integration, have increased recovery efficiency, product quality, and economic feasibility. With improvements in the production process, novel drug delivery modalities have been developed (e.g., drug carriers based on erythrocytes, drug nanocarriers based on hyaluronic acid) with increased efficiency and lower systemic toxicity. These developments indicate an evolution from pathway-level engineering to industrial-scale manufacturing and clinical application, underlining the evolution of daunomycin research and biotechnological production.

Fermentation doi: 10.3390/fermentation12070303

Authors: Kamon Yakul Chayatip Insomphun Phisit Seesuriyachan Thanongsak Chaiyaso Su Lwin Htike Yuthana Phimolsiripol Juan Manuel Castagnini Churairat Moukamnerd

Coffee cherry pulp (CCP; cascara), a major by-product of coffee processing, has gained increasing attention as a sustainable source of phenolic compounds, dietary fiber, and other bioactive constituents with applications in food, nutraceutical, feed, and biomaterial industries. However, its utilization remains limited by compositional variability, anti-nutritional compounds, and inefficiencies in conventional processing. Controlled fermentation has emerged as a promising strategy to enhance the release, transformation, and bioavailability of CCP-derived bioactive through targeted microbial biotransformation and controlled bioprocessing. This review summarizes recent advances in enzymatic pretreatment, microbial fermentation, and metabolite-directed processing, with emphasis on their effects on phenolic transformation, antioxidant activity, and functional properties. The roles of selected lactic acid bacteria, yeasts, and microbial consortia in improving the nutritional, sensory, and biological characteristics of CCP-derived products are critically discussed. Potential applications of fermented CCP in functional foods and beverages, bioactive ingredients, biopolymers, and animal feed are also highlighted within the framework of an integrated circular bioeconomy. Finally, current challenges and future perspectives related to process scalability, metabolite control, regulatory approval, and AI-assisted bioprocess optimization are addressed.

Fermentation doi: 10.3390/fermentation12070302

Authors: Yunhua Zhang Yifan Chen Lin Sun Xuebing Yan Siran Wang Zhumei Du

The global shortage of high-quality protein feed resources continues to widen, and the development of high-value-added woody plants is a key strategy for alleviating feed shortage. The mulberry (Morus alba L.) is a recognized high-protein woody forage resource. However, the inconsistent quality of its natural silage and the unclear risk of mycotoxins represent the core bottlenecks limiting its widespread adoption as feed. Four treatments were set up in this study: (1) control; (2) lactic acid bacteria inoculant (LAB, Lactiplantibacillus plantarum); (3) cellulase enzyme (AC, Acremonium cellulolyticum); (4) a mixture of LAB + AC. After 60 days of ensiling, a systematic analysis was conducted to examine the effects of exogenous microbial inoculant and enzyme preparation on the fermentation quality, bacterial community, and mycotoxin in mulberry silages. Fresh mulberry exhibited a high crude protein content of 23% on a dry matter (DM) basis, making it a high-quality feed resource. Compared to the control, the addition of LAB and AC either alone or in combination, significantly improved (p < 0.001) the fermentation quality and safety of silages: lactic acid content increased from 0.85% DM to 1.41–2.03% DM; pH, ammonia nitrogen, and deoxynivalenol decreased from 4.85, 0.88% DM, and 3.92 μg/kg to 3.53–3.95, 0.40–0.55% DM, and 1.21–3.04 μg/kg, respectively. The combined LAB and AC treatment resulted in the most favorable fermentation performance of mulberry silage. Bacterial community analysis revealed that fresh mulberry exhibited high bacterial alpha diversity, with Gram-negative bacteria as the dominant bacterial community, and Sphingomonas roseiflava as a representative dominant species. After ensiling, bacterial alpha diversity decreased in all the silages. Furthermore, the Lactiplantibacillus plantarum eventually prevailed as the dominant bacteria and exhibiting the highest relative abundance in the LAB + AC-treated silage (57.23%). Bugbase functional prediction indicated that the proportion of potential pathogenic bacteria was significantly higher (p < 0.05) in fresh mulberry than silage. Thus, the synergistic action of LAB + AC treatment effectively optimized the ensiling fermentation process.

Fermentation doi: 10.3390/fermentation12070301

Authors: Dingyue Zhang Fangzhuoqi Liu Tieyan Jin

The aim of this study was to investigate the dynamic changes in physicochemical properties, microbial community, metabolite profiles, and volatile compounds in watermelon soybean paste (WSP) during natural fermentation. Results showed that total acids, amino nitrogen, reducing sugar content, and umami-taste amino acids were significantly increased in WSP samples during the fermentation process. Various bacterial communities, including Enterobacter, Bacillus, Staphylococcus, Enterococcus, Weissella, and Lactobacillus, were detected as dominant genera. A total of 804 metabolites, mainly including lipids (18.78%) and amino acids and their derivatives (13.56%), were detected across the different fermentation stages. The correlation analysis between volatile compounds and bacterial community at the genus level revealed that 2-methylisoborneol, 1-octen-3-ol, benzene acetaldehyde, tetramethylpyrazine, and phenylethyl alcohol strongly correlated with Enterococcus, Bacillus, Weissella, and Pseudomonas. This study revealed the dynamics of the bacterial community and volatile compounds in the fermentation process and demonstrated their inter-relationship during WSP fermentation.

Fermentation doi: 10.3390/fermentation12070300

Authors: Assmaa Choukri Tilila Baganna Mohamed Sbahi Halima Chernane Lahcen Ouahmane Khalid Fares Ahde El Imache Williams Turpin Aayah Hammoumi

Pectinases are a group of enzymes widely applied in agri-food processes. This study aimed to isolate and characterize pectinase-producing yeasts and yeast-like fungi from soil and humus samples collected in a Moroccan argan forest, a region characterized by arid to semi-arid climatic conditions, with emphasis on screening and evaluating their pectinolytic activity. Among nine isolated strains, four exhibited detectable pectinolytic activity on pectin agar medium. Two promising isolates were molecularly identified by ITS region sequencing as Coniochaeta pulveracea PX765016 and Coniochaeta ligniaria PX765017. Notably, C. pulveracea PX765016 showed the highest pectinolytic potential, with a pectinolytic degradation index of 4.2 on pectin agar. This strain also exhibited maximal pectinase production after 96 h of submerged fermentation in YEPD medium under optimized conditions of pH 4, 30–35 °C, and 0.5% (w/v) pectin. The crude enzyme obtained under these conditions exhibited a specific activity of 559.90 ± 11.62 U/mg. The enzyme was subsequently subjected to sequential purification comprising ammonium sulfate precipitation, dialysis, and gel filtration chromatography on a Sephadex G-100 column, yielding a 2.99-fold purification with a final recovery of 14%. The purified enzyme exhibited optimal activity at pH 6.0 and 40–55 °C, with a reaction time of 20 min. Kinetic analysis of pectin hydrolysis revealed a Michaelis–Menten constant (Km) of 7.33 mg pectin per mL and a maximum reaction velocity (Vmax) of 1666.7 U/mg. To the best of our knowledge, this is the first report of pectinase production by a member of the genus Coniochaeta, and the first characterization of pectinase activity from C. pulveracea.

Fermentation doi: 10.3390/fermentation12070299

Authors: Yuliya Shamsiyeva Dmitriy Silayev Azamat Yermukhanov Bakhtiyar Yakupov Savva Timochshuk Daulet Abdishov Assel Kiribayeva

The growing amounts of agricultural residues require sustainable solutions for their use. Here, wheat, rice, barley, and oat straw were evaluated as renewable feedstocks for the enzymatic production of xylooligosaccharides (XOS). Hydrolysis used recombinant xylanase from Bacillus sonorensis T6 under optimized conditions (40 °C, pH 7.0), with stepwise enzyme addition. Subsequently, hydrolysis efficiency was found to vary by substrate, with wheat straw producing the highest reducing sugar yield (up to 40.1 g kg−1), followed by barley, oat, and rice straw. As hydrolysis progressed, the influence of enzyme concentration became less pronounced, suggesting that substrate accessibility and the accumulation of hydrolysis products may increasingly affect the overall hydrolysis efficiency. FTIR, NMR, SEM, and TLC analyses confirmed substantial structural changes in the biomass and the formation of carbohydrate-rich hydrolysis products. TLC analysis indicated the presence of low-degree polymerization oligosaccharides with migration behavior similar to X2 and X3 standards, while FTIR and NMR spectra were consistent with β-(1→4)-linked carbohydrate structures. The xylanase from Bacillus sonorensis T6 hydrolyzed all substrates, revealing broad specificity and suitability for diverse lignocellulosic feedstocks, despite differences in biomass structure. Overall, the results highlight the importance of substrate-dependent factors in enzymatic hydrolysis and demonstrate that xylanase from Bacillus sonorensis T6 converts cereal straw into value-added oligosaccharide-rich products, thereby supporting the development of cost-effective, region-specific biorefinery strategies.

Fermentation doi: 10.3390/fermentation12060298

Authors: Chi Zhang Xiaopeng Wang Yanrong Li Chunlin Wang Yueyue Zhou Yuanyuan Fu

Surfactin is a lipopeptide biosurfactant with significant industrial potential, but high production costs have hindered its commercialization. In this study, we developed a sustainable and cost-effective bioprocess for surfactin biosynthesis using Bacillus subtilis 55033, utilizing kitchen waste as the primary fermentation substrate without any previous pretreatment—an advantage that simplifies the process and reduces costs compared to previous reports. To maximize productivity, the fermentation parameters were systematically optimized through single-factor and orthogonal experimental designs. The optimal conditions were as follows: a fermentation temperature of 31 °C, a duration of 48 h, a 5% v/v inoculum, a 7% w/v solid-to-liquid ratio, an initial pH of 7.5, and an agitation speed of 200 rpm. Under these conditions, the surfactin yield reached 371.67 mg/L, an increase of 100.5% from 185.4 mg/L prior to optimization. We performed a comparative analysis of the surfactin biosynthetic gene clusters between B. subtilis 55033 and the model strain B. subtilis 168. The produced surfactin exhibited potent antagonistic activity against aquatic pathogens, significantly inhibiting the growth of several species of Vibrio and the division and hatching of Cryptocaryon irritans Tomonts. These findings demonstrate that our platform not only provides a high-value valorization route for organic waste but also enables preliminary exploration of surfactin applications in aquaculture, in line with the principles of a circular bioeconomy.

Fermentation doi: 10.3390/fermentation12060297

Authors: Son Nghia Hoang Linh Thi Mai Tran Linh Thi Anh Dinh Cuong Phan Minh Le Huy Nghia Quang Hoang Anh Thi Lan Vu Nhan Lu Chinh Phan Chi Nguyen Quynh Ho Quynh Thi Nhu Nguyen Trang Thi Xuan Nguyen Mai Thi Phuong Nguyen Han Thai Minh Nguyen Long Thanh Le

This study evaluated the effects of supplementing a mildly high-fat diet (HFD; 33.5% energy from lipids) with fermented passion fruit peel powder (FPFPP) on mice liver physiological chracteristics. Mice were fed HFD supplemented with FPFPP at three ratios of 0.5% (T-0.5 group), 1% (T-1 group), and 2.5% (T-2.5 group) for 30 days and compared with normal-diet control and an unsupplemented HFD group. The results showed that FPFPP supplementation induced an attenuation of weight gain in mice. Serum lipid profiles demonstrated the decrease in total serum cholesterol, and LDL-c in mice from T-1 and T-2.5 groups compared to HFD group, while there was no difference in HDL-c level in mice from these groups. FPFPP supplementation could retrieve several normal characteristics in the histological architecture and the expression of apoptosis and cell cycle-related proteins in mice liver. These results suggested that fermented passion fruit peel supplementation attenuates high-fat diet-induced hepatic dysfunction via modulation of lipid metabolism and apoptotic signaling in mice.

Fermentation doi: 10.3390/fermentation12060296

Authors: Xinhui Pang Xin Song Yongjun Xia Guangqiang Wang Xinxin Liu Zhiqiang Xiong Lianzhong Ai

Immunoglobulins exhibit important biological functions, including the neutralization of cytotoxins, enhancement of phagocytic activity, and activation of the complement system, which have driven their widespread application in both the food and pharmaceutical industries. Due to their low cost and short production cycles, microbial expression systems such as bacteria and yeast have been increasingly developed in recent years for immunoglobulin production. However, microbial systems face considerable challenges in ensuring proper protein folding, accurate chain assembly, and the soluble expression of full-length immunoglobulins. Recent optimization strategies have focused on host engineering (e.g., modulating secretion pathways and chaperone proteins), the coordinated regulation of expression elements (e.g., optimizing the light-to-heavy chain ratio), and regulation of fermentation processes. In addition to summarizing the above strategies, this review discusses the progress made in expressing both full-length immunoglobulins and antibody fragments across different microbial hosts, analyzes the advantages and limitations of each system, and explores potential future directions, aiming to provide a reference for the efficient heterologous expression of immunoglobulins.

Fermentation doi: 10.3390/fermentation12060295

Authors: Julivan Junior Magri Andrei Lucas Rebelatto Brunetto Matheus Wroblescki Silva Thiago Marangoni Renato Santos de Jesus Miklos Maximiliano Bajay Luiz Eduardo Lobo e Silva Roger Wagner Gilnei Bruno da Silva Daiane Manica Margarete Dulce Bagatini Aleksandro Schafer da Silva

This study evaluated the effects of monolaurin intake per finishing feedlot cattle on growth performance, metabolic status, ruminal environment, and meat fatty acid profile. Twenty-four castrated Holstein males (379 ± 8.5 kg; 12 months old) were randomly assigned to two treatments: basal diet (control) or basal diet with α-monolaurin (treated: 0.762 g/kg dry matter intake; ≈6.63 g/animal/day) for 79 days. Feed intake, body weight, and feed efficiency were recorded, and blood and ruminal samples were collected during the trial. Ruminal fermentation parameters, protozoa counts, hematological and biochemical variables, oxidative status biomarkers, ruminal microbiota composition (16S rRNA sequencing), and Longissimus dorsi fatty acid profile were analyzed. Monolaurin feed did not affect dry matter intake or final body weight, but increased total weight gain, average daily gain, and feed efficiency (p ≤ 0.05), indicating improved nutrient utilization. Hematological and serum biochemical variables were largely unchanged, although total leukocyte counts were lower in treated cattle. Animals receiving monolaurin showed reduced reactive oxygen species and lower superoxide dismutase activity, suggesting improved oxidative balance without changes in lipid peroxidation. During the adaptation phase (day 14), treated cattle exhibited lower acetate, propionate, valerate, and total volatile fatty acid concentrations and higher protozoa counts, but these differences disappeared by day 79, indicating ruminal adaptation. Microbiota diversity was not altered overall, although specific genera differed in relative abundance between treatments. In meat, monolaurin increased lauric, linoleic, and arachidonic acids, reduced palmitic and heptadecanoic acids, decreased total saturated fatty acids, and increased polyunsaturated fatty acids (p ≤ 0.05). Overall, dietary monolaurin improved feed efficiency, modulated oxidative status, induced transient ruminal microbial adjustments, and enhanced the nutritional quality of beef lipids without compromising metabolic health.

Fermentation doi: 10.3390/fermentation12060294

Authors: Maria Carla Cossu Francesco Fancello Marilena Budroni Ilaria Mannazzu Severino Zara Angela Bianco Giacomo Zara

In many industrial dairy products, yeasts are generally regarded as contaminants. However, in traditional fermented milks, they may contribute to distinctive sensory, technological, and functional properties through associations with bacterial partners, including lactic acid bacteria (LAB). Despite this, a structured synthesis of yeast–bacterium associations across fermented milk typologies is currently lacking. To address this gap, a PRISMA-informed literature search identified 42 studies across 24 traditional fermented milks reporting paired bacterial and fungal communities. A genus-level co-occurrence analysis was used to identify which yeast–bacterium pairs were most frequently co-detected across independently documented products. The main co-occurrence patterns selected for detailed bibliographical discussion were Kluyveromyces with Acetobacter and LAB, including Lactobacillus, Streptococcus, Lentilactobacillus and Lacticaseibacillus; Pichia with LAB; Saccharomyces with LAB, especially Lactobacillus; Kazachstania with Acetobacter; Candida with Leuconostoc and Enterococcus; and Geotrichum with Pseudomonas and Enterococcus. For the selected associations, possible interaction mechanisms and implications for sensory identity, technological potential, and microbiological safety were discussed by integrating evidence from milk co-cultures, controlled model systems, and related fermented foods. Overall, this review provides a structured synthesis of yeast–bacterium associations in traditional fermented milks and identifies candidate consortia for future experimental validation.

Fermentation doi: 10.3390/fermentation12060293

Authors: Akkapong Pochan Sudarat Thanonkeo Preekamol Klanrit Mamoru Yamada Huynh Xuan Phong Pornthap Thanonkeo

The economic viability of second-generation (2G) bioethanol production depends on the availability of robust, multistress-tolerant yeast strains capable of withstanding harsh industrial conditions. This study investigates animal manure as a novel ecological niche for discovering such strains, as microbes in these environments naturally adapt to high organic loading and fluctuating temperatures. From eighty-six initial isolates, twenty-nine demonstrated superior xylose fermentation at 37 °C. Eight high-performing isolates (C2-1, B1-2, B1-6, B2-6, B2-8, G1-4, G1-5, and G2-4) exhibited exceptional tolerance to ethanol, high temperatures, and lignocellulosic-derived inhibitors (acetic acid, formic acid, furfural, and vanillic acid). Molecular identification classified isolate C2-1 as Pichia kudriavzevii and the remaining seven as Candida tropicalis. In synthetic media, C. tropicalis B2-8 produced up to 16.33 g/L of ethanol using xylose (60 g/L) as the sole carbon source. While the undetoxified, highly acidic sugarcane bagasse hydrolysate completely inhibited yeast growth, the industrial potential of these strains was successfully validated using the concentrated, undetoxified enzymatic hydrolysate derived from the acid-pretreated sugarcane bagasse solids, which contained 30.15 g/L glucose and 25.58 g/L xylose. P. kudriavzevii C2-1 achieved ethanol titers of 6.02 g/L and 5.71 g/L at 37 °C and 40 °C, respectively. The C. tropicalis strains outperformed P. kudriavzevii, yielding 6.12–6.35 g/L at 37 °C and maintaining 5.75–6.19 g/L at 40 °C. These findings underscore the potential of manure-derived yeasts as resilient biocatalysts. Although their fermentation yields remain relatively low and require further metabolic optimization, their ability to survive and ferment in this concentrated, undetoxified enzymatic hydrolysate at elevated temperatures makes them promising candidates for further development in high-temperature ethanol fermentation (HTEF), offering a potential pathway toward reducing cooling costs associated with 2G biorefineries.

Fermentation doi: 10.3390/fermentation12060292

Authors: Mario Trupo Vincenzo Larocca Alfredo Ambrico Rosaria Alessandra Magarelli Maria Martino Salvatore Palazzo Anna Spagnoletta Stefania Moliterni Linda Bianco Nicola Fedele Antonio Molino

A newly isolated red-pigmented yeast, Sporobolomyces reniformis EMCC1691, was evaluated for its biotechnological potential in an integrated case study aimed at developing an efficient microbial cell factory for the valorization of delactosed whey. Fermentation trials in 5 L bioreactors demonstrated robust yeast growth on this dairy by-product, with complete consumption of glucose (21.86 g/L) and galactose (20.36 g/L), leading to the accumulation of approximately 6172 mg/L of lipids and 5634 µg/L of total carotenoids. Fatty acid analysis revealed a final concentration of 3924 mg/L, mainly represented by oleic (2037 mg/L), palmitic (779 mg/L), stearic (403 mg/L), and linoleic (362 mg/L) acids. HPLC analysis showed a pigment profile dominated by torularhodin, torulene, γ-carotene, and β-carotene. To complement downstream processing, the fermented culture was spray-dried into a stable powder and subsequently subjected to a simple, cost-effective, and unconventional mechanical pretreatment using a hydraulic press. This post-drying operation ensured extensive cell-wall disruption without the use of chemical agents or specialized equipment, thereby significantly enhancing the recoverability of intracellular lipids and carotenoids through supercritical CO2 extraction. Under optimized conditions, SFE-CO2 with ethanol recovered 92.18 ± 1.61 µg/g of total carotenoids, achieving an extraction efficiency of 84% relative to organic solvent extraction (109.17 ± 2.10 µg/g). Importantly, fermentation also reshaped the fatty acid composition of delactosed whey, shifting it toward a profile enriched in monounsaturated and polyunsaturated fatty acids, thereby further highlighting the metabolic impact and bioconversion potential of S. reniformis EMCC1691. Overall, this work highlights the technological relevance of a recently characterized yeast species and its potential to convert dairy by-products into high-value compounds within a proof-of-concept microbial cell factory framework, paving the way for future scale-up investigations.

Fermentation doi: 10.3390/fermentation12060291

Authors: Jennifer Badura Judith Muno-Bender Kerstin Zimmer Katrin Matti Silvia Brezina Heike Semmler Doris Rauhut Jürgen Wendland

This study investigates the breeding of the German wine yeast Oppenheimer Kreuz 1894, which carries a FOT1 allele of a fungal oligopeptide transporter, with Freya, a Kveik ale yeast, to enhance fermentation performance and aroma in beer and wine. By combining Kveik traits (osmotolerance, thermotolerance, and rapid fermentation kinetics) with those of a German wine yeast (ethanol tolerance, broadened nitrogen utilization, and aroma production) and introducing FOT1 into an ale background via classical breeding, we aimed to leverage the Saccharomyces biodiversity to improve fermentation activity and expand aromatic complexity. Fermentation products and volatile aroma compounds were quantified by HPLC and HS-SPME-GC-MS. Spore clone derivatives of initial hybrid strains (F2-generation) showed improved fermentation profiles with increased CO2 production. In wine fermentations, the best-performing spore clone, GYBC 901, yielded a rich aromatic profile with elevated fruity and floral notes. In beer fermentations, GYBC 899 produced the most diverse and complex aroma. FOT1 was of minor relevance to the breeding outcome, whereas meiotic recombination generated a set of diverse spore clones. These results highlight the potential of strategic yeast breeding to optimize fermentation processes and tailor flavor profiles to diverse product targets. Future work will elucidate metabolic pathways underlying these phenotypes and advance the development of application-specific strains, offering avenues to enhance beverage quality and product differentiation in the fermentation industry.

Fermentation doi: 10.3390/fermentation12060290

Authors: Zhongying Zhai Xiannian Zhu Yong Wan Qing Zheng

Huangshui (HS) is a key byproduct of Chinese strong-flavor Baijiu (a traditional distilled spirit) fermentation. This study investigated microbial succession and flavor formation across five key fermentation stages using high-throughput sequencing, physicochemical analysis, and untargeted GC-MS. The results show that Lactobacillus dominated the bacterial communities, while Thermoascus, Aspergillus, and Candida were core fungal genera. Redundancy analysis (RDA) identified acidity, available phosphorus, and ammonia nitrogen as the primary physicochemical drivers of microbial succession. Untargeted metabolomics detected 300 volatile compounds, with 29 discriminant volatile metabolites (VIP > 1.0 or p < 0.05), mainly enriched in carbohydrate and amino acid metabolism pathways associated with Lactobacillus, Thermomyces, Wickerhamomyces, and Kazachstania. These findings establish a link among physicochemical properties, microbiota assembly, and flavor metabolism, providing potential targets for optimizing Baijiu fermentation quality.

Fermentation doi: 10.3390/fermentation12060289

Authors: Bilge Sayın Zerrin Polat Güzin Kaban Mükerrem Kaya

Olive mill wastewater (OMW), due to its high organic load and phenolic content, represents both a major environmental challenge and a promising low-cost substrate for microbial bioprocesses. In this study, lipid production by Yarrowia lipolytica using OMW was optimized through a mixed-level Taguchi experimental design. The effects of OMW dilution (%), nitrogen supplementation, NaCl concentration, sterilization, and carbon source (glucose or glycerol) were evaluated in terms of biomass production, lipid accumulation, and fatty acid composition. The results demonstrated a clear inverse relationship between biomass formation and lipid accumulation. The highest lipid content (33.49%) was achieved under nitrogen-limited conditions combined with a high OMW dilution. After 168 h of fermentation, the calculated lipid yield was 0.51 g/L. Biomass and lipid productivities were calculated as 0.22 g/L/day and 0.073 g/L/day, respectively. ANOVA analysis revealed that nitrogen concentration was the dominant factor affecting lipid production (67.71%), followed by NaCl concentration (18.83%). In contrast, OMW dilution, sterilization, and carbon source type were not statistically significant (p > 0.05), indicating that lipid production can be effectively performed under non-sterile conditions with flexible substrate utilization. Fatty acid analysis revealed that the produced lipids were rich in oleic acid (C18:1n9c), reaching up to 57.97%, with unsaturated fatty acids generally accounting for the majority of the total fatty acid composition. Although the carbon source had a limited effect on lipid yield, it contributed to variations in fatty acid composition, suggesting the possibility of tailoring lipid quality through substrate selection.

Fermentation doi: 10.3390/fermentation12060288

Authors: Juan Feng Can Liu Yuxuan Zhang Jian Shi

Volatile fatty acids (VFAs) are essential precursors in chemical synthesis for various chemicals, polymers, pharmaceuticals, and fragrance compounds. Acidogenic anaerobic digestion (or arrested methanogenesis) is a promising method to stabilize organic wastes and convert them to value-added products such as VFAs. However, the VFAs’ accumulation could in turn suppress the fermentation process through product inhibition and limit the titer of VFA in the digestate. Therefore, in situ separation and recovery of VFAs from the fermentate is crucial to constructing an effective continuous VFA-producing system. Recent research has been dedicated to addressing these issues and advancing the utilization of biobased VFAs, particularly through process-intensified strategies employing novel green solvents such as natural deep eutectic solvents. Furthermore, in situ conversion of VFAs into esters is another potential strategy for VFA removal. However, VFA esterification in an aqueous medium is challenging due to the abundant water driving the reaction toward hydrolysis. Recent advances in free or immobilized enzyme catalysis in solvents have demonstrated improved ester yield by providing a hydrophobic space for the esterification reaction in aqueous solution. In this review, we present an overview of critical aspects on the state-of-the-art of green solvent-based process intensification strategies, including feedstock selection and pretreatment, operating condition optimization, advances in membrane- and solvent-based recovery methods, and biocatalytic in situ esterification. Lastly, we provide perspectives toward cost-effective, continuous, high-solid, environmental-benign, and industrial-relevant VFA production applications.

Fermentation doi: 10.3390/fermentation12060287

Authors: Esna Mete Ayşe Janseli Denizkara Gökhan Akarca

This research assessed the impact of probiotic culture incorporation and the sous vide manufacturing method on the physicochemical, textural, colorimetric, and microbiological characteristics of yoghurts during the storage duration. The trials used conventional and sous vide manufacturing techniques using probiotic and classical starting cultures, and the products were analyzed throughout the storage period. The findings indicate that the use of probiotic cultures significantly enhances organic acid synthesis. This rise resulted in a lower pH (≈4.54) and increased titratable acidity (≈1.60%). Furthermore, it has been shown that the total organic acid concentration, mostly lactic acid, rose (≈24,045 mg/kg), while concurrently, the yeast-mold load decreased (≈2.69 log CFU/g). Throughout the storage duration, a reduction in pH and an elevation in acidity and microbial activity were seen in all samples (p < 0.05). The sous vide manufacturing method, due to regulated heat processing and a sealed system design, has decreased syneresis (≈5.65%) and an enhanced dry matter content (≈13.09%). This circumstance has resulted in the development of a more uniform gel structure, thereby enhancing the textural attributes. Color investigations indicated that the integration of probiotics and sous vide decreased the ΔE values, and in samples with ΔE < 3, the color change was imperceptible to the human eye. In conclusion, the simultaneous application of probiotic culture addition and the sous vide production technique has exhibited a synergistic effect on acidity development, microbial stability, textural properties, and color stability, indicating its efficacy in producing higher-quality functional yoghurt.

Fermentation doi: 10.3390/fermentation12060286

Authors: Echua Elisabeth Jasmine Bilé Alahou André Gabaze Gadji Eric-Olivier Tiénébo Maïmou Junior N’Ganko Adjoa Marie-Joséphine Kouadia Kouakou Théodore Kouadio Ossey Bernard Yapo Rajeshwar D. Tyagi Kouabenan Abo

Large-scale production of Bacillus thuringiensis, one of the most widely used biopesticides, is often limited by the high cost of conventional culture media. In this study, fermented cassava paste water (EFM), ripe mango pulp juice (CM), and cashew apple juice (JPC) were evaluated as alternative substrates for the liquid fermentation of B. thuringiensis var. kurstaki HD-1. Physicochemical analyses revealed acidic pH values and classified the substrates into two clusters: CM with high C/N ratios, organic matter, total sugars, and proteins, and EFM and JPC with lower C/N ratios and nutrient levels. Fermentation results indicated that JPC supported the highest biomass production (8.29 × 1013 CFU mL−1), exceeding that in the standard Tryptone Soy Broth (TSB) medium. However, CM promoted the highest sporulation rate (1.46 × 1013 CFU mL−1) and the greatest bioactive lipopeptides—iturins (102.2 mg L−1) and surfactins (554.7 mg L−1)—surpassing TSB. The antifungal activity of crude fermented CM, EFM, and TSB was evaluated against Sclerotium rolfsii. All samples significantly inhibited mycelial growth of the pathogen with no significant differences among substrates or concentrations tested. This study highlights the potential of B. thuringiensis-fermented agrowaste as a cost-effective, environmentally friendly biocontrol tool for Sclerotium rolfsii.

Fermentation doi: 10.3390/fermentation12060285

Authors: Carolina Ramírez-Martínez Gael Jesús Molina-Benítez Mariana Franco-Morgado Alberto Ordaz

The increasing generation of agro-industrial residues like nejayote (maize lime-cooking wastewater from the maize nixtamalization process) poses significant environmental challenges in Mexico due to its elevated chemical oxygen demand (COD) and organic load. This study evaluates the physical separation of nejayote via membranes and its use as a low-cost substrate for producing lipids and carotenoids using Rhodotorula glutinis. A batch culture followed by pulse-feeding achieved a COD removal efficiency of 53.6% (0.22 g COD/(L h)) and a biomass concentration of 3.72 ± 0.45 g COD/L within 48 h. The yeast demonstrated a high specific metabolic efficiency, yielding 0.457 g of lipids and 0.0049 g of carotenoids per gram of biomass, with an oleaginous fraction of 46.21% in dry weight. Experimental data calibrated a process model in SuperPro Designer, simulating full-scale processes treating 100, 1000, and 10,000 m3 of nejayote per batch, producing up to 2137.11 MT of lipids and 22.90 MT of carotenoids annually. A techno-economic analysis estimated the investment, operating costs, and financial indicators for all scenarios. Strategies like evaporation and reverse osmosis to concentrate nejayote significantly improved profitability by reducing equipment size. Additionally, a circular economy approach was modeled, recovering process water and nutrient-rich side streams. These findings confirm that integrated physical and biological treatment, coupled with resource recovery, transforms this particularly agro-industrial residue into a technically robust and economically viable biorefinery feedstock, aligning industrial production with sustainable waste management.

Fermentation doi: 10.3390/fermentation12060284

Authors: Fei Li Pengbao Shi Xin Dong Wenqi Shi Yang Yang Hejing Yan

Phenolic compounds in Muscat grape juice contribute to antioxidant capacity, functional properties, and sensory quality; however, conventional enzymatic maceration is often limited in efficiency and typically requires elevated temperatures. This study systematically compared pectinase-assisted heat maceration (P45-HM), low-temperature pectinase maceration (P-CM), and low-temperature maceration mediated by the psychrotolerant yeast Metschnikowia pulcherrima (Mp-CM) in Muscat grape juice. Mp-CM significantly enhanced the extraction and transformation of phenolic compounds, with total phenolic and flavonoid contents increasing by 8.01% and 13.14%, respectively, compared with P-CM, and by 27.06% and 55.28%, respectively, compared with P45-HM. Moreover, Mp-CM exhibited higher antioxidant activities, as determined by DPPH, ABTS, and FRAP assays, as well as greater sodium glycocholate-binding capacity than P-CM (p < 0.05). Correlation analysis revealed strong positive correlations between phenolic composition and biological activities. Volatile compounds were analyzed by HS-SPME-GC-MS combined with principal component analysis (PCA), demonstrating distinct aroma profiles. Mp-CM was enriched in terpenes (14.63% higher than P-CM), whereas P-CM was dominated by esters, suggesting that M. pulcherrima possesses a distinct biotransformation capacity that modulates volatile compounds potentially contributing to the characteristic Muscat aroma. These findings indicate that Mp-assisted cold maceration represents an efficient and promising biological maceration strategy for enhancing the quality of grape juice.

Fermentation doi: 10.3390/fermentation12060283

Authors: Jian Yin Yu Zhang Tianming Chen Guolin Cai

Cottonseed hull is an abundant and low-cost cotton processing byproduct, but its feed application is severely limited by free gossypol. This study screened a gossypol-degrading fungal strain from naturally fermented cottonseed hulls and soy sauce koji, and evaluated its detoxification and feed improvement effects via solid-state fermentation. Strain TM-2 was identified as Aspergillus oryzae. It degraded over 60% of gossypol in liquid fermentation and 69.54% in cottonseed hull solid-state fermentation. Genome annotation revealed 409 CAZyme genes and key pathways for naphthalene and aromatic compound degradation. After fermentation, crude protein and acid-soluble protein were significantly increased, while cellulose, hemicellulose, lignin, neutral detergent fiber, and acid detergent fiber were notably reduced. Antioxidant activity was also greatly enhanced. Secretomic analysis identified 92 extracellular proteins, including hemicellulases, cellulases, proteases, and peptidases that jointly promoted detoxification and quality improvement. A. oryzae TM-2 efficiently degrades gossypol and improves feed quality, showing high value in fermented feed development and agricultural byproduct utilization.

Fermentation doi: 10.3390/fermentation12060282

Authors: Kuntao Xu Yuyang Sheng Yaoming Deng Hongtao Han Bin Zeng

Plant-derived bioactive compounds, such as polyphenols and saponins, possess significant pharmacological value. However, conventional extraction methods often suffer from low efficiency, poor bioavailability, and environmental burdens. Aspergillus-based biotransformation has emerged as a superior platform for overcoming these limitations due to their robust secretomes, versatile metabolic networks, and the GRAS (Generally Recognized as Safe) status of specific industrially relevant species (e.g., A. oryzae and A. niger). Existing literature frequently focuses on isolated compounds or general fungal processes. To fill this gap, this review systematically links specific Aspergillus enzymatic systems to an “enzymatic hydrolysis–transformation–synthesis” closed-loop framework, which is essential for industrial-scale valorization. In this review, we summarize recent advances in the biotransformation of phytochemicals by A. niger, A. oryzae, and A. nidulans. These fungi utilize specialized enzymes—including β-glucosidases, cellulases, and glycosidases—to enable precise hydrolysis, deglycosylation, and detoxification under mild conditions. We highlight representative transformations that demonstrate markedly enhanced bioactivity and solubility. Key examples include the conversion of polydatin to resveratrol (>90% yield) and ginsenoside Rb1 to ginsenoside compound K (94.4% conversion rate). Although industrial applications span the food, pharmaceutical, and cosmetic sectors, significant challenges persist in solid-state fermentation (SSF) scale-up, strain stability, target compound over-degradation, and downstream purification. Genetic engineering, process optimization and hybrid bioprocessing are highlighted as promising strategies to overcome these limitations and realize sustainable, high-value production of natural bioactive metabolites.

Fermentation doi: 10.3390/fermentation12060281

Authors: Junhao Yue Wanting Wu Fangfang Fan Weirui Zhao Sheng Hu Zhuhua Chan Lehe Mei Changjiang Lyu

γ-Aminobutyric acid (GABA), a vital bioactive component, is biosynthesized via the decarboxylation of L-glutamate (L-Glu) catalyzed by glutamate decarboxylase (GAD). However, the GADs from various sources commonly suffer from low thermal stability, which hampers their industrial applications. In this work, four ancestral sequences of GAD (Anc19, Anc20, Anc28, and Anc30) were designed via an ancestral sequence reconstruction (ASR) approach. Thereafter, the genes were synthesized and heterologously expressed in the probiotic Escherichia coli strain Nissle 1917 (EcN). Among all variants tested, Anc28 exhibited the highest catalytic performance. The Km and kcat values were determined to be 26.80 mM and 57.41 s−1, respectively, yielding a catalytic efficiency (kcat/Km) of 2.14 s−1mM−1, which was 2.71-fold higher than that of the wild-type enzyme. Meanwhile, compared with the wild-type GAD, Anc28 exhibited a 6.74 °C increase in T5015 and a 4.1-fold extension in t1/2 at 60 °C. Furthermore, the GABA synthesis system using dormant Escherichia coli Nissle (T7)/pET28a-gadBAnc28 cells as the biocatalyst and pure water as a sole medium was also constructed. Upon completion of the 4 h reaction, the GABA titer reached 307.53 g/L with a conversion ratio of 99.36%. The resulting engineered strains were successfully employed for the efficient biosynthesis of GABA.

Fermentation doi: 10.3390/fermentation12060280

Authors: Gilver Rosero-Chasoy Elda España-Gamboa Jesús Alejandro Vazquez-Barea José Martin Baas-López Tanit Toledano-Thompson Liliana Alzate-Gaviria Raúl Tapia-Tussell

Methane production from Brosimum alicastrum seed coat was evaluated using a logistic model through three alkaline concentrations (0.19 M, 0.26 M, and 0.28 M) and three enzymatic activity levels (3000 U mL−1, 5000 U mL−1, and 7000 U mL−1) as pretreatments. Laccase was produced through submerged fermentation using T. hirsuta Bm-2 fungi, while NaOH served as the alkaline agent. Enzymatic pretreatment resulted in the highest specific CH4 yield (427.43 ± 2.28 mL CH4/g VSadded), surpassing both alkaline pretreatment (235.61 ± 9.19 mL CH4/g VSadded) and the control (102.54 ± 5.55 mL CH4/g VSadded). Kinetic analysis of CH4 production indicated that cumulative CH4 production reached its stationary phase within 30 days of digestion. Moreover, enzymatic pretreatment exhibited the highest CH4 formation rate (0.15–0.16 h−1), except for the control, which had a slightly higher rate (0.22 h−1). The kinetic analysis revealed that the enzymatic pretreatment significantly improved the hydrolysis stage of Ramon’s seed coat, promoting higher cumulative CH4 production and leading to an increased specific CH4 yield.

Fermentation doi: 10.3390/fermentation12060279

Authors: Jiaying Xiong Meixia Chen Laiping Zhang Qi Zhou Zhenyu Huang Xiaobin Lin Xiaomin Fang Xiangdong Ye Weiping Zhu Wei Liu Aiqin Shi

In the original publication [...]

Fermentation doi: 10.3390/fermentation12060278

Authors: Hümeyra Çetin Babaoğlu Talha Demirci Nihat Akın Sultan Arslan Tontul

This study aimed to evaluate the technological, functional and nutritional effects of exopolysaccharide-producing lactic acid bacteria (LAB) strains, isolated from artisanal Tulum cheese as type II sourdough starters. The objective of this study was to improve bread quality, delay staling, and enhance bioactive properties, such as antioxidant capacity and estimated glycaemic index (eGI). Six LAB strains (Loigolactobacillus coryniformis, Lactiplantibacillus plantarum, Levilactobacillus brevis, Lacticaseibacillus paracasei, Lactobacillus helveticus, and Lacticaseibacillus rhamnosus) were individually used for sourdough fermentation. Bread samples were analyzed for pH, titratable acidity (TA), LAB counts, specific volume, colour, total phenolic content (TPC), antioxidant activity (DPPH and ABTS), starch digestibility, eGI, staling kinetics (Avrami model) and amylopectin retrogradation (DSC). Strain-dependent improvements in bread functionality were observed. L. brevis and L. coryniformis strains increased sourdough acidity to a greater extent, and resulting in lower pH values. Accordingly, bread produced with sourdough fermented by these strains exhibited higher specific volume than the control. Although higher ABTS radical scavenging activity and TPC were detected in sourdough bread compared to the control bread, no significant differences were observed among the breads in terms of total antioxidant activity measured by DPPH. L. rhamnosus significantly improved antioxidant activity and reduced the eGI. L. coryniformis, L. plantarum and L. brevis were the most effective at retarding staling, reducing the increase in hardness and limiting amylopectin retrogradation. This study is the first to demonstrate the functional potential of LAB strains from artisanal Tulum cheese as sourdough starters. These findings reveal the potential for developing clean-label bakery products with an extended shelf life and improved health-related functionality.

Fermentation doi: 10.3390/fermentation12060277

Authors: Yinglong Wang Shiguo Chen Keyu Lei Yunfeng Pu Yang Li Boqun Liu Xujie Hou

Musalais is a traditional fermented beverage of the Uyghur people in Xinjiang, China. Its production involves boiling grape juice at high temperatures to concentrate it and enhance its sugar content, followed by natural fermentation. However, this high-temperature concentration process leads to a significant loss of bioactive and flavor compounds, adversely affecting the quality of the final product. Adding composite ingredients may help mitigate this quality decline. This study compares Musalais new product with traditional Musalais. Phenolic analysis showed that total monomeric phenols were 182.36 mg·L−1 in the new product versus 14.76 mg·L−1 in traditional Musalais. Headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC-MS) identified 72 volatile compounds in the new product (total content of 569,848.88 μg·L−1) compared to 58 compounds (total content of 362,774.17 μg·L−1) in traditional Musalais. Compared to traditional Musalais, the new product exhibits a 24.14% increase in volatile compound variety and a 57.09% increase in total concentration, with more pronounced floral, fruity, and vinous aromas, as well as higher sensory scores. Non-targeted metabolomics suggests that the new product may have superior phenolic and volatile profiles.