Fermentation

16 pages, 2191 KB

Open AccessArticle

A Co-Fermentation Strategy from Corncob Hydrolysate to Enhance Simultaneous Co-Production of Lactic Acid and Ethanol

by Xiaona Wang, Yongsheng Li, Yuanchun Zhang, Yuanyuan Ren, Hongzhi Ma, Jianguo Liu and Qunhui Wang

Fermentation 2026, 12(2), 95; https://doi.org/10.3390/fermentation12020095 (registering DOI) - 7 Feb 2026

Abstract

Efficient co-utilization of mixed sugars from lignocellulosic hydrolysates is often hindered by carbon catabolite repression and pretreatment-derived inhibitors. In this study, a co-fermentation strategy using Saccharomyces cerevisiae (S. cerevisiae) and Enterococcus mundtii (E. mundtii) was developed to simultaneously produce [...] Read more.

Efficient co-utilization of mixed sugars from lignocellulosic hydrolysates is often hindered by carbon catabolite repression and pretreatment-derived inhibitors. In this study, a co-fermentation strategy using Saccharomyces cerevisiae (S. cerevisiae) and Enterococcus mundtii (E. mundtii) was developed to simultaneously produce ethanol and lactic acid from non-detoxified corncob hydrolysate. Co-fermentation performed at 39 °C significantly improved substrate utilization compared with monoculture systems, achieving pentose and total sugar utilization percentages of 67.1% and 83.7%, respectively. S. cerevisiae preferentially consumed glucose and effectively detoxified furfural and 5-hydroxymethylfurfural (5-HMF), thereby alleviating inhibitory stress and carbon catabolite repression on E. mundtii. By optimizing the inoculation sequence, a 3 h delayed inoculation of E. mundtii significantly enhanced pentose utilization from 68.6% to 80.2% and increased total sugar utilization to 90.4%. This synergistic co-fermentation strategy provides an effective approach for improving mixed-sugar utilization and multi-product bioconversion efficiency in lignocellulosic biorefineries. Full article

(This article belongs to the Topic Separation Techniques and Circular Economy)

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11 pages, 1101 KB

Open AccessArticle

A Kinetics Study on Co-Digestion of Cattle Manure, Macroalgae and Cheese Whey

by Figen Taşcı Durgut

Fermentation 2026, 12(2), 94; https://doi.org/10.3390/fermentation12020094 (registering DOI) - 7 Feb 2026

Abstract

In this research, cattle manure, macroalgae, and cheese whey were mixed in various proportions (cattle manure:macroalgae:cheese whey ratios of 50:30:20, 30:20:50 and 20:50:30) and subjected to co-digestion under laboratory conditions at two different digestion temperatures (30 and 45 °C). The modified Gompertz and [...] Read more.

In this research, cattle manure, macroalgae, and cheese whey were mixed in various proportions (cattle manure:macroalgae:cheese whey ratios of 50:30:20, 30:20:50 and 20:50:30) and subjected to co-digestion under laboratory conditions at two different digestion temperatures (30 and 45 °C). The modified Gompertz and first-order kinetic models were used to predict biomethane potentials. The highest experimental biochemical methane potential of 0.373 Nm³CH₄/kgVS was obtained from Mixture-2 at 45 °C, while the lowest, 0.154 Nm³CH₄/kgVS, was achieved with Mixture-1 at 30 °C. Feedstock rates in the mixture and digestion temperature significantly influenced the biochemical methane potential (p < 0.05). Cheese whey was observed to positively contribute to increasing biomethane potential. Increasing the whey ratio in the mixture from 20% to 50% resulted in a 62.5% increase in biomethane production. While R² values for the modified Gompertz model ranged from 0.993 to 0.999, those of the first-order model varied between 0.968 and 0.984. Of the two kinetic models employed for estimating biomethane potentials, the modified Gompertz model yielded values closer to the experimental biomethane potentials. Full article

(This article belongs to the Special Issue Fermentation Processes: Modeling, Optimization and Control: 3rd Edition)

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16 pages, 4522 KB

Open AccessArticle

Optimization of Lentilactobacillus buchneri Mediated Fermentation for Valorizing Tea By-Products into Feed: Process Parameters, Nutritional Quality Enhancement, and Bacterial Community

by Xinyan Wu, Yinying Xu, Caiyun Fan, Shuting Fu, Zirui Luo, Sana Zahra Naqvi, Zhao Zhuo and Jianbo Cheng

Fermentation 2026, 12(2), 93; https://doi.org/10.3390/fermentation12020093 (registering DOI) - 7 Feb 2026

Abstract

The massive annual production of tea generates substantial underutilized by-products, leading to resource waste. This study aimed to develop an efficient process for converting these by-products into high-quality feed via fermentation with Lentilactobacillus buchneri (L. buchneri). Using a response surface methodology, [...] Read more.

The massive annual production of tea generates substantial underutilized by-products, leading to resource waste. This study aimed to develop an efficient process for converting these by-products into high-quality feed via fermentation with Lentilactobacillus buchneri (L. buchneri). Using a response surface methodology, the key fermentation parameters (time, temperature, inoculum size, and moisture) were optimized to target pH and crude protein (CP) content. The optimal conditions (4.5 days, 34.5 °C, 5.00 × 10⁶ CFU/g, 54% moisture) yielded a product with a pH of 3.72 and CP content of 17.96%, which was similar to the predictions. Fermentation successfully reduced ether extract (EE), tea tannin (TTN), and propionic acid (PA), while increasing lactic acid (LA) and lowering pH. This process was driven by the dominance of Lactobacillus (99.29% relative abundance), as revealed by microbial analysis. This work provides a viable and optimized strategy for valorizing tea by-products into nutritionally enhanced feed, thereby contributing to sustainable agricultural practices. Full article

(This article belongs to the Section Fermentation Process Design)

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18 pages, 7862 KB

Open AccessArticle

Optimization of Fermentation and Mutagenesis for Enhanced Staurosporine Production in the Marine-Derived Streptomyces Strain OUCMDZ-3118

by Mingxing Zuo, Jiuman Xiang, Mingshen Zhang, Weiming Zhu and Liping Wang

Fermentation 2026, 12(2), 92; https://doi.org/10.3390/fermentation12020092 - 5 Feb 2026

Abstract

Background: Staurosporine is a potent broad-spectrum alkaloid antibiotic originally isolated from Streptomyces sp. It is renowned for its strong inhibitory activity against protein kinases by competitively binding to their ATP-binding sites. Therefore, staurosporine and its derivatives have been extensively investigated for their potential [...] Read more.

Background: Staurosporine is a potent broad-spectrum alkaloid antibiotic originally isolated from Streptomyces sp. It is renowned for its strong inhibitory activity against protein kinases by competitively binding to their ATP-binding sites. Therefore, staurosporine and its derivatives have been extensively investigated for their potential as anticancer agents. However, a major challenge in its utilization is the low production yield in wild-type strains. To overcome this limitation, this study aimed to enhance staurosporine yield in marine-derived staurosporine-producing strain OUCMDZ-3118. Methods: The fermentation conditions were tested by single-factor experiment, Plackett–Burman experiment, steepest ascent path and Box–Benhnken response surface method. Subsequently, the ultraviolet mutagenesis was employed to generate high-yielding mutant strain. Results: The optimal culture conditions were 50 g/L rice, 50 g/L soybean powder, 3 g/L NaCl, 10 g/L L-tryptophan, inoculum concentration of 3% (v/v) in 150 mL of medium within a 500 mL flask, and fermentation time of 10 days. Following UV mutagenesis, the mutant strain produced a final staurosporine titer of 496 mg/L, an approximately 9.5-fold higher titer than that of the wild-type strain. In a 30-day solid-state fermentation under the conditions of 40 g rice, 40 g soybean powder, moistened with 80 mL water containing NaCl (3 g/L) and L-tryptophan (10 g/L), a yield of 578 mg per 80 g of substrate was also achieved. A consistent yield of 7.22 g/kg was achieved across approximately 1000 replicate fermentations under identical conditions, demonstrating the robustness of the process. Conclusions: This study yielded a stable, high-yielding strain for staurosporine production, paving the way for the development of staurosporine-based antitumor drugs and their derivatives. Full article

(This article belongs to the Special Issue Novel and Old Insights for Biotechnological Exploitation of Actinomycetota Strain Fermentations)

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22 pages, 2194 KB

Open AccessArticle

Enhancing the Production of Sour Beers by Adding Blueberries and Fermenting with Lachancea and Metschnikowia

by Elena Alonso, Carmen López, María Antonia Bañuelos, Carmen González and Antonio Morata

Fermentation 2026, 12(2), 91; https://doi.org/10.3390/fermentation12020091 - 5 Feb 2026

Abstract

The increasing demand for alcohol-free craft beers with functional properties and distinctive sensory attributes has motivated the brewing industry to investigate alternative production strategies, such as the application of non-Saccharomyces yeasts, to obtain sour beers while reducing production time and associated costs. [...] Read more.

The increasing demand for alcohol-free craft beers with functional properties and distinctive sensory attributes has motivated the brewing industry to investigate alternative production strategies, such as the application of non-Saccharomyces yeasts, to obtain sour beers while reducing production time and associated costs. This study explores the combined use of Lachancea thermotolerans L31 and Metschnikowia pulcherrima M29 in the production of beers brewed with blueberries or enriched with grape anthocyanin concentrate. Physicochemical parameters such as pH, color, bitterness, total polyphenols, antioxidant capacity, and anthocyanin and volatile profiles were evaluated, and a sensory analysis was performed. The results showed that both the addition of blueberries and that of anthocyanin concentrate and fermentation with Lachancea and Metschnikowia significantly influenced the chemical and sensory properties of the beer. Mainly, pH values decreased from 4.35 to 3.50 and from 3.69 to 3.26, while antioxidant activity increased from 3 to 10 times, depending on the type of yeast and the addition of fruit. Alcohol content remained constant at approximately 5.0% v/v. This strategy allows for the production of beer with a distinctive profile and functional benefits, representing a step forward in craft beer development and opening new avenues for research and innovation in the sector. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Online Conference on Fermentation (IOCFE2025))

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19 pages, 629 KB

Open AccessArticle

From Probiotic Screening to Postbiotic Potential: An Integrated In Vitro Assessment of Endogenous Non-Saccharomyces Yeast Isolates

by Furkan Aydın, Halil İbrahim Kahve and Fatma Şahmurat

Fermentation 2026, 12(2), 90; https://doi.org/10.3390/fermentation12020090 - 4 Feb 2026

Abstract

Yeasts isolated from fermented foods have attracted increasing attention for their probiotic potential; however, studies on yeast-derived postbiotics remain limited. In this study, endogenous yeast strains belonging to Kluyveromyces marxianus (n = 3), Yarrowia lipolytica (n = 3), Pichia fermentans ( [...] Read more.

Yeasts isolated from fermented foods have attracted increasing attention for their probiotic potential; however, studies on yeast-derived postbiotics remain limited. In this study, endogenous yeast strains belonging to Kluyveromyces marxianus (n = 3), Yarrowia lipolytica (n = 3), Pichia fermentans (n = 3), and Debaryomyces hansenii (n = 3) were evaluated for their in vitro probiotic properties. A multi-criteria decision-making analysis using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) identified K. marxianus ETP12, P. fermentans SJ2023, and Y. lipolytica ARTP9.2 as the most promising strains for postbiotic production. Among them, K. marxianus ETP12 exhibited the highest functional potential and was subjected to comprehensive postbiotic characterization. The postbiotic of K. marxianus ETP12 was further characterized for total phenolic content, antioxidant capacity (DPPH and ABTS scavenging activities), phenolic compound profile, biofilm inhibition capacity, free amino acid composition, and fatty acid profile. The results revealed a diverse phenolic composition, primarily consisting of fumaric acid, quercetin, gallic acid, and quinic acid. A total of 29 essential, non-essential, and bioactive amino acids were identified, with lysine, leucine, and glycine as the predominant components. Fatty acid profiling indicated the predominance of palmitic and stearic acids, accompanied by medium-chain fatty acids. Notably, it exhibited strong biofilm-inhibition activity against S. aureus ATCC 25923 and C. sakazakii ATCC 29544. Overall, these findings demonstrate that K. marxianus ETP12 represents a valuable source of multifunctional postbiotics with potential applications in the development of functional foods and nutraceuticals. Full article

(This article belongs to the Special Issue Perspectives on Microbiota of Fermented Foods, 2nd Edition)

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18 pages, 1269 KB

Open AccessArticle

Ethnobiotechnological Analysis of the Lactic Bacterial Diversity in the Mezcal Fermentation of Four Palenques in Oaxaca, Mexico

by Claudia López-Sánchez, Víctor Adrián Espinoza-Martínez, Felipe de Jesús Palma-Cruz, Raúl Enríquez-Valencia, Marcos Pedro Ramírez-López, Lourdes Yaret Ortiz-Cortés and Peggy Elizabeth Álvarez-Gutiérrez

Fermentation 2026, 12(2), 89; https://doi.org/10.3390/fermentation12020089 - 4 Feb 2026

Abstract

Mezcal is an ancestral beverage from Oaxaca, Mexico, produced using traditional biotechnological procedures without artificial inoculation. The role of bacteria in fermentation has been studied less. Our work aimed to analyze the bacterial diversity in mezcal must and determine its relationship with ethnobiotechnological [...] Read more.

Mezcal is an ancestral beverage from Oaxaca, Mexico, produced using traditional biotechnological procedures without artificial inoculation. The role of bacteria in fermentation has been studied less. Our work aimed to analyze the bacterial diversity in mezcal must and determine its relationship with ethnobiotechnological variables. Fermentation must samples were collected from four Palenques in the Valles Centrales, Cañada, and Mixteca regions of Oaxaca. Molecular and phenotypic identification and characterization, including ethanol tolerance testing, were performed. Ethnobiotechnological data were acquired through interviews and official databases. Six bacterial genera were identified in mezcal must, including Lactiplantibacillus, Enterobacter, Enterococcus, Bacillus, Leuconostoc, and Levilactobacillus. Therefore, through a factorial experiment, it was determined that the selected Lactiplantibacillus plantarum strains were able to withstand 6% and 8% ethanol. A direct relationship was observed between species diversity and the degree of population marginalization. Palenque 2, representing the most urbanized population, exhibited the lowest diversity, with only two species detected. In contrast, Palenques characterized by high marginalization harbored a substantially greater diversity, ranging from six to ten species. These differences are likely associated with variations in microbiota composition, microbial growth dynamics, and ethanol tolerance. Overall, the findings suggest that ethnobiotechnological factors play a significant role in shaping bacterial diversity. In Oaxaca, “ethnobiotechnological” implies the deep relationship between biodiversity, Indigenous culture, and territory, with a strong emphasis on living traditional knowledge and its intergenerational transmission. Full article

(This article belongs to the Special Issue Women’s Special Issue Series: Fermentation)

76 pages, 17838 KB

Open AccessReview

Biochemical Conversion of Lignocellulosic Biomass in Biorefinery Systems

by Nei Pereira Junior

Fermentation 2026, 12(2), 88; https://doi.org/10.3390/fermentation12020088 - 4 Feb 2026

Abstract

Lignocellulosic biomass is one of the most abundant renewable carbon resources available, currently used predominantly for energy generation through direct combustion, yet still underutilized as a feedstock for higher-value biochemical conversion. Its structural complexity and intrinsic recalcitrance continue to challenge efficient biological processing. [...] Read more.

Lignocellulosic biomass is one of the most abundant renewable carbon resources available, currently used predominantly for energy generation through direct combustion, yet still underutilized as a feedstock for higher-value biochemical conversion. Its structural complexity and intrinsic recalcitrance continue to challenge efficient biological processing. Overcoming these barriers requires an integrated understanding of plant cell-wall architecture, pretreatment chemistry, enzymatic mechanisms, and process engineering. This review provides a clear and conceptually grounded synthesis of these elements, illustrating how they converge to enable the development of second-generation (2G) lignocellulosic biorefineries. This review examines the hierarchical organization of cellulose, hemicelluloses, and lignin; the principles and performance of modern pretreatment technologies; the synergistic action of cellulolytic systems, including lytic polysaccharide monooxygenases (LPMOs) and non-hydrolytic proteins such as swollenins; advances in C5/C6 sugar fermentation; and emerging strategies for lignin upgrading. In addition to a comprehensive analysis of the literature, representative industrial and experimental case studies reported in the literature are discussed to illustrate practical process behavior and design considerations. By integrating mechanistic insight with industrially relevant examples, this review highlights the technical feasibility, current maturity, and remaining challenges of lignocellulosic biorefineries, underscoring their strategic role in enabling a competitive, low-carbon bioeconomy. Full article

(This article belongs to the Special Issue Lignocellulosic Biomass in Biorefinery Processes)

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20 pages, 1529 KB

Open AccessArticle

How Does Methanogenic Inhibition Affect Large-Scale Waste-to-Energy Anaerobic Digestion Processes? Part 2—Life Cycle Assessment

by Ever Efraín García-Balandrán, Luis Ramiro Miramontes-Martínez, Alonso Albalate-Ramírez and Pasiano Rivas-García

Fermentation 2026, 12(2), 87; https://doi.org/10.3390/fermentation12020087 - 3 Feb 2026

Abstract

Anaerobic digestion under a Waste-to-Energy (WtE-AD) framework represents a sustainable alternative for managing organic waste and generating bioenergy in developing countries. However, most life cycle assessment (LCA) studies implicitly assume stable operation, overlooking the environmental implications of process instability. In practice, large-scale WtE-AD [...] Read more.

Anaerobic digestion under a Waste-to-Energy (WtE-AD) framework represents a sustainable alternative for managing organic waste and generating bioenergy in developing countries. However, most life cycle assessment (LCA) studies implicitly assume stable operation, overlooking the environmental implications of process instability. In practice, large-scale WtE-AD plants are frequently affected by methanogenic inhibition events that reduce methane production and compromise their technical, economic, and environmental performance. This study—Part 2 of a two-paper series—addresses this gap by quantifying, from a life cycle perspective, the environmental consequences of recurrent methanogenic inhibition events in large-scale WtE-AD systems, complementing the techno-economic analysis presented in Part 1. Large-scale WtE-AD plants were modeled using design equations based on treatment capacity (60–200 t d⁻¹), considering scenarios with up to ten inhibition events over a 25-year operational period. The LCA was conducted in accordance with ISO 14040:14044 standards, defining as the functional unit one ton of co-digested fruit and vegetable residues with meat industry wastes, under an attributional approach with system boundary expansion and evaluating midpoint indicators through the ReCiPe 2016 method. Results show that inhibition events increase greenhouse gas emissions by up to 400% (from 28.1 to 138.6 kg CO₂ eq t⁻¹ of waste treated), while plants with capacities above 125 t d⁻¹ exhibit environmental credits (negative emission balances), demonstrating greater environmental resilience. Electricity substitution from the Mexican grid generated savings of up to 0.624 kg CO₂ eq kWh⁻¹, although the magnitude of the benefits strongly depends on the regional electricity mix. This dependency was further explored through comparative electricity mix scenarios representative of different levels of power sector decarbonization, allowing the sensitivity of WtE-AD environmental performance to regional grid characteristics to be assessed. Compared to landfill disposal (1326 kg CO₂ eq t⁻¹), WtE-AD plants significantly reduce impacts across all assessed categories. By explicitly integrating operational instability into an industrial-scale LCA framework, this work highlights the importance of evaluating methanogenic inhibition events from a life cycle perspective, providing key insights for the design of more sustainable and resilient WtE-AD processes within a Latin American context. Full article

(This article belongs to the Special Issue Technological Advances in Lignocellulosic Biomass Conversion to Bioenergy)

29 pages, 709 KB

Open AccessReview

Bacterial Extracellular Vesicles in Biotechnology: Current Challenges and Strategies for Production Enhancement

by Flavia Cannizzaro, Annamaria Gallo, Silvia La Scala, Giuseppe Gallo and Teresa Faddetta

Fermentation 2026, 12(2), 86; https://doi.org/10.3390/fermentation12020086 - 3 Feb 2026

Abstract

Bacterial extracellular vesicles (BEVs) are nanosized (10–400 nm), membrane-enclosed particles naturally secreted by both Gram-negative and Gram-positive bacteria. Initially characterized as virulence factors in pathogenic species, BEVs are now recognized as multifunctional entities with significant biotechnological potential. Their cargo—comprising proteins, lipids, nucleic acids, [...] Read more.

Bacterial extracellular vesicles (BEVs) are nanosized (10–400 nm), membrane-enclosed particles naturally secreted by both Gram-negative and Gram-positive bacteria. Initially characterized as virulence factors in pathogenic species, BEVs are now recognized as multifunctional entities with significant biotechnological potential. Their cargo—comprising proteins, lipids, nucleic acids, and metabolites—enables diverse biological activities, including immune modulation, epithelial barrier protection, stress tolerance, and intercellular communication. Recent studies have highlighted BEVs from biotechnologically relevant bacteria—such as plant growth-promoting rhizobacteria, lactic acid bacteria, bifidobacteria, cyanobacteria, bacilli, and streptomycetes—for their different roles in biological and ecological interactions. These properties underpin emerging applications in health, agriculture, and bioprocessing, including next-generation postbiotics, vaccine platforms, drug and RNA delivery systems, and novel plant biostimulants. However, major challenges persist, particularly low production yields, variability in cargo composition, and scalability. Addressing these limitations requires a deeper understanding of vesiculation mechanisms and the development of process-oriented strategies for BEV recovery and purification. This review synthesizes recent advances in genetic analysis, physiological modulation, physicochemical stimuli, and bioprocess optimization aimed at enhancing BEV production and stabilizing cargo profiles, providing a comprehensive overview of approaches to unlock the full potential of BEVs as versatile biotechnological tools. Full article

(This article belongs to the Special Issue Systems Metabolic Engineering for the Production of Value-Added Compounds)

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28 pages, 11890 KB

Open AccessArticle

Anti-Coronavirus Activity of Extracts from Scenedesmus acutus cf. acutus Meyen Cultivated in Innovative Photobioreactor Systems

by Maya Margaritova Zaharieva, Dimitrina Zheleva-Dimitrova, Pelagia Foka, Eirini Karamichali, Tanya Chan Kim, Vessela Balabanova-Bozushka, Yana Ilieva, Anna Brachkova, Reneta Gevrenova, Stanislav Philipov, Sevda Naydenska, Urania Georgopoulou, Alexander Kroumov and Hristo Najdenski

Fermentation 2026, 12(2), 85; https://doi.org/10.3390/fermentation12020085 - 3 Feb 2026

Abstract

Coronaviruses are worldwide-distributed RNA viruses with zoonotic potential and the ability to jump from one host species to another, including humans. Even after the COVID-19 pandemic, the search for new, biologically active substances with anti-coronavirus activity continues to be a critical milestone for [...] Read more.

Coronaviruses are worldwide-distributed RNA viruses with zoonotic potential and the ability to jump from one host species to another, including humans. Even after the COVID-19 pandemic, the search for new, biologically active substances with anti-coronavirus activity continues to be a critical milestone for human health protection. In the framework of a complex engineering strategy, we cultivated the microalgal species Scenedesmus acutus in two different innovative types of flat-plate photobioreactors (PBR1 and K1) for CO₂ utilization and biomass production with special features. Isolated extracts from the microalgal biomass of each one were compared for their anti-coronavirus potential. The design of both PBRs allows a hydrodynamic regime to achieve best fluid flow distribution in their sections, therefore providing the optimal so-called flashing light effect. Of course, this is achieved under well-controlled operational conditions. A strain of beta coronavirus 1 (BCoV, bovine coronavirus) replicated in MDBK cells was used as an in vitro model for the evaluation of the antiviral activity of both extracts. The cell viability, number of survived BCoV particles, and cytopathic effect were evaluated after pre-incubation of the virus with the extracts or direct treatment. The extracts’ samples exhibited evident antiviral activity—extract 1 (from PBR1) in concentrations ≥ 200 µg/mL and extract 2 (from K1) in concentrations ≥150 µg/mL. The ddPCR result revealed significant diminishment of the BCoV particles in samples treated with higher concentrations of the extracts. The phytochemical analysis for certain main groups of compounds (flavonoids, polyphenols, carotenoids, and lipids) showed some differences for both extracts, which could be a possible reason for the observed difference in the antiviral activity. In conclusion, the innovative PBRs are a good platform for studying microalgal growth kinetics by applying different stress conditions from hydrodynamics and mass transfer subsystems. Both extracts showed promising potential for the isolation of metabolites with antiviral activity against BCoV and could be an object for future pharmacological investigations. Full article

(This article belongs to the Section Fermentation Process Design)

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15 pages, 430 KB

Open AccessReview

Pullulan Production from Lignocellulosic Plant Biomass or Starch-Containing Processing Coproduct Hydrolysates

by Thomas P. West

Fermentation 2026, 12(2), 84; https://doi.org/10.3390/fermentation12020084 - 3 Feb 2026

Abstract

The complex polysaccharide pullulan is characterized as a glucose-containing biopolymer that is both water-soluble and neutral in polarity. A variety of commercial applications exist for pullulan, including its utilization as a flocculant, a blood plasma substitute, a food additive, a dielectric material, an [...] Read more.

The complex polysaccharide pullulan is characterized as a glucose-containing biopolymer that is both water-soluble and neutral in polarity. A variety of commercial applications exist for pullulan, including its utilization as a flocculant, a blood plasma substitute, a food additive, a dielectric material, an adhesive, or a packaging film. The fungus Aureobasidium pullulans has used several hydrolysates derived from plant biomass or starch-containing processing coproducts to support polysaccharide production. These include various plant biomass or processing coproduct streams such as lignocellulosic-containing peat, prairie grass, stalks, hulls, straw, shells, and pods or starch-containing coproducts from the processing of corn, rice, jackfruit seeds, palm kernels, cassava, and potatoes. The pullulan concentration produced by A. pullulans and the pullulan content of the polysaccharide depend on the plant hydrolysate carbon content and the strain used. If a lower-cost culture medium for fungal pullulan production were to be developed, a more economical approach to synthesizing commercial pullulan would be the utilization of plant-derived hydrolysates. This review examines the ability of selected hydrolysates of lignocellulosic plant biomass or plant-derived starch-containing processing coproducts to support A. pullulans polysaccharide synthesis in order to identify those substrates with the greatest potential for reducing the cost of commercial pullulan. Full article

(This article belongs to the Special Issue Lignocellulosic Biomass Valorisation, 2nd Edition)

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15 pages, 2451 KB

Open AccessArticle

Impact of Freeze-Drying on the Viability and Microbial Community Structure of Traditional Mexican Pulque

by Mayrene Sarai Flores Montesinos, Fernando Astudillo-Melgar, Francisco Bolívar and Adelfo Escalante

Fermentation 2026, 12(2), 83; https://doi.org/10.3390/fermentation12020083 - 3 Feb 2026

Abstract

Pulque is a traditional Mexican fermented beverage produced by the spontaneous fermentation of the sap (aguamiel) produced by several Agave (maguey) species. Pulque fermentation starts with the addition of freshly collected aguamiel (harvested twice daily) into a traditional container known as the tinacal, [...] Read more.

Pulque is a traditional Mexican fermented beverage produced by the spontaneous fermentation of the sap (aguamiel) produced by several Agave (maguey) species. Pulque fermentation starts with the addition of freshly collected aguamiel (harvested twice daily) into a traditional container known as the tinacal, which contains previously fermented pulque serving as a microbial inoculum; the native microbiota associated with both the aguamiel and the inoculum ferments the available sugars, driving the development of the beverage’s characteristic sensorial properties. However, the preservation of its complex microbiota for research, fermentation standardization, and long-term conservation has not been systematically evaluated. In this study, we assessed the impact of freeze-drying on the viability, taxonomic composition, and diversity of the bacterial and yeast communities of pulque across five independent batches. Viable counts revealed no systematic loss of cultivable populations across major guilds. High-throughput sequencing of the V3-V4 16S rDNA and ITS1 regions demonstrated that the global taxonomic structure of pulque is preserved mainly after freeze-drying, with dominant genera, including Lactobacillus, Acetobacter, Zymomonas, Lactococcus, Saccharomyces, and Kazachstania, remaining stable. A modest decrease in richness, without major shifts in community architecture, was observed among minor yeasts, indicating that freeze-drying effectively preserves the core microbiota of pulque. Moreover, preserving pulque biomass safeguards the microbial dimension of this ancestral biocultural resource while enabling future efforts to standardize fermentation and establish microbial biobanks. Full article

(This article belongs to the Special Issue Starter Advances in Beverage and Dairy Fermentation)

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19 pages, 2236 KB

Open AccessReview

Extracellular Polymeric Substance Production in Rhodococcus: Advances and Perspectives

by Mariana P. Lanfranconi, Roxana A. Silva, Natalia E. Sandoval, José Sebastián Dávila Costa and Héctor M. Alvarez

Fermentation 2026, 12(2), 82; https://doi.org/10.3390/fermentation12020082 - 2 Feb 2026

Abstract

The genus Rhodococcus is relevant for its biosynthetic capabilities and metabolic versatility, resulting in the production of different metabolites to adapt to harsh environmental conditions. Exopolysaccharides are secreted by different members of Rhodococcus and have many biotechnological applications. Their use benefits different industries [...] Read more.

The genus Rhodococcus is relevant for its biosynthetic capabilities and metabolic versatility, resulting in the production of different metabolites to adapt to harsh environmental conditions. Exopolysaccharides are secreted by different members of Rhodococcus and have many biotechnological applications. Their use benefits different industries such as environmental remediation, medicine, pharmaceuticals, and food, among others, that appear in existing literature. This study presents the advances, weaknesses, and future directions in the production of this biopolymer by Rhodococcus. It also provides an overview of their taxonomic distribution within the genus, their composition, structures, yield, and the underexplored genes and possible mechanisms involved in the synthesis of extracellular polymeric substances. By combining past and current research with future directions on production in Rhodococcus, this work aims to present this genus as a serious alternative for obtaining these unique natural polymers. Full article

(This article belongs to the Special Issue Dissecting Actinobacteria: From Ecology and Biotechnological Value to Synthetic Biology)

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19 pages, 4137 KB

Open AccessArticle

Investigation of Nitrate Respiration in Cupriavidus necator for Application in Life Support System

by Pierre Joris, Eric Lombard, Alexis Paillet, Gregory Navarro, Stephane E. Guillouet and Nathalie Gorret

Fermentation 2026, 12(2), 81; https://doi.org/10.3390/fermentation12020081 - 2 Feb 2026

Abstract

Cupriavidus necator is a well-studied microorganism with potential application in bioregenerative life support systems for single-cell protein and bioplastic production. Most studies have been carried out in autotrophy or heterotrophy, requiring O₂ as the final electron acceptor. In the context of inhabited [...] Read more.

Cupriavidus necator is a well-studied microorganism with potential application in bioregenerative life support systems for single-cell protein and bioplastic production. Most studies have been carried out in autotrophy or heterotrophy, requiring O₂ as the final electron acceptor. In the context of inhabited missions, access to O₂ will primarily be limited to the crew. In this study, we investigated the capacity of C. necator to carry out nitrate respiration as a strategy to limit oxygen supply to the cultures by providing nitrate from another compartment of the Bioregenerative Life Support System (BLSS). Batch bioreactor experiments were carried out to determine the best conditions for nitrate utilization in terms of pH and aeration. Continuous cultures were then performed under two carbon sources (glucose vs. acetic acid) and two substrate limitations (nitrate vs. carbon). The optimal conditions were found to be pH 7.5 under anaerobiosis. They were applied in chemostats, where three steady-states were obtained at a low dilution rate. In all cases, the biomass consisted of a mixture of protein (from 29 ± 1% Cell Dry Weight (CDW) to 39 ± 2% CDW) and polyhydroxybutyrate (from 45 ± 2% CDW to 57 ± 3% CDW), which was found to be a key component for nitrate respiration metabolism. Microaerobic conditions were also tested in batch culture, reporting for the first time aerobic nitrate respiration in C. necator. Under these conditions, growth parameters improved during the nitrate phase; however, the specific growth rate during the nitrite phase was lower than that observed under strictly anaerobic conditions. Full article

(This article belongs to the Section Fermentation Process Design)

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20 pages, 1929 KB

Open AccessArticle

Fermentation Unlocks the Functional Role of Amaranth in Modulating Wheat/Amaranth Sourdough Microbiota and Inhibiting Yeast Growth of Refrigerated Doughs

by Carolina Dardis, Emiliano Bilbao, María Cristina Añón and Analía G. Abraham

Fermentation 2026, 12(2), 80; https://doi.org/10.3390/fermentation12020080 - 2 Feb 2026

Abstract

This study focuses on the development of refrigerated doughs without chemical preservatives to obtain a clean-label product. Sourdough-based strategies were applied to replace conventional preservatives, using both spontaneous flour fermentation and a defined starter culture of Lactiplantibacillus plantarum CIDCA 8327. In parallel, a [...] Read more.

This study focuses on the development of refrigerated doughs without chemical preservatives to obtain a clean-label product. Sourdough-based strategies were applied to replace conventional preservatives, using both spontaneous flour fermentation and a defined starter culture of Lactiplantibacillus plantarum CIDCA 8327. In parallel, a partial substitution of wheat flour with 7% amaranth flour was evaluated. To monitor fermentation, pH, titratable acidity, and viable microorganism counts were determined in the sourdoughs, along with culture-independent analyses of microbial communities in two independent spontaneously fermented trials. Dough discs prepared from these sourdoughs were analyzed for pH, titratable acidity, and viable microorganisms, and shelf life was determined based on the appearance of visible mould during refrigerated storage. No substantial differences were observed in the physicochemical parameters of the sourdoughs; however, significant differences in microbial communities were detected, influenced by both amaranth addition and wheat flour batch variability. Dough discs prepared with amaranth flour and spontaneous fermentation showed an extended shelf life and lower mould and yeast counts during refrigerated storage. The use of the starter increased shelf life compared to non-fermented doughs but was less effective than spontaneous sourdough with amaranth. Overall, these results highlight the potential of sourdough technology and amaranth flour for developing clean-label refrigerated products. Full article

(This article belongs to the Special Issue Fermented Cereals and Legumes: Innovation for the Development and Characterization of Functional Foods)

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20 pages, 1582 KB

Open AccessArticle

Functional Differentiation and Structural Disruption of Agave tequilana Bagasse by Lignocellulolytic Fungi Under Sterile and Non-Sterile Substrate Conditions

by Luis Ángel Alcalán-López, Marcos Alfonso Lastiri-Hernández, Dioselina Álvarez-Bernal, Eloy Conde-Barajas and María de la Luz Xochilt Negrete-Rodríguez

Fermentation 2026, 12(2), 79; https://doi.org/10.3390/fermentation12020079 - 2 Feb 2026

Abstract

Agave bagasse is a lignocellulosic residue generated after the extraction of fermentable sugars from agave hearts during tequila production. More than 0.5 million tons are generated annually, accumulating on a massive scale and posing a serious environmental challenge. In this regard, the objective [...] Read more.

Agave bagasse is a lignocellulosic residue generated after the extraction of fermentable sugars from agave hearts during tequila production. More than 0.5 million tons are generated annually, accumulating on a massive scale and posing a serious environmental challenge. In this regard, the objective of this study was to evaluate the degradative capacity of Trametes versicolor (Tv), Trametes hirsuta (Th), Irpex lacteus (Il), and Schizophyllum commune (Sc) on Agave tequilana Weber variety azul bagasse through the analysis of total sugars, cellulose, hemicellulose, and lignin reduction in a solid-static treatment. Under sterile conditions, Tv reduced total sugars by 95.0%, Th by 89.5%, Il by 91.8%, and Sc by 74.6%; whereas under non-sterile conditions, reductions were 81.6%, 71.4%, 84.9%, and 64.7%, respectively. Regarding structural fractions under sterile conditions, Tv showed reductions of 67.8% in cellulose, 61.9% in hemicellulose, and 68.8% in lignin. Th achieved 62.8%, 58.8%, and 66.1%, respectively; Il exhibited the highest values, with 72.9%, 66.9%, and 74.6%; while Sc recorded 55.9%, 44.2%, and 61.0%. In contrast, reductions were lower under non-sterile conditions: Tv recorded 57.8%, 34.2%, and 62.2%; Th, 53.9%, 32.1%, and 59.6%; Il, 58.8%, 47.1%, and 64.7%; and Sc, 49.9%, 30.0%, and 56.5%. Overall, sterile substrate conditions maximized lignocellulosic degradation; however, the sustained activity observed under non-sterile conditions demonstrates that effective biological pretreatment can be achieved without sterilization, which is more relevant for large-scale solid-state fermentation. The results demonstrate that T. versicolor and I. lacteus possess high potential as biological pretreatment agents by accelerating the depolymerization of the lignocellulosic matrix. This effect could reduce composting times and enable applications that favor its inclusion in circular economy frameworks. Full article

(This article belongs to the Section Industrial Fermentation)

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Graphical abstract

14 pages, 1973 KB

Open AccessArticle

Novel Silicone–Polyol Antifoam Emulsions: Impact on Foam Control and Physiology of Diverse Microbial Cultures

by Mikhail Frolov, Trofim A. Lozhkarev, Elmira A. Vasilieva, Leysan A. Vasileva, Almaz A. Zagidullin, Lucia Ya. Zakharova, Galim A. Kungurov, Natalia V. Trachtmann and Shamil Z. Validov

Fermentation 2026, 12(2), 78; https://doi.org/10.3390/fermentation12020078 - 1 Feb 2026

Abstract

The selection of an optimal antifoam is critical for efficient fermentation, as industrial agents often have detrimental side effects like growth inhibition, while some can enhance productivity. We studied the efficacy of novel silicone–polyol antifoam emulsions for use in fermentation as defoamers. Except [...] Read more.

The selection of an optimal antifoam is critical for efficient fermentation, as industrial agents often have detrimental side effects like growth inhibition, while some can enhance productivity. We studied the efficacy of novel silicone–polyol antifoam emulsions for use in fermentation as defoamers. Except for agent 3L10, all antifoams tested did not show inhibition on six bacterial and one fungal culture. Interestingly, agent 3L10 strongly inhibited Gram-positive bacteria (especially Corynebacterium glutamicum) but not Gram-negative strains. A comprehensive evaluation protocol—combining chemical design, cytotoxicity screening across diverse microorganisms, the determination of minimum effective concentrations (MECs), and validation in model bioreactor fermentations—was established. Through this process, 6T80 was identified as a promising antifoam agent for fermentation. It exhibited a low MEC, high emulsion stability, and no cytotoxicity and did not impair growth or recombinant protein production in Bacillus subtilis or Pseudomonas putida fermentations. This study concludes that agent 6T80 is suitable for further application in processes involving Gram-negative and certain Gram-positive hosts. The developed methodology enables the targeted selection of highly efficient and biocompatible antifoams for specific biotechnological processes. Full article

(This article belongs to the Section Fermentation Process Design)

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25 pages, 5919 KB

Open AccessArticle

Laser-Based Online OD Measurement of 48 Parallel Stirred Tank Bioreactors Enables Fast Growth Improvement of Gluconobacter oxydans

by Zeynep Güreli, Emmeran Bieringer, Elif Ilgim, Tanja Wolf, Kai Kress and Dirk Weuster-Botz

Fermentation 2026, 12(2), 77; https://doi.org/10.3390/fermentation12020077 - 1 Feb 2026

Abstract

A parallel-stirred tank bioreactor system on a 10 mL-scale automated with a liquid handling station introduces significant benefits in bioprocess analysis and design regarding preserving time, cost, and workload, thereby enabling quick generation of bioprocess results that can be easily scaled up. Although [...] Read more.

A parallel-stirred tank bioreactor system on a 10 mL-scale automated with a liquid handling station introduces significant benefits in bioprocess analysis and design regarding preserving time, cost, and workload, thereby enabling quick generation of bioprocess results that can be easily scaled up. Although up-to-date approaches enable the online analysis of individual reactors for pH, dissolved oxygen (DO), and optical density (OD), the automated calibration of a new online laser-based infrared OD sensor device and noise reduction are still required. Among the extensive research on the full-data smoothing tools, the Savitzky–Golay (Savgol) filter was determined as the most effective one. Scattered and transmitted online light values were successfully aligned with the reference at-line OD values measured at 600 nm by the liquid handler with a step time of a few hours. The growth of an engineered Gluconobacter oxydans designed for specific whole-cell oxidations has been investigated in two parallel batch process setups with varied sugar types at varying sugar concentrations, combinations of sugars, and altered concentrations of complex media. Simulation of real-time smoothing was applied with a Kalman filter. Rapid adaptation was observed within a few upcoming data points by altering the parameters for the estimation of the noise in the signal. For almost all tested reaction conditions, a successful alignment of the simulation of real-time smoothed online OD with at-line values was achieved. The best growth condition was determined in the presence of 120 g L⁻¹ glucose and 30 g L⁻¹ fructose with the tripled peptone concentration. Under these conditions, OD₆₀₀ increased by 109%, from 2.1 to 4.4, compared to the reference process. Full article

(This article belongs to the Special Issue The Future of Fermentation Technology in the Biorefining Process: 3rd Edition)

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