Fermentation

15 pages, 367 KiB

Open AccessArticle

The Effects of Solid-State Fermentation by Aspergillus spp. on the Nutritional Profile of Selected Agro-Industrial by-Products as Potential Feedstuffs for Weaner Rabbits

by Adedoyin Titi Amos, Damilola Uthman Kareem, Tolulope Modupe Adeleye, Emmanuel Abiodun Adeyeye, Munirat Olaide Abatan, Olusola Sarah Ayorinde, Esther Oluwasayo Adeboye, Maicon Sbardella, Adeboye Olusesan Fafiolu, Abimbola Oladele Oso and Olusegun Mark Obafemi Idowu

Fermentation 2025, 11(6), 356; https://doi.org/10.3390/fermentation11060356 - 19 Jun 2025

Abstract

This study evaluates the effects of solid-state fermentation inoculated with Aspergillus spp. on the nutritional profile of selected agro-industrial by-products (AIBPs: cowpea shell, groundnut shell, soybean hull, and maize shaft). These AIBPs were assessed as potential feedstuffs in weaner rabbit diets, which often [...] Read more.

This study evaluates the effects of solid-state fermentation inoculated with Aspergillus spp. on the nutritional profile of selected agro-industrial by-products (AIBPs: cowpea shell, groundnut shell, soybean hull, and maize shaft). These AIBPs were assessed as potential feedstuffs in weaner rabbit diets, which often exhibit digestive disorders when introduced to highly lignified feed ingredients. The AIBPs were milled to a particle size of 2 mm, sterilized, and subjected to fermentation with Aspergillus spp. under microaerophilic conditions at 28 ± 2 °C for 10 days. Samples (four replicates per treatment) were analyzed for chemical constituents (mineral and proximate composition, anti-nutritional factors, and fibre fractions) before and after fermentation. Digestible energy and digestibility coefficient of gross energy were calculated. Data were subjected to two-way analysis of variance (ANOVA). There was an increase (p < 0.05) in mineral profile, proximate composition, digestible energy, digestibility coefficient of gross energy, and dry matter, with a reduction (p < 0.05) in crude fibre, fibre fractions, and anti-nutritional factors. It was concluded that fermentation with Aspergillus spp. improved the nutritional value of the selected agro-industrial by-products. Therefore, fermented materials possess a better nutritional profile to be used in feeding programs for weaner rabbits. This will ensure sustainable animal production and add value to agricultural waste, which would otherwise constitute an environmental nuisance. Full article

(This article belongs to the Special Issue Exploring Fermentation Strategies for the Valorization of Food By-Products and Their Bioactive Potential)

► Show Figures

Figure 1

23 pages, 1683 KiB

Open AccessArticle

Evaluation of the Potential of Corynebacterium glutamicum ATCC 21492 for L-Lysine Production Using Glucose Derived from Textile Waste

by Paola Rodríguez Bello, Anahí Ginestá Anzola, Alberto Ortiz Becerril and David Fernández Gutiérrez

Fermentation 2025, 11(6), 355; https://doi.org/10.3390/fermentation11060355 - 18 Jun 2025

Abstract

The textile industry generates millions of tons of waste annually, posing significant environmental challenges. Addressing this issue, our study explores a sustainable biotechnological approach to convert cotton textile waste into valuable bioproducts. We evaluated the potential of Corynebacterium glutamicum ATCC 21492 for the [...] Read more.

The textile industry generates millions of tons of waste annually, posing significant environmental challenges. Addressing this issue, our study explores a sustainable biotechnological approach to convert cotton textile waste into valuable bioproducts. We evaluated the potential of Corynebacterium glutamicum ATCC 21492 for the production of L-lysine and other amino acids using glucose derived from cotton textile waste. Two experimental strategies were implemented: Sequential Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF). In SHF, optimization of initial glucose concentration, temperature, and inoculum size led to the highest L-lysine concentration of 2.38 g/L under conditions of 45 g/L glucose, 35 °C, and 2% inoculum. The production of L-lysine, along with varying proportions of other amino acids such as alanine, threonine, methionine, and leucine, was significantly influenced by these parameters. In SSF, the highest L-lysine yield of 3.10 mg/g untreated cotton was achieved at 14% cotton loading, 7% enzyme dose, 35 °C, and 10% inoculum concentration, corresponding to an L-lysine concentration of 0.5 g/L. This reduced concentration, compared to SHF, is primarily attributed to limitations in cotton hydrolysis under the studied conditions. Nevertheless, C. glutamicum utilized alternative carbon sources present in the culture medium, leading to a diversified amino acid profile in the final product. These findings support the feasibility of textile waste bioconversion using C. glutamicum and highlight its potential as a sustainable platform for amino acid production, aligning with circular economy principles and contributing to the reduction of the textile industry’s environmental impact. Full article

(This article belongs to the Special Issue Lignocellulosic Biomass Valorization)

22 pages, 1687 KiB

Open AccessArticle

Enhancement of Lipid Production in Rhodosporidium toruloides: Designing Feeding Strategies Through Dynamic Flux Balance Analysis

by María Teresita Castañeda, Sebastián Nuñez, Martín Jamilis and Hernán De Battista

Fermentation 2025, 11(6), 354; https://doi.org/10.3390/fermentation11060354 - 18 Jun 2025

Abstract

Fed-batch cultivation is a widely used strategy for microbial lipid production, offering flexibility in nutrient control and the potential for high lipid productivity. However, optimizing feeding strategies remains a complex challenge, as it depends on multiple factors, including strain-specific metabolism and process limitations. [...] Read more.

Fed-batch cultivation is a widely used strategy for microbial lipid production, offering flexibility in nutrient control and the potential for high lipid productivity. However, optimizing feeding strategies remains a complex challenge, as it depends on multiple factors, including strain-specific metabolism and process limitations. In this study, we developed a computational framework based on dynamic flux balance analysis and small-scale metabolic models to evaluate and optimize lipid production in Rhodosporidium toruloides strains. We proposed equations to estimate both the carbon and energy source mass feed rate (

F_{i n} \cdot s_{r}

) and its concentration in the feed (

s_{r}

) based on lipid accumulation targets, and defined minimum feeding flow rate (

F_{i n}

) according to process duration. We then assessed the impact of these parameters on commonly used bioprocess metrics—lipid yield, titer, productivity, and intracellular accumulation—across wild-type and engineered strains. Our results showed that the selection of

F_{i n} \cdot s_{r}

was strongly strain-dependent and significantly influenced strain performance. Moreover, for a given

F_{i n} \cdot s_{r}

, the specific values of

s_{r}

, and the resulting

F_{i n}

, had distinct and non-equivalent effects on performance metrics. This methodology enables the rational pre-selection of feeding strategies and strains, improving resource efficiency and reducing the probability of failed experiments. Full article

(This article belongs to the Special Issue Optimization and Analysis of the Fermentation Process for Microbial Products: 2nd Edition)

► Show Figures

Figure 1

28 pages, 2053 KiB

Open AccessSystematic Review

Benefits of Kombucha Consumption: A Systematic Review of Clinical Trials Focused on Microbiota and Metabolic Health

by Gabriela Macedo Fraiz, Dandara Baia Bonifácio, Rayanne Santos de Paulo, Carolynne Martins Teixeira, Hércia Stampini Duarte Martino, Frederico Augusto Ribeiro de Barros, Fermín I. Milagro and Josefina Bressan

Fermentation 2025, 11(6), 353; https://doi.org/10.3390/fermentation11060353 - 17 Jun 2025

Abstract

Background: Fermented foods rich in bioactive compounds have been proposed as potential strategy to combat non-communicable diseases. Among them is kombucha, a beverage fermented from sugared Camellia sinensis tea by a symbiotic culture of bacteria and yeasts (SCOBY). Recently, there has been an [...] Read more.

Background: Fermented foods rich in bioactive compounds have been proposed as potential strategy to combat non-communicable diseases. Among them is kombucha, a beverage fermented from sugared Camellia sinensis tea by a symbiotic culture of bacteria and yeasts (SCOBY). Recently, there has been an increased focus on assessing the actual effect of this beverage on human health. In this manner, this systematic review aimed to gather clinical evidence on the impact of kombucha consumption on human health. Methods: The databases Cochrane CENTRAL, MEDLINE/PubMed, and Embase^® were searched, and the risk of bias tool used was the Critical Appraisal Tools outlined in the Joanna Briggs Institute. This review followed the PRISMA guidelines and was registered on PROSPERO (CRD42024599464). Results: Eight clinical trials were included (two pre- and post-interventions and six randomized controlled trials) with durations ranging from 10 days to 10 weeks. Two studies reported beneficial effects of kombucha on gastrointestinal symptoms, such as reduced intensity of constipation-related complaints. Two trials observed changes in gut microbiota composition, including increased abundance in Bacteroidota, Akkermansiaceae, Saccharomyces, and Weizmannia coagulans, alongside reductions in Ruminococcus, Dorea, and Rhodotorula. Moreover, five clinical trials evaluated glucose metabolism, evidencing inconsistent results, and other studies identified improvements in salivary microbiota composition and serum metabolomic profile. Conclusion: These findings suggest that kombucha consumption may provide health benefits, particularly in alleviating gastrointestinal symptoms, and demonstrates a modest capacity for modulating gut and salivary microbiota, as well as metabolomic profiles. Although the results are promising, the heterogeneity of the studies and the limited number of available clinical trials highlight the need for further robust research to confirm these effects. Full article

(This article belongs to the Special Issue Fermentation and Bioactive Potential of Kombucha and Bee-Derived Compounds for Health and Wellness)

► Show Figures

Figure 1

17 pages, 4376 KiB

Open AccessArticle

Enhanced Biogas Production from Glucose and Glycerol by Artificial Consortia of Anaerobic Sludge with Immobilized Yeast

by Nikolay Stepanov, Olga Senko, Aysel Aslanli, Olga Maslova and Elena Efremenko

Fermentation 2025, 11(6), 352; https://doi.org/10.3390/fermentation11060352 - 17 Jun 2025

Abstract

Today, there is considerable interest in creating artificial microbial consortia to solve various biotechnological problems. The use of such consortia allows for the improvement of process indicators, namely, increasing the rate of accumulation of target products and enhancing the conversion efficiency of the [...] Read more.

Today, there is considerable interest in creating artificial microbial consortia to solve various biotechnological problems. The use of such consortia allows for the improvement of process indicators, namely, increasing the rate of accumulation of target products and enhancing the conversion efficiency of the original substrates. In this work, the prospects for creating artificial consortia based on anaerobic sludge (AS) with cells of different yeasts were confirmed to increase the efficiency of methanogenesis in glucose- and glycerol-containing media and obtain biogas with an increased methane content. Yeasts of the genera Saccharomyces, Candida, Kluyveromyces, and Pachysolen were used to create the artificial consortia. Their concentration in the biomass of consortium cells was 1.5%. Yeast cells were used in an immobilized form, which was obtained by incorporating cells into a cryogel of polyvinyl alcohol. The possibility of increasing the efficiency of methanogenesis by 1.5 times in relation to the control (AS without the addition of yeast cells) was demonstrated. Using a consortium composed of methanogenic sludge and yeast cells of the genus Pachysolen, known for their ability to convert glycerol into ethanol under aerobic conditions, the possibility of highly efficient anaerobic conversion of glycerol into biogas was shown for the first time. Analysis of the metabolic activity of the consortia not only for the main components of the gas phase (CH₄, CO₂, and H₂) and metabolites in the cell culture medium, but also for the concentration of intracellular adenosine triphosphate (ATP), controlled by the method of bioluminescent ATP-metry, showed a high level of functionality and thus, prospects for using such consortia in methanogenesis processes. The advantages and the prospect of using the developed consortia instead of individual AS for the treatment of methanogenic wastewater were confirmed during static tests conducted with several samples of real and model waste. Full article

(This article belongs to the Special Issue Anaerobic Digestion of Sewage Sludge: New Insights and Future Challenges)

► Show Figures

Graphical abstract

20 pages, 1206 KiB

Open AccessReview

Fungal Biomass Fermentation: Valorizing the Food Industry’s Waste

by Simas Borkertas, Jonas Viskelis, Pranas Viskelis, Paulina Streimikyte, Ugne Gasiunaite and Dalia Urbonaviciene

Fermentation 2025, 11(6), 351; https://doi.org/10.3390/fermentation11060351 - 16 Jun 2025

Abstract

Fungi, including filamentous organisms such as yeasts, play essential roles in various processes such as nutrient exchange in ecosystems, the cultivation of mushrooms, and solid-state fermentation (SSF). SSF involves microbial growth on solid substrates without free water, leading to the production of enzymes, [...] Read more.

Fungi, including filamentous organisms such as yeasts, play essential roles in various processes such as nutrient exchange in ecosystems, the cultivation of mushrooms, and solid-state fermentation (SSF). SSF involves microbial growth on solid substrates without free water, leading to the production of enzymes, bioactive compounds, and biofuels. This fermentation method offers advantages like lower production costs, reduced waste disposal issues, and the efficient utilization of agricultural residues and fruit and vegetable by-products. Filamentous fungi excel in SSF due to their enzyme secretion capacity and ability to produce valuable compounds. The process is influenced by biological, physico-chemical, and environmental factors, requiring careful optimization for optimal results. Fruit and vegetable by-products are increasingly recognized as valuable substrates for SSF, offering rich sources of bioactive compounds and high nutritional value. The optimization of SSF processes, compatibility with various substrates, and potential for producing diverse value-added products make SSF a promising method for sustainable resource utilization and enhanced product development. Future research should focus on improving process efficiency, expanding the substrate range, enhancing product quality and yield, and integrating SSF with other technologies for enhanced production capabilities. Full article

(This article belongs to the Section Industrial Fermentation)

► Show Figures

Figure 1

19 pages, 2028 KiB

Open AccessArticle

Characterization of a Vaginal Limosilactobacillus Strain Producing Anti-Virulence Postbiotics: A Potential Probiotic Candidate

by Tsvetelina Paunova-Krasteva, Petya D. Dimitrova, Dayana Borisova, Lili Dobreva, Nikoleta Atanasova and Svetla Danova

Fermentation 2025, 11(6), 350; https://doi.org/10.3390/fermentation11060350 - 16 Jun 2025

Abstract

The search for probiotics to help limit antibiotic resistance is a major scientific challenge. The exploration of Lactobacillus postbiotics represents a promising approach to prevent pathogen invasion. With this aim, Limosilactobacillus fermentum Lf53, with a broad-spectrum of antagonistic activity, was characterized as a [...] Read more.

The search for probiotics to help limit antibiotic resistance is a major scientific challenge. The exploration of Lactobacillus postbiotics represents a promising approach to prevent pathogen invasion. With this aim, Limosilactobacillus fermentum Lf53, with a broad-spectrum of antagonistic activity, was characterized as a candidate probiotic strain with promising transit tolerance and broad spectrum of activity. A study on growth and postbiotic production in modified MRS broth with different carbohydrates and its vegan variant was carried out. This study presents a comprehensive approach to characterizing the anti-virulence properties of postbiotics derived from Lf53. The promising antibacterial, antibiofilm, and anti-quorum sensing activities of the cell-free supernatants (CFS) were assessed as part of the probiotic’s barrier mechanisms. Biofilm inhibition of P. aeruginosa revealed remarkable suppressive effects exerted by the three tested postbiotics, two of which (nCFS and aCFS) exhibited over 50% inhibition and more than 60% for lysates. The postbiotics’ influence on the production of violacein and pyocyanin pigments of Chromobacterium violaceum and Pseudomonas aeruginosa, which are markers for quorum sensing, highlighted their potential in regulating pathogenic mechanisms. The Lf53 lysates showed the most significant inhibition of violacein production across multiple assays, showing 29.8% reduction. Regarding pyocyanin suppression, the postbiotics also demonstrated strong activity. These are the first reported data on complex postbiotics (metabiotics and parabiotics) demonstrating their potential as anti-virulence agents to help combat pathogens associated with antibiotic-resistant infections. Full article

(This article belongs to the Special Issue Lactic Acid Bacteria: Evaluation of Benefits on Human Health and Improvement of Food Safety)

► Show Figures

Figure 1

14 pages, 1642 KiB

Open AccessArticle

Composition Divergence and Synergistic Mechanisms in Microbial Communities During Multi-Varietal Wine Co-Fermentation

by Yuhan Zhang, Jiao Yang and Yuxi Yan

Fermentation 2025, 11(6), 349; https://doi.org/10.3390/fermentation11060349 - 16 Jun 2025

Abstract

The bacterial microbial community composition during wine fermentation is a key contributor to wine quality and flavor. However, studies on the regulatory effects of different grape varieties and co-fermentation processes on the microbial community structure and their synergistic mechanisms remain limited. In this [...] Read more.

The bacterial microbial community composition during wine fermentation is a key contributor to wine quality and flavor. However, studies on the regulatory effects of different grape varieties and co-fermentation processes on the microbial community structure and their synergistic mechanisms remain limited. In this study, Cabernet Sauvignon (CS) was subjected to single-variety fermentation and used as the base wine for co-fermentation with three other grape varieties—Marselan (CSMN), Merlot (CSMT), and Cabernet Gernischt (CSCG)—to systematically compare the differences in the microbial community composition and their effects on the production of metabolic compounds. The results showed that, compared with single-variety fermentation, co-fermentation significantly increased the α-diversity of microbial communities (the Shannon index increased) and exhibited significant differences in β-diversity (PERMANOVA analysis, R² = 0.421, p < 0.001). A neutral model analysis indicated that co-fermentation had a significant impact on microbial community assembly mechanisms, with the contribution of neutral processes to community assembly increasing from 45.5% (in the CSCG process) to 62.3% (in the CSMT process). A microbial co-occurrence network analysis revealed that co-fermentation enhanced the network complexity of microbial communities and strengthened the synergistic interactions between microbial taxa. A metabolic compound analysis revealed that co-fermentation significantly enhanced the production of key aroma compounds, resulting in increased concentrations of isoamyl acetate, ethyl hexanoate, linalool, and geraniol. These findings highlight the differences in microbial communities and their synergistic mechanisms among co-fermented grape varieties, providing theoretical guidance and practical insights for optimizing co-fermentation processes and improving wine quality. Full article

(This article belongs to the Section Microbial Metabolism, Physiology & Genetics)

► Show Figures

Figure 1

25 pages, 7385 KiB

Open AccessArticle

Anaerobic Digestion of Food Waste and Granular Inoculum: Study on Temperature Effect and Substrate-to-Inoculum Ratio on Biogas Production

by Madalina Ivanovici, Gabriela-Alina Dumitrel, Vasile Daniel Gherman, Teodor Todinca, Ana-Maria Pana and Valentin Laurentiu Ordodi

Fermentation 2025, 11(6), 348; https://doi.org/10.3390/fermentation11060348 - 15 Jun 2025

Abstract

The development of food waste anaerobic digestion (AD) is a contemporary research topic addressed in the scientific community to meet the requirements of food waste valorization and proper substrate configuration for an efficient AD process. In this study, multiple AD experiments were performed [...] Read more.

The development of food waste anaerobic digestion (AD) is a contemporary research topic addressed in the scientific community to meet the requirements of food waste valorization and proper substrate configuration for an efficient AD process. In this study, multiple AD experiments were performed on food waste together with industrial inoculum using laboratory-scale bioreactors. Food waste consisted mainly of fruits and vegetables (80.9%) and boiled rice (19.1%). The effect of operating temperature (33 °C, 37 °C, 41 °C, 45 °C) and the ratio between food waste mixture and inoculum-FIR (1:1, 3:2 and 2:1, w/w) on the production and composition of biogas, and the conversion yield for CH₄ and organic carbon, were investigated. The best results were obtained at an FIR of 2:1 and a temperature of 37 °C, with a total biogas production of 468.59 NL h⁻¹ kg⁻¹_VSadded (51% v/v CH₄ conc.) and a conversion yield of 36.42% for CH₄. A modified Gompertz model was applied on the accumulated CH₄ and biogas to evaluate the process performance. The model parameters were investigated in conjunction with the physico-chemical characteristics of the substrate, inoculum taxonomic profile, pH measurements, and TG-DTA analysis. The conducted analyses emphasized the susceptibility of the selected substrate towards easy degradation and improved biotransformation reactions when temperature and FIR were increased. Full article

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

► Show Figures

Figure 1

34 pages, 1585 KiB

Open AccessReview

Biological Potential of Extremophilic Filamentous Fungi for the Production of New Compounds with Antimicrobial Effect

by Vladislava Dishliyska, Jeny Miteva-Staleva, Yana Gocheva, Galina Stoyancheva, Lyudmila Yovchevska, Radoslav Abrashev, Boryana Spasova, Maria Angelova and Ekaterina Krumova

Fermentation 2025, 11(6), 347; https://doi.org/10.3390/fermentation11060347 - 14 Jun 2025

Abstract

Antimicrobial resistance represents one of the most critical public health challenges of the 21st century. The emergence of multidrug resistance (MDR) in bacterial and fungal pathogens to diverse chemical agents severely impedes the effective treatment of diseases such as cancer and systemic infections. [...] Read more.

Antimicrobial resistance represents one of the most critical public health challenges of the 21st century. The emergence of multidrug resistance (MDR) in bacterial and fungal pathogens to diverse chemical agents severely impedes the effective treatment of diseases such as cancer and systemic infections. The rapid escalation of microbial resistance underscores the urgent need for the discovery of novel antimicrobial agents and innovative approaches to drug development. In both clinical and industrial contexts, the identification of new antibiotics and antifungals remains pivotal for pathogen control. Current research efforts focus on the development of alternative formulations that offer high efficacy, reduced resistance potential, minimal side effects, and synergistic interactions, particularly those derived from natural sources. Filamentous fungi originating from extreme environments have evolved to thrive under harsh conditions, making them promising reservoirs of bioactive metabolites with unique structural and functional properties. These fungi exhibit potent antimicrobial activity through diverse mechanisms that disrupt essential cellular processes in pathogens. Despite their remarkable potential, the bioprospecting of extremophilic filamentous fungi for drug development remains underexplored. This highlights the necessity for expanded research into the efficacy and safety of their derived compounds. This review aims to emphasize the capacity of extremophilic fungi to produce antimicrobial agents, elucidate resistance mechanisms, characterize fungal bioactive extracts, and analyze their molecular actions in the context of their extreme ecological niches. Full article

(This article belongs to the Special Issue 10th Anniversary of Fermentation: Feature Papers in Section “Microbial Metabolism, Physiology & Genetics”)

► Show Figures

Figure 1

45 pages, 2757 KiB

Open AccessReview

Nutritional Enhancement of Plant-Based Fermented Foods: Microbial Innovations for a Sustainable Future

by Sunny Dhiman, Sukhminderjit Kaur, Babita Thakur, Pankaj Singh and Manikant Tripathi

Fermentation 2025, 11(6), 346; https://doi.org/10.3390/fermentation11060346 - 14 Jun 2025

Abstract

The rising demand for sustainable, nutritious, and functional food options has fueled growing interest in plant-based fermented foods. These products offer enhanced sensory, functional, and health-promoting properties, largely driven by microbial activity during fermentation. This review examines recent advances in microbial biotechnology—including the [...] Read more.

The rising demand for sustainable, nutritious, and functional food options has fueled growing interest in plant-based fermented foods. These products offer enhanced sensory, functional, and health-promoting properties, largely driven by microbial activity during fermentation. This review examines recent advances in microbial biotechnology—including the use of novel starter cultures, strain engineering, CRISPR-based genome editing, and precision fermentation that are reshaping the nutritional landscape of plant-based fermented foods. Key benefits such as improved protein digestibility, bioactive compound synthesis, antinutrient reduction, and micronutrient bioavailability are explored. Additionally, the review highlights the potential of microbial innovations to enhance sustainability, address global nutrition challenges, and improve consumer acceptance through better sensory quality. It also discusses challenges related to regulatory frameworks, scalability, and consumer perception. This review aims to provide a comprehensive understanding of how microbial processes can optimize the nutritional and functional value of plant-based fermented foods in alignment with future food system goals. Full article

(This article belongs to the Special Issue Recent Advances in Microbial Fermentation in Foods and Beverages)

► Show Figures

Figure 1

18 pages, 2523 KiB

Open AccessArticle

CRISPRa-Mediated Triple-Gene Activation of ARO10, ARO80, and ADH2 for Enhancing 2-Phenylethanol Biosynthesis via the Ehrlich Pathway in Saccharomyces cerevisiae

by Zijing Zhu, Shuaihu Fang, Pingping Huang, Dianqiang Luo and Xiaobao Qi

Fermentation 2025, 11(6), 345; https://doi.org/10.3390/fermentation11060345 - 12 Jun 2025

Abstract

2-phenylethanol (2-PE), a rose-like fragrance compound, is widely used in the food industry. Conventional chemical synthesis of 2-PE faces significant challenges due to environmental concerns and consumer preferences; thus, using Saccharomyces cerevisiae (S. cerevisiae) for 2-PE biosynthesis has become a preferable [...] Read more.

2-phenylethanol (2-PE), a rose-like fragrance compound, is widely used in the food industry. Conventional chemical synthesis of 2-PE faces significant challenges due to environmental concerns and consumer preferences; thus, using Saccharomyces cerevisiae (S. cerevisiae) for 2-PE biosynthesis has become a preferable option. This study aimed to develop a CRISPR activation (CRISPRa)-mediated S. cerevisiae engineered strain for efficient 2-PE biosynthesis by activating Ehrlich pathway key genes ARO10, ARO80, and ADH2. Three guide sequences (GSs) were designed for each gene ARO10, ARO80, and ADH2, and nine single-gene CRISPRa strains were constructed. Gene expression levels, 2-PE concentrations, and cell density were quantified using quantitative real-time PCR (qPCR), high-performance liquid chromatography (HPLC), and OD₆₀₀ measurement, respectively. The optimal GSs of ARO10, ARO80, and ADH2 were selected based on 2-PE concentrations of corresponding strains. The triple-gene CRISPRa strain INVScI-ARO10-ARO80-ADH2 achieved a 214.04 mg/L 2-PE titer after 48 h, representing a 77.62% increase over the control with no significant effect on cell growth. These findings demonstrate that CRISPRa-mediated multi-gene activation constitutes a robust strategy for engineering high-performance 2-PE production systems in S. cerevisiae. Full article

(This article belongs to the Section Microbial Metabolism, Physiology & Genetics)

► Show Figures

Figure 1

20 pages, 2901 KiB

Open AccessArticle

Ethanol and Xylitol Co-Production by Clavispora lusitaniae Growing on Saccharified Sugar Cane Bagasse in Anaerobic/Microaerobic Conditions

by David Guzmán-Hernández, Ana C. Ramos-Valdivia, Héctor Mario Poggi-Varaldo, Josefina Barrera-Cortés, Eliseo Cristiani-Urbina and Teresa Ponce-Noyola

Fermentation 2025, 11(6), 344; https://doi.org/10.3390/fermentation11060344 - 12 Jun 2025

Abstract

Ethanol and xylitol are valuable bioproducts synthesized by non-conventional yeasts from lignocellulosic sugars. However, their biosynthesis requires distinct cultivation conditions. This study evaluated the production of ethanol and xylitol by Clavispora lusitaniae using saccharified sugarcane bagasse (SSCB) under three aeration conditions: microaerobic (C1), [...] Read more.

Ethanol and xylitol are valuable bioproducts synthesized by non-conventional yeasts from lignocellulosic sugars. However, their biosynthesis requires distinct cultivation conditions. This study evaluated the production of ethanol and xylitol by Clavispora lusitaniae using saccharified sugarcane bagasse (SSCB) under three aeration conditions: microaerobic (C1), anaerobic (C2), and a combination of anaerobic followed by a microaerobic phase (C3). Ethanol production was maximum under anaerobic conditions (C2), followed by combined anaerobic–microaerobic conditions (C3). Meanwhile, xylitol production was most efficient under microaerobic conditions (C1). Notably, anaerobic conditions were ineffective for xylitol production. Enzyme activities of xylose reductase (XR) and xylitol dehydrogenase (XDH), key enzymes in xylose metabolism, were highest under microaerobic conditions with activities of 2.88 U/mg and 1.72 U/mg, respectively, after 48 h of culture. Gene expression analysis of XYL1 and XYL2 correlated with the corresponding enzyme activities (XR) and (XDH) with increased levels of 32.38 and 7.88 fold, respectively, compared to the control in C1. These findings suggest that C. lusitaniae co-produces ethanol efficiently under anaerobic conditions, while xylitol biosynthesis is optimized under microaerobic conditions when using xylose-rich saccharified lignocellulosic substrates. Full article

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

► Show Figures

Graphical abstract

12 pages, 528 KiB

Open AccessArticle

Probiotic Potential of Lactic Acid Bacteria Strains Isolated from Artisanal Cheeses: Impact on Listeria monocytogenes Infection

by Carla Burgos, Constanza Melian, Lucía M. Mendoza, Susana Salva and Patricia Castellano

Fermentation 2025, 11(6), 343; https://doi.org/10.3390/fermentation11060343 - 12 Jun 2025

Abstract

Listeriosis is a disease associated with the consumption of food contaminated with Listeria monocytogenes. Probiotic lactic acid bacteria (LAB) or their postbiotics have been of interest for their anti-listerial effect. This study focused on isolating LAB from artisanal cheeses and characterizing their [...] Read more.

Listeriosis is a disease associated with the consumption of food contaminated with Listeria monocytogenes. Probiotic lactic acid bacteria (LAB) or their postbiotics have been of interest for their anti-listerial effect. This study focused on isolating LAB from artisanal cheeses and characterizing their potential as probiotics. Twelve LAB isolates exhibiting typical LAB traits were evaluated for their ability to survive in simulated gastric juice, hydrolyze bile salts, auto-aggregate, hydrophobicity, and antagonistic activity against L. monocytogenes. The four most promising LAB strains demonstrated anti-listerial probiotic potential and were identified as Latilactobacillus (Lat.) curvatus SC076 and Lactiplantibacillus (Lact.) paraplantarum SC291, SC093, and SC425. The antimicrobial activity of these strains was mainly attributed to bacteriocin-like substances and organic acids. While three Lact. paraplantarum strains were resistant to ampicillin, Lat. curvatus was sensitive to all tested antibiotics. All selected strains exhibited no hemolytic, gelatinase, and lecithinase activity. Exposure to LAB supernatants resulted in a significant reduction in the adhesion and intracellular count of L. monocytogenes in Caco-2 cells, with Lat. curvatus SC076 showing the most significant effect. Based on its probiotic characteristics, Lat. curvatus SC076 is a promising candidate for functional foods, pending further in vivo studies to assess its potential in the food industry. Full article

(This article belongs to the Special Issue Lactic Acid Bacteria: Evaluation of Benefits on Human Health and Improvement of Food Safety)

► Show Figures

Graphical abstract

14 pages, 1350 KiB

Open AccessArticle

Lactic Acid Bacteria as Probiotics Improve Bioactive Compounds in Radix Angelica gigas (Danggui) via Solid-State Fermentation

by Jeong Heo, Youn-Kyung Ham, Ah Yeong Choi, Hyouk Yoon and Ha Gyun Sung

Fermentation 2025, 11(6), 342; https://doi.org/10.3390/fermentation11060342 - 12 Jun 2025

Abstract

Solid-state fermentation (SSF) is increasingly applied to enhance the functional properties of traditional herbal medicines. In this study, we investigated the effect of lactic acid bacteria (LAB) and other probiotic strains on the bioactive profile of Radix Angelica gigas (Danggui) during SSF. SSF [...] Read more.

Solid-state fermentation (SSF) is increasingly applied to enhance the functional properties of traditional herbal medicines. In this study, we investigated the effect of lactic acid bacteria (LAB) and other probiotic strains on the bioactive profile of Radix Angelica gigas (Danggui) during SSF. SSF was carried out by incubating a mixture of the herbal powder and distilled water (1:1, pH 7.0) with LAB strains (Lactobacillus rhamnosus, L. acidophilus, L. buchneri, L. reuteri, L. plantarum) and additional microbes (Bacillus subtilis, Saccharomyces cerevisiae) under controlled conditions. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and total phenolic and flavonoid contents were measured. L. buchneri exhibited the highest growth, with significant proliferation observed on days 4 and 6, especially at 30 °C (p < 0.05). The DPPH and ABTS radical scavenging activities and total phenol and total flavonoid contents were increased by up to 230% (35 °C), 111% (30 °C), 137% (30 °C and 35 °C), and 133% (35 °C), respectively, in fermented herbs compared with those in non-fermented herbs. Antioxidant levels (DPPH, phenol, and flavonoid) exhibited a significant positive correlation with bacterial growth and a significant negative correlation with pH in SSF, but ABTS did not exhibit any statistically significant correlation with bacterial growth or pH. Moreover, multi-strain fermentations involving L. acidophilus and L. plantarum significantly increased the antioxidant activities compared to single-strain fermentations (p < 0.05). These findings suggest that SSF using probiotic LAB can significantly improve the bioactive composition of Radix Angelica gigas, providing a scientific method for modernizing traditional herbal medicine with potential uses in human and animal health. Full article

(This article belongs to the Special Issue Bioactive Compounds and Functional Properties of Fermented Foods)

► Show Figures

Figure 1

13 pages, 1826 KiB

Open AccessArticle

Applied Bioelectrochemistry: Plastic Degradation and Energy Generation Using Klebsiella oxytoca in Microbial Fuel Cells

by Rojas-Flores Segundo, Cabanillas-Chirinos Luis, Nélida Milly Otiniano, Magaly De La Cruz-Noriega, Nancy Soto-Deza, Anibal Alviz-Meza and Ángel Darío González-Delgado

Fermentation 2025, 11(6), 341; https://doi.org/10.3390/fermentation11060341 - 12 Jun 2025

Abstract

Plastic pollution remains a critical global environmental challenge, with conventional disposal methods contributing to ecosystem degradation. Simultaneously, energy scarcity affects numerous rural communities, limiting development opportunities. This study presents an innovative approach that integrates microbial fuel cells (MFCs) with Klebsiella oxytoca to simultaneously [...] Read more.

Plastic pollution remains a critical global environmental challenge, with conventional disposal methods contributing to ecosystem degradation. Simultaneously, energy scarcity affects numerous rural communities, limiting development opportunities. This study presents an innovative approach that integrates microbial fuel cells (MFCs) with Klebsiella oxytoca to simultaneously degrade plastic waste and generate bioelectricity. The monitoring results over 40 days revealed optimal performance on day 28, with a peak voltage of 0.714 ± 0.026 V and an electric current of 3.149 ± 0.124 mA. The biocatalyst exhibited an electrical conductivity of 140.466 ± 5.180 mS/cm and an oxidation-reduction potential of 109.519 ± 5.35 mV, indicating efficient electron transfer. Furthermore, the MFCs achieved a maximum power density of 11.391 ± 0.814 mW/cm² with a current density of 5.106 mA/cm², demonstrating their potential for sustainable energy production. Fourier transform infrared (FTIR) analysis confirmed structural modifications in the plastic, with decreased vibrational peaks indicative of polymer degradation. Additionally, scanning electron microscopy (SEM) micrographs revealed porosity and surface cracks, highlighting Klebsiella oxytoca’s biodegradation capacity. These findings establish the viability of bioelectrochemical systems for simultaneous waste remediation and renewable energy generation, paving the way for scalable applications in environmental biotechnology. By coupling microbial degradation with electricity production, this research supports the development of sustainable solutions aligned with the principles of circular economy and climate change mitigation. Full article

(This article belongs to the Special Issue 10th Anniversary of Fermentation: Feature Papers in Section "Industrial Fermentation")

► Show Figures

Figure 1

16 pages, 301 KiB

Open AccessArticle

The Effect of Saliva with Different Nitrogen Compositions on Ruminal Fermentation in a Rumen Simulator Technique (Rusitec^®) System Fed a Lactating Dairy Cow Diet

by Ícaro Rainyer Rodrigues de Castro, Luiza de Nazaré Carneiro da Silva, Isabela Fonseca Carrari, Giulia Berzoini Costa Leite, Eduardo Marostegan de Paula, Amanda Moelemberg Cezar and Marcos Inácio Marcondes

Fermentation 2025, 11(6), 340; https://doi.org/10.3390/fermentation11060340 - 11 Jun 2025

Abstract

In vitro methods have advanced research on rumen microbiology and fermentation. However, artificial saliva formulation may need adjustments, particularly in urea content, for modern diets, warranting further research. This study investigated the effects of different nitrogen (N) levels in artificial saliva on ruminal [...] Read more.

In vitro methods have advanced research on rumen microbiology and fermentation. However, artificial saliva formulation may need adjustments, particularly in urea content, for modern diets, warranting further research. This study investigated the effects of different nitrogen (N) levels in artificial saliva on ruminal fermentation and digestion in diets for dairy cows using a Rusitec^® system. Eighteen fermenters tested three saliva treatments with different N levels: a standard saliva as the control and two treatments with N reduced by 15% and 30%. Data were analyzed as a completely randomized design using the MIXED procedure of SAS (v. 9.4), with linear and quadratic contrasts tested for treatment effects (significance set at p ≤ 0.05). Results showed that altering N content had no significant effect on pH, ammonia concentrations, or NH₃-N outflow, nutrient digestibility (dry matter, crude protein, fiber, and starch), gas and methane production, or volatile fatty acid concentrations. The efficiency of microbial protein synthesis and N flow exhibited quadratic responses, with the lowest values observed at the highest level of N reduction in the saliva (−30%). These findings suggest that although ruminal function and digestion remain stable with reduced N, microbial protein synthesis efficiency may decline beyond a threshold. Full article

(This article belongs to the Section Microbial Metabolism, Physiology & Genetics)

► Show Figures

Graphical abstract

17 pages, 1694 KiB

Open AccessArticle

Enhancing Bioconversion of Crude Glycerol into Butanol and 1,3-Propanediol After Pretreatment by Coupling Fermentation and In Situ Recovery: Effect of Initial pH Control

by Alejandro Ortega, Alejo Valles, Miguel Capilla, Carmen Gabaldón, Francisco Javier Álvarez-Hornos and Paula Marzal

Fermentation 2025, 11(6), 339; https://doi.org/10.3390/fermentation11060339 - 11 Jun 2025

Abstract

The sharp rise in the worldwide production of biodiesel has created an excess in the crude glycerol market, so it is essential to develop new added-value alternatives for crude glycerol. This paper describes a study on fermenting high concentrations of two types of [...] Read more.

The sharp rise in the worldwide production of biodiesel has created an excess in the crude glycerol market, so it is essential to develop new added-value alternatives for crude glycerol. This paper describes a study on fermenting high concentrations of two types of medium-pure crude glycerol to solvents by Clostridium pasteurianum. The effect of media composition (iron, yeast extract, and vitamins) on solvents production was assessed by a full factorial design with pure glycerol. Granular activated carbon (GAC) adsorption was highly effective in removing impurities from crude glycerol. Following GAC pretreatment, fermentation of glycerol at initial concentration as high as 60 g L⁻¹ was possible, resulting in a butanol production of ~9 g L⁻¹. Based on these results, a batch fermentation with in situ gas stripping and pH controlled at ≥6.5 was shown to be the best alternative to enhance biomass growth, glycerol uptake, and solvent production. The combination of controlling pH in the early stages of fermentation with in situ butanol removal stabilised the metabolism of the strain and showed that the fermentation performance with crude glycerol is very similar to that of pure glycerol. With a notable uptake of glycerol (>83%), solvent production was >11 g L⁻¹ butanol (yield > 0.21 g g⁻¹_{glycerol consumed}) and >6 g L⁻¹ 1,3-propanediol (yield > 0.13 g g⁻¹_{glycerol consumed}). Setting the fermentation conditions to achieve a high uptake of high levels of glycerol with a similar product distribution is of great interest for the viability of the industrial processing of crude glycerol into chemicals via biological conversion. Full article

(This article belongs to the Special Issue Valorisation of Agro-Industrial By-Products Through Fermentation or Eco-Friendly Techniques)

► Show Figures

Figure 1

21 pages, 710 KiB

Open AccessReview

Valorization of Maize Stover into Biogas for Heat and Power Generation: A South African Perspective

by Reckson Kamusoko and Patrick Mukumba

Fermentation 2025, 11(6), 338; https://doi.org/10.3390/fermentation11060338 - 11 Jun 2025

Abstract

Maize (Zea mays) is one of the most cultivated crops in South Africa, serving as a staple food, stock feed, and a key element in several industrial applications. It contributes significantly to the growth of the South African agricultural economy. The [...] Read more.

Maize (Zea mays) is one of the most cultivated crops in South Africa, serving as a staple food, stock feed, and a key element in several industrial applications. It contributes significantly to the growth of the South African agricultural economy. The cultivation of maize generates a large amount of agricultural waste, mainly in the form of maize stover (MS), which encapsulates leaves, stalks, cobs, and husks. Approximately 5.15 metric tons (Mt) yr⁻¹ of MS are generated in South Africa. This corresponds to an energy potential of 94 PJ. There is immense potential to surpass the annual yield of MS by 126% up to about 11.66 Mt yr⁻¹ through practices such as zero tillage and improved agricultural production systems. MS may pose a serious threat to the environment if not managed in a sustainable and eco-friendly manner. Valorization of MS into biogas presents an excellent opportunity to effectively control biomass waste while contributing to renewable energy production and mitigating dependence on depleting fossil fuels. However, MS continues to be overlooked as a sustainable bioenergy resource due to its lignocellulosic structure. This study explores the potential of converting MS into biogas for heat and power generation, addressing both energy needs and waste management in South Africa. The purpose is to provide knowledge that will inform researchers, innovators, industrialists, policy makers, investors, and other key stakeholders interested in renewable energy systems. Collaborative efforts among multiple stakeholders are vital to leverage biogas as a technology to promote socio-economic development in South Africa. Full article

(This article belongs to the Special Issue Lignocellulosic Biomass Valorization)

► Show Figures

Figure 1

Journal Description

Fermentation

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI