Search Results (1,420)

Corn fermentation in biorefineries produces residual biomass and by-products, particularly corn kernel fiber and outgassed carbon dioxide (CO₂), that have value-added potential for improving sugar and bioethanol conversions. Recovered corn kernel fiber contains lignocellulosic components which can be made accessible by pretreating the biomass with an alkaline sodium carbonate solution made with captured CO₂ and then used as supplemental biomass in corn ethanol production. In this work, different ratios of whole and degermed corn kernel fibers are pretreated and mixed with corn to be evaluated as beneficial ingredients in bioethanol co-fermentation. Sugar yields from enzymatic hydrolysis demonstrate the pretreatment promotes saccharification reaching over 70% total sugar conversion for the whole corn fibers. During co-fermentation, 10 and 20% corn solid loadings significantly increased ethanol yields while additional corn fiber loadings increased sugar yields. Conversion rates and yields were similar between the whole and degermed corn fibers supporting how a single recovery design can benefit multiple corn streams. Full article

Plant-based fermented foods are increasingly promoted for glycemic control, yet their mechanisms and clinical impact remain incompletely defined. This narrative review synthesizes mechanistic, preclinical, and human data for key matrices—kimchi and other fermented vegetables, tempeh/miso/natto, and related legume ferments, kombucha and fermented teas, plant-based kefir, and cereal/pulse sourdoughs. Across these systems, microbial β-glucosidases, esterases, tannases, and phenolic-acid decarboxylases remodel polyphenols toward more bioaccessible aglycones and phenolic acids, while lactic and acetic fermentations generate organic acids, exopolysaccharides, bacterial cellulose, γ-polyglutamic acid, γ-aminobutyric acid, and bioactive peptides. We map these postbiotic signatures onto proximal mechanisms—α-amylase/α-glucosidase inhibition, viscosity-driven slowing of starch digestion, gastric emptying and incretin signaling, intestinal-barrier reinforcement, and microbiota-dependent short-chain–fatty-acid and bile-acid pathways—and their downstream effects on AMPK/Nrf2 signaling and the gut–liver axis. Animal models consistently show improved glucose tolerance, insulin sensitivity, and hepatic steatosis under fermented vs. non-fermented diets. In humans, however, glycemic effects are modest and highly context-dependent: The most robust signal is early postprandial attenuation with γ-PGA-rich natto, strongly acidified or low-glycemic sourdough breads, and selected kombucha formulations, particularly in individuals with impaired glucose regulation. We identify major sources of heterogeneity (starters, process parameters, substrates, background diet) and safety considerations (sodium, ethanol, gastrointestinal symptoms) and propose minimum reporting standards and trial designs integrating metabolomics, microbiome, and host-omics. Overall, plant-based ferments appear best positioned as adjuncts within cardiometabolic dietary patterns and as candidates for “purpose-built” postbiotic products targeting early glycemic excursions and broader metabolic risk. Full article

Fermentation remains central to food manufacturing and to the bio-based production of organic acids, solvents, and functional metabolites. This review integrates the biochemical pathways, key microorganisms, and application space of five major industrial fermentations—alcoholic, acetic, butyric, lactic, and propionic. We summarize the principal metabolic routes (EMP/ED glycolysis; oxidative ethanol metabolism; butyrate-forming pathways; and the Wood–Werkman, acrylate, and 1,2-propanediol routes to propionate) and relate them to the dominant microbial groups involved, including yeasts, acetic acid bacteria, lactic acid bacteria, clostridia, and propionibacteria. We highlight how the resulting metabolite spectra—ethanol, acetic acid, butyrate, lactate, propionate, and associated secondary metabolites—underpin product quality and safety in fermented foods and beverages and enable the industrial synthesis of platform chemicals, polymers, and biofuels. Finally, we discuss current challenges and opportunities for sustainable fermentation, including waste stream valorization, process intensification, and the integration of systems biology and metabolic engineering within circular economy frameworks. Full article

Reducing the alcohol content of wines has received increasing attention, and various strategies have been proposed for this aim. In this study, non-Saccharomyces yeasts isolated from Uruguayan vineyards were screened to identify strains with low ethanol production for use in mixed cultures. Twenty-six strains belonging to six species were evaluated, considering key oenological parameters such as ethanol and glycerol production, glucose and fructose consumption, and absence of organoleptic defects. Based on these criteria, three strains from two genera were selected: Starmerella bacillaris (Sb1 and Sb2) and Metschnikowia fructicola (Mf2). In pure cultures, Starmerella bacillaris showed high sugar consumption along with high glycerol production. Subsequently, co-inoculation and sequential inoculation conditions were tested by combining the selected strains with commercial Saccharomyces cerevisiae (Sc). With Mf2 + Sc sequential inoculation, high sugar consumption, increased glycerol production, and a significant reduction in ethanol were observed compared to the control. For Starmerella bacillaris, only Sb1 achieved consistent alcohol reductions in sequential strategies. With co-inoculation, both strains reduced ethanol by 0.2–1% v/v, although only Sb1 showed complete sugar depletion. Overall, the results demonstrate a marked dependence of fermentation behavior on the strain and highlight the importance of studying biocompatibility and inoculation strategy in mixed cultures. Full article

Cassava is a major starch crop in Africa, generating substantial amounts of solid (peels and fibres) and liquid (process press water) residues that remain underutilised, particularly in smallholder and semi-industrial processing units. In Mozambique, where cassava is a staple and processed primarily by local farmer associations, these residues—readily available and low-cost feedstocks—have significant potential for value-added applications. This study evaluated the potential of enzymatically hydrolysed cassava residues—peel and fibre hydrolysates—as substrates for independent yeast fermentations targeting microbial lipid and ethanol production. Rhodotorula toruloides CBS 14 efficiently converted sugars from both hydrolysates, producing up to 17.14 g L⁻¹ of cell dry weight (CDW) and 35% intracellular lipid content from the peel hydrolysate, and 16.5 g L⁻¹ CDW with 50% lipids from the fibre hydrolysate. Supplementation with ammonium sulphate accelerated sugar utilisation and reduced fermentation time but did not significantly increase the biomass or lipid yields. Saccharomyces cerevisiae J672 fermented the available sugars anaerobically, achieving ethanol yields of 0.45 ± 0.03 g g⁻¹ glucose from peels and 0.37 ± 0.06 g g⁻¹ glucose from fibres. These findings highlight the regional relevance of valorising cassava processing residues in Mozambique and demonstrate a dual-product valorisation strategy, whereby the same feedstocks are converted into either microbial lipids or ethanol through independent fermentations. This approach supports the sustainable, low-cost utilisation of agro-industrial residues, contributing to circular bioeconomy principles and enhancing the environmental and economic value of local cassava value chains. Full article

Yeast biosensors represent a promising biotechnological innovation for ensuring the safety and quality of fermented beverages such as beer, wine, and kombucha. These biosensors employ genetically engineered yeast strains to detect specific contaminants, spoilage organisms, or hazardous compounds during fermentation or the final product. By integrating synthetic biology tools, researchers have developed yeast strains that can sense and respond to the presence of heavy metals (e.g., lead or arsenic), mycotoxins, ethanol levels, or unwanted microbial metabolites. When a target compound is detected, the biosensor yeast activates a reporter system, such as fluorescence, color change, or electrical signal, providing a rapid, visible, and cost-effective means of monitoring safety parameters. These biosensors offer several advantages: they can operate in real time, are relatively low-cost compared to conventional chemical analysis methods, and can be integrated directly into the fermentation system. Furthermore, as Saccharomyces cerevisiae is generally recognized as safe (GRAS), its use as a sensing platform aligns well with existing practices in beverage production. Yeast biosensors are being investigated for the early detection of contamination by spoilage microbes, such as Brettanomyces and lactic acid bacteria. These contaminants can alter the flavor profile and shorten the product’s shelf life. By providing timely feedback, these biosensor systems allow producers to intervene early, thereby reducing waste and enhancing consumer safety. In this work, we review the development and application of yeast-based biosensors as potential safeguards in fermented beverage production, with the overarching goal of contributing to the manufacture of safer and higher-quality products. Nevertheless, despite their substantial conceptual promise and encouraging experimental results, yeast biosensors remain confined mainly to laboratory-scale studies. A clear gap persists between their demonstrated potential and widespread industrial implementation, underscoring the need for further research focused on robustness, scalability, and regulatory integration. Full article

Port wine production involves the addition of grape spirit to halt fermentation and retain natural sweetness. This spirit, produced by distilling wine and its by-products, must comply with legal standards, including a mandatory sensory assessment. Because grape spirit influences Port wine’s volatile composition, this study investigated the odour-active compounds present in several grape spirits intended for fortification. Volatile compounds were extracted by liquid–liquid extraction, concentrated, and analysed using gas chromatography–olfactometry (GC-O) and gas chromatography–mass spectrometry (GC-MS). In GC-O, based on frequency detection, a panel of assessors sniffed the extracts to determine the presence of aroma compounds. The results revealed a wide range of odour-active compounds in grape spirits, belonging to several chemical families such as esters, alcohols, terpenic compounds and acids. These compounds exhibited both pleasant aromas, such as fruity, floral and caramel notes as well as undesirable ones like cheese and foot odour. Most of these compounds originate from the fermentation process and are also found in other unaged distilled beverages, including young Cognac, Calvados and fruit spirits. This research highlights the aromatic complexity of grape spirits and, for the first time, determined the aroma thresholds for 25 of 36 the compounds studied at an ethanol content of 20%. Full article

Fermented forest litter (FFL) is a biofertilizer obtained by anaerobic fermentation of forest litter combined with agricultural by-products. Its production involves an initial one-month solid-state fermentation of oak litter mixed with whey, molasses and wheat bran, followed by a one-week submerged fermentation-called the “activation” phase-during which the solid FFL is fermented with sugarcane molasses diluted in water. This study aimed to evaluate the effects storage duration (6, 18 and 30 months), and temperature (ambient and 29 °C) on the activation phase. For this purpose, pH, sugar consumption and metabolite production dynamics were monitored. Under all experimental conditions, the pH dropped to values close to 3.5, sucrose was rapidly hydrolyzed, and glucose was preferentially consumed over fructose. Fructose was metabolized only after glucose was depleted, suggesting the involvement of fructophilic microorganisms. The time-course evolution of lactic acid (LA) concentration was adequately fitted by the Gompertz model (R² > 0.970). The highest LA_max concentration (6.30 g/L) and production rate (2.16 g/L·d) were obtained with FFL stored for 6 months. Acetic acid (AA) and ethanol were also detected reaching maxima values of 1.19 g/L and 0.96 g/L, respectively. Their profiles varied depending on the experimental conditions. Notably, the AA/LA ratio increased with the age of the FFL. Overall, sugar consumption and metabolite production were significantly slower at ambient temperature, than at 29 °C. These results contribute to a better understanding of the metabolic dynamics during FFL activation and highlight key parameters that should be considered to optimize future biofertilizer production processes. Full article

This study aimed to modify metabolite synthesis in Saccharomyces cerevisiae (S. cerevisiae) under simulated wine fermentation conditions by regulating the glycerol metabolic pathway. We systematically analyzed the effects of overexpressing the aquaporin gene AQY1 and co-expressing AQY1 with the glycerol-3-phosphate dehydrogenase gene GPD1 on the metabolism of ethanol, higher alcohols, and esters. Our results indicate that AQY1 overexpression increased glycerol yield by 6.58%, reduced higher alcohol content by 14.60%, and elevated ester content by 7.15%. The downregulation of related amino acid metabolism genes correlated with the observed decrease in higher alcohol levels. Notably, co-expression of AQY1 and GPD1 further enhanced glycerol yield by 10.66% while decreasing ethanol content by 6.32%. By analyzing changes in gene expression alongside metabolic mechanisms, we hypothesize that the redistribution of carbon flux and NADH toward the glycerol pathway not only decreases the precursors for ethanol synthesis but also directly inhibits the activity of aldehyde dehydrogenase (ALD2/3/4/6), thereby constraining ethanol production. In comparison to AQY1 overexpression alone, the co-expression strategy did not significantly alter glycerol accumulation; however, it reduced both ethanol and ester content by 8.38% and 8.40%, respectively, while markedly increasing higher alcohol content by 22.30%. This increase may result from enhanced glycolytic flux and pyruvate accumulation, which promote metabolic flow toward amino acid synthesis pathways. In summary, this study effectively remodeled the central carbon metabolism network by targeting glycerol metabolism, achieving diverse metabolic product synthesis and providing important references for the selection and breeding of industrial S. cerevisiae strains. Full article

Driven by the energy transition within the framework of the United Nations Framework Convention on Climate Change, second-generation (2G) ethanol stands out as a technical and sustainable alternative to fossil fuels. Although first-generation ethanol, produced from saccharine and starchy feedstocks, represents an advance in mitigating emissions, its expansion is limited by competition with areas destined for food production. In this context, 2G ethanol, obtained from residual lignocellulosic biomass, emerges as a strategic route for diversifying and expanding the renewable energy matrix. Thus, this work discusses the current state of 2G ethanol technology based on the gradual growth in production and the consolidation of this route over the last few years. Industrial second-generation ethanol plants operating around the world demonstrate the high potential of agricultural waste as a raw material, particularly corn straw in the United States, which offers a lower cost and significant yield in the production of this biofuel. Similarly, in Brazil, sugarcane by-products, especially bagasse and straw, are consolidating as the main sources for 2G ethanol, integrated into the biorefinery concept and the valorization of by-products obtained during the 2G ethanol production process. However, despite the wide availability of lignocellulosic biomass and its high productive potential, the consolidation of 2G ethanol is still conditioned by technical and economic challenges, especially the high costs associated with pretreatment stages and enzymatic cocktails, as well as the formation of inhibitory compounds that compromise the efficiency of the process. Genetic engineering plays a particularly important role in the development of microorganisms to produce more efficient enzymatic cocktails and to ferment hexoses and pentoses (C₆ and C₅ sugars) into ethanol. In this scenario, not only are technological limitations important but also public policies and tax incentives, combined with the integration of the biorefinery concept and the valorization of (by)products, which prove fundamental to reducing costs, increasing process efficiency, and ensuring the economic viability and sustainability of second-generation ethanol. Full article

Simultaneous conversion of syngas and sugars is a promising approach to overcome limitations of syngas fermentation. Clostridium autoethanogenum LAbrini, obtained by adaptive laboratory evolution, is known to show improved autotrophic process performance. Under purely autotrophic conditions, C. autoethanogenum LAbrini exhibits substantially faster growth and biomass formation compared to the wild-type in fully controlled, stirred-tank bioreactors with a continuous gas supply. In mixotrophic processes, the pre-culture strategy has a significant impact on the growth and metabolic activity of C. autoethanogenum LAbrini. C. autoethanogenum LAbrini can metabolize sugars (D-fructose, D-xylose, or L-arabinose) and CO simultaneously. All mixotrophic batch processes showed increased growth and product formation compared to the autotrophic process. The mixotrophic batch process with D-fructose enabled superior production of alcohols (10.7 g L⁻¹ ethanol and 3.2 g L⁻¹ D-2,3-butanediol) with a heterotrophic pre-culture. Using an autotrophic pre-culture and L-arabinose resulted in a total alcohol formation of more than 13 g L⁻¹. The formation of meso-2,3-butanediol (>0.50 g L⁻¹) occurred exclusively under mixotrophic conditions. Thus, C. autoethanogenum LAbrini, clearly representing notable improvements over the wild-type strain in mixotrophic batch processes, offers a good basis for further strain improvements to shift the product range even further towards more reduced products. Full article

This study examined how different fertilisation strategies (mineral, compost, vermicompost and non-fertilised control) influence vine nutrient status, must composition and wine chemical characteristics over two consecutive seasons (2024–2025) in two semi-arid Mediterranean vineyards, one deficit-irrigated and other rainfed. Compost and vermicompost were produced from winery residues, in line with a circular management approach. Organic fertilisation improved vine nitrogen and potassium levels, particularly at veraison, with cumulative effects observed over time. Musts from fertilised vines (mineral, compost and vermicompost) exhibited higher levels of yeast-assimilable nitrogen (YAN) and pH, as well as lower titratable acidity, compared to the control group (without fertilization). Wines obtained from these treatments exhibited higher ethanol content and modified acidity parameters, with compositional changes being more evident in the rainfed vineyard. Analysis of volatile compounds revealed that organic fertilisers, particularly vermicompost, promoted the formation of esters, higher alcohols, and terpenes linked to grape metabolism and fermentation. These results demonstrate that organic amendments derived from winery waste can serve as efficient nutrient sources, thereby enhancing the nutritional balance of vines and the composition of wines, while also promoting sustainable and circular practices in viticulture. Full article

Beer is a drink that has been a staple in human history, evolving from its beginning in antiquity to the present day. Nowadays, large breweries and other companies have set up laboratories focused on finding and developing new yeast strains for the brewing sector to meet consumers’ demand for new beer styles. Monascus spp. are ascomycota that have been known for hundreds of years. They are widely popular in Asian cuisine, especially in fermented foods. Studies show that Monascus spp. produce numerous food dyes and substances that positively influence human health. In the presented work, Monascus ruber was tested as a potential microorganism for the beer industry. Experiments included fermentation trials with Monascus ruber in four regimes: in aerobic condition, anaerobic condition, anaerobic condition with pH kept above 4.5, and in anaerobic condition with pH set to 4.5. As a reference, commercial Saccharomyces cerevisiae and Saccharomyces pastorianus were used. Fermentation parameters were evaluated by measurements of ethanol and extract level. The final product was tested for its colour in order to evaluate if monascus-derived pigments were present in the beverage. Moreover, a qualitative analysis of lovastatin and citrinin was performed in order to check if those monascus metabolites were present. Finally, small-scale consumer tests were performed in order to check the organoleptic properties of the obtained beverage. Results show that Monascus ruber is able to ferment beer wort in a similar manner as Saccharomyces strains, reaching a slightly lower degree of attenuation. Nevertheless, a longer lag phase was observed in monascus trials, except for the trial with preset pH at 4.5. The most visible change in the product was a reddish colour that appeared in the sample in aerobic conditions. The qualitative analysis showed that lovastatin and citrinin were present in the tested samples. Consumer tests show that experimental beer has a different taste than Saccharomyces-fermented products. Although the presented results are preliminary, they could be a good starting point for further research on monascus-based beverages. Full article

Robust yeast tolerance to inhibitors is essential for lignocellulosic biorefinery. Although cell flocculation is known to enhance acetic acid stress tolerance, the impact of its intensity remains unclear. In this study, engineered S. cerevisiae strains with distinct floc sizes were constructed through promoter engineering. The native FLO1 promoter in the non-flocculating laboratory strain BY4741 was replaced with either the constitutive strong promoter PGK1p or the ethanol-inducible promoter TPS1p using CRISPR-Cas9-mediated genome editing, resulting in strongly and moderately flocculating strains BY4741 PGK1p-FLO1 and BY4741 TPS1p-FLO1, respectively. It was revealed that the BY4741 PGK1p-FLO1 showed a survival advantage in the late-stage fermentation and severe stress condition in the presence of 7.5 g/L acetic acid, while BY4741 TPS1p-FLO1 exhibited superior growth and fermentation performance under 5.0 g/L acetic acid stress. Further studies suggested that the enhanced acetic acid tolerance in flocculating cells was associated with their ability to maintain significantly higher intracellular ATP levels under stress. Our work highlights the importance of optimizing flocculation properties for robust industrial fermentation, and also provides a strategic basis for engineering stress-tolerant yeast strains for efficient fermentation in inhibitor-rich cellulosic hydrolysates. Full article

This study aimed to evaluate the feasibility of producing vinegar from organic third-category apples, peaches, and clementines on a laboratory scale. Two-step fermentation with Saccharomyces cerevisiae and Gluconobacter oxydans was applied, monitoring production of ethanol and acetic acid and microbial dynamics. Fruit vinegars were subjected to analyses of sensory traits, color, volatile organic compounds (VOCs), and antioxidant activity. Comparable ethanol yields across substrates were obtained, ensuring consistent acetous fermentation and achieving acetic acid concentrations of 5.0–5.6%. Dynamics of yeasts and acetic acid bacteria reflected the production of and subsequent decrease in ethanol. Overall, fermentation proceeded a bit faster in peach juice. Overall, the fruit vinegars, particularly those from peaches and clementines, exhibited darker and more saturated tones. The values of colorimetric indexes fell within the range reported for vinegars. Sensory analysis highlighted large differences among the vinegars. Notwithstanding the highest scores of color, aroma intensity, and floral aroma received by the peach vinegar (PV), it received the lowest acceptability. Clementine vinegar (CV) was especially appreciated. Multivariate analysis based on the VOC profile showed that apple vinegar (AV) was quite similar to the commercial one, whereas PV and CV were well distinguished from it. CV showed the highest antioxidant activity followed by PV. Full article