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Torulaspora delbrueckii is an emerging yeast species in the beverage and food industry that is suitable for alcoholic fermentation and to improve the organoleptic quality of wine, beer, mead, and other beverages. Modern consumer preference toward new flavors and products drives the application of T. delbrueckii to ferment less traditional fruits and vegetables. Thus, it has become increasingly relevant to define those metabolites produced in minute quantities by T. delbrueckii, because they may have an impact when producing these new alcoholic beverages. In this study, we have identified metabolites of T. delbrueckii and have compared them with those of Saccharomyces cerevisiae in a controlled setting with a synthetic, high glucose medium using gas chromatography coupled to flame ionization detector (GC–FID) and stir bar sorptive extraction (SBSE) with GC coupled to mass spectrometry (MS). Results showed that T. delbrueckii produced metabolites with higher changes in odor activity complexes than S. cerevisiae: ethyl propanoate, 1,1-diethoxyethane, ethyl isobutyrate, ethyl butyrate, isoamyl acetate, ethyl heptanoate, nonanal, and decanal. We also report seven metabolites detected for the first time in T. delbrueckii. This datum serves to expand the knowledge of T. delbrueckii performance and shows that application of this yeast species is more suitable to a wide array of beverage producers.

Several industries require getting information of products as soon as possible during fermentation. However, the trade-off between sensing speed and data quantity presents challenges for forecasting fermentation product yields. In this study, we tried to develop AI models to forecast ethanol yields in yeast fermentation cultures, using cell morphological data. Our platform involves the quick acquisition of yeast morphological images using a nonstaining protocol, extraction of high-dimensional morphological data using image processing software, and forecasting of ethanol yields via supervised machine learning. We found that the neural network algorithm produced the best performance, which had a coefficient of determination of >0.9 even at 30 and 60 min in the future. The model was validated using test data collected using the CalMorph-PC(10) system, which enables rapid image acquisition within 10 min. AI-based forecasting of product yields based on cell morphology will facilitate the management and stable production of desired biocommodities.

Background The aim of this study was the production of bioethanol generated during the fermentation of CCN-51 Cocoa mucilage with Saccharomyces cerevisiae yeast and the fitting of experimental data to the mathematical models: Logistic, modified Gompertz, and Andrews and Levenspiel. There are limited studies regarding the high energy potential of cocoa mucilage from Ecuador for bioethanol production as a gasoline additive. Currently, this by-product of the cocoa industry is considered as waste. Methods Discontinuous fermentation was performed in a batch bioreactor under different conditions of pH, temperature and yeast concentration. During the reaction, bioethanol concentration, yeast and consumed substrate were evaluated by means of microdiffusion, dry weight by lyophilization and UV spectrophotometry, respectively. Significant Findings The result of the final bioethanol concentration was 25.41 g/L at a temperature of 35 °C, pH of 4 and yeast concentration of 3 g/L. The models were fitted with determination coefficients greater than 0.9. From the results, the logistic model was used to describe yeast growth. Modified Gompertz model is considered appropriate for modeling bioethanol production. Both models fit the data adequately; however, Andrews and Levenspiel model, besides of the good adjustment, considered inhibition terms of the substrate and product.

This work aims to characterize the alcoholic fermentation of whey on a laboratory scale. It was carried out in the Pilot Plant of the University of Camagüey. By means of a mass balance, the amounts of lactose necessary to standardize the serum were calculated to concentrations of 50, 75, 100 and 125 g / l of lactose. The yeast of the genus Saccharomyces cerevisiae used by the Cuban Alcohol Industry does not ferment lactose as a substrate, so it was necessary to hydrolyze it following the acid hydrolysis procedure, to check the result of the hydrolysis Polarimetry, Colorimetry and Chromatography tests were carried out. Fermentations were carried out with two replicates at each concentration studied, to which ammonium phosphate and yeast were added. The results of partial hydrolysis of lactose allowed to obtain in the fermentation process percentages in volumes of ethanol above those proposed from lactose concentrations of 75 g / l, the increase in lactose concentrations up to 125 g / l was in correspondence with the best yields and productivity of the fermentation process. The duration of the fermentation maintained a growth of the microorganisms with the transformation of the substrate and the generation of CO2 as foreseen and registered in the literature. Keywords: alcoholic fermentation; whey; hydrolysis., Este trabajo tiene como objetivo caracterizar la fermentación alcohólica del lactosuero a escala de laboratorio. Se llevó a cabo en la Planta Piloto de la Universidad de Camagüey. Mediante un balance de masa se calcularon las cantidades de lactosa necesarias para estandarizar el suero hasta concentraciones de 50, 75, 100 y 125 g/l de lactosa. La levadura del género Saccharomyces cerevisiae utilizado por la Industria Alcoholera Cubana no fermenta la lactosa como sustrato, por lo que se hizo necesario hidrolizarla siguiendo el procedimiento de hidrólisis ácida, para comprobar el resultado de la hidrólisis se realizaron pruebas de Polarimetría, Colorimetría y Cromatografía. Las fermentaciones se realizaron con dos réplicas a cada concentración estudiada, a las cuales se les añadió fosfato de amonio y levadura. Los resultados de hidrólisis parcial de la lactosa permitieron obtener en el proceso fermentativo porcientos en volúmenes de etanol por encima de los propuestos a partir de concentraciones de lactosa de 75 g/l, el incremento de las concentraciones de lactosa hasta 125 g/l estuvo en correspondencia con los mejores rendimientos y productividad del proceso fermentativo. La duración de la fermentación mantuvo un crecimiento de los microorganismos con la transformación del sustrato y generación del CO2 según lo previsto y registrado en la literatura. Palabras claves: fermentación alcohólica; lactosuero; hidrólisis. Abstract This work aims to characterize the alcoholic fermentation of whey on a laboratory scale. It was carried out in the Pilot Plant of the University of Camagüey. By means of a mass balance, the amounts of lactose necessary to standardize the serum were calculated to concentrations of 50, 75, 100 and 125 g / l of lactose. The yeast of the genus Saccharomyces cerevisiae used by the Cuban Alcohol Industry does not ferment lactose as a substrate, so it was necessary to hydrolyze it following the acid hydrolysis procedure, to check the result of the hydrolysis Polarimetry, Colorimetry and Chromatography tests were carried out. Fermentations were carried out with two replicates at each concentration studied, to which ammonium phosphate and yeast were added. The results of partial hydrolysis of lactose allowed to obtain in the fermentation process percentages in volumes of ethanol above those proposed from lactose concentrations of 75 g / l, the increase in lactose concentrations up to 125 g / l was in correspondence with the best yields and productivity of the fermentation process. The duration of the fermentation maintained a growth of the microorganisms with the transformation of the substrate and the generation of CO2 as foreseen and registered in the literature. Keywords: alcoholic fermentation; whey; hydrolysis. Información del manuscrito:Fecha de recepción: 26 de julio de 2021.Fecha de aceptación: 29 de septiembre de 2021.Fecha de publicación: 11 de octubre de 2021.

With the consumption of energy and the spread of COVID-19, the demand for ethanol production is increasing in the world. The industrial ethanol fermentation microbes cannot metabolize the alginate component of macro algae, which affects the ethanol yield. In this research, the ethanol production process from macro algae by an alginate fermentation yeast Meyerozyma guilliermondii, especially the pretreatment process of Colpomenia sinuosa, was studied. At the same time, the experimental design of Box-Behnken was carried out to achieve the optimum fermentation performance. The concentration of KH2PO4 (A: 2–6 g.L−1), pH (B: 4–7), reaction time (C: 60–120 h) and temperature (D: 24–34 °C) were variable input parameters. During the ethanol production process, the algae powder was firstly mixed with water at 90 °C for 0.5 h. Later the fermentation culture medium was prepared and then it was fermented by the yeast Meyerozyma guilliermondii to produce ethanol. And the optimal fermentation parameters were as follows: fermentation temperature of 28 °C, KH2PO4 dosage of 4.7 g.L−1, initial pH of 6, and fermentation time of 99 h. The ethanol yield reached 0.268 g.g−1 (ethanol to algae), close to the predicted value of model. The generation of alginate lyase during the fermentation of algae was also examined. The highest alginate lyase activity reached 46.42 U.mL−1.

The presence of high concentrations of organic acids is known to adversely affect the efficiency and quality of ethanol fermentation. The growing popularity of sour beers warranted the exploration ...

Arginine uptake and yeast arginase activity were studied throughout the alcoholic fermentation of a white grape must (Vitis vinifera L. cv Fiano), carried out by sequential inoculation (Torulaspora delbrueckii and S. cerevisiae, TD-SC) and compared with a S. cerevisiae single fermentation (SC). In both samples, yeast assimilable nitrogen (YAN) consumption was mainly during the early phase of alcoholic fermentation (before S. cerevisiae addition in the sequential fermentation). T. delbrueckii alone and S. cerevisiae similarly metabolized YAN, which was further consumed in TD-SC sample following the S. cerevisiae inoculation. The only relevant arginine uptake was found about 3 days after the first inoculum (simultaneously with the greatest YAN consumption) and it appeared to be higher in SC (0.24 g/L) than in TD-SC (0.12 g/L). The kinetic parameters, estimated by means of the Hill equation, and in particular Vmax values (56.0 ± 1.6 U/mgBSAeq at 48 h for SC and 73.3 ± 2.7 U/mgBSAeq at 66 h for TD-SC) indicated the maximum arginase activity at the same point of time corresponding to the lowest YAN amount (48 h for S. cerevisiae and 66 h for T. delbrueckii).

This review examines the different types of interactions between the microorganisms involved in the fermentation processes of alcoholic beverages produced all over the world from cereals or fruit juices. The alcoholic fermentation converting sugars into ethanol is usually carried out by yeasts, mainly Saccharomyces cerevisiae, which can grow directly using fruit sugars, such as those in grapes for wine or apples for cider, or on previously hydrolyzed starch of cereals, such as for beers. Some of these beverages, or the worts obtained from cereals, can be distilled to obtain spirits. Besides S. cerevisiae, all alcoholic beverages can contain other microorganisms and especially in spontaneous fermentation when starter cultures are not used. These other microbes are mostly lactic acid bacteria and other yeasts-the non-Saccharomyces yeasts. The interactions between all these microorganisms are very diverse and complex, as in any natural occurring ecosystem, including food fermentations. To describe them, we have followed a simplified ecological classification of the interactions. The negative ones are amensalism, by which a metabolic product of one species has a negative effect on others, and antagonism, by which one microbe competes directly with others. The positive interactions are commensalism, by which one species has benefits but no apparent effect on others, and synergism, by which there are benefits for all the microbes and also for the final product. The main interactions in alcoholic beverages are between S. cerevisiae and non-Saccharomyces and between yeasts and lactic acid bacteria. These interactions can be related to metabolites produced by fermentation such as ethanol, or to secondary metabolites such as proteinaceous toxins, or are feed-related, either by competition for nutrients or by benefit from released compounds during yeast autolysis. The positive or negative effects of these interactions on the organoleptic qualities of the final product are also revised. Focusing mainly on the alcoholic beverages produced by spontaneous fermentations, this paper reviews the interactions between the different yeasts and lactic acid bacteria in wine, cider, beer, and in spirits such as tequila, mezcal and cachaça.

The novel extremophilic yeast Rhodotorula frigidialcoholis, formerly R. JG1b, was isolated from ice-cemented permafrost in University Valley (Antarctic), one of coldest and driest environments on Earth. Phenotypic and phylogenetic analyses classified R. frigidialcoholis as a novel species. To characterize its cold-adaptive strategies, we performed mRNA and sRNA transcriptomic analyses, phenotypic profiling, and assessed ethanol production at 0 and 23 °C. Downregulation of the ETC and citrate cycle genes, overexpression of fermentation and pentose phosphate pathways genes, growth without reduction of tetrazolium dye, and our discovery of ethanol production at 0 °C indicate that R. frigidialcoholis induces a metabolic switch from respiration to ethanol fermentation as adaptation in Antarctic permafrost. This is the first report of microbial ethanol fermentation utilized as the major energy pathway in response to cold and the coldest temperature reported for natural ethanol production. R. frigidialcoholis increased its diversity and abundance of sRNAs when grown at 0 versus 23 °C. This was consistent with increase in transcription of Dicer, a key protein for sRNA processing. Our results strongly imply that post-transcriptional regulation of gene expression and mRNA silencing may be a novel evolutionary fungal adaptation in the cryosphere.

For yeast cells, tolerance to high levels of ethanol is vital both in their natural environment and in industrially relevant conditions. We recently genotyped experimentally evolved yeast strains adapted to high levels of ethanol and identified mutations linked to ethanol tolerance. In this study, by integrating genomic sequencing data with quantitative proteomics profiles from six evolved strains (data set identifier PXD006631) and construction of protein interaction networks, we elucidate exactly how the genotype and phenotype are related at the molecular level. Our multi-omics approach points to the rewiring of numerous metabolic pathways affected by genomic and proteomic level changes, from energy-producing and lipid pathways to differential regulation of transposons and proteins involved in cell cycle progression. One of the key differences is found in the energy-producing metabolism, where the ancestral yeast strain responds to ethanol by switching to respiration and employing the mitochondrial electron transport chain. In contrast, the ethanol-adapted strains appear to have returned back to energy production mainly via glycolysis and ethanol fermentation, as supported by genomic and proteomic level changes. This work is relevant for synthetic biology where systems need to function under stressful conditions, as well as for industry and in cancer biology, where it is important to understand how the genotype relates to the phenotype. ispartof: JOURNAL OF PROTEOME RESEARCH vol:20 issue:8 pages:3840-3852 ispartof: location:United States status: published

The yeast Lachancea thermotolerans can produce lactic acid during alcoholic fermentation (AF) and thereby acidify wines with insufficient acidity. However, little is known about the impact of L. thermotolerans on Oenococcus oeni, the primary lactic acid bacterium used in malolactic fermentation (MLF). This study explored the impact of sequential cultures of L. thermotolerans and Saccharomyces cerevisiae on MLF performance in white and red wines. Four L. thermotolerans strains were tested in Sauvignon blanc with sequential S. cerevisiae inoculation, compared to an S. cerevisiae control and the initially un-inoculated treatments. The L. thermotolerans wines showed large differences in acidification, and progression of MLF depended on lactic acid production, even at controlled pH. The highest and lowest lactic acid producing strains were tested further in Merlot fermentations with both co-inoculated and sequentially inoculated O. oeni. The low lactic acid producing strain enabled successful MLF, even when this failed in the S. cerevisiae treatment, with dramatically quicker malic acid depletion in O. oeni co-inoculation than in sequential inoculation. In contrast, a high lactic acid producing strain inhibited MLF irrespective of the O. oeni inoculation strategy. In a follow-up experiment, increasing concentrations of exogenously added lactic acid slowed MLF and reduced O. oeni growth across different matrices, with 6 g/L of lactic acid completely inhibiting MLF. The results confirm the inhibitory effect of lactic acid on O. oeni while highlighting the potential of some L. thermotolerans strains to promote MLF and the others to inhibit it.

Wine is a product of biochemical transformations, compounds present in grape juice, by controlled alcoholic fermentation, that is, effervescence. Grape and yeast enzymes play a key role in the processing of grapes and the preparation of wine, influencing all biotechnological processes of winemaking. Adding liquid or dry active yeast to the wort allows better control of the fermentation process. Under the influence of these yeasts, sugar is converted mainly into alcohol or carbon dioxide, but the yeast itself during fermentation produces many molecules (higher alcohols, esters) that affect the aroma and taste of wine. These transformations take about two weeks and lead to a significant increase in temperature, which must be regulated, not allowing it to rise above 18-20°C: otherwise, some of the aromatic substances may evaporate and the fermentation process itself will stop. The amount of yeast that determines the correct and complete fermentation depends both on the quality of the wort itself, and on the more or less prolonged access of air, the ambient temperature. The air, or rather the oxygen of the air, has a beneficial effect on fermentation as long as there are still many nutrients (sugars) in the wort; as the latter are consumed, extremely small yeast cells are formed, which persist for a long time in the form of turbidity. The rapid course of fermentation can be greatly facilitated by the periodic stirring of yeast, which, settling to the bottom, lose direct contact with nutrients — the lower layers almost do not function. You can mix the wort mechanically or by adding healthy whole grapes to it; in this case, the wort is constantly and automatically mixed: the berries, rising up in the fermenting liquid, carry the yeast with them. In order to speed up the fermentation, the wort is sometimes ventilated, that is, air is introduced into it, by mixing. This article shows the influence of the yeast race on the fermentation dynamics of white grape must, the composition of organic acids and aroma-forming components. The races that ensure the production of highquality wine materials are identified.

Yeast immobilization with low-cost carrier materials is a suitable strategy to optimize the fermentation of lignocellulosic hydrolysates for the production of second-generation (2G) ethanol. It is defined as the physical confinement of intact cells to a certain region of space (the carrier) with the preservation of their biological activity. This technological approach facilitates promising strategies for second-generation bioethanol production due to the enhancement of the fermentation performance that is expected to be achieved. Using immobilized cells, the resistance to inhibitors contained in the hydrolysates and the co-utilization of sugars are improved, along with facilitating separation operations and the reuse of yeast in new production cycles. Until now, the most common immobilization technology used calcium alginate as a yeast carrier but other supports such as biochar or multispecies biofilm membranes have emerged as interesting alternatives. This review compiles updated information about cell carriers and yeast-cell requirements for immobilization, and the benefits and drawbacks of different immobilization systems for second-generation bioethanol production are investigated and compared. © 2021 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

FAS2 encoding α subunit of fatty acid synthetase is one of essential genes in S. cerevisiae, and theFAS2‐G1250S mutation decreases carbon chain elongation activity during fatty acid synthesis, resulting in high productivity of ethyl caproate. Evaluation for mutant gene dosage using polyploids with isogenic background revealed the trade‐off relationship between ethyl caproate productivity and cell growth rate. We further demonstrated the possibility to increase mutant gene dosage via loss of heterozygosity in diploid and tetraploid strains., Summary The yeast Saccharomyces cerevisiae, widely used for ethanol production, is one of the best‐understood biological systems. Diploid strains of S. cerevisiae are preferred for industrial use due to the better fermentation efficiency, in terms of vitality and endurance as compared to those of haploid strains. Whole‐genome duplications is known to promote adaptive mutations in microorganisms, and allelic variations considerably contribute to the product composition in ethanol fermentation. Although fermentation can be regulated using various strains of yeast, it is quite difficult to make fine adjustment of each component in final products. In this study, we demonstrate the use of polyploids with varying gene dosage (the number of copies of a particular gene present in a genome) in the regulation of ethanol fermentation. Ethyl caproate is one of the major flavouring agents in a Japanese alcoholic beverage called sake. A point mutation in FAS2 encoding the α subunit of fatty acid synthetase induces an increase in the amount of caproic acid, a precursor of ethyl caproate. Using the FAS2 as a model, we generated and evaluated yeast strains with varying mutant gene dosage. We demonstrated the possibility to increase mutant gene dosage via loss of heterozygosity in diploid and tetraploid strains. Productivity of ethyl caproate gradually increased with mutant gene dosage among tetraploid strains. This approach can potentially be applied to a variety of yeast strain development via growth‐based screening.

Starmerella bacillaris is a non-Saccharomyces yeast recently proposed for grape fermentation in association with Saccharomyces cerevisiae. Due to its high glycerol and moderate volatile acidity production this yeast can contribute to improving wine quality. Some strains have been demonstrated to exhibit antifungal activity against grey mould on grape, which is caused by Botrytis cinerea. The simultaneous presence of these traits in S. bacillaris is of great interest. Indeed, this yeast can be potentially used as a biocontrol agent in vineyards. Research on the ability of S. bacillaris to survive or, even to grow on the surface of grapes is a starting point in the evaluatation of its potential use in vineyards. The preliminary results of our study showed that when applied to the grape surface under laboratory condictions, inoculum sized S. bacillaris with antifungal activity developed and lasted for at least 6 days in high concentrations. In addition, it positively influenced the fermentation process by producing high concentrations of glycerol (average value 4.89 ± 0.47 g/L). Interestingly, a positive effect on wine quality was also observed when the inoculum size was 10 times higher or lower than the reference concentration. When sprayed on the vines in the vineyard and present on the grape skin surface after harvest, S. bacillaris cells can start alcoholic fermentation.

The consumption of alcoholic drinks have highly risen recently to a situation whereby there is a deficit in the stores, this is due to the higher demand compared to supply. Due to the high prices of most of the industrialized brews, consumers have opted for locally brewed drinks. Although locally manufactured brews are not recognized and certified by law, most are of good quality and with low cost of production. The use of Tithonia diversifolia can be employed to aid in improvement of the rate of production of local and industrialized brews. The main aim of this project was to improve the rate of fermentation of alcoholic beverage using both Tithonia diversifolia leaves extracts and iron II nanoparticles derived from it. It was observed that the plant catalyst reduced the time taken to produce alcohol. Alcohol fermentation rate in presence of yeast and with a tithonia extract as catalyst was measured, Rates of alcohol production was measured by UV VIS at intervals of one hour and deduced from a calibration curve. From the data, the alcohol content was higher in the sample catalyzed by the complexed extract and the one containing extracts as the catalyst as compared to the one without a catalyst. The percentage ethanol was able to be detected by finding absorbances (beer lambert law A = e l c.).

The use of fruit residues from domestic consumption for energy purposes is a perspective of innovation in the search for a more sustainable fuel, due to the low cost of this biomass, combined with its large amounts of generation, which has sugars readily available in its composition and does not require process pretreatment hydrolysis complexes of the material. This work evaluated residues of melon, pineapple, banana, apple, and mango, to compose a mixture of fruit waste (MFW), simulating a household waste for bioethanol production by a non-conventional yeast Wickerhamomyces sp. UFFS-CE-3.1.2. Sugar extraction was optimized by experimental design (MFW: 12% g dry mass v−1; 25 °C; 5 min) and resulted in the liberation of 36.32 ± 0.72 g L−1 fermentable sugar. MFW was used for alcoholic fermentation with and without nitrogen supplementation (urea and yeast extract). The results demonstrated that it is not necessary for the supplementation, making the process more economically viable. The maximum ethanol productivity (2.50±0.06 g L−1 h−1) was achieved in 9 h of the operation. The MFW extracted is an alternative for the bioethanol process as low cost and straightforward, adapted for different fruit residues, and used as a unique or diluent medium in the biorefinery context. Moreover, non-conventional yeast demonstrated the more new one in this study that explores the potential of yeast recently isolated.

The thermotolerant yeast Kluyveromyces marxianus is a promising bioethanol producer, but its fermentation arrested earlier at high temperatures. Untargeted metabolomic analysis was used to explore K. marxianus’s stress responses during high-temperature fermentation. Fermentation experiments were conducted at 45 °C, with a group conducted at 30 °C as control. Samples were collected from both groups at 14 and 22 h and were subjected to metabolomic analysis. The results show that pathways related to biosynthesis of amino acids, metabolism of purine, pyridoxine and riboflavin, etc. were induced at high temperature. More oleic acid, less palmitic acid and less palmitoleic acid were synthesized at 45 °C than at 30 °C, indicating that K. marxianus can adapt to high temperature by increasing the mean fatty acid chain length. In addition, most of the metabolic pathways stopped after the fermentation arrest, but pathways related to amino acids metabolism, riboflavin metabolism, etc. were still active. This is the first study about comprehensive metabolomic profiling of K. marxianus during high-temperature fermentation. The findings in this study offer deeper insight in mechanisms of K. marxianus’s stress responses during high-temperature fermentation at the metabolome level, and provide potential target pathways for further metabolic engineering towards improved stress tolerance and efficient bioethanol production.

The objective was to study the optimization of fermentation conditions for fermented green jujube wine and quality analysis. This study investigated the fermentation process conditions, the changes in physicochemical indexes, antioxidant capacity and volatile compounds measured from green jujube wine during winemaking. The optimized conditions (the initial sugar, yeast addition, fermentation time and SO(2) treatments) for green jujube wine were 24%, 0.3%, 8 d, 80 mg/L, respectively. The results showed that the variation trend of different substances in green jujube wine in different fermentation periods were different. In the process of alcohol fermentation, the green jujube wine had a high 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, 2,2′-amino-di (2-ethyl-benzothiazoline sulphonic acid-6) ammonium salt (ABTS) free radical scavenging ability and reducing power. Furthermore, a total of 50 volatile compounds were identified in green jujube wine, in which the relative content of aldehydes, ketones, heterocyclic and aromatic compounds were significantly reduced after fermentation.

Spathaspora passalidarum is a naturally pentose-fermenting yeast with the potential to be applied for biotransformation of sugars from lignocellulosic biomasses. Despite being mostly investigated for ethanol production from sugarcane bagasse sugars (mainly xylose and glucose), this microorganism is also capable of producing high xylitol concentrations as a by-product of the ethanol fermentation. The integration of ethanol and xylitol production can improve the economic viability of the process due to the lower sale price of ethanol and the higher added-value of xylitol, a sucrose-substitute sugar with healthier properties. Considering the metabolic pathways interaction from glucose and xylose, it is essential to understand the effect of different glucose and xylose concentrations in the production of ethanol and xylitol by S. passalidarum. In this way, a simultaneous production of both products for the development of an integrated platform for food and chemical and biofuel industries can be accessed. Yeast biomass can also be recovered and applied as a protein source. Therefore, in this study, the fermentative performance of S. passalidarum was investigated in batch fermentations with different xylose and glucose concentrations, using synthetic substrate. The ATP levels and the enzymatic activities of xylose reductase (XR), xylitol dehydrogenase (XDH), and alcohol dehydrogenase (ADH) were also determined for each condition. The results indicated that low amounts of glucose (35%) were necessary to promote a higher xylitol production (10.58 ± 0.29 g/L) without losses on ethanol yield (78.99 ± 4.41%), being the most interesting condition for simultaneous formation of both products.

This research was carried out to produce ethanol for use as a sanitizer in today’s COVID-19 pandemic situation, via cost-effective and eco-friendly techniques. The waste of seasonal fruit, i.e. apple, grape and Indian blueberry, was used in the study. Saccharomyces cerevisiae (baker’s yeast) was used with KMnO4 (5%), sucrose (47 g) and urea (1.5 g) for the fermentation process. All the selected overripe fruits were analyzed for variations in parameters including specific gravity, pH, temperature and concentration during complete fermentation for ethanol production. After complete fermentation, it was clear that the use of Indian blueberry at a temperature of 33 °C, specific gravity of 0.875 and pH value of 5.2 yielded the highest ethanol concentration of 6.5%. The concentration of ethanol obtained from grape samples was 5.23% at 30 °C with specific gravity of 0.839 and pH 4.3. Lastly, the ethanol concentration obtained from apple waste was about 4.52% at 32 °C with specific gravity of 0.880 and pH of 4.7 pH. The FTIR curve of each sample shows an absorbance peak in a wave number range of 3000 cm−1 to 3500 cm−1, which indicates the absence of alcohol in the samples after fermentation.

During ethanol fermentation, ethanol accumulates in the medium and becomes a significant stress factor for yeast. Trehalose and glycogen are major carbohydrate storages and presumably protect cells from such stress conditions. In this study, batch cultivations of wild and adapted Saccharomyces cerevisiae were performed to evaluate the fermentation kinetics and carbohydrate storages, interrelatedly. Trehalose and glycogen were determined by both High Performance Liquid Chromatography (HPLC) and Fourier Transform-Infrared (FT-IR) spectroscopy for comparison. The obtained maximum trehalose and glycogen (7.5 and 10.5 %) contents of the adapted strain was remarkably higher compared to the wild strain (5 and 6.5 %). The adapted S. cerevisiae displayed an enhanced fermentation stresses coping ability resulting in a higher ethanol productivity (2.03 vs 1.65 g ethanol/h) as well as higher ethanol titer (7.7 vs 6.4 %). This study contributes to the understanding of the cellular response of S. cerevisiae cells to fermentation stresses in relation to culture history together with the evaluation of fermentation performance, as well as the process kinetics. This study also confirms that FT-IR spectroscopy of whole S. cerevisiae cells for determination of storage compounds without pretreatment has valuable advantages compared to HPLC with intensive sample handling.

The development of dependable mathematical models to describe cell metabolism dynamics is essential to ensure the success of bioprocess-enhancement strategies. Regarding ethanol fermentation, for e...

Alcoholic fermentation is a crucial step of winemaking, during which yeasts convert sugars to alcohol and also produce or biotransform numerous flavour compounds. In this context, nutrients are essential compounds to support yeast growth and ultimately ensure complete fermentation, as well as optimized production of flavour compounds over that of off-flavour compounds. In particular, the vitamin thiamine not only plays an essential cofactor role for several enzymes involved in various metabolic pathways, including those leading to the production of wine-relevant flavour compounds, but also aids yeast survival via thiamine-dependent stress protection functions. Most yeast species are able to both assimilate exogenous thiamine into the cell and synthesize thiamine de novo. However, the mechanism and level of thiamine accumulation depend on several factors. This review provides an in-depth overview of thiamine utilization and metabolism in the model yeast species Saccharomyces cerevisiae, as well as the current knowledge on (1) the intracellular functions of thiamine, (2) the balance between and regulation of uptake and synthesis of thiamine and (3) the multitude of factors influencing thiamine availability and utilization. For the latter, a particular emphasis is placed on conditions occurring during wine fermentation. The adequacy of thiamine concentration in grape must to ensure successful fermentation is discussed together with the effect of thiamine concentration on fermentation kinetics and on wine sensory properties. This knowledge may serve as a resource to optimise thiamine concentrations for optimal industrial application of yeasts. KEY POINTS: • Thiamine uptake is preferred over biosynthesis and is transcriptionally repressed. • Multiple factors affect thiamine synthesis, availability and uptake for wine yeast. • Thiamine availability impacts fermentation kinetics and wine's sensory properties.

Bioethanol is thought to be a renewable source of energy, because the biomasses used to make ethanol, such as sugar cane and its residual substance, molasses, are resources that can be continuously produced. But the practical use of ethanol to replace fossil fuels or atomic energy has been limited, because the production efficiencies of ethanol in relation to its substrates are not so high. Thus, for industrial production of the bioethanol, yeast fermentation would ideally be carried out in biomasses containing more highly concentrated carbohydrates. However, the environmental stresses in highly concentrated cultures might weaken the yeast’s physiological activities. From various kinds of aquatic yeast with stress tolerance, Torulaspora derbrueckii F2-11 and Wicherhamomyces anomalus AN2-64 were selected as candidates for high-sugar-tolerance yeasts as they showed remarkable growth in the YPD + sorbitol (600 g/L) medium at 25°C for 120 hrs. When the amounts and kinds of sugar alcohols in the cells of the two strains were measured in cultures containing 20 g/L or 400 g/L of D-glucose, maltose, or sucrose, the main two sugar alcohols that accumulated as the sugar concentration increased were glycerol and arabitol. Mutation by ethyl methanesulfonate of the parent strains T. derbrueckii F2-11 and W. anomalus AN2-64 induced mutants F2-11M or AN2-64M, which showed higher sugar, heat, and ethanol tolerances than their respective parents. Ethanol productivities and sugar assimilation activities of the mutants were also higher than those of the parents in the 25% (v/v) molasses.

This study evaluated the effects of yeast extracts (YE) addition (0 % and 0.25 %, w/v) on the no-volatile and volatile compounds of spent coffee grounds (SCG) hydrolysates fermented with single-cultures of two non-Saccharomyces wine yeasts, Torulaspora delbrueckii and Pichia kluyveri. The added YE improved the growth of both T. delbrueckii and P. kluyveri, especially P. kluyveri, resulting in higher ethanol production (1.98 % vs 1.47 %, v/v) by the latter yeast. In addition, the added YE did not impact on most of the alkaloids production regardless of yeast type, while significantly decreasing the contents of chlorogenic, and caffeic acids in SCG hydrolysates fermented with P. kluyveri. Furthermore, more odor-active compounds such as acetate esters and 2-phenylethyl alcohol were produced when YE was added, and P. kluyveri generated significantly higher amounts of esters compared to that of T. delbrueckii. Moreover, YE addition showed a more noticeable effect on the fermentation performance of P. kluyveri relative to that of T. delbrueckii. These findings indicated the potential of SCG hydrolysates fermented with evaluated non-Saccharomyces yeasts and may expand the applications on utilizing SCG to develop new value-added alcoholic products., Graphical abstract Image 1, Highlights • Spent coffee grounds (SCG) hydrolysate was fermented with non-Saccharomyces yeasts. • Yeast extracts (YE) promoted growth of Torulaspora delbrueckii and Pichia kluyveri. • YE elevated production of ethanol by P. kluyveri. • YE boosted odor-active compound diversity of fermented SCG hydrolysates.

The high-glucose tolerance of yeast is the main factor determining the efficiency of high-density alcohol fermentation. Zygosaccharomyces mellis LGL-1 isolated from honey could survive under 700 g/L high-glucose stress and its tolerant characteristics were identified in our previous study. This study was performed to explore and clarify the high-glucose tolerance mechanism of Z. mellis LGL-1. Comparative transcriptomic analysis was used to analyze the genes with differential expression in Z. mellis under high-glucose conditions of 300, 500 and 700 g/L. With 300 g/L samples as reference, there were 937 and 2380 differentially expressed genes (DEGs) in the 500 and 700 g/L samples, respectively. Meanwhile, there was 825 significant DEGs in the 700 g/L samples compared with that of the 500 g/L samples. The result revealed that transcriptional changes in multiple metabolic pathways occur in response to high-glucose stress. q-RT PCR analysis further confirmed that several stress response pathways, such as the high osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) signal transduction pathway, trehalose synthesis pathway and oxidative stress response are closely related to high-glucose tolerance in Z. mellis. This study clarifies mechanisms of Z. mellis in response to high-glucose osmotic stress, providing theoretical basis for the process control of high-density alcohol fermentation.

Lactic acid bacteria (LAB) contamination during fuel ethanol fermentation can lead to significant economic loses. To circumvent this, fuel ethanol plants add antibiotics prophylactically, but their overuse has resulted in the emergence of antibiotic-resistant LAB strains. Lignin is a sustainable biopolymer that can be found as a waste product from lignocellulosic biorefineries. Technical lignins and their smaller phenolic subunits have been shown to exhibit broad-spectrum antimicrobial properties, but there is a lack of demonstrations of lignin derivatives with highly selective properties in the literature. Here, corn stover lignin from a biorefinery was oxidatively depolymerized using an environmentally benign organic oxidant, peracetic acid, into a bio-oil that has selective antimicrobial properties against LAB and not yeasts. The resulting bio-oil demonstrated up to 90% inhibition of commercially sampled LAB (including antibiotic-resistant strains) at 4 mg ml−1 with no inhibition against an industrial yeast strain. These antimicrobial properties of the bio-oil are attributed to larger unidentified lignin oligomers, compared to monolignols, that have a membrane damaging mode of action. Using the bio-oil (4 mg ml−1) during simultaneous saccharification and fermentation (SSF) of raw corn starch showed no inhibition of enzymatic activity, and in LAB contaminated fermentations the bio-oil treatments showed an 8% increase in ethanol yields at higher bacterial contamination ratios (l : 100 yeast to LAB, CFU per ml). This study illustrates the efficacy of using lignin bio-oil as an antibiotic replacement during fuel ethanol fermentation and demonstrates the highly selective antimicrobial properties of lignin oligomers, which creates a viable lignin valorization strategy for biorefineries.

A large diversity of yeasts can be involved in alcoholic fermentation; however, Starmerella bacillaris strains have gained great attention due to their relevant and particular characteristics. S. bacillaris is commonly known as an osmotolerant, acidogenic, psychrotolerant, and fructophilic yeast. Most strains of this species are high producers of glycerol and show low ethanol production rates, being highlighted as promising alternatives to the manufacture of low-alcohol beverages. The increased production of high alcohols, such as benzyl alcohol that has antifungal and antibacterial properties, highlights S. bacillaris potential as a biocontrol agent. After harvest, antifungal yeasts become part of the must microbiota and may also improve the fermentation process. Moreover, during the fermentation, S. bacillaris releases important molecules with biotechnological properties, such as mannoproteins and glutathione. Considering the potential biotechnological properties of S. bacillaris strains, this review presents an overview of recent trends concerning the application of S. bacillaris in fermented beverages. KEY POINTS: •S. bacillaris as an alternative to the production of low-alcohol beverages. •S. bacillaris strains present biocontrol potential. •Molecules released by S. bacillaris may be of great biotechnological interest.

AIM Tyrosol, a quorum sensing molecule in yeasts, was reported to reduce lag phase and induces hyphae formation during cell proliferation. However, evidence of any enhancing effect of tyrosol in cellular proliferation within fermentative environment is unclear. In this investigation, selected yeast cells were assessed for their ability to synthesize tyrosol followed by examining the role of the molecule during fermentation. METHODS AND RESULTS Tyrosols were characterized in four fermentative yeasts viz., Saccharomyces cerevisiae, Wickerhamomyces anomalus, Candida glabrata and Candida tropicalis isolated from traditional fermentative cakes of northeast India. All the isolates synthesized tyrosol while C. tropicalis exhibited filamentous growth in response to tyrosols retrieved from other isolates. Purified tyrosols showed protective behaviour in C. tropicalis and S. cerevisiae under ethanol mediated oxidative stress. During fermentation, tyrosol significantly enhanced growth of W. anomalus in starch medium while C. tropicalis exhibited growth enhancement in starch and glucose sources. The chief fermentative yeast S. cerevisiae showed notable enhancement in fermentative capacity in starch medium under the influence of tyrosol con-commitment of ethanol production. CONCLUSION The study concludes that tyrosol exerts unusual effect in cellular growth and fermentative ability of both Saccharomyces and non-Saccharomyces yeasts. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first report of expression of tyrosol by non-conventional yeasts, where the molecule was found to exert enhancing effect during fermentation, thereby augmenting the process of metabolite production during traditional fermentation.

Among several renewable energy sources produced in the country, ethanol manufactured from sugarcane occupies a prominent position. Therefore, ethanol is a very important economic factor, leading to internal and external interests. This process only had its improvement because of technological advances, both in the agricultural and industrial sectors. With the fermentation process could not be different, from the improvement of the batch fed and continuous system with the use of centrifue, with recirculation and yeast treatment, combined with the selection of yeasts of high fermentative capacity and improvements in distillation processes. Thus, this study aimed to study the increase of bacterial contamination, due to variations in temperature, pH and fermentation time in fermentation and metabolism of Saccharomyces cerevisiae yeasts, during the entire alcoholic fermentation process. Through the results of physicochemical, microbiological and supervisory data analyses, it was possible to conclude that at temperatures above 32oC contamination is favored, and contamination increases with the decrease in pH, and it is necessary to control what is usually done with the use of antibiotics. When fermentation time increases contamination is also favored.

Wine contains a large number of different chemical compounds, the interaction of which influences the formation of its quality defined by the intensity and quality of the color, its aromatic and taste properties. It is the presence of organic acids and their interrelationship that plays a significant role in the formation of taste quality whereby those with lower concentrations of certain acids will be palatably empty and dull, potentially more exposed to microbial contamination, while those with excessive acidity will taste rough and unbalanced. Tartaric, malic and citric acids are the main organic acids in grapes and wine and at the same time play the most important role in the formation of an acidity profile. However, during alcoholic fermentation, other organic acids such as succinic, pyruvic, lactic and acetic acids can also be produced by the yeasts and/or bacteria activity, thereby directly affecting the acidity profile of the wine. The contribution of Saccharomyces yeast to the change in the concentrations of individual organic acids is significantly lower compared to non-Saccharomyces species and is mainly related to the synthesis of succinic acid. In the past non-Saccharomyces species were treated exclusively as spoilage yeasts but nowadays it is somewhat different, with particular attention being paid to exploring their ability to modify the acidic profile of wine by increasing and/or reducing the synthesis of lactic, succinic, malic and pyruvic acid.

This paper aimed to use the major part of carbohydrate fractions in enzymatic hydrolysate of sweet sorghum bagasse, acetone-butanol-ethanol (ABE) fermentation was performed following the ethanol fermentation of hexoses. In batch ethanol fermentation stage, 50.8 ± 3.2 g/L of ethanol was produced from 111.5 g/L of glucose in hydrolysate. After ethanol recovery by batch vacuum distillation, 123.6 ± 15.6 g/L of ethanol was obtained in the distillate, while 47.2 ± 2.5 g/L of xylose was remained in the fermentation broth. The ethanol-free broth was further used as the substrate for ABE fermentation. Compared with yeast remaining scenario, the cell-free ethanol fermentation broth showed a better performance in ABE production. 7.37 ± 0.33 g/L of butanol and 10.93 ± 0.54 g/L of ABE solvent were produced after 120 h of batch fermentation. Based on the biorefinery strategy that cascade two-types of fermentation process, the overall solvents yield boosted significantly, about 144.8 g of ethanol, 17.3 g of butanol and 4.8 g of acetone can be produced from 1 kg sweet sorghum bagasse.

An effective method for monitoring the progress of rice wine fermentation (saccharification, glycolysis system, ethanol fermentation, and the TCA cycle) is required owing to the decreasing human resources in rice wine brewing and dramatically increasing export quantity of rice wine. This study aimed to develop an anion-exclusion/size-exclusion/reversed-phase chromatographic (AEC/SEC/RPC) separation protocol for the simultaneous determination of sugars, ethanol, inorganic, and organic acids for the effective monitoring of rice wine fermentation processes. Optimal chromatographic resolutions were obtained by the combination of a polymer-based size-exclusion column and H+-form weakly acidic cation-exchange resin column with a 20.0 mM phthalic acid eluent. The optimized AEC/SEC/RPC separation system determined 16 different species during rice wine fermentation in a single analysis. The developed AEC/SEC/RPC method demonstrated the below useful advantages for (1) evaluating the progress of rice wine fermentation; (2) evaluating the activity of brewing yeast from the behaviors of glucose, phosphate, and ethanol concentration; and (3) obtaining good correlation between the developed and official methods for monitoring glucose and ethanol. Consequently, several beneficial information was obtained for the process control of rice wine brewing by the developed method.

Growth and ethanol fermentation ability of the acetate-tolerant yeast Saccharomyces cerevisiae KU 002-3 strain were investigated in acetate-addition medium. Under simulated industrial conditions, acetate did not affect on sugar consumption and ethanol production of KU 002-3. Moreover, KU 002-3 strain demonstrated a higher capability for ethanol production than other commercial strains. Co-fermentation was conducted with Lactobacillus fermentum IFRPD 2021, the major contaminating bacteria, during the ethanol production at 0.8% (v/v) acetate (130 mM of the undissociated form of acetate). Under these conditions, growth of L. fermentum IFRPD 2021 was inhibited but the growth and ethanol production ability of S. cerevisiae KU 002-3 strain were not significantly affected. Data indicated the possibility of producing ethanol under high acetate accumulation and reducing Lactobacillus sp. in molasses medium or acetate-containing condition. Producing ethanol under high acetate accumulation and lower the contamination of Lactobacillus sp. in a molasses medium can be useful at industrial scale to produce ethanol with S. cerevisiae KU 002-3 under non-sterilized conditions.