Lachancea yeast species: Origin, biochemical characteristics and oenological significance

Physical cell-cell contact elicits specific transcriptomic responses in wine yeast species

Fermenting grape juice provides a habitat for a well-mapped and evolutionarily relevant microbial ecosystem consisting of many natural or inoculated strains of yeasts and bacteria. The molecular nature of many of the ecological interactions within this ecosystem remains poorly understood, with the partial exception of interactions of a metabolic nature such as competition for nutrients and production of toxic metabolites/peptides. Data suggest that physical contact between species plays a significant role in the phenotypic outcome of interspecies interactions. However, the molecular nature of the mechanisms regulating these phenotypes remains unknown. Here, we present a transcriptomic analysis of physical versus metabolic contact between two wine relevant yeast species, Saccharomyces cerevisiae and Lachancea thermotolerans. The data show that these species respond to the physical presence of the other species. In S. cerevisiae, physical contact results in the upregulation of genes involved in maintaining cell wall integrity, cell wall structural components, and genes involved in the production of H2S. In L. thermotolerans, HSP stress response genes were the most significantly upregulated gene family. Both yeasts downregulated genes belonging to the FLO family, some of which play prominent roles in cellular adhesion. qPCR analysis indicates that the expression of some of these genes is regulated in a species-specific manner, suggesting that yeasts adjust gene expression to specific biotic challenges or interspecies interactions. These findings provide fundamental insights into yeast interactions and evolutionary adaptations of these species to the wine ecosystem.IMPORTANCEWithin the wine ecosystem, yeasts are the most relevant contributors to alcoholic fermentation and wine organoleptic characteristics. While some studies have described yeast-yeast interactions during alcoholic fermentation, such interactions remain ill-defined, and little is understood regarding the molecular mechanisms behind many of the phenotypes observed when two or more species are co-cultured. In particular, no study has investigated transcriptional regulation in response to physical interspecies cell-cell contact, as opposed to the generally better understood/characterized metabolic interactions. These data are of direct relevance to our understanding of microbial ecological interactions in general while also creating opportunities to improve ecosystem-based biotechnological applications such as wine fermentation. Furthermore, the presence of competitor species has rarely been considered an evolutionary biotic selection pressure. In this context, the data reveal novel gene functions. This, and further such analysis, is likely to significantly enlarge the genome annotation space.

Sequential Fermentation in Red Wine cv. Babić Production: The Influence of Torulaspora delbrueckii and Lachancea thermotolerans Yeasts on the Aromatic and Sensory Profile

This research aimed to analyze the impact of two different non-Saccharomyces yeast species on the aromatic profile of red wines made from the cv. Babić (Vitis vinifera L.) red grape variety. The grapes were obtained from two positions in the Middle and South of Dalmatia. This study compared a control treatment with the Saccharomyces cerevisiae (Sc) strain as a type of sequential inoculation treatment with Lachancea thermotolerans (Lt x Sc) and Torulaspora delbrueckii (Td x Sc). The focus was on the basic wine parameters and volatile aromatic compound concentrations determined using the SPME-Arrow-GC/MS method. The results revealed significant differences in cis-linalool oxide, geraniol, neric acid, and nerol, which contribute to the sensory profile with floral and rose-like aromas; some ethyl esters, such as ethyl furoate, ethyl hexanoate, ethyl lactate, ethyl 2-hydroxy-3-methylbutanoate, ethyl 3-hydroxy butanoate, diethyl glutarate, and diethyl succinate, contribute to the aromatic profile with fruity, buttery, overripe, or aging aromas. A sensory evaluation of wines confirmed that Td x Sc treatments exhibited particularly positive aromatic properties together with a more intense fullness, harmony, aftertaste, and overall impression.

A comparative study of Lachancea thermotolerans fermentative performance under standardized wine production conditions

The study explores diverse strains of Lachancea thermotolerans in single-inoculum wine fermentation conditions using synthetic grape must. It aims to analyze the role of the species without external influences like other microorganisms or natural grape must variability. Commercial strains and selected vineyard isolates, untested together previously, are assessed. The research evaluates volatile and non-volatile chemical compounds in final wine, revealing significant strain-based variations. L. thermotolerans notably produces lactic acid and consumes malic acid, exhibiting moderate ethanol levels. The volatile profile displays strain-specific impacts, affecting higher alcohol and ester concentrations compared to S. cerevisiae. These effects vary based on the specific compounds. Using a uniform synthetic must enables direct strain comparisons, eliminating grape-related, environmental, or timing variables in the experiment, facilitating clearer insights into the behavior of L. thermotolerans in wine fermentation. The study compares for the first time all available commercial strains of L. thermotolerans.

The Influence of Chitosan on the Chemical Composition of Wines Fermented with Lachancea thermotolerans

Chitosan exerts a significant influence on various chemical parameters affecting the quality of wine produced using multiple strains of Lachancea thermotolerans. The impact of chitosan on these parameters varies depending on the specific strain studied. We observed that, under the influence of chitosan, the fermentation kinetics accelerated for all examined strains. The formation of lactic acid increased by 41% to 97% across the studied L. thermotolerans strains, depending on the specific strain. This effect also influenced acidity-related parameters such as total acidity, which increased by 28% to 60%, and pH, which experienced a decrease of over 0.5 units. The consumption of malic acid increased by 9% to 20% depending on the specific strain of L. thermotolerans. Nitrogen consumption also rose, as evidenced by all L. thermotolerans strains exhibiting a residual value of Primary Amino Nitrogen (PAN) of below the detection limit, and ammonia consumption increased by 90% to 100%, depending on the strain studied. However, certain parameters such as acetic acid, succinic acid, and glycerol showed contradictory results depending on the strain under investigation. In terms of volatile composition, chitosan supplementation led to increased production of i-butanol by 32% to 65%, 3-methylbutanol by 33% to 63%, and lactic acid ethyl ester by 58% to 91% across all studied strains of L. thermotolerans. Other analyzed aroma compounds exhibited varying changes depending on the specific strain of L. thermotolerans.

Emerging biotechnologies and non-thermal technologies for winemaking in a context of global warming

In the current situation, wine areas are affected by several problems in a context of global warming: asymmetric maturities, pH increasing, high alcohol degree and flat wines with low freshness and poor aroma profile. The use of emerging biotechnologies allows to control or manage such problems. Emerging non-Saccharomyces as Lachancea thermotolerans are very useful for controlling pH by the formation of stable lactic acid from sugars with a slight concomitant alcohol reduction. Lower pH improves freshness increasing simultaneously microbiological stability. The use of Hanseniaspora spp. (specially H. vineae and H. opuntiae) or Metschnikowia pulcherrima promotes a better aroma complexity and improves wine sensory profile by the expression of a more complex metabolic pattern and the release of extracellular enzymes. Some of them are also compatible or synergic with the acidification by L. thermotolerans, and M. pulcherrima is an interesting biotool for reductive winemaking and bioprotection. The use of bioprotection is a powerful tool in this context, allowing oxidation control by oxygen depletion, the inhibition of some wild microorganisms, improving the implantation of some starters and limiting SO2. This can be complemented with the use of reductive yeast derivatives with high contents of reducing peptides and relevant compounds such as glutathione that also are interesting to reduce SO2. Finally, the use of emerging non-thermal technologies as Ultra High-Pressure Homogenization (UHPH) and Pulsed Light (PL) increases wine stability by microbial control and inactivation of oxidative enzymes, improving the implantation of emerging non-Saccharomyces and lowering SO2 additions. GRAPHICAL ABSTRACT.

Metagenomic analysis of the relationship between the microorganisms and the volatiles' development in the wines during spontaneous fermentation from the eastern foothills of the Ningxia Helan mountains in China

BACKGROUND

The natural fermentation of multispecies microbial communities is responsible for unique flavors of winery regions of the eastern foothills of the Ningxia Helan Mountains in China. However, the participation of different microorganisms in the metabolic network for the development of important flavor substances is not clearly defined. Microbial population and diversity on different fermentation phases of Ningxia wine were analyzed by metagenomic sequencing approach.

RESULTS

Gas chromatography-mass spectrometry and ion chromatography were used to identify flavor components, and 13 esters, 13 alcohols, nine aldehydes and seven ketones were detected in volatile substances with odor activity values > 1, and eight organic acids were detected as important flavor components in young wine. Thus, 52 238 predicted protein-coding genes from 24 genera were identified in the Kyoto Encyclopedia of Genes and Genomes level 2 pathways of global and overview maps, and the genes were primarily involved in amino acid metabolism and carbohydrate metabolism. Major microbial genera (Saccharomyces, Tatumella, Hanseniaspora, Lactobacillus, and Lachancea) were closely related to self-characteristic compound metabolism and further contributed to wine flavor.

CONCLUSION

This study clarifies the different metabolic roles of microorganisms in flavor formation during Ningxia wine spontaneous fermentation. Saccharomyces, dominant fungi involved in glycolysis and pyruvate metabolism, produces not only ethanol but also two important precursors, pyruvate and acetyl-CoA, which are necessary for the tricarboxylic acid cycle, fatty acid metabolism, amino acid metabolism, and flavor formation. Lactobacillus and Lachancea, dominant bacteria involved in lactic acid metabolism. Tatumella, dominant bacteria involved in amino acid metabolism, fatty acid metabolism, and acetic acid metabolism to produce esters in the Shizuishan City region samples. These findings provide insights into the use of local functional strains to generate unique flavor formation, as well as improved stability and quality, in wine production. © 2023 Society of Chemical Industry.

Lachancea quebecensis a Novel Isolate for the Production of Craft Beer

Yeasts are ubiquitously present in different natural sources. Some of these yeasts have interesting characteristics for the production of fermented food products. This study characterized Lachancea thermotolerans and L. quebecensis isolated from insects to determine their brewing potential. The yeasts were evaluated according to their fermentative potential in glucose and maltose-defined media and their resistance to ethanol and hop. Finally, craft beer was elaborated at a laboratory scale (10 L). The yeasts utilized glucose as the only carbon source and produced 3.25 ± 1.77, and 4.25 ± 1.06% (v/v), of ethanol for L. thermotolerans and quebecensis, respectively. While in the maltose-defined medium, ethanol content reached 3.25 ± 0.45, and 3.92 ± 0.36, respectively. The presence of alpha acids and ethanol affected the growth of L. quebecensis, which showed lower growth at 90 IBU and 8 ethanol% (v/v) mixtures. The craft beer brewed with L. quebecensis in monoculture experiments showed fruity flavors associated with ethyl acetate and isoamyl acetate. The ethanol content reached 3.50 ± 0.46% (v/v). The beer pH was 4.06 ± 0.20, with a lactic acid concentration of 1.21 ± 0.05 g/L. The sensory panel identified the beer as "fruity", "floral", "hoppy", "sweet", and "sour". To our knowledge, this is the first time L. quebecensis was reported as a potential candidate for sour beer production with reduced ethanol content.

The Life of Saccharomyces and Non-Saccharomyces Yeasts in Drinking Wine

Drinking wine is a processed beverage that offers high nutritional and health benefits. It is produced from grape must, which undergoes fermentation by yeasts (and sometimes lactic acid bacteria) to create a product that is highly appreciated by consumers worldwide. However, if only one type of yeast, specifically Saccharomyces cerevisiae, was used in the fermentation process, the resulting wine would lack aroma and flavor and may be rejected by consumers. To produce wine with a desirable taste and aroma, non-Saccharomyces yeasts are necessary. These yeasts contribute volatile aromatic compounds that significantly impact the wine's final taste. They promote the release of primary aromatic compounds through a sequential hydrolysis mechanism involving several glycosidases unique to these yeasts. This review will discuss the unique characteristics of these yeasts (Schizosaccharomyces pombe, Pichia kluyveri, Torulaspora delbrueckii, Wickerhamomyces anomalus, Metschnikowia pulcherrima, Hanseniaspora vineae, Lachancea thermotolerans, Candida stellata, and others) and their impact on wine fermentations and co-fermentations. Their existence and the metabolites they produce enhance the complexity of wine flavor, resulting in a more enjoyable drinking experience.

Microsatellite typing of Lachancea thermotolerans for wine fermentation monitoring

Climate change is causing a lack of acidity during winemaking and oenologists use several solutions to cope with such a problem. Lachancea thermotolerans, which has the potential to tolerate the harsh physicochemical conditions of wine, has emerged as a promising alternative for pH management during winemaking and, currently, it is the most valuable yeast used for acidity control in wine. In this work a manageable method for L. thermotolerans genotyping based on a multiplexed microsatellite amplification in 6 different loci was developed. The proposed method was used to distinguish between 103 collection strains obtained from different geographical and isolation sources, and then challenged against a 429 L. thermotolerans isolates from several wineries and harvests. The procedure was also tested for fermentation monitoring and strain implantation. This approach was conceived to simplify the methodology available for L. thermotolerans genotyping, making it easy for applying in wine-related laboratories. This method can be applied to distinguish between L. thermotolerans strains in selection programs and to follow implantation of inoculated strains during winemaking with optimal results.

Effect of oil-born yeasts on the quality of extra-virgin olive oils of Basilicata region

The olive oil microbiota mainly consists of yeasts, which may positively or negatively affect the physicochemical and sensory features of product. In this study, 17 yeast strains belonging to Candida boidinii, Lachancea fermentati, Nakazawaea molendinolei, N. wickerhamii and Schwanniomyces polymorphus species were collected during olive oil production, identified and tested for the ability to ferment sugars, to grow at low temperatures, for the occurrence of different enzymatic activities, for the tolerance and degradation of phenolic compounds, radical scavenging activities, biofilm formation, survival to simulated gastro-intestinal (GIT) tract. Yeasts were also inoculated in extra virgin olive oils (EVOO; from Leccino and Coratina cultivar) to evaluate their survival and their effect on EVOO quality (changes in analytical indices) during 6-months of storage. Most of strains were able to grow at 15°C, while the ability to ferment different sugars was strain-specific. All strains had β-glucosidase activity, while none exhibited lipolytic activity; peroxidase was widespread among the strains, while protease activity was strain-dependent. Esterase and the ability to hydrolyse oleuropein and form hydroxytyrosol was present only in N. wickerhamii strains. All strains were able to survive in olive mill wastewater, used as a model of phenolic compounds-rich matrix. A potential biofilm formation was observed only in N. wickerhamii, while the ability to scavenge radical and to cope with GIT-associated stresses were strain-dependent. High levels of survival were observed for almost strains (except S. polymorphus), in both Leccino and Coratina samples. Yeasts limited the acidity rise in olive oils, but overtime they contributed to increase the parameters related to oxidative phenomena (i.e. peroxides, K₂₃₂, K₂₇₀), resulting in a declassification of EVOOs. The total phenolic content (TPC) was correlated to the presence of yeasts and, at the end of storage period (6 months) inoculated samples had significantly lower concentrations compared to the control oils. This study confirms that yeasts are able to survive in olive oils and, therefore, the control of their occurrence during extraction process and storage conditions is needed to obtain high-quality products and to maintain the standards of EVOO classification.

Late Pleistocene-dated divergence between South Hemisphere populations of the non-conventional yeast L. cidri

Most organisms belonging to the Saccharomycotina subphylum have high genetic diversity and a vast repertoire of metabolisms and lifestyles. Lachancea cidri is an ideal yeast model for exploring the interplay between genetics, ecological function and evolution. Lachancea cidri diverged from the Saccharomyces lineage before the whole-genome duplication and is distributed across the South Hemisphere, displaying an important ecological success. We applied phylogenomics to investigate the genetic variation of L. cidri isolates obtained from Australia and South America. Our approach revealed the presence of two main lineages according to their geographic distribution (Aus and SoAm). Estimation of the divergence time suggests that SoAm and Aus lineages diverged near the last glacial maximum event during the Pleistocene (64-8 KYA). Interestingly, we found that the French reference strain is closely related to the Australian strains, with a recent divergence (405-51 YA), likely associated to human movements. Additionally, we identified different lineages within the South American population, revealing that Patagonia contains a similar genetic diversity comparable to that of other lineages in S. cerevisiae. These findings support the idea of a Pleistocene-dated divergence between South Hemisphere lineages, where the Nothofagus and Araucaria ecological niches likely favoured the extensive distribution of L. cidri in Patagonia.

Synergetic Effect of Metschnikowia pulcherrima and Lachancea thermotolerans in Acidification and Aroma Compounds in Airén Wines

On the one hand, the species Lachancea thermotolerans is known for its high genetic diversity, allowing for the existence of strains that produce high concentrations of lactic acid. In contrast, the species Metschnikowia pulcherrima is renowned for its high enzymatic activity capable of producing aromatic esters during fermentation. By enhancing acidity and boosting the concentration of aromatic compounds, both species are currently used to enhance the organoleptic profile of wines. In this regard, ternary fermentations with M. pulcherrima and L. thermotolerans were carried out and the wines produced were further analysed with GC-FID, FTIR, and UV-Vis spectrophotometry. The outcomes showed that the species M. pulcherrima favored an increase in ethyl lactate (between 37 and 41 mg/L) along with an increased concentration of 2-phenylethyl alcohol (between 30 and 35 mg/L), whereas the species L. thermotolerans was able to produce 1 g/L of lactic acid in ternary fermentations. Additionally, pH levels were slightly lower in these fermentations and the color of the white wines produced showed less chemical oxidation as hue values were lower than the control. Finally, the ternary fermentations of L. thermotolerans and M. pulcherrima had higher overall rating in the tasting. In conclusion, ternary fermentations involving these two non-Saccharomyces species are suggested as a substitute for spontaneous fermentations in the production of wines from neutral varieties to express freshness more vividly. This biotechnology may be further favored by the possibility of applying emerging technologies for the removal of microorganisms in grapes and musts.

Cultivar-Dependent Effects of Non-Saccharomyces Yeast Starter on the Oenological Properties of Wines Produced from Two Autochthonous Grape Cultivars in Southern Italy

Global warming poses a threat to winemaking worldwide, especially in dry-warm regions such as Southern Italy. Must fermentation with non-Saccharomyces yeast starter is a possible approach to limit the negative effects of climate change, leading to desirable effects such as an increase in total acidity and/or aroma improvement. The aim of this study was to evaluate the effects of the use of a non-Saccharomyces starter (Lachancea thermotolerans) on the chemical and sensory properties of wines obtained by the the fermentation of two autochthonous Apulian grape cultivars, namely Bombino nero and Minutolo, as compared to the traditional Saccharomyces cerevisiae-driven fermentation. Bombino and Minutolo wines fermented with either Lachancea thermotolerans or Saccharomyces cerevisiae were characterized for their oenological parameters, volatile profiles, and sensory properties. Both chemical and sensory properties were affected by the yeast starter. Inoculation of L. thermotolerans increased sensory complexity, with different floral and sweet-like attributes for both cultivars. Bombino nero, a neutral cultivar, showed a clear effect on wine composition, with both an increase in lactic acid and a change in the volatile profile. On the contrary, the impact of L. thermotolerans was partially masked in Minutolo due to the strong primary aroma background of this highly terpenic cultivar. In this work, we evidenced a notable cultivar × yeast interaction, showing how generalizations of the effects of non-Saccharomyces yeasts on vinification are difficult to achieve, as they show a cultivar-specific outcome.

Metabolomics of Non-Saccharomyces Yeasts in Fermented Beverages

Fermented beverages have been consumed for millennia and today support a global industry producing diverse products. Saccharomyces yeasts currently dominate the fermented beverage industry, but consumer demands for alternative products with a variety of sensory profiles and actual or perceived health benefits are driving the diversification and use of non-Saccharomyces yeasts. The diversity of flavours, aromas, and other sensory characteristics that can be obtained by using non-Saccharomyces yeasts in fermentation is, in large part, due to the diverse secondary metabolites they produce compared to conventional Saccharomyces yeast. Here, we review the use of metabolomic analyses of non-Saccharomyces yeasts to explore their impact on the sensory characteristics of fermented beverages. We highlight several key species currently used in the industry, including Brettanomyces, Torulaspora, Lachancea, and Saccharomycodes, and emphasize the future potential for the use of non-Saccharomyces yeasts in the production of diverse fermented beverages.

Role of Yeasts on the Sensory Component of Wines

The aromatic complexity of a wine is mainly influenced by the interaction between grapes and fermentation agents. This interaction is very complex and affected by numerous factors, such as cultivars, degree of grape ripeness, climate, mashing techniques, must chemical−physical characteristics, yeasts used in the fermentation process and their interactions with the grape endogenous microbiota, process parameters (including new non-thermal technologies), malolactic fermentation (when desired), and phenomena occurring during aging. However, the role of yeasts in the formation of aroma compounds has been universally recognized. In fact, yeasts (as starters or naturally occurring microbiota) can contribute both with the formation of compounds deriving from the primary metabolism, with the synthesis of specific metabolites, and with the modification of molecules present in the must. Among secondary metabolites, key roles are recognized for esters, higher alcohols, volatile phenols, sulfur molecules, and carbonyl compounds. Moreover, some specific enzymatic activities of yeasts, linked above all to non-Saccharomyces species, can contribute to increasing the sensory profile of the wine thanks to the release of volatile terpenes or other molecules. Therefore, this review will highlight the main aroma compounds produced by Saccharomyces cerevisiae and other yeasts of oenological interest in relation to process conditions, new non-thermal technologies, and microbial interactions.

Wine yeast selection in the Iberian Peninsula: Saccharomyces and non-Saccharomyces as drivers of innovation in Spanish and Portuguese wine industries

Yeast selection for the wine industry in Spain started in 1950 for the understanding of the microbial ecology, and for the selection of optimal strains to improve the performance of alcoholic fermentation and the overall wine quality. This process has been strongly developed over the last 30 years, firstly on Saccharomyces cerevisiae, and, lately, with intense activity on non-Saccharomyces. Several thousand yeast strains have been isolated, identified and tested to select those with better performance and/or specific technological properties. The present review proposes a global survey of this massive ex-situ preservation of eukaryotic microorganisms, a reservoir of biotechnological solutions for the wine sector, overviewing relevant screenings that led to the selection of strains from 12 genera and 22 species of oenological significance. In the first part, the attention goes to the selection programmes related to relevant wine-producing areas (i.e. Douro, Extremadura, Galicia, La Mancha and Uclés, Ribera del Duero, Rioja, Sherry area, and Valencia). In the second part, the focus shifted on specific non-Saccharomyces genera/species selected from different Spanish and Portuguese regions, exploited to enhance particular attributes of the wines. A fil rouge of the dissertation is the design of tailored biotechnological solutions for wines typical of given geographic areas.

Yeasts from temperate forests

Yeasts are ubiquitous in temperate forests. While this broad habitat is well-defined, the yeasts inhabiting it and their life cycles, niches, and contributions to ecosystem functioning are less understood. Yeasts are present on nearly all sampled substrates in temperate forests worldwide. They associate with soils, macroorganisms, and other habitats, and no doubt contribute to broader ecosystem-wide processes. Researchers have gathered information leading to hypotheses about yeasts' niches and their life cycles based on physiological observations in the laboratory as well as genomic analyses, but the challenge remains to test these hypotheses in the forests themselves. Here we summarize the habitat and global patterns of yeast diversity, give some information on a handful of well-studied temperate forest yeast genera, discuss the various strategies to isolate forest yeasts, and explain temperate forest yeasts' contributions to biotechnology. We close with a summary of the many future directions and outstanding questions facing researchers in temperate forest yeast ecology. Yeasts present an exciting opportunity to better understand the hidden world of microbial ecology in this threatened and global habitat.

Bioprotection strategies in winemaking

Worldwide the interest for biological control of food spoilage microorganisms has significantly increased over the last decade. Wine makes no exception to this trend, as consumer demands for wines free of preservatives that are considered negative for human health, increase. Biological control during wine fermentation aims at producing high quality wines, while minimizing, or even eliminating, the use of chemical additives. Its success lies in the inoculation of microorganisms to prevent, inhibit or kill undesired microbes, therefore maintaining wine spoilage at the lowest level. The food industry already makes use of this practice, with dedicated commercial microbes already on the market. In winemaking, there are commercial microbes currently under investigation, particularly with the aim to reduce or replace the use of sulphur dioxide. In this review, the potential of wine yeasts and lactic acid bacteria as bioprotection agents and their mechanisms of action during wine fermentation are presented.

An Integrative View of the Role of Lachancea thermotolerans in Wine Technology

The interest in Lachancea thermotolerans, a yeast species with unusual characteristics, has notably increased in all ecological, evolutionary, and industrial aspects. One of the key characteristics of L. thermotolerans is the production of high quantities of lactic acid compared to other yeast species. Its evolution has mainly been driven by the influence of the environment and domestication, allowing several metabolic traits to arise. The molecular regulation of the fermentative process in L. thermotolerans shows interesting routes that play a complementary or protective role against fermentative stresses. One route that is activated under this condition is involved in the production of lactic acid, presenting a complete system for its production, showing the involvement of several enzymes and transporters. In winemaking, the use of L. thermotolerans is nowadays mostly focused in early–medium-maturity grape varieties, in which over-ripening can produce wines lacking acidity and with high concentrations of ethanol. Recent studies have reported new positive influences on quality apart from lactic acid acidification, such as improvements in color, glutathione production, aroma, malic acid, polysaccharides, or specific enzymatic activities that constitute interesting new criteria for selecting better strains. This positive influence on winemaking has increased the availability of commercial strains during recent years, allowing comparisons among some of those products. Initially, the management of L. thermotolerans was thought to be combined with Saccaharomyces cerevisiae to properly end alcoholic fermentation, but new studies are innovating and reporting combinations with other key enological microorganisms such as Schizosaccharomyces pombe, Oenocous oeni, Lactiplantibacillus plantarum, or other non-Saccharomyces.

Isolation, identification, and characterization of wild budding yeasts from rose flowers in Fukuyama city, Hiroshima, Japan, and their application in bread and wine production

In this study, we isolated 741 wild budding yeast strains from the flowers of 45 rose cultivars growing in Fukuyama city, Hiroshima, Japan. Of these 741 strains, 21 were found to have high fermentation abilities in yeast extract-peptone-dextrose (YPD) medium. Four of the 21 strains were able to ferment bread dough to make bread. These yeasts were identified as Saccharomyces cerevisiae, Lachancea fermentati, Lachancea kluyveri, and a Torulaspora sp. based on DNA sequences from the 26S rDNA D1/D2 regions. The CO₂ production profiles of the bread dough generated by the rose yeasts were evaluated using a Fermograph. Saccharomyces cerevisiae FRY2915 exhibited the highest fermentation capacity. Furthermore, FRY2915 was able to ferment grape juice to produce wine, yielding an alcohol concentration of more than 12%. The four rose yeasts isolated during this study have the potential to produce various types of unique fermented foods, thus enhancing the value of the microbiota associated with rose flowers.

Lachancea fermentati FST 5.1: an alternative to baker's yeast to produce low FODMAP whole wheat bread

A diet low in fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) is a successful therapeutic approach to alleviate symptoms of irritable bowel syndrome. However, wheat, as a fructan accumulating grain, is a major source of FODMAPs. Baker's yeast degrades fructans during fermentation, yet conventional whole wheat bread is often still high in FODMAPs. In this study, 96 yeast isolates from different environments were screened regarding their capability to metabolise FODMAPs. Two promising isolates were identified: Lachancea fermentati FST 5.1 and Cyberlindnera fabianii NTCyb, and their potential to produce low FODMAP whole wheat bread was compared to baker's yeast (Saccharomyces cerevisiae). A comprehensive characterisation of the carbohydrate metabolism by the different yeasts was achieved via HPAEC-PAD analysis of flour, doughs, and breads. L. fermentati FST 5.1 fermented fructans and excess fructose much more efficiently than baker's yeast and resulted in bread low in FODMAPs (below all cutoff levels known to induce symptoms). In contrast, C. fabianii NTCyb was unable to ferment FODMAPs in the wheat-dough-matrix. Furthermore, the yeasts' impact on the GC/MS-TOF profile of volatile aroma compounds, the sensory profile, the breads' ultrastructure, and the technological quality was examined. While C. fabianii NTCyb bread had poor technological and sensory attributes, the quality characteristics (volume, crumb structure, texture, sensory, aroma) of L. fermentati FST 5.1 bread were comparable to the baker's yeast bread. Ultimately, this study identified Lachancea fermentati FST 5.1 as an alternative to baker's yeast to produce low FODMAP whole wheat bread while maintaining optimal bread quality and consumer acceptance.

Wine Yeasts Selection: Laboratory Characterization and Protocol Review

Wine reflects the specificity of a terroir, including the native microbiota. In contrast to the use of Saccharomyces cerevisiae commercial starters, a way to maintain wines' microbial terroir identities, guaranteeing at the same time the predictability and reproducibility of the wines, is the selection of autochthonous Saccharomyces and non-Saccharomyces strains towards optimal enological characteristics for the chosen area of isolation. This field has been explored but there is a lack of a compendium covering the main methods to use. Autochthonous wine yeasts from different areas of Slovakia were identified and tested, in the form of colonies grown either on nutrient agar plates or in grape must micro-fermentations, for technological and qualitative enological characteristics. Based on the combined results, Saccharomyces cerevisiae PDA W 10, Lachancea thermotolerans 5-1-1 and Metschnikowia pulcherrima 125/14 were selected as potential wine starters. This paper, as a mixture of experimental and review contributions, provides a compendium of methods used to select autochthonous wine yeasts. Thanks to the presence of images, this compendium could guide other researchers in screening their own yeast strains for wine production.

Non-conventional yeasts for food and additives production in a circular economy perspective

Yeast species have been spontaneously participating in food production for millennia, but the scope of applications was greatly expanded since their key role in beer and wine fermentations was clearly acknowledged. The workhorse for industry and scientific research has always been Saccharomyces cerevisiae. It occupies the largest share of the dynamic yeast market, that could further increase thanks to the better exploitation of other yeast species. Food-related 'non-conventional' yeasts (NCY) represent a treasure trove for bioprospecting, with their huge untapped potential related to a great diversity of metabolic capabilities linked to niche adaptations. They are at the crossroad of bioprocesses and biorefineries, characterized by low biosafety risk and produce food and additives, being also able to contribute to production of building blocks and energy recovered from the generated waste and by-products. Considering that the usual pattern for bioprocess development focuses on single strains or species, in this review we suggest that bioprospecting at the genus level could be very promising. Candida, Starmerella, Kluyveromyces and Lachancea were briefly reviewed as case studies, showing that a taxonomy- and genome-based rationale could open multiple possibilities to unlock the biotechnological potential of NCY bioresources.

Phenotypic characterization of cell-to-cell interactions between two yeast species during alcoholic fermentation

Microbial multispecies ecosystems are responsible for many biotechnological processes and are particularly important in food production. In wine fermentations, in addition to the natural microbiota, several commercially relevant yeast species may be co-inoculated to achieve specific outcomes. However, such multispecies fermentations remain largely unpredictable because of multilevel interactions between naturally present and/or co-inoculated species. Understanding the nature of such interactions has therefore become essential for successful implementation of such strategies. Here we investigate interactions between strains of Saccharomyces cerevisiae and Lachancea thermotolerans. Co-fermentations with both species sharing the same bioreactor (physical contact) were compared to co-fermentations with physical separation between the species in a membrane bioreactor ensuring free exchange of metabolites. Yeast culturability, viability and the production of core metabolites were monitored. The previously reported negative interaction between these two yeast species was confirmed. Physical contact greatly reduced the culturability and viability of L. thermotolerans and led to earlier cell death, compared to when these yeasts were co-fermenting without cell-cell contact. In turn, in the absence of cell-cell contact, L. thermotolerans metabolic activity led to an earlier decline in culturability in S. cerevisiae. Cell-cell contact did not result in significant differences in the major fermentation metabolites ethanol, acetic acid and lactic acid, but impacted on the production of some volatile compounds.

Dissection of quantitative trait loci in the Lachancea waltii yeast species highlights major hotspots

Dissecting the genetic basis of complex trait remains a real challenge. The budding yeast Saccharomyces cerevisiae has become a model organism for studying quantitative traits, successfully increasing our knowledge in many aspects. However, the exploration of the genotype-phenotype relationship in non-model yeast species could provide a deeper insight into the genetic basis of complex traits. Here, we have studied this relationship in the Lachancea waltii species which diverged from the S. cerevisiae lineage prior to the whole-genome duplication. By performing linkage mapping analyses in this species, we identified 86 quantitative trait loci (QTL) impacting the growth in a large number of conditions. The distribution of these loci across the genome has revealed two major QTL hotspots. A first hotspot corresponds to a general growth QTL, impacting a wide range of conditions. By contrast, the second hotspot highlighted a trade-off with a disadvantageous allele for drug-free conditions which proved to be advantageous in the presence of several drugs. Finally, a comparison of the detected QTL in L. waltii with those which had been previously identified for the same trait in a closely related species, Lachancea kluyveri was performed. This analysis clearly showed the absence of shared QTL across these species. Altogether, our results represent a first step toward the exploration of the genetic architecture of quantitative trait across different yeast species.

Beta-glucosidase activity of wine yeasts and its impacts on wine volatiles and phenolics: A mini-review

Beta-glucosidase is an important enzyme for the hydrolysis of grape glycosides in the course of winemaking. Yeasts are the main producers of β-glucosidase in winemaking, therefore play an important role in determining wine aroma and flavour. This article discusses common methods for β-glucosidase evaluation, the β-glucosidase activity of different Saccharomyces and non- Saccharomyces yeasts and the influences of winemaking conditions, such as glucose and ethanol concentration, low pH environment, fermentation temperature and SO₂ level, on their activity. This review further highlights the roles of β-glucosidase in promoting the release of free volatile compounds especially terpenes and the modification of wine phenolic composition during the winemaking process. Furthermore, this review proposes future research direction in this area and guides wine professionals in yeast selection to improve wine quality.

Identification of new ethanol-tolerant yeast strains with fermentation potential from central Patagonia

The quest for new wild yeasts has increasingly gained attention because of their potential ability to provide unique organoleptic characters to fermented beverages. In this sense, Patagonia offers a wide diversity of ethanol-tolerant yeasts and stands out as a bioprospecting alternative. This study characterized the genetic and phenotypic diversity of yeast isolates obtained from Central Chilean Patagonia and analyzed their fermentation potential under different fermentative conditions. We recovered 125 colonies from Nothofagus spp. bark samples belonging to five yeast species: Saccharomyces eubayanus, Saccharomyces uvarum, Lachancea cidri, Kregervanrija delftensis, and Hanseniaspora valbyensis. High-throughput microcultivation assays demonstrated the extensive phenotypic diversity among Patagonian isolates, where Saccharomyces spp and L. cidri isolates exhibited the most outstanding fitness scores across the conditions tested. Fermentation performance assays under wine, mead, and beer conditions demonstrated the specific potential of the different species for each particular beverage. Saccharomyces spp. were the only isolates able to ferment beer wort. Interestingly, we found that L. cidri is a novel candidate species to ferment wine and mead, exceeding the fermentation capacity of a commercial strain. Unlike commercial strains, we found that L. cidri does not require nutritional supplements for efficient mead fermentation. In addition, L. cidri produces succinic and acetic acids, providing a distinct profile to the final fermented product. This work demonstrates the importance of bioprospecting efforts in Patagonia to isolate novel wild yeast strains with extraordinary biotechnological potential for the fermentation industry.

Understanding Wine through Yeast Interactions

Wine is a product of microbial activities and microbe–microbe interactions. Yeasts are the principal microorganisms responsible for the evolution and fulfillment of alcoholic fermentation. Several species and strains coexist and interact with their environment and with each other during the fermentation course. Yeast–yeast interactions occur even from the early stages of fermentation, determining yeast community structure and dynamics during the process. Different types of microbial interactions (e.g., mutualism and commensalism or competition and amensalism) may exert positive or negative effects, respectively, on yeast populations. Interactions are intimately linked to yeast metabolic activities that influence the wine analytical profile and shape the wine character. In this context, much attention has been given during the last years to the interactions between Saccharomyces cerevisiae (SC) and non-Saccharomyces (NS) yeast species with respect to their metabolic contribution to wine quality. Yet, there is still a significant lack of knowledge on the interaction mechanisms modulating yeast behavior during mixed culture fermentation, while much less is known about the interactions between the various NS species or between SC and Saccharomyces non-cerevisiae (SNC) yeasts. There is still much to learn about their metabolic footprints and the genetic mechanisms that alter yeast community equilibrium in favor of one species or another. Gaining deeper insights on yeast interactions in the grape–wine ecosystem sets the grounds for understanding the rules underlying the function of the wine microbial system and provides means to better control and improve oenological practices.

Growth of Non-Saccharomyces Native Strains under Different Fermentative Stress Conditions

The selection of yeast strains adapted to fermentation stresses in their winegrowing area is a key factor to produce quality wines. Twelve non-Saccharomyces native strains from Denomination of Origin (D.O.) “Vinos de Madrid” (Spain), a warm climate winegrowing region, were tested under osmotic pressure, ethanol, and acidic pH stresses. In addition, mixed combinations between non-Saccharomyces and a native Saccharomyces cerevisiae strain were practised. Phenotypic microarray technology has been employed to study the metabolic output of yeasts under the different stress situations. The yeast strains, Lachancea fermentati, Lachancea thermotolerans, and Schizosaccharomyces pombe showed the best adaptation to three stress conditions examined. The use of mixed cultures improved the tolerance to osmotic pressure by Torulaspora delbrueckii, S. pombe, and Zygosaccharomyces bailii strains and to high ethanol content by Candida stellata, S. pombe, and Z. bailii strains regarding the control. In general, the good adaptation of the native non-Saccharomyces strains to fermentative stress conditions makes them great candidates for wine elaboration in warm climate areas.

Effects of Simultaneous Co-Fermentation of Five Indigenous Non-Saccharomyces Strains with S. cerevisiae on Vidal Icewine Aroma Quality

In this study, Vidal grape must was fermented using commercial Saccharomyces cerevisiae F33 in pure culture as a control and in mixed culture with five indigenous non-Saccharomyces yeast strains (Hanseniaspora uvarum QTX22, Saccharomycopsis crataegensis YC30, Pichia kluyveri HSP14, Metschnikowia pulcherrima YC12, and Rhodosporidiobolus lusitaniae QTX15) through simultaneous fermentation in a 1:1 ratio. Simultaneous fermentation inhibited the growth of S. cerevisiae F33 and delayed the time to reach the maximum biomass. Compared with pure fermentation, the contents of polyphenols, acetic esters, ethyl esters, other esters, and terpenes were increased by R. lusitaniae QTX15, S. crataegensis YC30, and P. kluyveri HSP14 through simultaneous fermentation. S. crataegensis YC30 produced the highest total aroma activity and the most abundant aroma substances of all the wine samples. The odor activity values of 1 C13-norisoprenoid, 3 terpenes, 6 acetic esters, and 10 ethyl esters improved significantly, and three lactones (δ-decalactone, γ-nonalactone, and γ-decalactone) related to coconut and creamy flavor were only found in this wine. Moreover, this sample showed obvious “floral” and “fruity” note odor due to having the highest amount of ethyl ester aromatic substances and cinnamene, linalool, citronellol, β-damascenone, isoamyl ethanoate, benzylcarbinyl acetate, isobutyl acetate, etc. We suggest that simultaneous fermentation of S. crataegensis YC30 with S. cerevisiae might represent a novel strategy for the future production of Vidal icewine.

The Combined Use of Lachancea thermotolerans and Lactiplantibacillus plantarum (former Lactobacillus plantarum) in Wine Technology

Most commercialized red wines are produced through alcoholic fermentation performed by yeasts of the Saccharomyces genus, and a second fermentation performed by lactic bacteria of the Oenococus oeni species once the first is completely finished. However, the classical process can suffer complications, of which the risks can increase in grape juices with high contents of sugar and pH. Due to climate change, these situations are becoming more common in the winemaking industry. The main risks in those scenarios are alcoholic-fermentation stops or sluggish and undesirable bacteria development while alcoholic fermentation is not finished yet and wine still contains residual sugars. The study propose a novel alternative that offers a solution or reduces the risk of those scenarios while increasing acidity, which is another serious problem of warm viticulture regions. The alternative consists of the combined use of Lachancea thermotolerans to reduce the pH of musts that suffer from a lack of acidity, Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) to achieve malic acid stability during the first stages of alcoholic fermentation, and Saccharomyces bayanus to complete the alcoholic fermentation in difficult wines of high potential alcohol degree of over 15% (v/v). The new proposed biotechnology produced wines with higher final concentrations in lactic acid, glycerol, color intensity, ethyl lactate and 2-phenyl ethyl acetate in 2.39 g/L, 0.52 g/L, 21%, 48% and 37% respectively than the classical methodology where Saccharomyces genus performs alcoholic fermentation and later Oenococus oeni performs malolactic fermentation. Additionally, the new alternative produced wines with lower concentration in ethanol, pH, acetic acid, ethyl acetate, diacetyl and 1-propanol in 0.37% (v/v), 0.26, 0.08 g/L, 22%, 69% and 28% respectively than the classic method.

[Non-conventional yeasts as tools for innovation and differentiation in brewing]

Yeasts play a crucial role in brewing. During fermentation, besides ethanol and carbon dioxide, yeasts produce a considerable number of organic compounds, which are essential for beer flavor. In particular, Saccharomyces cerevisiae and Saccharomyces pastorianus are traditionally used in the production of ale and lager beers, respectively. Nowadays, the continuous growth of the craft beer market motivates the production of differential and innovative beers; leading specialists and brewers focus on non-conventional yeasts as tools for new product development. In this work, we describe the potential application of non-conventional yeast species such as those of the genera Brettanomyces, Torulaspora, Lachancea, Wickerhamomyces, Pichia and Mrakia in the craft brewing industry, as well as non-traditional brewing yeasts of the Saccharomyces genus. Furthermore, the fermentation conditions of these non-conventional yeasts are discussed, along with their abilities to assimilate and metabolize diverse wort components providing differential characteristics to the final product. In summary, we present a comprehensive review of the state-of-the-art of non-conventional yeasts, which is highly relevant for their application in the production of novel craft beers including flavored beers, non-alcoholic beers, low-calorie beers and functional beers.

High Potential of Pichia kluyveri and Other Pichia Species in Wine Technology

The surfaces of grapes are covered by different yeast species that are important in the first stages of the fermentation process. In recent years, non-Saccharomyces yeasts such as Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, and Pichia kluyveri have become popular with regard to winemaking and improved wine quality. For that reason, several manufacturers started to offer commercially available strains of these non-Saccharomyces species. P. kluyveri stands out, mainly due to its contribution to wine aroma, glycerol, ethanol yield, and killer factor. The metabolism of the yeast allows it to increase volatile molecules such as esters and varietal thiols (aroma-active compounds), which increase the quality of specific varietal wines or neutral ones. It is considered a low- or non-fermentative yeast, so subsequent inoculation of a more fermentative yeast such as Saccharomyces cerevisiae is indispensable to achieve a proper fermented alcohol. The impact of P. kluyveri is not limited to the grape wine industry; it has also been successfully employed in beer, cider, durian, and tequila fermentation, among others, acting as a promising tool in those fermentation processes. Although no Pichia species other than P. kluyveri is available in the regular market, several recent scientific studies show interesting improvements in some wine quality parameters such as aroma, polysaccharides, acid management, and color stability. This could motivate yeast manufacturers to develop products based on those species in the near future.

Characterization of Microbial Dynamics and Volatile Metabolome Changes During Fermentation of Chambourcin Hybrid Grapes From Two Pennsylvania Regions

Microbial diversity present on grapes in wineries, and throughout fermentation has been associated with important metabolites for final wine quality. Although microbiome-metabolome associations have been well characterized and could be used as indicators of wine quality, the impact of regionality on the microbiome and metabolome is not well known. Additionally, studies between microbiome and metabolome have been conducted on single species grape such as Vitis vinifera instead of other species and interspecific hybrids. Although the Pennsylvania wine industry is relatively young compared to California, the industry has been experiencing rapid growth over the past decade and is expected to continue to grow in the future. Pennsylvania's climate of cold winters and high levels of rainfall throughout the growing season favors cultivation of interspecific hybrid grapes such as Vitis ssp. Chambourcin, one of the most commonly grown hybrid varieties in the state. Chambourcin is a prime candidate for studying the impact of regionality on microbiome-metabolome interactions as interspecific hybrid varieties could shape the future of winemaking. Here, we identify for the first time the regional distribution of microbial communities and their interactions with volatile metabolome during fermentation (0-20 days) by integrating high throughput Illumina sequencing (16S and ITS) and headspace-solid phase microextraction-gas chromatography-mass spectrometry. Analyzing 88 samples from nine wineries in the Central and East Pennsylvania regions, we observed high microbial diversity during early stages of fermentation (1-4 days) where non-Saccharomyces yeasts such as Starmerella and Aureobasidium and non-Oenococcus bacteria, Sphingomonas, likely contribute to microbial terroir to the resulting wines. Furthermore, key differentiators between two regions in Pennsylvania, as identified by LEfSe analysis, include the fungal genera Cladosporium and Kazachstania and the bacterial genera Lactococcus and Microbacterium. Moreover, 29 volatile fermentation metabolites were discriminated significantly (variable importance in projection > 1) between the two regions as shown by Partial Least Squares-Discriminant Analysis. Finally, Spearman's correlation identified regional differences of microbial-metabolite associations throughout fermentation that could be used for targeted microbiome manipulation to improve wine quality and preserve regionality. In summary, these results demonstrate the microbial signatures during fermentation and differential microorganisms and metabolites further support impact of regionality on Chambourcin wines in Pennsylvania.

The Important Contribution of Non-Saccharomyces Yeasts to the Aroma Complexity of Wine: A Review

Non-Saccharomyces yeast plays an important role in the initial stages of a wild ferment, as they are found in higher abundance in the vineyard than Saccharomyces cerevisiae. As such, there has been a focus in recent years to isolate these yeast species and characterize their effect on wine fermentation and subsequent aroma. This effect on wine aroma is often species and strain dependent, as the enzymatic profile of each yeast will determine which aroma compounds are formed as secondary metabolites. Semi-fermentative yeast, such as Hanseniaspora spp., Candida spp. and Metschnikowia pulcherrima, are commonly in high abundance in fresh grape must and have diverse enzymatic profiles, however they show a weak tolerance to ethanol, limiting their impact to the initial stages of fermentation. Fully fermentative non-Saccharomyces yeast, characterized by high ethanol tolerance, are often found at low abundance in fresh grape must, similar to Saccharomyces cerevisiae. Their ability to influence the aroma profile of wine remains high, however, due to their presence into the final stages of fermentation. Some fermentative yeasts also have unique oenological properties, such as Lanchancea thermotolerans and Schizosaccharomyces pombe, highlighting the potential of these yeast as inoculants for specific wine styles.

Combinatorial analysis of population dynamics, metabolite levels and malolactic fermentation in Saccharomyces cerevisiae/ Lachancea thermotolerans mixed fermentations

The outcome of co- or sequential inoculation of Lachancea thermotolerans in winemaking remains unpredictable due to a lack of integrated data regarding the impact of grape juice composition on L. thermotolerans fermentation behaviour. Here, we investigate the impact of nitrogen composition on fermentation characteristics and aroma compound production in grape juice sequentially inoculated with commercial L. thermotolerans and S. cerevisiae strains. Subsequently, all treatments were subjected to malolactic fermentation (MLF) using two commercial strains of Oenococcus oeni. Addition of amino acids led to faster growth for S. cerevisiae fermentations, compared to the nitrogen-equivalent addition of diammonium phosphate (DAP). L. thermotolerans persistence in the mixed fermentations was significantly higher following DAP addition, with higher glycerol and lactic acid production. Interestingly, the lower total Nitrogen content in DAP-treated musts compared to other treatments did not alter the subsequent growth of S. cerevisiae. MLF was more similar between musts fermented with L. thermotolerans, regardless of nutrient regime, whereas significant differences in MLF completion times were observed for different nitrogen treatments in S. cerevisiae fermentations. Collectively, the data present an integrated view of the impact of nitrogen treatment on multispecies co-inoculation (growth kinetics and aromatic outcomes) and the downstream impact on MLF.

Exploration of yeast communities in fresh coconut, palmyra, and nipa palm saps and ethanol-fermenting ability of isolated yeasts

This study aimed to explore communities and the ethanol-fermenting ability of yeasts in fresh coconut, palmyra, and nipa palm saps. From the 90 samples of coconut, palmyra, and nipa palm saps, 204 yeast isolates were isolated and identified as 15 species in the phylum Ascomycota and a species (one strain) in Basidiomycota. Saccharomyces cerevisiae, Hanseniaspora guilliermondii, and Lachancea thermotolerans were found in the saps of all three palm species. Candida tropicalis and Pichia kudriavzevii were obtained from the coconut and palmyra palm saps, Hanseniaspora vineae, Lachancea fermentati, and Pichia manshurica were present in the coconut and nipa palm saps, whereas Torulaspora delbrueckii was found in the palmyra and nipa palm saps. The species with the highest occurrence in the saps of coconut, palmyra, and nipa palms was S. cerevisiae with 76.67%, 86.70%, and 100% frequency of occurrence, respectively. Using principal coordinates analysis for ordination, no marked difference was observed in the yeast communities from the saps of the three palm species. A total of 199 isolates were found to possess ethanol-fermentation ability when cultivated using shake flask in 160 g/L of glucose medium at 28°C for 48 h. Lachancea fermentati YSP-383, isolated from nipa palm sap, produced the highest amount of ethanol (76.74 g/L). Twenty-six isolates of Candida sanyaensis (1), C. tropicalis (1), H. guilliermondii (7), L. fermentati (8), L. thermotolerans (1), Pichia kudriavzevii (2), and S. cerevisiae (6) produced high amounts of ethanol ranging from 69.57 to 76.74 g/L. The result demonstrated that yeasts in the palm saps could play roles in the natural fermentation of palm saps.

The transcriptomic response of a wine strain of Lachancea thermotolerans to oxygen deprivation

The yeast Lachancea thermotolerans is of significant biotechnological interest, and selected strains of this species have become commonly used starter cultures in wine fermentation. However, the impact of this species on wine is frequently limited by the rapid dominance of Saccharomyces cerevisiae strains which are better adapted to wine alcoholic fermentation conditions. Previous studies have shown that the major limiting factor for L. thermotolerans competitive performance in the wine ecosystem is oxygen availability, and not ethanol levels as had been previously suggested. Here we investigated the transcriptional response of L. thermotolerans to anaerobiosis in wine fermentation conditions. The data show that L. thermotolerans broadly redirects gene expression towards genes involved in central carbon metabolism, lipid metabolism, remodeling of the cell wall as well as autophagy. Furthermore, the induction of genes that are likely involved in the generation of lactate indicates a redirection of metabolic flux towards this metabolite. The data provide the first insight into the oxygen-dependent response of L. thermotolerans and suggest potential genetic targets to improve lactate production and/or anaerobic fermentation performance of this yeast.

The Impact of Chitosan on the Chemical Composition of Wines Fermented with Schizosaccharomyces pombe and Saccharomyces cerevisiae

This study investigates the influence of the antimicrobial agent chitosan on a selected Schizosaccharomyces pombe strain during the alcoholic fermentation of ultra-pasteurized grape juice with a high concentration of malic acid. It also studies a selected Saccharomyces cerevisiae strain as a control. The study examines several parameters relating to wine quality, including volatile and non-volatile compounds. The principal aim of the study is to test the influence of chitosan on the final chemical composition of the wine during alcoholic fermentation, and to compare the two studied fermentative yeasts between them. The results show that chitosan influences the final concentration of acetic acid, ethanol, glycerol, acetaldehyde, pyruvic acid, α-ketoglutarate, higher alcohols, acetate esters, ethyl esters, and fatty acids, depending on the yeast species.

The Role of Yeasts and Lactic Acid Bacteria on the Metabolism of Organic Acids during Winemaking

The main role of acidity and pH is to confer microbial stability to wines. No less relevant, they also preserve the color and sensory properties of wines. Tartaric and malic acids are generally the most prominent acids in wines, while others such as succinic, citric, lactic, and pyruvic can exist in minor concentrations. Multiple reactions occur during winemaking and processing, resulting in changes in the concentration of these acids in wines. Two major groups of microorganisms are involved in such modifications: the wine yeasts, particularly strains of Saccharomyces cerevisiae, which carry out alcoholic fermentation; and lactic acid bacteria, which commonly conduct malolactic fermentation. This review examines various such modifications that occur in the pre-existing acids of grape berries and in others that result from this microbial activity as a means to elucidate the link between microbial diversity and wine composition.

The Effect of Non-Saccharomyces and Saccharomyces Non-Cerevisiae Yeasts on Ethanol and Glycerol Levels in Wine

Non-Saccharomyces and Saccharomyces non-cerevisiae studies have increased in recent years due to an interest in uninoculated fermentations, consumer preferences, wine technology, and the effect of climate change on the chemical composition of grapes, juice, and wine. The use of these yeasts to reduce alcohol levels in wines has garnered the attention of researchers and winemakers alike. This review critically analyses recent studies concerning the impact of non-Saccharomyces and Saccharomyces non-cerevisiae on two important parameters in wine: ethanol and glycerol. The influence they have in sequential, co-fermentations, and solo fermentations on ethanol and glycerol content is examined. This review highlights the need for further studies concerning inoculum rates, aeration techniques (amount and flow rate), and the length of time before Saccharomyces cerevisiae sequential inoculation occurs. Challenges include the application of such sequential inoculations in commercial wineries during harvest time.