Cerevisiae Wine Strains Research Articles

Activation of the yeast Retrograde Response pathway by adaptive laboratory evolution with S-(2-aminoethyl)-L-cysteine reduces ethanol and increases glycerol during winemaking

BackgroundGlobal warming causes an increase in the levels of sugars in grapes and hence in ethanol after wine fermentation. Therefore, alcohol reduction is a major target in modern oenology. Deletion of the MKS1 gene, a negative regulator of the Retrograde Response pathway, in Saccharomyces cerevisiae was reported to increase glycerol and reduce ethanol and acetic acid in wine. This study aimed to obtain mutants with a phenotype similar to that of the MKS1 deletion strain by subjecting commercial S. cerevisiae wine strains to an adaptive laboratory evolution (ALE) experiment with the lysine toxic analogue S-(2-aminoethyl)-L-cysteine (AEC).ResultsIn laboratory-scale wine fermentation, isolated AEC-resistant mutants overproduced glycerol and reduced acetic acid. In some cases, ethanol was also reduced. Whole-genome sequencing revealed point mutations in the Retrograde Response activator Rtg2 and in the homocitrate synthases Lys20 and Lys21. However, only mutations in Rtg2 were responsible for the overactivation of the Retrograde Response pathway and ethanol reduction during vinification. Finally, wine fermentation was scaled up in an experimental cellar for one evolved mutant to confirm laboratory-scale results, and any potential negative sensory impact was ruled out.ConclusionsOverall, we have shown that hyperactivation of the Retrograde Response pathway by ALE with AEC is a valid approach for generating ready-to-use mutants with a desirable phenotype in winemaking.

Effect of CUP1 copy number and pH on copper resistance of Saccharomyces cerevisiae enological strains

The widespread use of copper-based pesticides in winemaking can affect wine fermentation. Therefore, it is crucial to assess the resistance levels of Saccharomyces cerevisiae wine strains in enological growth conditions. In the context of winemaking, grape juice is a complex environment capable of chelating copper and is characterized by a distinctly acidic pH. In this work, the effects of copper concentration on the growth of 10 S. cerevisiae strains, isolated from an enological environment, and one commercial starter were tested in YNB minimal medium and synthetic must, mimicking enological conditions.In minimal medium, resistance to copper varied among yeasts (50–600 μM), revealing the presence of three resistance levels (high, intermediate, and low). Representative strains of the three groups were tested at a pH range from 5.2 to 3.0 at the copper concentration that showed a 20–25 % growth reduction. At pH range 5.2–4.5, a growth reduction was observed, while, conversely, a strain-specific recovery was observed at pH range 3.2–3.0.In synthetic must, the strains showed higher copper resistance levels than in minimal medium (50–4000 μM). In both synthetic must and minimal medium, a significant logarithmic correlation was found between copper resistance and CUP1 gene copy number. The copy number tended to better explain resistance in minimal medium compared to synthetic must. The results shed light on the role of CUP1 copy number within an enological environment.

Strain prevalence and killer factor only partially influence the fermentation activity of pairwise Saccharomyces cerevisiae wine strains inoculation.

Commercial Saccharomyces cerevisiae starters are single-strain cultures widely used in winemaking to optimise the fermentation process and improve the organoleptic quality of wine. Unfortunately, the worldwide extensive use of a limited number of industrial strains led to the standardisation of the sensory properties, reducing the identity of wines. Therefore, the use of multi-strain S. cerevisiae starters can be an alternative tool to alter the sensory profile of wines, increasing the diversity of wine styles. However, this strategy may be interesting only if the overall fermentation kinetics is not affected. To date, there is a lack of information regarding the influence of multi-strain starters on the overall fermentation process in wine. In this context, killer toxins, affecting the viability of sensitive strains, can play a significant role. This study aimed to evaluate the effects of pairing eight wine strains of S. cerevisiae (two sensitive, three neutral and three killer) in co-fermentations compared to single-strain fermentations. Results evidenced that, among co-fermentations where the strain prevalence was significant, the killer strains constituted 79% to 100% of the total yeast population when co-inoculated with a sensitive one. However, in most of the cases, co-fermentations kinetics were similar to those of sensitive strains or worse than both strains. Thus, the presence of a killer strain alone is not sufficient to predict the overall fermentation progress, which is an essential information in winemaking. Interestingly, the neutral strain P304.4 was always prevalent, regardless of the second strain and, in most of the co-fermentations, the overall fermentation trend was similar to the P304.4 single-strain fermentation. Regardless of killer activity, our results suggest that the effect of strains on fermentative kinetics is still unpredictable, and further studies are needed to thoroughly explore strain to strain interactions in winemaking.

Impact of two new non-conventional yeasts, Candidaoleophila and Starmerella lactis-condensi, isolated from sugar-rich substrates, on Frappato wine aroma

The interest of non-Saccharomyces yeasts in wine fermentation increased constantly in last years. This study reports for the first time the enological potential of two strains Starmerella lactis-condensi MN412 and Candida oleophila YS209. In an innovative way, these strains were used in winemaking to improve floral and fruity aroma of Frappato red wine, which has not been explored. The enological performances of the two non-Saccharomyces strains were compared to a wine strain of Starmerella bacillaris, namely Cz3, previously characterized in winemaking conditions. In these three cases, the non-Saccharomyces strain was sequentially inoculated with S. cerevisiae wine strain NF213, used as control. The St. lactis-condensi MN412 was isolated from Sicilian manna, a sugar-rich matrix, extracted from Fraxinus angustifolia trees (Oleaceae). The strain C. oleophila YS209 was isolated from honey by-products. Microbiological counts showed the ability of MN412 and YS209 to maintain high counts up to 6 days of alcoholic fermentation. Regarding chemical parameters, Cz3 showed the highest glycerol production. Analysis of VOCs revealed that the trials with non-Saccharomyces yeasts were characterized by a higher concentration of esters that contributed positively to the fruity aroma of the wines. The sensory analysis confirmed that the use of MN412 and YS209 impacted positively the final wines in terms of fruity and floral intensity, respectively, while did not generate sensory defects. In conclusion, non-conventional yeasts represent strategy to improve floral-fruity freshness of wine aroma and sugar-rich matrices such as manna ash and honey might represent novel ecological niches as source of potential oenological yeast.

Unlocking the secrets of peptide transport in wine yeast: insights into oligopeptide transporter functions and nitrogen source preferences.

Limited nitrogen supply can prevent the completion of alcoholic fermentation. Supplementation through peptides as an alternative, natural source of nitrogen for yeast offers an interesting solution for this issue. In this work, the S. cerevisiae peptide transporters of the Opt and Fot families were studied. We demonstrated that Fot and Opt2 have a broader peptide length preference than previously reported, enabling yeasts to acquire sufficient nitrogen from peptides without requiring additional ammonia or amino acids to complete fermentation. On the contrary, Opt1 was unable to consume any peptide in the given conditions, whereas it has been described elsewhere as the main peptide transporter for peptides longer than three amino acid residues in experiments in laboratory conditions. This controversy signifies the need in applied sciences for approaching experimental conditions to those prevalent in the industry for its more accurate characterization. Altogether, this work provides further evidence of the importance of peptides as a nitrogen source for yeast and their consequent positive impact on fermentation kinetics.

Ethyl Carbamate in Fermented Food Products: Sources of Appearance, Hazards and Methods for Reducing Its Content.

Ethyl carbamate, the ethyl ester of carbamic acid, has been identified in fermented foods and alcoholic beverages. Since ethyl carbamate is a probable human carcinogen, reduction of its content is important for food safety and human health. In alcoholic beverages, ethyl carbamate is mostly formed from the reaction of ethanol with urea, citrulline and carbamyl phosphate during fermentation and storage. These precursors are generated from arginine metabolism by wine yeasts and lactic acid bacteria. This review summarizes the mechanisms of ethyl carbamate formation, its impact on human health and methods used in winemaking to minimize its content. These approaches include genetic modification of Saccharomyces cerevisiae wine strains targeting pathways of arginine transport and metabolism, the use of lactic acid bacteria to consume arginine, direct degradation of ethyl carbamate by enzymes and microorganisms, and different technological methods of grape cultivation, alcoholic fermentation, wine aging, temperature and duration of storage and transportation.

Application of FTIR Microspectroscopy in Oenology: Shedding Light on Cell Wall Composition of Saccharomyces cerevisiae Strains

The evaluation of cell parietal components of yeasts is an important criterium for the selection of wine starters since they play a key role in the vinification process. The aim of this study was to characterize and compare the cell wall composition of four industrial (BM45, D47, EC1118, K1) and three native Saccharomyces cerevisiae (MY8, MY11, PEDRO2000E) wine strains by means of scanning and transmission electron microscopy and ATR-FTIR microspectroscopy. A statistically significant variability in the cell wall thickness and cell diameter was observed among the yeast cells, with native strains showing higher cell diameter values. FTIR microspectroscopy applied on the intact cells without any previous invasive treatment and on the separated cell walls highlighted profound differences among the strains in terms of the overall content of parietal polysaccharides as related to the thickness of the cell walls and in terms of the relative concentration of β-glucans and mannans in the cell walls. The strains EC1118, MY11, and PEDRO2000E showed a higher overall content of β-glucans and mannans, whose lower relative concentration in PEDRO2000E was compensated by a thicker cell wall; BM45 and D47 were characterized by a high relative concentration of polysaccharides in a thinner wall, while K1 and MY8 displayed a low relative concentration of polysaccharides. ATR-FTIR microspectroscopy allows identifying polysaccharide-rich yeast strains and can become a smart option for the selection of starter cultures to be used in oenology and for other applications in food industry, thanks to the interesting technological properties of parietal polysaccharides.Graphical

Saccharomyces cerevisiae wine strains show a wide range of competitive abilities and differential nutrient uptake behavior in co-culture with S. kudriavzevii

The wine industry has implemented complex starters with multiple yeast species as an efficient method to improve certain wine properties. Strains’ competitive fitness becomes essential for its use in such cases. In the present work, we studied this trait in 60 S. cerevisiae strains from different origins, co-inoculated with a S. kudriavzevii strain, and confirmed it to be associated with the strains' origin. To gather deeper knowledge about the characteristics of strains with highly competitive ability versus the rest, microfermentations using representative strains from each group were performed and the carbon and nitrogen sources uptake was analysed. Our results demonstrate that despite wine strains being the subclade with the highest competitive ability, they present a wide range of behaviors as well as nutrient uptake dynamics, which points to a heterogeneous nature of domestication processes. An interesting strategy was observed in the highly competitive strains (GRE and QA23), the nitrogen sources uptake in the competition was accelerated and the sugar fermentation was slowing despite the fermentation finish at the same time. Therefore, this competition study, using particular combinations of strains, expands the knowledge in the field of the usage of mixed starters in wine manufactured products.

The Riboflavin Metabolism in Four Saccharomyces cerevisiae Wine Strains: Assessment in Oenological Condition and Potential Implications with the Light-Struck Taste.

Riboflavin (RF), or vitamin B2, is an essential compound for yeast growth and a precursor of the flavin coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), involved in redox and non-redox processes. RF is a photosensitive compound involved in the light-struck taste (LST), a fault causing the formation of off-flavors that can develop when the wine is exposed to light in the presence of methionine (Met), as well. As both RF and Met can be associated with detrimental changes in wines, a better comprehension of its yeast-mediated production is relevant to predict the maintenance of the desired character of the wine. This study aims at assessing the production of flavin derivatives (FDs) and Met by S. cerevisiae oenological starters under laboratory conditions. The results showed the presence of extra- and intracellular FDs, and Met is a strain-dependent characteristic being also affected by the initial content of RF in the medium. This finding was confirmed when the winemaking was carried out in a relevant environment. Our results evidenced the important impact of the yeast strain on the content of RF and its derivatives.

Redox cofactor metabolism in Saccharomyces cerevisiae and its impact on the production of alcoholic fermentation end-products

The alcoholic fermentation of organic carbon sources by Saccharomyces cerevisiae produces many by-products, with the most abundant originating from central carbon metabolism. The production of these metabolites involves redox reactions and largely depends on the maintenance of redox homeostasis. Despite the metabolic pathways being mostly conserved across strains of S. cerevisiae, their production of various amounts of metabolic products suggests that their intracellular concentration of redox cofactors and/or redox balance differ. This study explored the redox status dynamics and NAD(H) and NADP(H) cofactor ratios throughout alcoholic fermentation in four S. cerevisiae strains that exhibit different carbon metabolic fluxes. This study focussed on the molecular end-products of fermentation, redox cofactor ratios and the impact thereof on redox homeostasis. Strain-dependent differences were identified in the redox cofactor levels, with NADP(H) ratios and levels remaining stable while NAD(H) levels decreased drastically as the fermentation progressed. Changes in the NAD+/NADH ratio were also observed. Total levels of NAD(H) decreased drastically as the fermentation progressed despite the cells remaining viable until the end of fermentation. NAD+ was found to be favoured initially while NADH was favoured towards the end of the fermentation. The change in the NAD+/NADH redox cofactor ratio during fermentation was linked with the production of end-products. The findings in this study could steer further research in the selection of S. cerevisiae wine strains for desirable aroma contributions based on their intracellular redox balance management.

Influence of ergosterol and phytosterols on wine alcoholic fermentation with Saccharomyces cerevisiae strains

Sterols are a fraction of the eukaryotic lipidome that is essential for the maintenance of cell membrane integrity and its good functionality. During alcoholic fermentation, they enhance yeast growth, metabolism and viability, as well as resistance to high sugar content and ethanol stress. Grape musts clarified in excess lead to the loss of solid particles rich in sterols, resulting in sluggish and stuck fermentations. Two sterol sources can help Saccharomyces cerevisiae yeasts to adapt to fermentation stress conditions: ergosterol (synthesized by yeast under aerobic conditions) and phytosterols (plant sterols imported by yeast cells from grape musts under anaerobiosis). Little is known about the physiological impact of phytosterols assimilation in comparison with ergosterol and the influence of sterol type on fermentation kinetics parameters. Moreover, studies to date have analyzed a limited number of yeast strains. Thus, the aim of this work was to compare the performances of a set of Saccharomyces cerevisiae wine strains that represent the diversity of industrial wine yeast, fermenting with phytosterols or ergosterol under two conditions: sterol limitation (sterol starvation) and high sugar content (the most common stress during fermentation). Results indicated that yeast cell viability was negatively impacted by both stressful conditions, resulting in sluggish and stuck fermentations. This study revealed the huge phenotype diversity of the S. cerevisiae strains tested, in particular in terms of cell viability. Indeed, strains with better viability maintenance completed fermentation earlier. Interestingly, we showed for the first time that sterol type differently affects a wide variety of phenotype, such as viability, biomass, fermentation kinetics parameters and biosynthesis of carbon central metabolism (CCM) metabolites. Ergosterol allowed preserving more viable cells at the end of fermentation and, as a consequence, a better completion of fermentation in both conditions tested, even if phytosterols also enabled the completion of alcoholic fermentation for almost all strains. These results highlighted the essential role of sterols during wine alcoholic fermentation to ensure yeast growth and avoid sluggish or stuck fermentations. Finally, this study emphasizes the importance of taking into account sterol types available during wine fermentation.

Evaluation of the Biocontrol Potential of a Commercial Yeast Starter against Fuel-Ethanol Fermentation Contaminants

Lactic acid bacteria (LAB) and Brettanomyces bruxellensis are the main contaminants of bioethanol fermentations. Those contaminations affect Saccharomyces cerevisiae performance and reduce ethanol yields and productivity, leading to important economic losses. Currently, chemical treatments such as acid washing and/or antibiotics are used to control those contaminants. However, these control measures carry environmental risks, and more environmentally friendly methods are required. Several S. cerevisiae wine strains were found to secrete antimicrobial peptides (AMPs) during alcoholic fermentation that are active against LAB and B. bruxellensis strains. Thus, in the present study, we investigated if the fuel-ethanol commercial starter S. cerevisiae Ethanol Red (ER) also secretes those AMPs and evaluated its biocontrol potential by performing alcoholic fermentations with mixed-cultures of ER and B. bruxellensis strains and growth assays of LAB in ER pre-fermented supernatants. Results showed that all B. bruxellensis strains were significantly inhibited by the presence of ER, although LAB strains were less sensitive to ER fermentation metabolites. Peptides secreted by ER during alcoholic fermentation were purified by gel-filtration chromatography, and a bioactive fraction was analyzed by ELISA and mass spectrometry. Results confirmed that ER secretes the AMPs previously identified. That bioactive fraction was used to determine minimal inhibitory concentrations (MICs) against several LAB and B. bruxellensis strains. MICs of 1–2 mg/mL were found for B. bruxellensis strains and above 2 mg/mL for LAB. Our study demonstrates that the AMPs secreted by ER can be used as a natural preservative in fuel-ethanol fermentations.

PECULIARITIES OF GROWTH PARAMETERS OF $SACCHAROMYCES~CEREVISIAE$ UNDER DIFFERENT CONDITIONS

Saccharomyces cerevisiae is an essential component of human civilization because of its extensive use in food industry. At the point of industrial usage it is very important to get large amount of biomass but many factors causes yeast's viability loss and death. The aim of this work was to study the peculiarities of growth parameters – specific growth rate (SGR, μ, growth yield) of S. cerevisiae wine and beer strains under different external conditions, as well as pH and oxidation-reduction potential (ORP) changes during growth. It was shown that under aerobic cultivation, the conditions 30℃ and pH 6.5 are more favorable for the growth of 2 strains (ATCC 9804, μ = 0.398; ATCC 13007, μ = 0.407), where they can enhance the biomass, and under microaerobic conditions the pH 5.0 and 37℃ are more favorable (ATCC 9804, μ = 0.35; ATCC 13007, μ = 0.436). During aerobic conditions, lower ORP values are established which did not depend on growth temperature and external pH. Under microaerobic conditions until the establish¬ment of the stationary phase (24 h) pH dependent changes of ORP were established. Obtained results will help to clarify the biochemical, biophysical and bioenergetic phenomena of yeast survival that can enhance the biomass growth and yield and thus applied industrial scale.

Yeast Plasma Membrane Fungal Oligopeptide Transporters Display Distinct Substrate Preferences despite Their High Sequence Identity.

Fungal Oligopeptide Transporters (Fot) Fot1, Fot2 and Fot3 have been found in Saccharomyces cerevisiae wine strains, but not in strains from other environments. In the S. cerevisiae wine strain EC1118, Fot1 and Fot2 are responsible for a broader range of oligopeptide utilization in comparison with strains not containing any Fot. This leads to better fermentation efficiency and an increased production of desirable organoleptic compounds in wine. Despite the benefits associated with Fot activity in S. cerevisiae within the wine environment, little is known about this family of transporters in yeast. The presence of Fot1, Fot2 and Fot3 in S. cerevisiae wine strains is due to horizontal gene transfer from the yeast Torulaspora microellipsoides, which harbors Fot2Tm, FotX and FotY proteins. Sequence analyses revealed that Fot family members have a high sequence identity in these yeast species. In this work, we aimed to further characterize the different Fot family members in terms of subcellular localization, gene expression in enological fermentation and substrate specificity. Using CRISPR/Cas9, we constructed S. cerevisiae wine strains containing each different Fot as the sole oligopeptide transporter to analyze their oligopeptide preferences by phenotype microarrays. The results of oligopeptide consumption show that Fot counterparts have different di-/tripeptide specificities, suggesting that punctual sequence divergence between FOT genes can be crucial for substrate recognition, binding and transport activity. FOT gene expression levels in different S. cerevisiae wine strains during enological fermentation, together with predicted binding motifs for transcriptional regulators in nitrogen metabolism, indicate that these transporters may be under the control of the Nitrogen Catabolite Repression (NCR) system. Finally, we demonstrated that Fot1 is located in the yeast plasma membrane. This work contributes to a better understanding of this family of oligopeptide transporters, which have demonstrated a key role in the utilization of oligopeptides by S. cerevisiae in enological fermentation.

Exploring the suitability of Saccharomyces cerevisiae strains for winemaking under aerobic conditions

Aerobic fermentation was previously proposed to reduce the ethanol content of wine. The main constraint found for Saccharomyces cerevisiae to be used under these conditions was the high levels of acetic acid produced by all S. cerevisiae strains previously tested. This work addressed the identification of S. cerevisiae wine yeast strains suitable for aerobic fermentation and the optimization of fermentation conditions to obtain a reduced ethanol yield with acceptable volatile acidity. This approach unveiled a great diversity in acetic acid yield for different S. cerevisiae strains under aerobic conditions, with some strains showing very low volatile acidity. Three strains were selected for further characterization in bioreactors, with natural grape must, under aerobic and anaerobic conditions. Ethanol yields were lower under aerobic than under anaerobic conditions for all strains, and acetic acid levels were low for two of them. Strain-dependent changes in volatile compounds were also observed between aerobic and anaerobic conditions. Finally, the process was optimized at laboratory scale for one strain. This is the first report of S. cerevisiae wine strains showing low acetic acid production under aerobic conditions and paves the way for simplified aerobic fermentation protocols aimed to reducing the alcohol content of wines.

Truth in wine yeast.

SummaryEvolutionary history and early association with anthropogenic environments have made Saccharomyces cerevisiae the quintessential wine yeast. This species typically dominates any spontaneous wine fermentation and, until recently, virtually all commercially available wine starters belonged to this species. The Crabtree effect, and the ability to grow under fully anaerobic conditions, contribute decisively to their dominance in this environment. But not all strains of Saccharomyces cerevisiae are equally suitable as starter cultures. In this article, we review the physiological and genetic characteristics of S. cerevisiae wine strains, as well as the biotic and abiotic factors that have shaped them through evolution. Limited genetic diversity of this group of yeasts could be a constraint to solving the new challenges of oenology. However, research in this field has for many years been providing tools to increase this diversity, from genetic engineering and classical genetic tools to the inclusion of other yeast species in the catalogues of wine yeasts. On occasion, these less conventional species may contribute to the generation of interspecific hybrids with S. cerevisiae. Thus, our knowledge about wine strains of S. cerevisiae and other wine yeasts is constantly expanding. Over the last decades, wine yeast research has been a pillar for the modernisation of oenology, and we can be confident that yeast biotechnology will keep contributing to solving any challenges, such as climate change, that we may face in the future.

Mild Pretreatments to Increase Fructose Consumption in Saccharomyces cerevisiae Wine Yeast Strains.

The present research investigates the effect of different pretreatments on glucose and fructose consumption and ethanol production by four Saccharomyces cerevisiae wine strains, three isolated and identified from different wine regions in Turkey and one reference strain. A mild stress temperature (45 °C, 1 h) and the presence of ethanol (14% v/v) were selected as pretreatments applied to cell cultures prior to the fermentation step in synthetic must. The goodness fit of the mathematical models was estimated: linear, exponential decay function and sigmoidal model were evaluated with the model parameters R2 (regression coefficient), RMSE (root mean square error), MBE (mean bias error) and χ2 (reduced Chi-square). Sigmoidal function was determined as the most suitable model with the highest R2 and lower RMSE values. Temperature pretreatment allowed for an increase in fructose consumption rate by two strains, evidenced by a t90 value 10% lower than the control. One of the indigenous strains showed particular promise for mild temperature treatment (45 °C, 1 h) prior to the fermentation step to reduce residual glucose and fructose in wine. The described procedure may be effective for indigenous yeasts in preventing undesirable sweetness in wines.

Global distribution of IRC7 alleles in Saccharomyces cerevisiae populations: a genomic and phenotypic survey within the wine clade

The adaptation to the different biotic and abiotic factors of wine fermentation has led to the accumulation of numerous genomic hallmarks in Saccharomyces cerevisiae wine strains. IRC7, a gene encoding a cysteine-S-β-lyase enzyme related volatile thiols production in wines, has two alleles: a full-length allele (IRC7F ) and a mutated one (IRC7S ), harbouring a 38bp-deletion. Interestingly, IRC7S -encoding a less active enzyme- appears widespread amongst wine populations. Studying the global distribution of the IRC7S allele in different yeast lineages, we confirmed its high prevalence in the Wine clade and demonstrated a minority presence in other domesticated clades (Wine-PDM, Beer and Bread) while it is completely missing in wild clades. Here we show that IRC7S -homozygous (HS) strains exhibited both fitness and competitive advantages compared to IRC7F -homozygous (HF) strains. There are some pieces of evidence of the direct contribution of the IRC7S allele to the outstanding behaviour of HS strains (i.e. improved response to oxidative stress conditions and higher tolerance to high copper levels); however, we also identified a set of sequence variants with significant co-occurrence patterns with the IRC7S allele, which can be co-contributing to the fitness and competitive advantages of HS strains in wine fermentations. This article is protected by copyright. All rights reserved.

Metabolic differences between a wild and a wine strain of Saccharomyces cerevisiae during fermentation unveiled by multi-omic analysis.

Saccharomyces cerevisiae, a widespread yeast present both in the wild and in fermentative processes, like winemaking. During the colonization of these human-associated fermentative environments, certain strains of S. cerevisiae acquired differential adaptive traits that enhanced their physiological properties to cope with the challenges imposed by these new ecological niches. The advent of omics technologies allowed unveiling some details of the molecular bases responsible for the peculiar traits of S. cerevisiae wine strains. However, the metabolic diversity within yeasts remained poorly explored, in particular that existing between wine and wild strains of S. cerevisiae. For this purpose, we performed a dual transcriptomic and metabolomic comparative analysis between a wild and a wine S. cerevisiae strains during wine fermentations performed at high and low temperatures. By using this approach, we could correlate the differential expression of genes involved in metabolic pathways, such as sulfur, arginine and thiamine metabolisms, with differences in the amounts of key metabolites that can explain some important differences in the fermentation performance between the wine and wild strains.

Diversity of Oligopeptide Transport in Yeast and Its Impact on Adaptation to Winemaking Conditions.

Nitrogen is an essential nutrient for yeasts and its relative abundance is an important modulator of fermentation kinetics. The main sources of nitrogen in food are ammonium and free amino acids, however, secondary sources such as oligopeptides are also important contributors to the nitrogen supply. In yeast, oligopeptide uptake is driven by different families of proton–coupled transporters whose specificity depends on peptide length. Proton-dependent Oligopeptide Transporters (POT) are specific to di- and tri-peptides, whereas the Oligopeptide Transport (OPT) family members import tetra- and pentapeptides. Recently, the novel family of Fungal Oligopeptide Transporters (FOT) has been identified in Saccharomyces cerevisiae wine strains as a result of a horizontal gene transfer from Torulaspora microellipsoides. In natural grape must fermentations with S. cerevisiae, Fots have a broader range of oligopeptide utilization in comparison with non-Fot strains, leading to higher biomass production and better fermentation efficiency. In this review we present the current knowledge on the diversity of oligopeptide transporters in yeast, also discussing how the consumption of oligopeptides provides an adaptive advantage to yeasts within the wine environment.