Different Wines from Different Yeasts? "Saccharomyces cerevisiae Intraspecies Differentiation by Metabolomic Signature and Sensory Patterns in Wine"

Influence of different stress factors during the elaboration of grape must's pieddecuve on the dynamics of yeast populations during alcoholic fermentation

The pieddecuve (PdC) technique involves using a portion of grape must to undergo spontaneous fermentation, which is then used to inoculate a larger volume of must. This allows for promoting autochthonous yeasts present in the must, which can respect the typicality of the resulting wine. However, the real impact of this practice on the yeast population has not been properly evaluated. In this study, we examined the effects of sulphur dioxide (SO2), temperature, ethanol supplementation, and time on the dynamics and selection of yeasts during spontaneous fermentation to be used as PdC. The experimentation was conducted in a synthetic medium and sterile must using a multi-species yeast consortium and in un-inoculated natural grape must. Saccharomyces cerevisiae dominated both the PdC and fermentations inoculated with commercial wine yeast, displaying similar population growth regardless of the tested conditions. However, using 40 mg/L of SO2 and 1% (v/v) ethanol during spontaneous fermentation of Muscat of Alexandria must allowed the non-Saccharomyces to be dominant during the first stages, regardless of the temperature tested. These findings suggest that it is possible to apply the studied parameters to modulate the yeast population during spontaneous fermentation while confirming the effectiveness of the PdC methodology in controlling alcoholic fermentation.

Targeted 1-H-NMR wine analyses revealed specific metabolomic signatures of yeast populations belonging to the Saccharomyces genus

This study aimed to explore the non-volatile metabolomic variability of a large panel of strains (44) belonging to the Saccharomyces cerevisiae and Saccharomyces uvarum species in the context of the wine alcoholic fermentation. For the S. cerevisiae strains flor, fruit and wine strains isolated from different anthropic niches were compared. This phenotypic survey was achieved with a special focus on acidity management by using natural grape juices showing opposite level of acidity. A 1H NMR based metabolomics approach was developed for quantifying fifteen wine metabolites that showed important quantitative variability within the strains. Thanks to the robustness of the assay and the low amount of sample required, this tool is relevant for the analysis of the metabolomic profile of numerous wines. The S. cerevisiae and S. uvarum species displayed significant differences for malic, succinic, and pyruvic acids, as well as for glycerol and 2,3-butanediol production. As expected, S. uvarum showed weaker fermentation fitness but interesting acidifying properties. The three groups of S. cerevisiae strains showed different metabolic profiles mostly related to their production and consumption of organic acids. More specifically, flor yeast consumed more malic acid and produced more acetic acid than the other S. cerevisiae strains which was never reported before. These features might be linked to the ability of flor yeasts to shift their metabolism during wine oxidation.

Impact of Saccharomyces cerevisiae yeast inoculation mode on wine composition

Inoculation modes are known to affect yeast behavior. Here, we characterized the impact of ADY and pre-culturing on the composition of the resulting wine, fermented by four commercial strains of Saccharomyces cerevisiae. Classical oenological parameters were not affected by the yeast inoculation mode. Using an untargeted metabolomic approach, a significant distinction in wine composition was noted regardless of the strain between the two inoculation modes, each associated with a specific metabolomic signature. 218 and 895 biomarkers were annotated, respectively, for ADYs associated with the preservation of wine polyphenols, and for pre-cultures related to the modulation of yeast nitrogen metabolism. Volatilome analysis revealed that the ester family was that most impacted by the inoculation mode whatever the strain. Ester production was enhanced in ADY condition. For the first time, the complete reprogramming of the yeast metabolism was revealed as a function of yeast preparation, which significantly impacts its volatilome and exometabolome.

From the grapevine to the glass: A wine metabolomics tale by FT-ICR-MS

Wine is one of the most consumed beverages around the world. Its unique characteristics arise from numerous processes, from the selection of grapevine varieties and grapes, the effect of the terroir and geographical origin, through the biochemical process of fermentation by microorganisms, until its aging. All molecules found in wine define its chemical fingerprint and can be used to tell the story of its origin, production, authenticity and quality. Wine's chemical composition can be characterized using an untargeted metabolomics approach based on extreme resolution mass spectrometry. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is currently the most powerful analytical technique to analyse such complex sample, providing the most comprehensive analysis of the chemical fingerprint of wine.

Must protection, sulfites versus bioprotection: A metabolomic study

The reduction of chemical inputs in wine has become one of the main challenges of the wine industry. One of the alternatives to sulfites developed is bioprotection, which consists in using non-Saccharomyces strains to prevent microbial deviation. However, the impact of substituting sulfites by bioprotection on the final wine remains poorly studied. For the first time, we characterized this impact on Chardonnay wine through an integrative approach. Interestingly, physico-chemical analysis did not reveal any difference between both treatments regarding classical oenological parameters. Nevertheless, bioprotection did not seem to provide as much protection against oxidation as sulfites, as observed through phenolic compound analysis. At a deeper level, untargeted metabolomic analyses revealed substantial changes in wine composition according to must treatment. In particular, the specific footprint of each treatment revealed an impact on nitrogen-containing compounds. This observation could be related to modifications in S. cerevisiae metabolism, in particular amino acid biosynthesis and tryptophan metabolism pathways. Thus, the type of must treatment seemed to impact metabolic fluxes of yeast differently, leading to the production of different compounds. For example, we observed glutathione and melatonin, compounds with antioxidant properties, which were enhanced with sulfites, but not with bioprotection. However, despite substantial modifications in wines regarding their chemical composition, the change in must treatment did not seem to impact the sensory profile of wine. This integrative approach has provided relevant new insights on the impact of sulfite substitution by bioprotection on Chardonnay wines.

Influence of Different Types, Utilization Times, and Volumes of Aging Barrels on the Metabolite Profile of Red Wine Revealed by 1H-NMR Metabolomics Approach

It is well recognized that the aging process is a critical step in winemaking because it induces substantial chemical changes linked to the organoleptic properties and stability of the finished wines. Therefore, this study aimed to investigate the influence of different types, utilization times, and volumes of aging barrels on the metabolite profile of red wines, produced from Thai-grown Shiraz grapes, using a non-targeted proton nuclear magnetic resonance (1H-NMR) metabolomics approach. As a result, 37 non-volatile polar metabolites including alcohols, amino acids, organic acids, carbohydrates and low-molecular-weight phenolics were identified. Chemometric analysis allowed the discrimination of wine metabolite profiles associated with different types of aging containers (oak barrels vs. stainless-steel tanks), as well as the utilization times (2, 6 and >10 years old) and volumes (225, 500 and 2000 L) of the wooden barrels employed. Significant variations in the concentration of formate, fumarate, pyruvate, succinate, citrate, gallate, acetate, tyrosine, phenylalanine, histidine, γ-aminobutyrate, methionine and choline were statistically suggested as indicators accountable for the discrimination of samples aged under different conditions. These feature biomarkers could be applied to manipulate the use of aging containers to achieve the desired wine maturation profiles.

Thiamine and Biotin: Relevance in the Production of Volatile and Non-Volatile Compounds during Saccharomyces cerevisiae Alcoholic Fermentation in Synthetic Grape Must

Vitamins are major cofactors to numerous key metabolic pathways in enological yeasts, and both thiamine and biotin, notably, are believed to be essential to yeast fermentation and growth, respectively. In order to further assess and clarify their role in winemaking, and in the resulting wine, alcoholic fermentations of a commercial Saccharomyces cerevisiae active dried yeast were conducted in synthetic media containing various concentrations of both vitamins. Growth and fermentation kinetics were monitored and proved the essential character of biotin in yeast growth, and of thiamine in fermentation. The synthetic wine volatile compounds were quantified, and notable influences of both vitamins appeared, through a striking positive effect of thiamine on the production of higher alcohols, and of biotin on fatty acids. Beyond the evidence of this influence on fermentations and on the production of volatiles, this work proves, for the first time, the impact held by vitamins on wine yeasts' exometabolome, investigated through an untargeted metabolomic analysis. This highlighted chemical differences in the composition of synthetic wines through a notably marked influence of thiamine on 46 named S. cerevisiae metabolic pathways, and especially in amino acid-associated metabolic pathways. This provides, overall, the first evidence of the impact held by both vitamins on the wine.

Expanding the diversity of Chardonnay aroma through the metabolic interactions of Saccharomyces cerevisiae cocultures

Yeast co-inoculations in winemaking are often studied in the framework of modulating the aromatic profiles of wines. Our study aimed to investigate the impact of three cocultures and corresponding pure cultures of Saccharomyces cerevisiae on the chemical composition and the sensory profile of Chardonnay wine. Coculture makes it possible to obtain completely new aromatic expressions that do not exist in the original pure cultures attributed to yeast interactions. Esters, fatty acids and phenol families were identified as affected. The sensory profiles and metabolome of the cocultures, corresponding pure cultures and associated wine blends from both pure cultures were found to be different. The coculture did not turn out to be the addition of the two pure culture wines, indicating the impact of interaction. High resolution mass spectrometry revealed thousands of cocultures biomarkers. The metabolic pathways involved in these wine composition changes were highlighted, most of them belonging to nitrogen metabolism.

Comparing the hierarchy of inter- and intra-species interactions with population dynamics of wine yeast cocultures

In winemaking, the development of new fermentation strategies, such as the use of mixed starter cultures with Saccharomyces cerevisiae (Sc) yeast and non-Saccharomyces (NS) species, requires a better understanding of how yeasts interact, especially at the beginning of fermentation. Despite the growing knowledge on interactions between Sc and NS, few data are available on the interactions between different species of NS. It is furthermore still unclear whether interactions are primarily driven by generic differences between yeast species or whether individual strains are the evolutionarily relevant unit for biotic interactions. This study aimed at acquiring knowledge of the relevance of species and strain in the population dynamics of cocultures between five yeast species: Hanseniaspora uvarum, Lachancea thermotolerans, Starmerella bacillaris, Torulaspora delbrueckii and Sc. We performed cocultures between 15 strains in synthetic grape must and monitored growth in microplates. Both positive and negative interactions were identified. Based on an interaction index, our results showed that the population dynamics seemed mainly driven by the two species involved. Strain level was more relevant in modulating the strength of the interactions. This study provides fundamental insights into the microbial dynamics in early fermentation and contribute to the understanding of more complex consortia encompassing multiple yeasts trains.

Effect of Saccharomyces cerevisiae and Saccharomyces pastorianus Co-Inoculation on Alcoholic Fermentation Behavior and Aromatic Profile of Sauvignon Blanc Wine

Enhancing the sensory profile of wines by exposing the aromas of the grape variety through the involvement of microorganisms has always been a challenge in winemaking. The aim of our work was to evaluate the impact of different fermentation schemes by using mixed and pure cultures of different Saccharomyces species to Sauvignon blanc wine chemical composition and sensory profile. The Sauvignon blanc must has been inoculated with mixed and pure cultures of S. pastorianus and S. cerevisiae strains. For the mixed fermentation schemes, one strain of S. pastorianus has been inoculated with different proportions of S. cerevisiae (S. pastorianus to S. cerevisiae: 99%–1%, 95%–5%, 90%–10%, 80%–20% and 70%–30% w/w) in co-inoculation with two commercial strains of S. cerevisiae. A total of 13 fermentations trials, three monocultures and 10 mixed cultures were performed in biological triplicate. The fermentation kinetics have been controlled by density measurement and classical oenological analyses were performed based on the International Organisation of Vine and Wine (OIV) analytical methods. The population dynamics were evaluated by the specific interdelta PCR reaction of the Saccharomyces species at the beginning and at the end of the fermentation process. The volatile compounds of the wine aroma, such as the esters, higher alcohols and thiols were analyzed by GC/MS. Sensory assessment by trained panel was carried out for all produced wines. Complete depletion of the sugars was achieved between 10 and 13 days for all the fermentation trials. The population dynamics analysis revealed that the S. cerevisiae strain was the most predominant at the end of the fermentation process in all inoculation ratios that were tested. The wines that were fermented with S. pastorianus, either in pure or mixed cultures, were characterized by significantly lower acetic acid production and higher malic acid degradation when compared to the wines that were fermented only with S. cerevisiae strains. The aroma profile of the produced wines was highly affected by both inoculation ratio and the S. cerevisiae strain that was used. The presence of S. pastorianus strain enhanced the production of the varietal thiols when compared to the samples that were fermented with the S. cerevisiae pure cultures. The mixed inoculation cultures of Saccharomyces species could lead to wines with unique character which can nicely express the varietal character of the grape variety.

Ecological Distribution and Oenological Characterization of Native Saccharomyces cerevisiae in an Organic Winery

The relation between regional yeast biota and the organoleptic characteristics of wines has attracted growing attention among winemakers. In this work, the dynamics of a native Saccharomyces cerevisiae population was investigated in an organic winery. In this regard, the occurrence and the persistence of native S. cerevisiae were evaluated in the vineyard and winery and during spontaneous fermentation of two nonconsecutive vintages. From a total of 98 strains, nine different S. cerevisiae biotypes were identified that were distributed through the whole winemaking process, and five of them persisted in both vintages. The results of the oenological characterization of the dominant biotypes (I and II) show a fermentation behavior comparable to that exhibited by three common commercial starter strains, exhibiting specific aromatic profiles. Biotype I was characterized by some fruity aroma compounds, such as isoamyl acetate and ethyl octanoate, while biotype II was differentiated by ethyl hexanoate, nerol, and β-damascenone production also in relation to the fermentation temperature. These results indicate that the specificity of these resident strains should be used as starter cultures to obtain wines with distinctive aromatic profiles.