The Impact of Saccharomyces cerevisiae on a Wine Yeast Consortium in Natural and Inoculated Fermentations

Abstract

Natural, also referred to as spontaneous wine fermentations, are carried out by the native microbiota of the grape juice, without inoculation of selected, industrially produced yeast or bacterial strains. Such fermentations are commonly initiated by non-Saccharomyces yeast species that numerically dominate the must. Community composition and numerical dominance of species vary significantly between individual musts, but Saccharomyces cerevisiae will in most cases dominate the late stages of the fermentation and complete the process. Nevertheless, non-Saccharomyces species contribute significantly, positively or negatively, to the character and quality of the final product. The contribution is species and strain dependent and will depend on each species or strain’s absolute and relative contribution to total metabolically active biomass, and will therefore, be a function of its relative fitness within the microbial ecosystem. However, the population dynamics of multispecies fermentations are not well understood. Consequently, the oenological potential of the microbiome in any given grape must, can currently not be evaluated or predicted. To better characterize the rules that govern the complex wine microbial ecosystem, a model yeast consortium comprising eight species commonly encountered in South African grape musts and an ARISA based method to monitor their dynamics were developed and validated. The dynamics of these species were evaluated in synthetic must in the presence or absence of S. cerevisiae using direct viable counts and ARISA. The data show that S. cerevisiae specifically suppresses certain species while appearing to favor the persistence of other species. Growth dynamics in Chenin blanc grape must fermentation was monitored only through viable counts. The interactions observed in the synthetic must, were upheld in the natural must fermentations, suggesting the broad applicability of the observed ecosystem dynamics. Importantly, the presence of indigenous yeast populations did not appear to affect the broad interaction patterns between the consortium species. The data show that the wine ecosystem is characterized by both mutually supportive and inhibitory species. The current study presents a first step in the development of a model to predict the oenological potential of any given wine mycobiome.

Challenges of the Non-Conventional Yeast Wickerhamomyces anomalus in Winemaking

“…Interestingly, in the absence of S. cerevisiae, W. anomalus suppressed the rest of non-Saccharomyces species suggesting that the yeast can survive in the early stages of the fermentation better than the other yeast species and may utilize the nitrogen released by dead cells. However, in the presence of S. cerevisiae, W. anomalus specifically declined early in fermentation, suggesting an antagonistic interaction between both yeasts [30]. This interaction has also been proposed in apple cider fermentations [31].…”

“…Yeast isolations from Malvar grape musts pointed out W. anomalus as one of the most frequent non-Saccharomyces species, and in addition, the yeast was a good producer of extracellular enzymes which may be beneficial in winemaking [29]. Recently, the dynamics of several non-Saccharomyces species were evaluated in synthetic must in the presence or absence of S. cerevisiae [30]. The study showed that the behaviour of the non-Saccharomyces species was differentially influenced by the presence of S. cerevisiae.…”

Characterization of Old Wine Yeasts Kept for Decades under a Zero-Emission Maintenance Regime

“…The strive for more volatile aromas has spurred the search for alternative yeasts and renewed the interest in spontaneous fermentations [26]. Yet, due to the unpredictable and inconsistent outcomes of spontaneous fermentations, the development of improved starter cultures or consortia may provide better alternatives [27,28].…”

The importance and prevalence of allopolyploidy in Aotearoa New Zealand

“…The establishment of New Zealand vineyards also began in the early 1800s. Domesticated allopolyploid S. cerevisiae of course plays a central role in wine making too, dominating the initial (Mangado et al 2018) and late (Bagheri et al 2017) stages of fermentation due to its high sugar processing rates and ethanol tolerance. Recent evidence suggests that S. cerevisiae not only dominates this ecosystem, but also directly influences the other constituent species (Bagheri et al 2017).…”

“…Domesticated allopolyploid S. cerevisiae of course plays a central role in wine making too, dominating the initial (Mangado et al 2018) and late (Bagheri et al 2017) stages of fermentation due to its high sugar processing rates and ethanol tolerance. Recent evidence suggests that S. cerevisiae not only dominates this ecosystem, but also directly influences the other constituent species (Bagheri et al 2017). Seemingly in parallel with the allopolyploidy observed in brewing yeasts, strains of Dekkera bruxellensis, a prominent industrial wine fermentation contaminant, also appear to be allopolyploids (Borneman et al 2014).…”