Non-Saccharomyces Yeasts from Organic Vineyards as Spontaneous Fermentation Agents

Currently, non-Saccharomyces yeasts are the subject of interest, among other things, for their contribution to the aromatic complexity of wines. In this study, the characterisation of non-Saccharomyces yeasts was addressed by their isolation during spontaneous fermentations of organic Verdejo grapes, obtaining a total of 484 isolates, of which 11% were identified by molecular techniques as non-Saccharomyces yeasts. Fermentative isolates belonging to the species Hanseniaspora meyeri, Hanseniaspora osmophila, Pichia guilliermondii, Pichia kudriavzevii, Torulaspora delbrueckii, and Wickerhamomyces anomalus were analysed. Significant differences were found in the yeast populations established at the different fermentation stages. Interestingly, W. anomalus stood up as a widely distributed species in vineyards, vintages, and fermentation stages. Several of the strains studied stood out for their biotechnological potential in the production of Verdejo wine, showing the presence of relevant enzymatic activity for the release of varietal aromas and the technological improvement of the winemaking process. Three enzymatic activities were found in an important number of isolates, β-glucosidase, protease, and β-lyase, implicated in the positive aromatic impact on this style of white wine. In that sense, all the isolates of W. anomalus presented those activities. T. delbrueckii isolates were highlighted for their significant β-lyase activity. In addition, T. delbrueckii was outlined because of its potential to achieve an elevated fermenting power, as well as the lack of lag phase. The results obtained highlight the importance of maintaining the microbial diversity that contributes to the production of wines with unique and distinctive characteristics of the production region.