Microbiota Diversity During Grape Drying and Spontaneous Fermentations of Vin Santo

Vin Santo is a passito wine produced mainly in Tuscany. In the traditional production of Vin Santo, fermentation occurs naturally. Only a few reports have explored the microbial ecology of Vin Santo. Therefore, the present study aimed to investigate the microbial ecology and its impact on the fermentative kinetics in traditional processes of Vin Santo carried out in two different Tuscan wineries. Despite the different systems used for drying the grapes, both wineries showed similar microbial ecology. Non-Saccharomyces yeasts were the dominant microbial population during grape drying in different succession, even though in the end, the dominant species (at different percentages) in both were Metschnikowia pulcherrima, Kloeckera apiculata, and Starmerella bacillaris. The spontaneous fermentations were instead both dominated by Saccharomyces cerevisiae, however in different concentration throughout the process, leading to a different ethanol content—12% (v/v) and 10.8% (v/v) in winery A and B, respectively. In both wineries, acetic bacteria and moulds did not grow. Considering the intraspecific biodiversity of S. cerevisiae populations, the vinifications of both wineries displayed very similar biodiversity indices. No single strain of S. cerevisiae dominated the entire fermentation process. The analysis identified 30 distinct genetic patterns in the fermentations of winery A and 23 in the fermentations of winery B. The work provided an insight into the microbial communities and their metabolomic interactions during Vin Santo production which could improve the management and control of the process.