Yeast diversity during the spontaneous fermentation of wine in a winery and in a laboratory using sterilized equipment.

A recent trend in some wineries is the return to using spontaneous fermentation, but it is not clear whether winery flora or vineyard microorganisms drive fermentation. We compared fungal communities during the spontaneous fermentation of wine produced in a winery and in a laboratory with sterilized equipment using three grape cultivars (Chardonnay, Merlot, and Muscat Bailey A) obtained from the same harvest. High-throughput sequencing analysis based on the ITS1 region showed that Saccharomyces cerevisiae was the dominant species in winery batches at the end of fermentation, but it was not always dominant in laboratory batches. The number of laboratory batches where S. cerevisiae reached more than 50% at the end of fermentation was only 10 of 26. Consistent with this, in the grape juice/must before fermentation, S. cerevisiae accounted for 1.71% of fungal species identified in winery batches and 0.04% in laboratory batches. In addition, in laboratory-based winemaking, juice clarification of Chardonnay and cold maceration of Merlot influenced the microbial communities observed during fermentation. Our findings suggest that S. cerevisiae present in the winery environment participates at an early stage of fermentation, leading to its dominance at the end in wine produced by spontaneous fermentation in a winery.