Population Dynamics ofSaccharomyces cerevisiaeduring Spontaneous Fermentation at a British Columbia Winery

Abstract

Spontaneous fermentation is thought to provide conditions where diversity of indigenous Saccharomyces cerevisiae strains can flourish. A broad diversity of strains may provide unique characteristics to a wine and enhance its sensorial attributes. Population dynamics of S. cerevisiae strains were followed during a spontaneous fermentation of Vitis vinifera L. var. Pinot noir grapes at a winery in Kelowna, British Columbia, Canada, to determine the relative contribution of commercial active dry yeast (ADY) and indigenous strains during fermentation. Grapes were harvested, processed, and fermented separately. Yeasts from grapes were isolated and plated onto culture media. Fermentation tanks were sampled at early, mid, and late stages of fermentation. Yeast strains were isolated onto culture media at each stage. DNA was extracted from yeast cultures and amplified using primers defining six different microsatellite loci. Results were compared with a database comprising DNA fingerprints from commercially produced ADY strains used previously by the winery. Strains isolated from fermentation tanks were all ADY strains closely related or identical to those in the winery database. Strain richness tended to be greater in the mid and final stages than in the early stage. Lalvin ICV D254/Fermol Premier Cru and Red Star Premier Cuvee were the dominant yeasts during the mid and final stages. The former was the only strain found in all tanks in the mid and final stages. An ADY strain, Fermol Arome-Plus, was isolated from both grapes and spontaneous fermentation. This strain could represent a resident strain, where it persists year after year and cycles annually between the winery and vineyard.