Identification and characterization of indigenous B.C. wine yeast strains

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In competitive wine markets, British Columbian (BC) wineries must create high-value wines that express the unique character, or terroir, of their region. Wines are produced by inoculated fermentation with commercial strains of the wine yeast Saccharomyces cerevisiae (S. cerevisiae) or by spontaneous fermentation, which relies on yeast residing on grapes and winery equipment. Spontaneous fermentations are risky but can produce organoleptically complex wines if indigenous yeast species dominate the fermentation. The goal of my research is to identify indigenous yeast present in BC vineyards with enological potential that showcase BC terroir. Since 2013, we have collaborated with two BC wineries that perform Pinot Gris and Pinot Noir spontaneous fermentations. Concurrent with winery fermentations, we harvested the same grape varietals and fermented them in the lab. We isolated S. cerevisiae strains from winery and vineyard fermentations, performed microsatellite profiling and compared the data to a microsatellite database that we compiled of over 120 commercial S. cerevisiae wine yeast strains. We have identified a unique indigenous subpopulation of S. cerevisiae and unexpectedly identified strains of S. bayanus in the fermentations. Both our novel S. cerevisiae and S. bayanus strains have enological potential. Objective 1. Phenotypic and Metabolic profiling of S. cerevisiae strains isolated from spontaneous fermentations. Bayesian clustering analysis of our S. cerevisiae strains revealed 12 population clusters. We will perform small-scale fermentations with representative strains from each cluster. Strains with vigorous fermentation profiles will be analyzed for positive flavor compounds. Phenotypic analysis of traits important for wine production and whole genome sequencing of strains with enological potential will be performed. Objective 2. Identification of yeast/fungal species during spontaneous fermentation. Nonconventional yeasts such as Metschnikowia are found in spontaneous fermentations and contribute sensorial complexity to the wine. We will identify non-Saccharomyces species present in our winery and vineyard fermentations by direct DNA extraction from wine samples and Illumina next generation sequencing. Our goal is to analyze the contribution of nonconventional yeast to the winery and vineyard fermentations. Objective 3. Genetic characterization of BC S. bayanus isolates and evaluation of S. bayanus and non-Saccharomyces yeast fermentation potential. We isolated unique strains of S. bayanus from Pinot Gris spontaneous fermentations. We will generate an S. bayanus reference database using commercial and published strains to classify subpopulations. S. bayanus and non-Saccharomyces strains will be co-inoculated with S. cerevisiae strains to identify ideal strain combinations for high quality wine production.