Garrett McCarthy,* Sydney Morgan, Vivien Measday, and Dan Durall
*University of British Columbia, 3333 University Way, Kelowna / BC / V1V 1V7, Canada (gmccarthy3@hotmail.com)

Most wines are produced by inoculated fermentations using known, commercialized strains of Saccharomyces cerevisiae, but there is a growing trend in winemaking of performing spontaneous fermentations, which rely on microflora present on grape berries or winery equipment. An advantage for spontaneous over inoculated fermentation includes a more complex sensory profile due to a wider range of metabolites being produced by differing yeast species, which may help to define the microbial terroir of the wine. Spontaneous fermentations are characterized initially by a diversity of yeasts coming from the winery and vineyard environments, but strains of ethanol-tolerant S. cerevisiae eventually dominate the end of fermentation. However, previous studies in our lab identified Saccharomyces uvarum (a non-inoculated yeast) in spontaneous Chardonnay winery fermentations of grapes from the Okanagan Valley in British Columbia as the dominate yeast over S. cerevisiae during all later stages of fermentation. Although the overall objective of this study was to determine the origin (winery or vineyard) of Okanagan S. uvarum, we report here on the abundance of S. uvarum in relation to S. cerevisiae, and the S. uvarum strain diversity of 2017 spontaneous Chardonnay fermentations coming from two different Okanagan vineyards. Using culture-dependent methods, we identified nearly 1000 isolates from winery fermentations and discovered that S. uvarum was again dominant over S. cerevisiae in all fermentations, as in 2015 in the same winery. We will also report strain results from an S. uvarum 11-loci microsatellite multiplex screening. Overall, our results indicate there may be commercial interest in using S. uvarum as a potential alternative fermenting yeast to S. cerevisiae.

Funding Support: Natural Sciences and Engineering Research Council of Canada – Collaborative Research and Development Grant (NSERC-CRD)