Characterization and identification of saccharomyces uvarum from Okanagan white wine grapes and from their spontaneous fermentations

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Commercial wines are typically produced either by inoculated fermentation, in which a single commercial strain of Saccharomyces cerevisiae is added to the fermentation, or by spontaneous fermentation, which relies on resident wine yeasts from the vineyard and winery environments. Spontaneous fermentation is characterized by a diverse succession of yeast genera, species, and strains, with either one or multiple strains of the more ethanol-tolerant S. cerevisiae usually dominating the mid and final stages. One motivation for a winery to use spontaneous fermentations is to produce wine with a more complex sensory profile, which islikely due to the production of a diversity of metabolic by-products derived from a diverse yeast community. Spontaneous fermentations may be used because they can produce a regional character (terroir) in the wine due to the presence of region-specific yeast. We have identified Saccharomyces uvarum, a cryotolerant, high glycerol and low acetic acid-producing yeast, in spontaneous fermentations of Chardonnay and Pinot Gris grapes. Our objectives are to determine: 1) whether S. uvarum is able to dominate fermentations in multiple years; 2) whether S. uvarum is originating from the winery or vineyard; 3) whether S. uvarum strains on grapes and in fermentations differ between Okanagan vineyards at different latitude; and 4) whether there is aregionally distinct population of S. uvarum that could potentially enhance the fermentation properties and sensory profiles of Okanagan white wines. To address the first and second objectives, we will collect Chardonnay grapes from one vineyard and compare the S. uvarum populations between grapes, wine surfaces and in-lab fermentations. To address the third objective of region specific S. uvarum yeasts, we will compare the relative abundance of S. uvarum strains between vineyards at different latitudes. We will use Illumina DNA sequencing to identify yeast species and microsatellite typing to characterize S. uvarum strains from grape and wine samples from objectives 1, 2 and 3,. For the fourth objective, S. uvarum isolates will be screened forspecific chemicals produced during in-lab fermentations.