Yeast communities before and after spontaneous fermentation of wine grapes: a case study from Nova Scotia.

Wine fermentations are generally completed by the domestic yeast , but many indigenous vineyard yeasts also influence wine flavour and aroma. Despite the flourishing wine industry in Nova Scotia, there has yet to be any systematic evaluation of these yeasts in Atlantic Canada. The yeast communities of pressed L'Acadie blanc grapes sampled from an organic vineyard in the Annapolis Valley in 2018 and 2019 were characterized before and after spontaneous fermentation by both Illumina and PacBio sequencing, to address and compare potential platform biases. Chemical and sensory evaluations were also conducted. Basidiomycete yeasts, including , , and , dominated pre-fermentation diversity. Species of made up ∼0.04% of sequences prior to fermentation, but 85%-100% after fermentation, with some replicates dominated by and some by . PacBio sequencing detected high proportions of , while Illumina sequencing did not. A better understanding of Nova Scotia vineyard yeast communities will allow local wine makers to make better use of non-traditional yeasts and spontaneous fermentations to produce high-quality wines unique to the region.