Yeast communities of Nova Scotia wine grapes: characterization and implications for winemaking

Abstract

Wine grapes host a community of yeasts that reflects the unique geography, climate, and management of a vineyard. After grapes are crushed to produce must, a dynamic succession of yeasts takes place as fermentation unfolds. Initially, many basidiomycete and ascomycete species may be abundant, before one or few fermentative ascomycete yeasts, most often Saccharomyces cerevisiae (Desm.) Meyen 1838, become dominant and complete the fermentation. However, all yeasts contribute to the chemistry of a fermentation via interactions with each other and by using nutrients, secreting enzymes, and producing aromatic compounds. The cumulative result is the distinctive aroma and body of the wine. Despite the importance of yeast communities during fermentation, wine grape yeasts in Nova Scotia have yet to be evaluated. This emerging wine region generates >$245 M/year, supports >1100 jobs, and stimulates tourism. Therefore, the yeast communities of L’Acadie blanc grapes, a cool-climate hybrid cultivar, were characterized using high throughput sequencing. Considering rising demand for sustainable products, vineyards using organic and conventional cultivation practices were sampled. Yeast communities in musts were composed of predominantly basidiomycete yeasts and were significantly different among vineyard sites and between cultivation practices. One organic vineyard was selected for further analysis using two sequencing platforms (Illumina MiSeq and PacBio) to address biases and evaluate changes following spontaneous fermentation. Both S. cerevisiae and Saccharomyces uvarum Beij. 1898 were found to complete fermentations, but discrepancies in the proportions of these and Hanseniaspora uvarum (Niehaus) Shehata, Mrak and Phaff ex MT Sm 1956 were detected between the sequencing systems. Finally, considering their abundance, a review of wine grape associated basidiomycete yeasts and their potential applications in winemaking was conducted, highlighting known effects on wine aroma. Understanding the complexity of yeast diversity in wine musts and during fermentation can inform both vineyard management and winemaking.