Identification and Characterization of Non- Saccharomyces Species Isolated from Port Wine Spontaneous Fermentations

In winemaking, non- yeast species contribute important organoleptic complexity. Current interest focuses on abundant and dominant strains characteristically present in the early phase of spontaneous alcoholic fermentations. Non- species are particularly relevant in Port wine production such that the fermentation is prematurely stopped, after the metabolism of only one half of the available sugar, through fortification with aguardente. This work aimed to isolate, identify and characterize non- species present in spontaneously fermenting Port. To accomplish these goals, yeasts were isolated from a selection of frozen must samples (2012-2016 harvests), using a pre-screening process choosing only the best candidates based on the organoleptic quality of the corresponding fortified wine. From five hundred non- isolates, twelve species were identified. The three most abundant species, , , and , representing 89% of the isolates, exhibited particularly high diversity with high growth performance variability when exposed to typical stress conditions associated with common enological parameters. Less abundant species included , , , , , , , , and . This is the first study providing insights into the identification and characterization of non- species responsible for spontaneous Port wine production.