A Rapid Growth Rate Underpins the Dominance of Hanseniaspora uvarum in Spontaneous Grape Juice Fermentations.

Hanseniaspora uvarum is consistently observed as the dominant non-Saccharomyces species in spontaneous grape juice fermentations. However, the physiological mechanisms and physicochemical variables influencing the prevalence of H. uvarum over other non-Saccharomyces species remain unclear. We tested the factors contributing to H. uvarum dominance by inoculating a chemically diverse set of grape juices with a mock community whose composition was based on a previously published comprehensive microbial survey of commercial spontaneous fermentations. The diverse composition of these grape juices appeared to have minimal impact on the overall microbial dynamics of fermentation, with H. uvarum consistently emerging as the dominant non-Saccharomyces species in nearly all conditions tested. Flow cytometry analysis confirmed that H. uvarum has a faster growth rate than Saccharomyces cerevisiae and several other Hanseniaspora species. Moreover, its growth was not affected by the presence of S. cerevisiae. H. uvarum negatively affected the growth of S. cerevisiae, with significant implications for fermentation performance and sugar consumption. Our study suggests that the fast growth rate of H. uvarum enables it to dominate the grape juice environment quickly during early fermentation stages. This physiological advantage may be critical to the outcome of spontaneous fermentations, as evidenced by its direct impact on S. cerevisiae and fermentation performance.