Competition between Saccharomyces cerevisiae and Saccharomyces uvarum in Controlled Chardonnay Wine Fermentations

Abstract

Saccharomyces cerevisiae is usually the dominant yeast in winemaking. However, other yeast species such as Saccharomyces uvarum are also able to conduct and complete alcoholic fermentation. S. uvarum is a cryotolerant yeast that has been found dominating low-temperature fermentations at commercial wineries around the world, but little research has been conducted to investigate its competitive abilities relative to commercial S. cerevisiae strains. Here, controlled Chardonnay fermentations were conducted with a commercial S. cerevisiae strain and an indigenous S. uvarum strain inoculated at different initial ratios and two different temperatures. Both strains fermented well at 24°C, and both strains fermented slowly at 15°C. S. cerevisiae was more competitive than S. uvarum when inoculated at an equal or greater ratio. However, S. uvarum was better able to grow and compete with S. cerevisiae at a lower fermentation temperature and, when inoculated at an equal ratio, was able to maintain a 25% relative abundance throughout fermentation, contributing to the volatile-compound profile of the wine. Volatile-compound production was distinct for the two yeast strains, with S. uvarum producing generally higher amounts of volatile compounds, especially at the lower fermentation temperature, including higher amounts of 2-phenylethyl acetate (honey/spice/floral) and ethyl 2-methyl butanoate (apple/strawberry). When both strains co-existed in fermentation, the resulting volatile profile was unique in that it differed from either single-strain fermentation. This study is the first to test co-inoculation of S. cerevisiae and S. uvarum at different ratios and different fermentation temperatures and highlights the potential for the use of indigenous S. uvarum strains in isolation or in combination with S. cerevisiae to produce unique, quality wines.