Evaluation of the Yeast Schizosaccharomyces japonicus for Use in Wine Production

Abstract

Schizosaccharomyces japonicus UCD2489 was evaluated for potential use as a starter culture in wine-making. Laboratory-scale fermentations of Trebbiano grape juice were set up to compare fermentation kinetics of pure cultures of Sch. japonicus, immobilized Sch. japonicus cells, a commercial strain of Saccharomyces cerevisiae (EC1118), and mixed cultures of both species. The fermentation kinetics of the sequential and coinoculated fermentations were largely driven by the presence of S. cerevisiae. UCD2489 cell immobilization resulted in a significant reduction in ethanol levels in mixed fermentations compared with EC1118. Acetic acid levels similar to those of EC1118 in pure culture were produced when fermentations were coinoculated. The ability of UCD2489 to consume malic acid was adversely affected by EC1118, particularly in the coinoculated fermentation, suggesting that acid levels could be manipulated by adjusting the relative ratios of the two yeasts and the timing of inoculation with S. cerevisiae. Depending upon the inoculation conditions used, Sch. japonicus produced a quantity of glycerol ~2-fold higher than those released by S. cerevisiae. The analyses of volatile compounds showed increases in aroma-impacting compounds such as ethyl acetate in all Sch. japonicus wines, and acetaldehyde in the free-cell coinoculated fermentation that exceed reported sensory thresholds for these compounds, and for other important aroma compounds such as isoamyl acetate, hexyl acetate, phenyl ethyl acetate, ethyl isobutyrate, and ethyl butyrate. Polysaccharide release by UCD2489 was ~4.7-fold greater than that of S. cerevisiae alone. Reduction of induced wine protein haze was correlated with the concentration of polysaccharides. Our findings suggest that Sch. japonicus could be useful in wine production to reduce acidity and final ethanol levels and to increase glycerol, volatile compounds, and active polysaccharides with potential beneficial enhancement of protein stability.