Evaluation of the Yeast Schizosaccharomyces japonicus for Use in Wine Production

Schizosaccharomyces japonicus UCD2489 was evaluated for potential use as a starter culture in winemaking. Laboratory-scale fermentations of Trebbiano grape juice compared pure cultures of S. japonicus, immobilized S. japonicus, a commercial strain of Saccharomyces cerevisiae (EC1118), and mixed cultures of the two species. The fermentation kinetics of sequential and co-inoculated fermentations were largely driven by the presence of S. cerevisiae. UCD2489 cell immobilization resulted in a significant reduction in ethanol levels in mixed fermentation when compared to EC1118. Acetic acid levels similar to those of EC1118 in pure culture were produced when fermentations were co-inoculated. The ability of UCD2489 to consume malic acid was adversely affected by EC1118 particularly in the co-inoculated 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, S. japonicus produced a quantity of glycerol approximately 2-fold higher than that released by S. cerevisiae. The analyses of volatile compounds showed increases in aroma impact compounds such as ethyl acetate in all S. japonicus wines and acetaldehyde in the free cell co-inoculated fermentation that exceed reported sensory thresholds for these compounds, and other important 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 S. japonicus could be useful in wine production to reduce acidity and final ethanol levels, to increase glycerol, volatile compounds and active polysaccharides with potential beneficial enhancement of protein stability.