Abstract: Objective: The aim of this study was to explore the growth and esterase activities in the mixed culture fermentation of non-Saccharomyces yeast and Saccharomyces cerevisiae. Methods: Esterase activities of non-Saccharomyces yeast from southern Sichuan liquor pits were measured in liquid fermentation medium. One yeast strain with the highest esterase activity was selected and identified through sequence analysis of the D1/D2 domain of 26S rDNA. Then, the alcoholic fermentation of mixed cultures of the isolate and S. cerevisiae were performed in model grape juice medium to explore the yeast growth kinetics and the evolution of esterase activities from substrates with different carbon chain lengths (C2–C8). Three experimental groups were set up by inoculating the non-Saccharomyces yeast strain 48 and 96 h before or at the same time as S. cerevisiae, and their pure cultures were used as controls. Results: The isolate was identified as Pichia fermentans. The fermentation rate of pure S. cerevisiae was the fastest. The yeast population in mixed culture fermentation was higher, especially with 96 h sequential inoculation. During fermentation, the highest esterase activities were accumulated with simultaneous inoculation (574 mU/mL). The C8 substrate accumulated the highest esterase activity (178–227 mU/mL), while the C2 accumulated esterase activity was the lowest (46–66 mU/mL). Comparison of the cell growth kinetics and the evolution of esterase activities during fermentations revealed that esterase activities were correlated with the growth of yeasts and arrived at the highest value in the stationary growth phase. Conclusion: The simultaneous inoculation of the isolate and S. cerevisiae in model juice with higher C4-C8 accumulated esterase activities has a good application potential for aroma enhancement.

Key words: non-Saccharomyces, Pichia fermentans, esterase, model grape juice, yeast growth kinetics