A Primary Study on the Factors Affecting Yeast Growth in a Mixed Culture
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Abstract:
To investigate the factors affecting the growth of different yeast strains in a mixed culture, the effects of initial glucose concentration and pH value on the growth of Saccharomyces cerevisiae (Sc) and Issatchenkia orientalis (Io) were investigated. The differences in organic acid metabolism of the two types of yeasts in a mixed culture were compared using pure cultures as controls. The results showed that low initial glucose concentration, low pH, and differences in organic acid metabolism were the main factors inhibiting the growth of Sc. The glucose consumption rate of Io was faster than that of Sc; in the mixed culture with an initial glucose concentration of 1%, Io consumed glucose preferentially, and the Io/Sc (the ratio of colony numbers) value was 70. Io was more acid tolerant than Sc, and the Io/Sc was 56 in pH 3.5. Regarding organic acid metabolism, Io produced 2.52 g/L lactic acid specifically, and Sc produced 1.14 g/L acetic acid specifically. In a mixed culture, Io could absorb the acetic acid produced by Sc, whereas the lactic acid produced by Io could inhibit the growth of Sc. The factors influencing cell behavior of wine yeasts in a mixed culture were analyzed in terms of cell growth and organic acid metabolism, and this study provides a theoretical basis for the application of multi-strain mixed fermentation in the wine industry.
