Physiological characterization of two native yeasts in pure and mixed culture using fermentations of agave juice

[摘要] Yeast cells are subjected to diverse environmental conditions during the alcoholic fermentation of agave juice, causing different kinetic behaviors. Agave juice was used as culture medium to evaluate the kinetic behavior ofSaccharomyces cerevisiaeITD-00185 andTorulaspora delbrueckiiITD-00014a, as pure and mixed cultures, under different inoculum sizes (1×10 5 , 1×10 6 , 1×10 7and 1×10 8cells mL -1 ), and combined pH levels (3.5, 4.0 and 4.5) and temperatures (18 °C, 28 °C and 38 °C).Saccharomyces cerevisiaedisplayed high fermentation capacities at all inoculum concentrations assayed. However,T. delbrueckiirequired a high inoculum concentration (≥1×10 7cells mL -1 ) to perform at fermentation levels similar toS. cerevisiae . Low temperatures (18 °C) slowed fermentation, while high temperatures (38 °C) adversely affected the development of the yeast strains, especiallyT. delbrueckii . The best temperature was 28 °C in all fermentations. The pH level had a strong effect on the performance of the coculture, since the fermentation kinetics suggested a synergistic effect at pH 4.5, while an antagonistic effect was postulated at pH 3.5. In all of the mixed culture cases, a positive effect at 28 °C, especially at pH 4.0 and 4.5, was demonstrated by greater levels of sugar consumption and ethanol production (~20%, p<0.05) compared to fermentations of theS. cerevisiaemonoculture. The coculture results allow us to postulate that a complex interaction exists between the two yeasts, which could be synergistic or antagonistic, as the environmental conditions change.

[学科分类] 农业科学（综合）

[关键词] Coculture;inoculum concentration;pH;Temperature