优选非酿酒酵母与酿酒酵母在模拟葡萄汁发酵中生长动力学及酯酶活性分析

目的:探究非酿酒酵母与酿酒酵母混合发酵过程中酵母的生长状况及酯酶活性的变化规律。方法:通过测定川南白酒窖池中分离的非酿酒酵母在液体发酵培养基中的酯酶活性,从中优选1株高产酯酶的酵母,经26S r DNA D1/D2区域序列分析鉴定种属。随后利用模拟葡萄汁进行优选酵母和酿酒酵母的混合发酵,设立同时接种、提前48 h接种和提前96 h接种优选酵母3个实验处理,以两株酵母的纯发酵为对照,研究发酵过程中的酵母生长动力学及不同碳链长度底物(C_2~C_8)对应的酯酶活性变化。结果:优选的非酿酒酵母为发酵毕赤酵母。酵母生长动力学研究发现,单一酿酒酵母的发酵速率最快,但混合发酵中的酵母数量更多,尤其是提前96 h接种。模拟发酵处理中,同时接种处理的酯酶活性累积量最大(574 m U/mL),酯酶活性在C_2~C_8有底物特异性,其中C8酯酶活性累积量最高(178~227 m U/mL),C_2酯酶活性累积量最低(46~66 m U/mL)。结合发酵动力学与发酵中酯酶活性变化,发现酯酶活性与酵母的生长状况有关,当酵母生长达到稳定期,酯酶活性达到最大值。结论:优选酵母与酿酒酵母的同时接种发酵具有较高的C4~C8酯酶活性累积量,有增香酿造的应用潜力。

Growth Kinetics and Esterase Activities of Selected Non-Saccharomyces Yeast and Saccharomyces cerevisiae in the Fermentation of Model Grape Juice

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.