College of Food Science and Engineering, Northwest A&F University, Yangling, 712100, China.
Appl Biochem Biotechnol. 2019 Feb;187(2):540-555. doi: 10.1007/s12010-018-2840-1. Epub 2018 Jul 13.
The effects of different wort gravity or ethanol concentration in initial wort on the fermentation performance of lager yeast and assimilation of free amino acids (FAAs) were studied. Results showed that compared with high wort gravity (24°P), high ethanol concentration (10%, v/v) decreased yeast growth, cell viability, and wort fermentability significantly. The assimilation of FAAs was changed dramatically by high ethanol toxicity, and positive correlations between the assimilation amounts of 10 FAAs (Asp, Ser, Gly, Arg, Tyr, Val, Met, Lys, Ile, and Leu) and fermentation performance (cell viability, fermentability, and ethanol production) were identified, especially for Arg and Lys exhibiting extremely significant positive correlations. Furthermore, confirmatory testing was carried out by supplementing 24°P worts with 10 FAAs of 0.5, 1, and 2 times of their standard concentrations, respectively. Results exhibited that 10 FAA supplementations improved physiological characteristics and fermentation performance of lager yeast significantly, especially for 1 times FAA supplementation increasing wort fermentability and ethanol yield by 6 and 17%, respectively, and upregulated the expression level of HSP12 and increased more intracellular trehalose accumulation in yeast cells, indicating that stronger protective function was stimulated in yeast cells. Therefore, it was suggested that these 10 FAAs could regulate yeast cells to adapt to high gravity environmental stresses.
研究了麦汁初始比重或乙醇浓度对拉格酵母发酵性能和游离氨基酸（FAAs）同化的影响。结果表明，与高麦汁比重（24°P）相比，高乙醇浓度（10%，v/v）显著降低了酵母生长、细胞活力和麦汁发酵性能。高乙醇毒性显著改变了 FAAs 的同化，鉴定出 10 种 FAAs（Asp、Ser、Gly、Arg、Tyr、Val、Met、Lys、Ile 和 Leu）的同化量与发酵性能（细胞活力、发酵性能和乙醇产量）之间存在显著正相关，尤其是 Arg 和 Lys 表现出极显著的正相关。此外，通过分别补充麦汁中 10 种 FAAs 标准浓度的 0.5、1 和 2 倍进行了验证性测试。结果表明，10 种 FAA 补充剂显著改善了拉格酵母的生理特性和发酵性能，特别是 1 倍 FAA 补充剂分别将麦汁发酵性能和乙醇产量提高了 6%和 17%，并上调了 HSP12 的表达水平，增加了酵母细胞内更多的海藻糖积累，表明酵母细胞中刺激了更强的保护功能。因此，建议这 10 种 FAAs 可以调节酵母细胞以适应高重力环境应激。
