高耐受性酿酒酵母的适应性驯化选育与发酵

A Saccharomyces cerevisiae strain with high tolerance: breeding by gradual acclimation and fermentation performance

摘要:

【背景】酿酒酵母(Saccharomyces cerevisiae)是葡萄糖发酵产乙醇的重要菌株，然而在生物乙醇发酵过程中，常会出现高乙醇浓度、高糖、高温和低pH等胁迫环境，从而影响酿酒酵母菌株的发酵效果。【目的】获得乙醇耐受性及高温、高糖等相关耐受性能提高的优良菌株，并讨论驯化菌株和出发菌株的高糖发酵乙醇性能。【方法】采用高浓度乙醇胁迫环境逐步驯化实验室保存的酿酒酵母菌株(CICC 33068)，通过对比驯化菌株和出发菌株在高浓度乙醇、高糖、高温和低pH环境中的生长曲线及高糖发酵乙醇性能，探讨驯化菌株的高耐受特性。【结果】相较于出发菌株，获得的驯化菌株可在含13%乙醇的液体培养基中生长，并保持完整的细胞生长周期和细胞形态，能耐受葡萄糖浓度450 g/L、温度45 ℃和pH 3.5。该驯化菌株能够在糖浓度450 g/L、45 ℃和pH 3.5的环境下生长，糖醇转化率可达79.22%，较出发菌株提高7.72%，通过检测相关基因表达发现，该菌株耐受性能提高与胞内海藻糖合成代谢上调相关。【结论】获得了具有耐受高浓度乙醇、高糖、高温和低pH特性的优良酿酒酵母菌株，该菌株通过上调菌株胞内海藻糖合成代谢提高耐受性能，使其发酵高浓度葡萄糖的能力显著高于出发菌株，可为后续其他菌株的驯化筛选提供研究基础。

Abstract:

[Background] Saccharomyces cerevisiae is an important microorganism in the fermentation of glucose to yield ethanol. However, high concentrations of ethanol and sugar, high temperature, low pH, and other highly stressful conditions often occur during the fermentation, which affect the fermentation efficiency of S. cerevisiae. [Objective] To obtain a S. cerevisiae strain with improved tolerance to high concentrations of ethanol and sugar and high temperatures and evaluate the fermentation performance of the domesticated strain in the case of high sugar levels. [Methods] A laboratory-preserved strain (CICC 33068) of S. cerevisiae was gradually acclimated to an environment of highly concentrated ethanol. The domesticated strain was compared with the original strain in terms of the growth curves and fermentation performance under high concentrations of ethanol and sugar, high temperature, and low pH for the evaluation of its tolerance. [Results] Compared with the original strain, the domesticated strain displayed a complete growth cycle and normal morphology in the broth medium with 13% ethanol. The domesticated strain was capable of growing in the presence of 450 g/L glucose and at 45 ℃ and pH 3.5, with the glucose-to-ethanol conversion rate of 79.22%, which was 7.72% higher than that of the original strain. The gene expression levels indicated that the improved tolerance was associated with the up-regulation of intracellular trehalose synthesis pathway. [Conclusion] A S. cerevisiae strain with improved tolerance to high concentrations of ethanol and sugar and high temperatures and low pH was obtained by environmental acclimation to high levels of ethanol. The domesticated strain outperformed the original strain in the fermentation with high glucose for ethanol production. The results demonstrate that adaptive acclimation could enhance the strain tolerance by upregulating intracellular trehalose synthesis. The findings provide fundamental data for subsequent domestication and screening of other strains.