松萝内生酿酒酵母菌株耐酸生理特性与分子机制探究

Physiological characteristics of low pH tolerance of an endophytic Saccharomyces cerevisiae strain isolated from Usnea sp. and exploration of the underlying molecular mechanism

【目的】对我国西藏地区来源的不同酵母菌株进行有机酸发酵性能测试,此外,对具有良好产酸性能的分离自松萝内部的酿酒酵母菌株Saccharomy cescerevisiae 2-2进行耐酸性能分析,并探究其耐酸较强的分子机制。【方法】比较不同糖浓度培养基液体发酵培养过程中pH的变化,并比较低pH胁迫条件下菌株的生长,检测酿酒酵母菌株的产酸潜力和耐酸特性;对菌株2-2和模式酵母菌株S288C进行比较基因组分析,并利用实时荧光定量聚合酶链式反应(real-time fluorescence quantitative polymerase chain reaction,RT-qPCR)分析关键基因的转录,探究菌株2-2耐酸分子机制。【结果】松萝内生酿酒酵母2-2在所有检测的菌株中产酸潜力较大,耐酸性能较好。在菌株2-2中与胁迫耐受性相关的基因PDR15、PDR12和SUR1在低pH胁迫条件下存在显著的上调或下调,但这些基因转录变化趋势与菌株S288C相反。【结论】松萝内生酿酒酵母2-2是一株产酸耐酸性能较好的菌株,对其独特的调节机制进行深入分析,有希望选育性能更好的产酸酵母菌株。

[Objective]To detect the physiological characteristics related to organic acid production and low pH tolerance of the endophytic Saccharomyces cerevisiae 2-2 strain isolated from Usnea sp. in Tibet, China, and explore the molecular mechanism. [Methods]The pH of different strains was compared during liquid fermentation using different initial sugar concentrations, and the growth under stress conditions was monitored. The organic acid production potential and low pH resistance characteristics of S. cerevisiae strains were detected. Comparative genomic analysis was performed to explore the molecular mechanism of acid production and acid tolerance of S. cerevisiae strain 2-2 by real-time fluorescence quantitative polymerase chain reaction(RT-qPCR). [Results]S. cerevisiae 2-2had higher acid-producing potential among the tested yeast strains, which also showed better acid tolerance than that of the model strain S. cerevisiae strain S288C. The transcription levels of PDR15,PDR12 and SUR1 that affect the acid stress tolerance of S. cerevisiae in 2-2 were up-regulated or down-regulated under acid stress conditions, but the trends of these key genes were opposite to that of the strain S288C. [Conclusion]Endophytic S. cerevisiae 2-2 is a strain with potential in organic acid production and shows strong tolerance to low pH. An in-depth analysis of its unique regulatory mechanism will benefit the development of acid-producing yeast strains with improved performance.