啤酒酵母细胞壁葡聚糖合成代谢与抗自溶性能研究

在啤酒生产过程中发生的啤酒酵母自溶现象严重影响了成品啤酒的质量和酵母的连续使用代数。为了提高我国啤酒的质量和降低生产成本，抗自溶能力提高的酵母选育和啤酒酵母抗自溶机制成为研究的热点。在以往的研究中，大多数研究都集中在啤酒酵母自溶产物对成品带来的影响，而并没有从源头解决这个问题。我们前期分析抗自溶能力不同的两株啤酒酵母的比较转录组学信息，发现了细胞壁葡聚糖合成代谢在抗自溶能力好的酵母中转录水平显著上调。研究报道细胞壁葡聚糖对酵母细胞有一定的保护作用，所以我们推测葡聚糖合成的加强是啤酒酵母应答自溶压力的一个新机制。为证实这一假设，我们拟通过对葡聚糖合成途径的基因进行敲除和表达，揭示葡聚糖浓度与菌株抗自溶能力的关系；分析细胞壁葡聚糖合成的启动子序列和上游调控元件阐明酵母自溶应答机制。本课题将从新的方面探索啤酒酵母的自溶机制，为指导工业啤酒酵母的抗自溶菌株选育提供重要理论依据。

The autolysis of brewer's yeast during beer brewing siginificantly affects the beer quality and also it affects the usage of yeast. In order to improve the beer quality and reduce the production cost, researches have been focused on the improvement of anti-autolytic capability of brewer's yeast, moreover,understanding the mechanism of brewer's autolysis is the key to the yesat breeding. A lot of researches were focused on the sequential effects caused by yeast autolysis, but not the reason of autolysis. We analyzed the comparative transcriptone of two brewer's yeasts with different anti-autolytic capacity in our early research, and found that in the yeast with better anti-autolytic capacity, the expression levels of cell wall glucan synthesis genes were siginificantly higher than the other yeast. It has been reported that cell wall glucan provide a protection for yeast cells during fermentation, thus, we build the hypothesis that the improved cell wall glucan synthesis is the key to brewer's yeasts' autolysis responses. In order to prove this hypothesis, we plan to knock out and overexpress the genes involved in cell wall glucan biosynthesis pathway so as to reveal the relationship between the cell wall glucan concentration and yeasts' anti-autolytic ability. Moreover, we want to clarify the yeast autolysis response mechanism via anlyzing the promoter sequences and upstream control elements of glucan biosynthesis. This project will explore the autolysis mechanism of brewer's yeast in a new aspect, and provide important theoretical basis for breeding brewer's yeast with better anti-autolytic capability.