面包酵母麦芽糖酶耐冷冻的分子机制研究

Freezing resistance has always been one of the major research goals of stress tolerance in baker’s yeast. Previously, we constructed a strain of baker’s yeast B+MAL62 with the MAL62 overexpressed which can ferment maltose faster. Unexpectedly, the strain B+MAL62 also showed enhanced freezing tolerance in frozen dough. This project intends to annotate and verificate the differentially expressed gene and protein through transcriptome analysis and proteome analysis. A series of strains with gene overexpression and deletion were constructed, and the differences on the metabolism of maltose and trehalose will be monitored. And then the metabolic mechanism of maltase affecting on the freezing resistance in baker’s yeast B+MAL62 will be better understood. These efforts will reveal a new way of enhancing baker's yeast’s freezing tolerance and improve the mechanism of how the maltose metabolism affects the freezing tolerance of baker’s yeast. This study could provide a valuable insight into breeding of novel freeze-tolerant baker's yeast strains and a better understanding of other sugar metabolic metabolism, which has the potential to promote the technological level of yeast industry.

耐冷冻面包酵母的选育一直是酵母抗逆性研究的重要内容。我们前期在工业酵母中高表达麦芽糖酶编码基因（MAL62），得到菌株B+MAL62，发现该菌株不仅具备了麦芽糖高代谢能力，还额外提高了耐冷冻的能力。本课题拟通过对B+MAL62进行转录组学和蛋白质组学分析，对表达差异的基因与蛋白进行标注和功能验证。构建一系列基因过表达和缺失菌株，结合生长代谢情况分析，揭示面包酵母麦芽糖酶抗冷冻的分子遗传机制。研究结果将会揭示一种新的面包酵母抗冷冻途径，进一步完善麦芽糖代谢提高酵母冷冻耐性的机制，对耐冷冻面包酵母菌种的选育及其它糖代谢机制的研究具有重要的指导意义，且能够为提高我国面包酵母行业科技水平奠定坚实的基础。

耐冷冻面包酵母的选育一直是酵母抗逆性研究的重要内容。本课题针对面包酵母麦芽糖酶耐冷冻机制进行了深入研究。通过分析过表达麦芽糖酶基因的面包酵母的转录组学和蛋白质组学数据，对表达差异的基因与蛋白进行标注和功能验证，从分子水平上首次阐明麦芽糖酶是通过UDPG海藻糖合成通路，增强面包酵母细胞内海藻糖水平，从而实现了菌株耐冷冻。通过高表达UDPG通路中的关键基因TPS1，同时过表达麦芽糖酶基因MAL62，获得了优良的耐冷冻面包酵母菌株，与出发菌株相比，该菌株胞内海藻糖积累速度加快，预发酵冷冻后细胞存活数增加，实际冷冻面团环境下发酵力折损减少，这些特点使其具备潜在的商业应用价值，并证明了高表达海藻糖合成酶基因TPS1，可以增强麦芽糖酶的耐冷冻能力。通过敲除海藻糖合成酶基因TPS1，检测菌株麦芽糖与海藻糖代谢性能和冷冻耐受能力变化，证明UDPG路径中的TPS1基因是麦芽糖酶耐冷冻的关键因素。研究结果不仅完善了麦芽糖代谢提高酵母冷冻耐性的机制，而且对耐冷冻面包酵母菌种的选育及其它糖代谢机制的研究具有重要的指导意义。