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Studies on the Mechanism of Freeze-Injury and Freeze-Tolerance of Yeast

酵母冻伤及耐冻机制的研究

基本信息

批准号：
02680063
负责人：
KAWAI Hiroyasu
金额：
$ 1.28万
依托单位：
Nara Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Factors that influence the freeze-injury of yeast was investigated to clarify the mechanism of freeze-tolerance of yeast in frozen-dough system. It was found that the temperature and period for freeze-storage influenced markedly the viability of yeast cells in a liquid medium, which depended on the freeze-sensitivity of yeast strains.The fermentative activity of freeze-sensitive strain after frozen-thawed with purothionin, ananti-yeast protein from wheat, was depressed with increasing amounts of the compound, while little effect was observed in freeze-tolerant strain. The amount of UV-absorbing materials leaking out from frozen-thawed cells reached a maxiniuni at PH 3-4 in both strains, and it increased by the concentration of purothionin depending on the freeze-sensitive strain than the freeze-tolerant strain. The result indicated that the lysis of yeast cells, probably their cell membranes, might occur by the freeze-thaw treatment in the presence of purothionin, depending on the freeze-sensitivity of yeast strains.It was also found that the phospholipase activity of yeast cell membrane fraction from the freeze-sensitive strain was highly accelerated by addition of durothionin, while the enzyme activity of freeze-tolerant strain was not affected by purothionin. Therefore, the susceptibility to freeze-injury of yeast was assumed to depend on the activity of phospholipase that catalyzes the degradation of phospholipids in cell membranes of yeast. As the activation of phospholipase from the freeze-sensitive strain by purothionin was depressed by addition of phosphatidylserine or phosphatidylinositol, we concluded that the freeze-sensitivity of yeast was related to the composition of phospholipid in yeast cells.

为阐明酵母在冷冻面团体系中的耐冻机理，对影响酵母冻害的因素进行了研究。结果表明，冷冻温度和冻存时间对酵母细胞在液体培养中的活力有显著影响，这取决于酵母菌株对冻融的敏感性；小麦抗酵母蛋白腐硫素冻融后，冻敏菌株的发酵活力随化合物用量的增加而降低，而耐冻菌株的冻融效果不明显。在PH3-4时，两个菌株的冻融细胞中的紫外线吸收物质渗出量均达到最大值，且依赖于腐硫素浓度的增加，敏感菌株比耐冻菌株的紫外吸收物质渗出量增加。结果表明，依赖于酵母菌株对冷冻的敏感性，在腐硫素存在的情况下，冻融处理可能会引起酵母细胞，可能是细胞膜的裂解；添加腐硫素对冷冻敏感菌株的细胞膜磷脂酶活性有显著的促进作用，而耐冻菌株的磷脂酶活性不受腐硫素的影响。因此，推测酵母对冻害的敏感性取决于磷脂酶的活性，磷脂酶催化酵母细胞膜中磷脂的降解。由于磷脂酰丝氨酸或磷脂酰肌醇的加入抑制了腐硫素对冷冻敏感菌株磷脂酶的激活，因此，酵母的冷冻敏感性与酵母细胞中磷脂的组成有关。