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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抗冻机理，研究了影响酵母冻损伤的因素。结果表明，冻存温度和冻存时间对酵母细胞在液体培养基中的存活率有显著影响，这种影响取决于酵母菌的冻敏性，小麦抗酵母蛋白嘌呤硫素对冻敏性菌株的发酵活性有抑制作用，而对耐冻性菌株的影响不大。两株菌在pH 3-4时，紫外线吸收物质从冻融细胞中漏出的量均达到最大值，且随嘌呤硫素浓度的增加，冻敏菌株的漏出量高于耐冻菌株。结果表明，在嘌呤硫堇存在下，酵母细胞（可能是其细胞膜）的冻融处理可能发生裂解，这取决于酵母菌株的冷冻敏感性。还发现，来自冷冻敏感菌株的酵母细胞膜组分的磷脂酶活性被加入Durothionin高度加速，而对耐冻菌株的酶活性没有影响。因此，推测酵母对冷冻损伤的敏感性取决于催化酵母细胞膜中磷脂降解的磷脂酶的活性。由于加入磷脂酰丝氨酸或磷脂酰肌醇可抑制嘌呤硫堇对冷冻敏感菌株磷脂酶的激活作用，因此我们得出结论，酵母的冷冻敏感性与酵母细胞中磷脂的组成有关。