Study on freeze-tolerant baker's yeast

耐冷冻面包酵母的研究

• 批准号: 04454077
• 负责人: HATANO Shoji
• 金额: $ 4.29万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04454077/
• 关键词: Baker's yeast; Freeze tolerance; Bake off system; Actin; Glycolytic system

After a 7-d-frozen storage, the viability and CO_2 productivity of conventional baker's yeast decreased to 35% and 25% of those of unfrozen cells, respectively. A freeze-tolerant yeast for frozen dough method kept 75% viability even after the same storage, but the CO_2 productivity decreased to 30%. The CO_2 productivity and DNase I inhibitory activity of action of the cell-free extracts prepared immediately after thawing from 7-d-frozen-stored yeasts largely decreased. Only in the freeze-tolerant yeast, however, the productivity and the activity were increased by incubating the frozen-stored cells at 30 ﾟC after thawing. The increase tool place in actin before in CO_2 productivity. These results suggest that glycolytic system and actin in yeast cells are subject to damages during frozen storage. Both the yeasts released A_<262>-absorbing substances and Ca^<2+> during frozen storage. In cell-free extracts of both yeasts, two peaks of actin were detected by a gel filtration. These two peaks decreased in the extract of the conventional yeast prepared after frozen storage. In contrast, the freeze-tolerant yeast did not decrease the peak of actin deven after the same storage. Both yeasts decreased hexokinase and pyruvate kinase activity after the frozen storage. The decrease was greater in the conventional yeast than the tolerant one. Phosphofruktokinase was eluted at a fraction of higher molecular weight side of the enzyme. The peak moved to the lower molecular weight side after the frozen storage in the conventional yeast. The decrease in hexokinase and pyruvate kinase activity adn the dissociation of phosphofructokinase from enzyme complex cause the decrease in CO_2 productivity after frozen storage.

经过7d的冷冻保存，普通面包酵母的活力和二氧化碳产率分别下降到未冷冻细胞的35%和25%。一种耐冻酵母冻面法即使在相同的储藏条件下也能保持75%的存活率，但CO_2产率下降到30%。7d冻藏酵母解冻后立即制备的无细胞提取物的CO_2产生率和DNase I抑制活性显著降低。然而，只有在耐冻酵母中，解冻后将冻存细胞在30ﾟC下孵育，才能提高产量和活性。在CO_2生产率中，增加工具放在肌动蛋白之前。这些结果表明，酵母细胞中的糖酵解系统和肌动蛋白在冷冻保存过程中容易受到破坏。两种酵母菌在冷冻保存过程中都释放出吸附A_(262)和Ca~(2+)的物质。在两种酵母菌的无细胞提取物中，通过凝胶过滤检测到两个肌动蛋白峰。常规酵母冻藏后抽提物中这两个峰的含量均有所下降。相比之下，耐冻酵母即使在相同的贮藏条件下，肌动蛋白D值的峰值也没有降低。两种酵母菌在冷冻保存后都降低了己糖激酶和丙酮酸激酶的活性。常规酵母菌的降幅大于耐受型酵母。磷酸核糖核酸激酶在酶的一小部分较高分子量一侧洗脱。常规酵母经冷冻保存后，峰向低分子量侧移动。己糖酶和丙酮酸酶活性下降以及磷酸果糖酶从酶复合体中解离，导致冻藏后CO_2产量下降。