Simple improvement in freeze-tolerance of Bakers' yeast with poly-γ-glutamate
Simple improvement in freeze-tolerance of Bakers' yeast with poly-γ-glutamate
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DOI：
10.1263/jbb.102.215
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发表时间：
2006-09
影响因子：
2.8
通讯作者：
K. Yokoigawa;Machiko Sato;K. Soda
中科院分区：
文献类型：
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作者：
K. Yokoigawa;Machiko Sato;K. Soda
研究了聚-γ-谷氨酸（PGA）对耐冻酵母、耐低温酵母、低温敏感酵母和普通酵母抗冻性的影响。在培养基（0.5%酵母提取物、0.5%蛋白胨和2%葡萄糖：YPD培养基）中于-30 °C冷冻3 d的普通面包酵母细胞的存活率通过向培养基中添加超过1%的PGA而提高;存活率从约10%提高到70%以上。平均分子量不同（50、2000、4000、6000、8000和10，000 kDa）的所有PGA制剂对细胞显示出相似的冷冻保护作用。用其它类型的面包酵母、清酒酵母和啤酒酵母也获得了类似的结果。当四种类型的面包酵母细胞在添加超过1%的PGA的面团中于-30 °C冷冻3 d时，细胞（冷冻和解冻后）显示出比在不含PGA的面团中冷冻的细胞更高的发酵能力，而与PGA的分子量无关。因此，PGA似乎可以保护面包酵母免受致命的冷冻损伤，导致冷冻和解冻后的高发酵能力。PGA不降低面包酵母的原始发酵能力，也不被酵母细胞分解。PGA抑制发酵能力的下降，在延长发酵时间，可能是因为PGA吸附抑制代谢产物积累在面团。PGA添加到面团中可提高面包酵母的抗冻性。
We examined the effect of poly-γ-glutamate (PGA) on the freeze-tolerance of four types of commercial bakers' yeast (freeze-tolerant, osmotic-tolerant, low-temperature-sensitive, and ordinary bakers' yeasts). The survival ratio of ordinary bakers' yeast cells frozen at −30°C for 3 d in a medium (0.5% yeast extract, 0.5% peptone, and 2% glucose: YPD medium) was improved by adding more than 1% PGA to the medium; the survival ratio increased from about 10% to more than 70%. All PGA preparations, which differed in average molecular mass (50, 2000, 4000, 6000, 8000, and 10,000 kDa), showed a similar cryoprotecive effect on the cells. Similar results were also obtained with other types of bakers' yeast, sake yeast and beer yeast. When the four types of bakers' yeast cell were frozen at −30°C for 3 d in dough supplemented with more than 1% PGA, the cells (after freezing and thawing) showed higher leavening ability than those frozen in dough without PGA, irrespective of the molecular mass of PGA. Thus, PGA appears to protect bakers' yeast from lethal freeze injury, leading to a high leavening ability after freezing and thawing. PGA did not decrease the original leavening ability of the bakers' yeast, and was not decomposed by the yeast cells. PGA suppressed the decrease in leavening ability during a prolonged fermentation time, probably because PGA adsorbed inhibitory metabolites accumulated in the dough. PGA could prove useful for improving the freeze-tolerance of bakers' yeast by its addition to dough.