pep4変異を持つ清酒酵母の造成

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Yeast cells begin to die at the final stage of sake brewing because of the high concentration of alcohol (about 20%), especially after the addition of brewer's alcohol.It has been reported that the amino acid content of the sake moromi mash increase after alcohol addition and that the increase lowers the quality of the sake. It is presumed that this is mainly caused by activation of carboxypepridase Y, a yeast vacuolar peptidase.To elucidate genetically the role of vacuolar enzymes of yeast in sake brewing, we contructed a sake yeast harboring the pep4 mutation, which had very low activity of the vacuolar enzymes proteinase A, proteinase B, carboxypeptidase Y, RNase, and alkaline phosphatese at same time.In the paper, we demonstrate the construction of a sake yeast harboring the homozygous pep4/pep4 mutation by repeated back crossing and pep4 mutant isolation from sake yeast, and analysis of components of sake moromi mash using the pep4 sake yeast.The increase of amino acid content after alcohol addition of sake moromi mash using the pep4 sake yeast was lower than that using the parental sake yeast, indicating that vacuolar pepridases produce amino acids after alcohol addition. But the amino acid content at the alcohol addition was a little higher than that using the parental sake yeast. The increase of OD at 260 nm of sake moromi mash using the pep4 sake yeast was significantly lower then thet using parental sake yeast, suggesting that a vacuolar enzyme, RNase, may be activated in sake moromi mash. Unexpectedly, the sake brewed using the pep4 sake yeast had a lower content of organic acid than that using the parental sake yeast.
社団法人日本生物工学会の論文
1988-01-25

pep4変異を持つ清酒酵母の造成

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