清酒酵母の生理的研究 : (第12報) 静置培養時における乳酸の菌体中への移行と代謝

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Previous studies in this laboratory showed that lactic acid exerted physiologically adverse effects on Saccharomyces sake, particularly on its growth and the content of respiratory enzymes, depending on whether the yeast was cultivated aerobically or anaerobically.In this paper, we studied the uptake and metabolism of exogenous lactic acid 1-^<14>C and lactic acid 2-^<14>C under static cultivation. Under the experimental conditions employed, the amount of lactic acid taken into yeast cells was only about 1% of the total lactic acid added. A time-course study on the fate of 1-^<14>C and 2-^<14>C revealed that a greater part of 1-^<14>C was lost from the cells at a relatively early stage of the growth.Radioactivity of lactic acid was mainly incorporated into sterols and fatty acids of lipid fractions in the cells and a small part of it was recovered from organic acids of TCA cycle and amino acids. These facts indicated that lactic acid is not easily uptaken and metabolized in the case of static cultivation. A small part of the acid taken into the cells was first dehydrogenated to yield pyruvic acid by lactic acid dehydrogenase, then converted to the substances mentioned above via acetyl-CoA. Abnormal metabolites, which might have caused coagulation and death of the cells under anaerobic conditions, were not detected.
社団法人日本生物工学会の論文
1970-02-25