Abstract
In this paper, the production of tyramine by microbes from the Miso (soybean paste) and the physiological characters of these bacteria were investigated. By these bacteria, varried the amount of amine formation, especially, the amount of tyramine formation in medium varied remarkably. Using the yeast extract medium, less amount of tyramine was produced than in the mixed yeast and beef (BY) extract medium.
Tyramine in culture increased when the BY medium was added with CaCO3 or radish extract, but K2HPO4 addition decreased it. Among these bacteria did not growth in medium contained more than 15% NaCl, therefore these bacteria were able to grow in this medium and were formed in small amount of lactic acid under such condition, namely in the medium added with radish extract or mixed cystine, leucine and tyramine (C. L. T.) solution. Especially, with the medium added with C. L. T., these lactic acid bacteria were changed having a halophylic character, and these halophylic bacteria have physiological characters, such as film state growth on vertical side in test tube, decreases in lactic acid formation and tyrosine decarboxylase activity, and changes in essential amino acid requirement with the synthetic medium. It was considered that this tendency seemed to have originated from the halophylic characters of these bacteria.
Among these characters, decrease in tyrosine decarboxylase activity was assumed to be caused by the deficiency of B6, because tyrosine decarboxylase recovers its activity when pyridoxal phosphate is added in the medium with acetone powder.
Using these strains, the changes in the components of cell were also studied. In general, as halotolerance increases lactic acid bacteria contained higher concentration of ash, inorganic phosphorus, total lipid and RNA than original lactic acid bacteria did. As for variance in total lipid content, it could be found that, halotolerant lactic acid bacteria had higher content of acetone insoluble fraction than acetone soluble fraction, and halotolerant strains also showed larger P/N molar a ratio of acetone insoluble lipid than original bacteria.
