Abstract
It was demonstrated in our previous papers that some of the home-made Miso (soybean paste) contain a great quantities of the tyramine and histamine. In this paper, isolation of microbes from the Miso containing a large amount of tyramine, and production of tyramine by these microbes in liquid medium were investigated.
(1) Tyramine formation was observed by lactic acid bacteria strains. On the other hand, no activities of tyrosine decarboxylase were observed in the representative Bacilli and Yeasts cultivated in the medium containing 1% yeast extract, 1% peptone, 1% glucose, 0.01% K2HPO4, 0.4% CaCO3, 0.025% tyrosine and 1% NaCl with an initial pH value 7.0.
(2) Tyramine formation in the medium was observed with mixed culture of two of these strains, the amount of tyramine formed in Streptococcus faecalis culture was larger than in any other cases. It is considered that the formation of tyramine by Streptococcus faecalis was controlled other strains, because these strains did not degradate the tyramine in medium but utilized it nutritively.
On the other hand, lactic acid bacteria and fungi (Aspergillus oryzae, spore color white, greenish yellow and black) were tested by a mixed culture method of two strains. These fungi degraded tyramine almost perfectly with induced amine oxidase in the medium.
(3) Tyramine formation was decreased with increasing concentration of NaCl in culture medium. It was found that in medium tyramine was not produced in the medium containing NaCl over 13%.
