L-VALINE PRODUCTION USING MICROBIAL AUXOTROPH

Abstract

1. Isoleucine-less and leucine-less mutants of glutamic acid producing bacteria accumulated a considerable amount of valine in culture broth. Accumulation of this amino acid also occurred in the following mutants: threonine-less, threonine and methionine-less, arginine-less, (tryptophane+phenylalanine+tyrosine)-less and arginine or citrulline or ornithine-less.2. Valine accumulation by isoleucine-less and leucine-less mutants occurred in limited concentration of requiring amino acids in media. And no accumulation occurred where these amino acids added in excess.3. Lactic acid was found to accumulate in the presence of excessive amount of required amino acid and sufficient biotin in media. Valine accumulation took place in the presence of proper concentration of requiring amino acids. The tendency of glutamic acid accumulation was recognized in a small concentration of biotin.4. It was suggested from cell suspension experiments that isoleucine inhibits enzyme formation rather than enzyme action, of valine accumulating system of a isoleucine-less mutant.5. With the isoleucine-less mutant valine accumulation when cultured on a synthetic medium containg isoleucine was much low compared to those on NZ-amine medium. Addition of leucine or valine markedly increased the valine accumulation on the above synthetic medium.6. Antagonisms among isoleucine, leucine and valine were observed in growth and valine accumulation. Speculation on the effect of leucine and valine mentioned above was made from these antagonisms and inhibiting action of isoleucine on enzyme formation of valine accumulating system.