Abstract
A bacterium that stereospecifically produces L-valine from 5-isopropylhydantoin was isolated from soil. It was identified as Bacillus brevis and given the number AJ-12299. L-Valine productivity from L-, D- or DL-5-isopropylhydantoin by B. brevis AJ-12299 was rather low because this bacterium had L-valine degrading-activity. In contrast, the productivity was improved by a mutant the L-valine degradation pathway of which was genetically blocked, and the 5-isopropylhydantoin consumed was stoichiometrically converted to L-valine. The optimal temperature and pH of the reaction were 30°C and 7.0-7.5. The enzyme involved in the reaction was inducible and was strongly induced by the addition of 5-isopropylhydantoin. In addition to L-valine production, this bacterium also produced various aliphatic and aromatic L-amino acids from the corresponding 5-substituted hydantoins.
