Enzymatic production of l-tryptophan from dl-5-indolylmethylhydantoin by Flavobacterium sp.

Abstract

An enzymatic production of l-tryptophan from dl-5-indolylmethylhydantoin by the action of hydantoinase and carbamoylase has been investigated. A strain identified as ( Flavobacterium) sp. I-3 isolated from soil was found to form l-tryptophan from dl-5-indolylmethylhydantoin. Cultural conditions for the formation of the l-tryptophan-forming activity were investigated, and the highest activity of 0.81 μmol min −1 of l-tryptophan formed per 1 ml of culture broth (hydantoinase, 3.6 μmol min −1 of N-carbamoyl- l-tryptophan formed per 1 ml of culture broth; carbamoylase, 0.92 μ mol min −1 of l-tryptophan formed per 1 ml of culture broth) was obtained. These activities were found to be inducible and intracellular. Optimization of the parameters of the conversion reaction resulted in accumulation of 50 mg of l-tryptophan per 1 ml of cultural broth per day. The conversion yield from dl-5-indolylmethylhydantoin was about 100 %. Accumulated l-tryptophan was readily isolated in pure form by ordinary procedures.