Production of aromatic amino acids by microorganisms. IX. L-Tryptophan production by analog-resistant mutants derived from a phenylalanine and tyrosine double auxotroph of Corynebacterium glutamicum.

Abstract

Mutants producing a large amount of L-tryptophan were derived from a phenylalanine and tyrosine double auxotroph of Corynebacterium glutamicum, KY 9456 which produced only a trace amount of L-tryptophan (150 μg/ml) and anthranilate. A mutant, 4 MT-11, resistant to 5-methyltryptophan, tryptophanhydroxamate, 6-fluorotryptophan and 4-methyltryptophan which was derived by stepwise mutagenic treatments produced L-tryptophan at a concentration of 4.9mg/ml in a molasses medium containing 10% of sugar calculated as glucose. L-Tryptophan production with 4 MT-11 was inhibited by L-phenylalanine and L-tyrosine. Accordingly, mutants resistant to phenylalanine and tyrosine analogs such as p-fluorophenylalanine, p-aminophenylalanine, tyrosinehydroxamate, and phenylalaninehydroxate were derived from 4 MT-11. One of the mutants, thus obtained, Px-115-97 produced L-tryptophan at a concentration of 12.0mg/ml in the molasses medium. L-Tryptophan production with the mutant was still sensitive to L-phenylalanine and L-tyrosine.