L-Phenylalanine Production by Analog-resistant Mutants of Corynebacterium glutamicum

Abstract

Mutants resistant to phenylalanine- or tyrosine-analogs were isolated from a wild type strain of Corynebacterium glutamicum ATCC 13032 and a tyrosine auxotroph TL-3 by mutagenic treatment with N-methyl-N’-nitro-N-nitroso guanidine (NTG) and screened for l-phenylalanine production. The growth of C. glutamicum ATCC 13032 was strongly inhibited by a phenylalanine analog, p-fluorophenylalanine (PFP), at a concentration of 1 mg/ml. C. glutamicum TL-3 was inhibited by PFP and another phenylalanine analog, β-2-thienylalanine (TA), at a concentration of 50 μg/ml and 400 μg/ml respectively. A prototrophic mutant resistant to PFP (4 mg/ml) produced l-phenylalanine at a concentration of 5.5 mg/ml and a trace amount of l-tyrosine in a cane molasses medium containing 10% of sugar calculated as glucose. A tyrosine auxotrophic mutant resistant to PFP (100 μg/ml) and p-aminophenyl-alanine (PAP) (1 mg/ml), 31–PAP–20–22, produced L-phenylalanine at a concentration of 9.5 mg/ml in the molasses medium. l-Phenylalanine production in these mutants was inhibited by l-tyrosine and stimulated by l-tryptophan.