Excretion of L-tryptophan by analogue-resistant mutants of Pseudomonas hydrogenothermophila TH-1 in autotrophic cultures.

Abstract

Cells of a thermophilic hydrogen bacterium, Pseudomonas hydrogenothermophila TH-1 were treated with N-methyl-N′-nitro-N-nitrosoguanidine and resulting mutants resistant to tryptophan analogues were selected under autotrophic culture conditions (energy source, H2; carbon source, CO2). A mutant strain, 7922, which was resistant to 2000 µg/ml of 5-methyltryptophan and 200–500 µg/ml of 5-fluorotryptophan, was obtained by two step mutations. This mutant excreted 38–70 µg/ml of tryptophan into flask culture broth and a maximum of 200 µg/ml into jar fermentor broth.