L-METHIONINE PRODUCTION BY DOUBLE AUXOTROPHIC MUTANTS OF A ETHIONINE RESISTANT STRAIN OF BREVIBACTERIUM-HEALI

A number of lysine plus threonine double auxotrophs have been isolated from a ethionine resistant methionine producing strain of Brevibacter ium heali previously isolated from soil by mutagenesis with N-methyl N '-nitro-N-nitrosoguanidine in two steps. This strain excreted L-methio nine in sufficient amounts. For the three potent mutants tested, the m edium of ALFOLDI was judged to be the best. Biotin and ammonium nitrat e were found to be optimal at 5 mug/l and at a 40 mM level, respective ly. With such an optimal dose, the strain BhLT 27 yielded 25.5 g/l met hionine in a flask culture containing methionine-analogue ethionine at a minimal inhibitory concentration.