Microbial Production of L-lysine I. Production by Auxotropiis of Brevibacterium Elavum

Seven homoserine, 42 methionine, 42 threonine, and 15 isoleucine auxotrophs were obtained from Brevibacterium flavum No. 2247 (ATCC No. 14067) by X-ray irradiation and N-methyl-N'-nitro-N-nitrosoguanidine treatment. Concerning the L-lysine-producing ability, the homoserine auxotrophs were the best and about one-half of the threonine auxotrophs ranked next. The rest of threonine auxotrophs and all of the methionine and isoleucine auxotrophs produced little of L-lysine. Investigation on enzyme activities of threonine synthesis revealed that L-lysine-producing threonine auxotrophs lacked homoserine kinase and accumulated the substrate, L-homoserine. On the other hand, the rest which produced little L-lysine and fairly much phosphohomoserine last the threonine synthase activity.