MICROBIAL PRODUCTION OF L-LYSINE

III. PRODUCTION BY MUTANTS RESISTANT TO S-(2-AMINOETHYL)-L-CYSTEINE

Abstract

S-(2-Aminoethyl)-L-cysteine (AEC), a sulphur analog of L-lysine, inhibited the growth of Bacillus subtilis and Escherichia coli. In the case of Brevibacterium flavum, AEC alone inhibited the growth rather weakly but in the presence of threonine the inhibitory effect was markedly enhanced. These inhibitory effects were diminished by the addition of L-lysine.
AEC-Resistant mutants were derived from B. flavum No. 2247. Some of them produced much lysine in minimal medium and were not affected by threonine, differing from the lysine-producing auxotrophs or the threonine- or methionine-sensitive lysine producer. Therefore, the mutation site of lysine-producing AEC-resistants is deduced as the feedback site of aspartokinase.