用亮氨酸抗性法选育L-甲硫氨酸高产突变株

用亮氨酸(Leu)抗性为标记筛选L-甲硫氨酸(L-Met)高产突变株．以一株具有M-海因水解酶系统的芽孢杆菌MV0073为出发菌株，经过6轮紫外诱变，筛选出27株抗亮氨酸的L-Met高产突变株．其中突变株M604的L-Met产量是出发菌株的3倍，且培养液中积累的高含量L-Met能在培养后期稳定持续，M604连续传代6次，遗传性状稳定，表明用Leu抗性选育L-Met高产突变株是一种切实可行的方法。

Breeding of L-Methionine High-yielding Strains by Leucine Resistance Selection

L-Methionine high-yielding strains are bred by use of leucine resistance selection. UV mutagenesis is performed on strain MV0073 of Bacillus containing L-5-thiomethyl hydantoin system. The mutants are selected directionally on the agar plate containing Leucine, and 27 candidate mutants are obtained by six continuous generations of UV mutagenesis. The L-methionine production of M604, one of the mutant strains, is 3 times as high as that in original strain, and the high level of L-methionine in the culture liquid can last during the late stage of culture. Moreover the L-methionine high-yielding capacity still maintain after six generations. It prove that the use of leucine resistant selection to breed L-methionine high-yielding strains is a practicable method.