| 摘要 |
PURPOSE:To industrially more efficiently produce amino acid such as L-threonine or L-lysine at a low cost by culturing microorganism having amino acid- producibility in a medium containing methanol as a principal carbon source. CONSTITUTION:A strain having improved sensitivity to at least a species belonging to genus Methylobacillus selected from an antibiotic substance and an antagonistic substance against amino acid metabolism is subjected to mutation treatment as a parent strain to obtain microorganism having resistance to at least a species selected from L-threonine, L-lysine and an antagonistic substance against amino acid metabolism and having amino acid-producibility. Next, said microorganism is cultured in a medium containing methanol as a principal carbon source to generate and accumulate amino acid in the resultant cultured substance and amino acid is collected from the cultured substance. The mutant is obtained by subjecting the parent strain to an usual mutation treatment such as ultraviolet rays irradiation or N-methyl-N'-nitrosoguanidine (NTG) treatment. As the antagonistic substance against amino acid metabolism, alpha- amino-beta-hydroxyvaleric acid or S-2-aminoethyl-L-cysteine, etc., is exemplified.
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