l-threonine production by l-aspartate- and l-homoserine-resistant mutant of Escherichia coli |
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Authors: | Satoru Furukawa Akio Ozaki Toshihide Nakanishi |
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Affiliation: | (1) Technical Research Laboratories, Hofu Plant, Kyowa Hakko Kogyo Co., Ltd., 1-1, Kyowa-machi, 747 Hofu-shi, Yamaguchi, Japan |
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Abstract: | Summary Growth and l-threonine productivity of l-threonine producer Escherichia coli H-4290 were inhibited by precursor amino acids, l-homoserine and l-aspartate. l-Threonine hyper-producers were isolated among the mutants resistant to l-homoserine and l-aspartate. Mutants H-4351 (Homr) and H-4578 (Homr, Aspr) accumulated 22.2 g/l and 24.3 g/l of l-threonine in test tube cultures, while the parental strain H-4290 accumulated 18.2 g/l. The enzyme level of aspartokinase I (first enzyme of the threonine operon) was enhanced 2.3 times (H-4351) and 3 times (H-4578) that of H-4290. Mutant H-4578 accumulated 76 g/l of l-threonine in a 2-l jar fermentor after 75 h cultivation.Abbreviations DAP diaminopimeric acid - Metl poor growth in methionine-free medium - AHV -amino--hydroxyvaleric acid - Thr-N- lack of ability to utilize l-threonine as a nitrogen source - Rif rifampicin - Lys+Metr resistant to l-lysine and dl-methionine |
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