L-Threonine Production by a Mutant of Arthrobactev paraffineus |
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Authors: | Hiroshi Kase Kiyoshi Nakayama |
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Institution: | Tokyo Research Laboratory, Kyowa Hakko Kogyo Co., Ltd., Machida-shi, Tokyo |
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Abstract: | An isoleucine leaky auxotroph of Arthrobacter paraffineus, which was isolated by Takayama et al.3) as a mutant producing L-threonine and L-valine from n-paraffin, was subjected to further mutagenesis in an attempt to obtain better L-threonine producers. Some of the double auxotrophs derived from the isoleucine auxotroph and some of their revertants with respect to isoleucine requirement produced more L-threonine than the original isoleucine auxotroph. In contrast to the original isoleucine auxotroph, a revertant derived from a methionine plus isoleucine double auxotroph, KY7135, produced an increased amount of L-threonine and a decreased amount of L-valine. The optimum level of L-methionine for L-threonine production in KY7135 was much higher (1000 ~ 2000 μg/ml) with n-paraffin medium than with sorbitol or mannitol medium (10 ~ 50 μg/ml). L-Threonine production reached a maximum level (11.5 mg/ml) in 7 days incubation with the medium containing 10% n-paraffin (C12 ~ C14 rich). Several mutants which produce L-threonine more than 12 mg/ml were obtained from KY 7135 by monocolony isolation procedure. |
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