Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1996-12-12
1999-11-02
Jones, W. Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
435106, 435110, 43525253, C07H 2102, C12P 1304, C12P 1314, C12N 120
Patent
active
059773316
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to breeding and utilization of coryneform bacteria used for fermentative production of L-glutamic acid and L-lysine. In particular, the present invention relates to coryneform L-glutamic acid-producing bacteria deficient in .alpha.-ketoglutarate dehydrogenase (.alpha.-KGDH), a method of producing L-glutamic acid by using the bacteria, a gene coding for an enzyme having .alpha.-KGDH activity (.alpha.-KGDH gene) originating from coryneform L-glutamic acid-producing bacteria, recombinant DNA containing the gene, coryneform bacteria harboring the recombinant DNA, and a method of producing L-lysine by using coryneform bacteria harboring the recombinant DNA and having L-lysine productivity.
BACKGROUND ART
L-Glutamic acid has been hitherto industrially produced by a fermentative method using coryneform bacteria belonging to the genus Brevibacterium or Corynebacterium.
Recently, it has been revealed that a mutant strain of Escherichia coli, in which the .alpha.-KGDH activity is deficient or lowered, and the glutamic acid-decomposing activity is lowered, has high L-glutamic acid productivity (Japanese Patent Laid-open No. 5-244970).
On the contrary, it was reported that a mutant strain having lowered .alpha.-KGDH activity had approximately the same L-glutamic acid productivity as that of its parent strain in the case of a bacterium belonging to the genus Brevibacterium (Agric. Biol. Chem., 44, 1897 (1980), Agric. Biol. Chem., 46, 493 (1982)). Therefore, it has been believed that the level of .alpha.-KGDH activity is not important for production of L-glutamic acid in coryneform bacteria.
On the other hand, it was found that a mutant strain of a L-glutamic acid-producing bacterium belonging to the genus Brevibacterium having lowered .alpha.-KGDH activity produces L-glutamic acid at high efficiency (maximum yield of 53%) when the bacterium is cultivated in a medium which contains a material containing an excessive amount of biotin as a carbon source without addition of materials which suppress an effect of biotin such as penicillins and surface active agents (Japanese Patent Laid-open No. 6-23779). However, since it has been believed that the level of .alpha.-KGDH activity is not important for production of L-gultamic acid in the coryneform bacteria as described above, there has been no example in which an .alpha.-KGDH gene of a coryneform L-glutamic acid-producing bacterium is cloned and analyzed. Further, mutant strains of coryneform bacteria being completely deficient in .alpha.-KGDH have been unknown.
DISCLOSURE OF THE INVENTION
An object of the present invention is to obtain an .alpha.-KGDH gene originating from coryneform L-glutamic acid-producing bacteria, prepare recombinant DNA containing the gene, clarify the influence of the level of .alpha.-KGDH activity on fermentative production of L-glutamic acid by using microorganisms transformed with the recombinant DNA, and thus provide a new methodology in breeding of coryneform L-glutamic acid-producing bacteria. More specifically, an object of the present invention is to obtain a coryneform L-glutamic acid-producing bacterium deficient in .alpha.-KGDH activity by destroying an .alpha.-KGDH gene existing on chromosomal DNA, and provide a method of producing L-glutamic acid by using the bacterium. Further, the present invention is contemplated to provide a coryneform bacterium harboring recombinant DNA containing an .alpha.-KGDH gene, and a method of producing L-lysine by using a coryneform bacterium harboring the recombinant DNA and having L-lysine productivity.
The present inventors have obtained an .alpha.-KGDH gene originating from a coryneform L-glutamic acid-producing bacterium, clarified its structure, transformed a coryneform L-glutamic acid-producing bacterium by using a plasmid into which the gene is incorporated, and investigated the level of .alpha.-KGDH activity and L-glutamic acid productivity of obtained transformants. As a result, it has been found that the .alpha.-KGDH activity remarkably affects
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Abe Chizu
Asakura Yoko
Kawahara Yoshio
Kimura Eiichiro
Kurahashi Osamu
Ajinomoto Co. Inc.
Jones W. Gary
Whisenant Ethan
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