Methods for producing L-valine and L-leucine

Details Methods for producing L-valine and L-leucine Methods for producing L-valine and L-leucine

1997-02-28

1999-03-30

Lilling, Herbert J.

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Preparing alpha or beta amino acid or substituted amino acid...

435116, 43525233, 4352528, 4353201, C12N 121, C12N 120, C12P 1308, C12P 1306

Patent

active

058887830

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a microorganism belonging to the genus Escherichia having the capability of producing L-valine or L-leucine and, more particularly, a microorganism whose capability of producing L-valine or L-leucine is enhanced.


BACKGROUND ART

In the past, L-valine and L-leucine have been produced by a method of fermentation primarily using a microorganism belonging to the genus Brevibacterium, Corynebacterium or Serratia or a mutant thereof which produces L-valine or L-leucine (Amino acid fermentation, JAPAN SCIENTIFIC SOCIETY'S PRESS, pp.397-422, 1986). Although the conventional methods have considerably enhanced the productivity of these amino acids, the development of a more efficient, cost-effective technique is required in order to meet increasing demand for L-valine and L-leucine in the future.
On the other hand, a microorganism belonging to the genus Escherichia is potentially utilized as a potent L-valine or L-leucine-producing microorganism due to its rapid growth rate, progress in genetic analysis and plentiful genetic materials. However, there are few reports documenting the production of these amino acids with from Escherichia microorganisms, and as for L-branched chain amino acids, only a few reports deal with the production of L-isoleucine (Japanese Patent Application Laid-Open No. 5-304969(1993) and Japanese Patent Application Laid-Open No. 5-130882(1993).


DISCLOSURE OF THE INVENTION

The object of the present invention, in view of the aforementioned points, is to provide an efficient and cost-effective method for producing L-valine and L-leucine by enhancing the capability of producing L-valine or L-leucine of a microorganism belonging to the genus Escherichia.
As a result of a wholeheartedly conducted study of the production of L-valine and L-leucine by mutants of microorganisms belonging to the genus Escherichia, the present inventors have found that a mutation, whereby lipoic acid is required for growth and/or H.sup.+ -ATPase is deficient, enhances the capability of producing L-valine or L-leucine of a L-valine or L-leucine-producing microorganism.
Thus, a first microorganism of the present invention is a microorganism belonging to the genus Escherichia and having the capability of producing L-valine or L-leucine, which requires lipoic acid for growth. A second microorganism of the present invention is a microorganism belonging to the genus Escherichia and having the capability of producing L-valine or L-leucine, which is deficient in H.sup.+ -ATPase. Furthermore, a third microorganism of the present invention is a microorganism belonging to the genus Escherichia and having the capability of producing L-valine or L-leucine, which requires lipoic acid for growth and is deficient in H.sup.+ -ATPase.
The present invention also provides a method for producing L-valine or L-leucine comprising culturing the aforementioned microorganism in a liquid medium to allow the L-valine or L-leucine to be produced and accumulated in the medium and collecting it.
In the specification, the phrase "H.sup.+ -ATPase deficient" means that cells do not substantially express H.sup.+ -ATPase activity, and includes both of that an H.sup.+ -ATPase gene does not express due to entire or partial deletion of an atp operon coding for eight subunits of H.sup.+ -ATPase or split of the atp operon and that the H.sup.+ -ATPase gene has substitution, insertion or deletion of one or more nucleotides therein so that the H.sup.+ -ATPase protein which is produced by expression of the gene does not have H.sup.+ -ATPase activity. The ilvGMEDA operon means a operon including each of ilvG, ilvM, ilvE and ilvD genes, and the operon may additionally include ilvA gene, which expresses inactivated threonine deaminase, or may not include ilvA gene substantially.
The invention will be described in detail as follows:
A microorganism of the invention is one which belongs to the genus Escherichia and has the capability of producing L-valine or L-leucine and has any one of the following properties: deficient.


REFERENCES:
Derwent Abstract 93-093644 JP05137568 Ajinomoto KK, Jun. 1, 1993.

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