Patent ID: 8008047

Claim:
A method of producing an L-amino acid comprising I) culturing an L-amino acid-producing Escherichia coli bacterium in a medium to produce and accumulate an L-amino acid in the medium or cells of the Escherichia coli bacterium and II) collecting the L-amino acid from the medium or the cells, wherein said Escherichia coli bacterium has been modified so that Na + /H + antiporter activity is enhanced as compared to a non-modified Escherichia coli bacterium by increasing expression of a gene selected from the group consisting of nhaA, nhaB, nhaR, chaA, mdfA, and combinations thereof, wherein said L-amino acid is selected from the group consisting of L-lysine, L-threonine, and combinations thereof, wherein the nhaA gene encodes a protein selected from the group consisting of: (A) a protein comprising the amino acid sequence of SEQ ID NO: 2, and (B) a protein comprising the amino acid sequence of SEQ ID NO: 2, but which includes substitution, deletion, insertion or addition of one to 10 amino acids, and has Na + /H + antiporter activity, wherein the nhaB gene encodes a protein selected from the group consisting of: (C) a protein comprising the amino acid sequence of SEQ ID NO: 4, and (D) a protein comprising the amino acid sequence of SEQ ID NO: 4, but which includes substitution, deletion, insertion or addition of one to 10 amino acids, and has Na + /H + antiporter activity, wherein the nhaR gene encodes a protein selected from the group consisting of: (E) a protein comprising the amino acid sequence of SEQ ID NO: 6, and (F) a protein comprising the amino acid sequence of SEQ ID NO: 6, but which includes substitution, deletion, insertion or addition of one to 10 amino acids, and is able to increase expression of an Na + /H + antiporter, wherein the chaA gene encodes a protein selected from the group consisting of: (G) a protein comprising the amino acid sequence of SEQ ID NO: 24, and (H) a protein comprising the amino acid sequence of SEQ ID NO: 24, but which includes substitution, deletion, insertion or addition of one to 10 amino acids, and has Na + /H + antiporter activity, wherein the mdfA gene encodes a protein selected from the group consisting of: (I) a protein comprising the amino acid sequence of SEQ ID NO: 26, and (J) a protein comprising the amino acid sequence of SEQ ID NO: 26, but which includes substitution, deletion, insertion or addition of one to 10 amino acids in SEQ ID NO: 26, and has Na + /H + antiporter activity.