Method for producing an L-amino acid using a bacterium of the Enterobacteriaceae family with attenuated expression of the kefB gene

A method for producing an L-amino acid comprising:

• cultivating an L-amino acid producing bacterium of Escherichia coli or Pantoea ananatis in a medium, and
• collecting said L-amino acid from the medium,
• wherein said bacterium has been modified to attenuate expression of the kefB gene on the chromosome of said bacterium by a method selected from the group consisting of
• A) deleting a part of said gene,
• B) shifting the reading frame of said gene,
• C) introducing missense/nonsense mutation(s) into said gene,
• D) modifying a region controlling expression of said gene, and
• E) combinations thereof,
• wherein, prior to being modified, the kefB gene encodes a protein having potassium efflux activity.