Method of constructing amino acid producing bacterial strains, and method of preparing amino acids by fermentation with the constructed amino acid producing bacterial strains

Abstract

A method of producing coryneform bacteria having an improved amino acid or nucleic acid-productivity comprises the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium so that it is close to a consensus sequence or introducing a change in the promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on the chromosome of a coryneform bacterium by gene recombination so that it is close to a consensus sequence, obtaining mutants of the coryneform amino acid- or nucleic acid-producing microorganism, culturing the mutants and select a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method allows one of skill in the art to construct a mutant capable of enriching or controlling the expression of an intended gene without using a plasmid and to promote production of amino acids in a high yield, by the recombination or mutation.