Abstract: A method is provided for producing an L-amino acid by culturing a microorganism belonging to the Enterobacteriaceae family and having the ability to produce an L-amino acid, in a medium to produce and accumulate the L-amino acid in the medium. The microorganism has been modified by introduction of a DNA fragment which includes a pho regulon promoter and a structural gene encoding an L-amino acid biosynthetic enzyme, which is ligated downstream of the promoter so that the gene is expressed by the promoter, and so that the activity of the L-amino acid biosynthetic enzyme is increased by the expression of the gene by the promoter. In this way, the L-amino acid that is produced in the medium can be collected. Furthermore, the phosphorus concentration in the medium is such that the expression of the gene by the promoter is induced.

Abstract: A method is provided for producing an L-amino acid by culturing a microorganism belonging to the Enterobacteriaceae family and having the ability to produce an L-amino acid, in a medium to produce and accumulate the L-amino acid in the medium. The microorganism has been modified by introduction of a DNA fragment which includes a pho regulon promoter and a structural gene encoding an L-amino acid biosynthetic enzyme, which is ligated downstream of the promoter so that the gene is expressed by the promoter, and so that the activity of the L-amino acid biosynthetic enzyme is increased by the expression of the gene by the promoter. In this way, the L-amino acid that is produced in the medium can be collected. Furthermore, the phosphorus concentration in the medium is such that the expression of the gene by the promoter is induced.