Patent ID: 7186531

Claim:
A method for producing L-threonine which comprises cultivating an L-threonine-producing bacterium belonging to the genus Escherichia wherein said bacterium has been modified to increase expression of an aspartate-β-semialdehyde dehydrogenase gene, in a culture medium to cause accumulation of L-threonine in the culture medium, and collecting the L-threonine from the culture medium, wherein said aspartate-β-semialdehyde dehydrogenase gene comprises a DNA selected from the group consisting of: (a) a DNA which comprises the nucleotide sequence of nucleotides 1 to 1101 in SEQ ID NO: 1; and (b) a DNA which is hybridizable with the nucleotide sequence of nucleotides 1–1101 in SEQ ID NO: 1 under stringent conditions comprising washing at 60° C. at a salt concentration of 1×SSC and 0.1% SDS for 15 minutes, and wherein said DNA encodes a protein having an activity of aspartate-β-semialdehyde dehydrogenase, wherein said bacterium has been further modified to increase expression of the mutant thrA gene which codes for aspartokinase homoserine dehydrogenase I which is resistant to feedback inhibition by threonine, the thrB gene which codes for homoserine kinase, the thrC gene which codes for threonine synthase, and the rhtA gene which codes for a putative transmembrane protein, and wherein the mutant thrA gene, the ThrB gene, the thrC gene, and the rhtA gene are genes of Escherichia coli.