TH63009A - A method for producing L-threonine using bacteria of the Escherichia family. - Google Patents

Abstract

DC60 (21/04/46) A method for producing L-threonine using bacteria of the Escherichia family has been disclosed, where the bacteria are capable of producing L-threonine. And has been modified to enhance the function of the aminotransferase aspartate. A method for producing L-threonine using bacteria of the Escherichia family has been disclosed, where the bacteria are capable of producing L-threonine. And has been modified to enhance the function of the aminotransferase aspartate.

Claims (11)

1. L-threonine producing bacteria of the Escherichia genus, which have been modified to exhibit aspartate aminotransferase activity, where the aspartate aminotransferase gene of Escherichia genus encodes the following proteins (A) or (B): (A) a protein containing the amino acid sequence shown in sequence No. 2 in Sequence List; (B) a protein containing the amino acid sequence including the deletion, substitution, addition or addition of one or more amino acids in the amino acid sequence shown in sequence No. 2 in Sequence List, and where aspartate aminotransferase activity is present. 2. In bacteria pursuant to claim 1, the function of aspartate aminotransferase is dominantized by increasing the expression level of the aspartate aminotransferase gene. 3. Bacteria pursuant to claim 1, where the function of aspartate aminotransferase is enhanced by increasing the number of duplicate copies of the aspartate aminotransferase gene or by modifying the sequence of the gene's expression regulator so that its expression is dominant. 4. Bacteria pursuant to claim 3, where the number of repeats is increased by transforming the bacteria with a low repeat vector containing the gene. 5. Bacteria pursuant to claims 2 through 4 in which the aspartate aminotransferase gene originates from bacteria of the Escherichia genus. 6. Bacteria pursuant to claim 5 where the aspartate aminotransferase gene encodes the following proteins: (A) or (B); (A) a protein consisting of the amino acid sequence shown in sequence 2 of the sequence list; (B) a protein consisting of an amino acid sequence that includes the deletion, substitution, addition or addition of one or more amino acids in the amino acid sequence shown in sequence 2 of the sequence list and where the aspartate aminotransferase gene is activated. 7. Bacteria pursuant to claim 5 where the aspartate aminotransferase gene contains the following DNA (a) or (b): (a) DNA containing the nucleotide sequences of nucleotides 1 through 1196 in sequence 1; or (b) DNA which is recombinant with the nucleotide sequences of nucleotides 1-1196 in sequence 1; or a test which can be prepared from that sequence under strict conditions and transcribed for an aspartate aminotransferase functional protein. 8. Bacterial infection as per claim 7, where the stringent conditions are that washing is performed at 60°C, and the salt concentration corresponds to 1 x SSC and 0.1% SDS. 9. Bacteria pursuant to claims 1 through 8, whereby the bacteria have been further modified to express one or more genes selected from a group comprising: - a central thrA gene transcribing for aspartokine-resistant homoserine dehydrogenase, - a thrB gene transcribing for homoserine kinase, - a thrC gene transcribing for threonine synthase, - a thtA gene transcribing for a membrane-transmitting protein. 10. Bacteria pursuant to claim clause 9, whereby the bacteria have been modified to increase the expression of the mutant thrA gene, thrB gene, thrC gene, and rhtA gene. 11. The method for the production of L-threonine, which involves culturing the bacteria according to patents 1 through 10 in a culture medium for the production and accumulation of L-threonine in the culture medium and the collection of L-threonine from the culture medium.