Patent ID: 7531332

Claim:
A method for producing a lower alkyl ester of α-L-aspartyl-L-phenylalanine selected from the group consisting of methyl ester, ethyl ester, propyl ester, and combinations thereof, comprising A) producing L-phenylalanine by cultivating an Escherichia coli bacterium in a medium, wherein said bacterium has the ability to produce L-phenylalanine, B) esterifying the L-phenylalanine to generate a lower alkyl ester of L-phenylalanine selected from the group consisting of methyl ester, ethyl ester, propyl ester, and combinations thereof, C) condensing said lower alkyl ester of L-phenylalanine with N-acyl-L-aspartic anhydride to obtain the lower alkyl ester of N-acyl-α-L-aspartyl-L-phenylalanine, D) separating the lower alkyl ester of N-acyl-α-L-aspartyl-L-phenylalanine from the reaction mixture obtained in step C), and E) hydrogenating the lower alkyl ester of N-acyl-α-L-aspartyl-L-phenylalanine to generate the lower alkyl ester of α-L-aspartyl-L-phenylalanine, wherein said bacterium has been modified so that the L-phenylalanine production by said bacterium is increased as compared to the corresponding unmodified bacterium by increasing the expression of a DNA selected from the group consisting of: a) a DNA comprising the nucleotide sequence of SEQ ID NO: 1, and b) a DNA encoding a protein comprising the amino acid sequence of SEQ ID NO: 2, except that the sequence may include deletions, substitutions, insertions, or additions of 1 to 5 amino acids, and wherein said protein has an activity of imparting upon a bacterium resistance to an L-amino acid selected from the group consisting of L-phenylalanine, L-threonine, L-homoserine, L-cysteine and L-histidine, and/or imparting upon a bacterium resistance to an amino acid analog selected from the group consisting of p-fluoro-phenylalanine, 5-fluoro-DL-tryptophan, S-(2-aminoethyl) cysteine, and 4-aza-DL-leucine, and wherein said expression is increased by a method selected from the group consisting of increasing the copy number of said DNA in said bacterium, locating said DNA under the control of a potent promoter instead of the native promoter on the chromosome of the bacterium, and a combination thereof.