Patent ID: 8293506

Claim:
A method for producing a compound selected from the group consisting of L-cysteine, L-cystine, and a derivative or precursor thereof, which comprises culturing a bacterium belonging to the family Enterobacteriaceae in a medium and collecting the compound from the medium, wherein the bacterium is able to produce L-cysteine and has been modified to increase the activity of a protein encoded by the dsbA gene as compared to a non-modified bacterium, wherein the activity of the protein is increased by a method selected from the group consisting of: i) increasing expression of the dsbA gene by increasing the copy number of the dsbA gene or by modifying an expression control sequence of the dsbA gene, ii) increasing translation of the dsbA gene, and iii) combinations thereof, wherein the protein is selected from the group consisting of: (A) a protein comprising the amino acid sequence of SEQ ID NO: 2, 4, 6, 8, 10 or 12, and (B) a protein comprising the amino acid sequence of SEQ ID NO: 2, 4, 6, 8, 10 or 12, but which includes substitutions, deletions, insertions or additions of one to 5 amino acid residues, and wherein the increase of the protein's activity in the bacterium improves the ability of the bacterium to produce L-cysteine.