Patent ID: 8748136

Claim:
A method for the production of methionine and/or its derivatives, in a fermentative process comprising the following steps: culturing a modified E. coli cell in an appropriate culture medium comprising a source of carbon, a source of sulphur and a source of nitrogen; and recovering methionine and/or its derivatives from the culture medium, wherein the accumulation of N-acyl methionine in the culture medium is reduced compared to a corresponding E. coli cell that produces methionine, wherein the corresponding E. coli cell comprises a deletion in the endogenous metJ gene and overexpresses a gene encoding a serine acetyltransferase (cysA) and a gene encoding a methionine synthase (metH), by increasing the number of copies of the genes and/or using a stronger promoter, and wherein the modified E. coli cell comprises a deletion in the endogenous metJ gene, overexpresses said gene encoding the serine acetyltransferase and said gene encoding the methionine synthase by increasing the number of copies of the genes and/or using a stronger promoter, and comprises a disruption in an endogenous yncA, argA, yjdJ, yfaP, yedL, and/or yjhQ gene.