Producing methionine without N-acyl-methionine

1. 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.

2. The method of claim 1 , wherein the modified E. coli cell comprises a disruption in the endogenous yncA gene.

3. The method of claim 1 , wherein the modified E. coli cell comprises a disruption in the endogenous argA gene.

4. The method of claim 1 , wherein the modified E. coli cell comprises a disruption in the endogenous yjdJ, yfaP, yedL, and yjhQ genes.

5. The method of claim 2 , wherein the modified E. coli cell comprises a disruption in the endogenous argA gene.

6. The method of claim 1 , wherein the N-acyl methionine whose accumulation is reduced is N-acetyl-methionine and/or N-propionyl-methionine.

7. The method of claim 1 , wherein the modified E. coli cell further overexpresses a homoserine succinyltransferase allele encoding a homoserine succinyltransferase with reduced feedback sensitivity to its inhibitors S-adenosyl-methionine (SAM) and methionine by increasing the number of copies of the allele and/or using a stronger promoter.

8. The method of claim 1 , wherein the modified E. coli cell further overexpresses a gene encoding a methylenetetrahydrofolate reductase (metF) by increasing the number of copies of the gene and/or using a stronger promoter.

9. The method of claim 1 , wherein the source of sulphur in the culture medium is sulfate, thiosulfate, hydrogen sulfide, dithionate, dithionite, sulfite, methylmercaptan, dimethyldisulfide or a combination thereof.

10. The method of claim 1 , wherein the source of sulphur in the culture medium is sulfate, thiosulfate, or a mixture thereof.

11. The method of claim 1 , wherein the source of carbon is derived from renewable feed-stock.

12. The method of claim 1 , wherein the source of carbon is glucose or sucrose.

13. The method of claim 1 , wherein the source of nitrogen is supplied in the form of ammonium (NH 4 + ) or ammonia (NH 3 ).

14. The method of claim 1 , wherein the recovering comprises isolating methionine.

15. The method of claim 1 , wherein the modified E. coli cell is limited or starved for phosphate and/or potassium.

16. The method of claim 1 , wherein the production of N-acyl-methionine is reduced by expressing at least one native or heterologous N-acyl-L-amino-acid amidohydrolase enzyme in the modified E. coli cell, wherein said N-acyl-L-amino-acid amidohydrolase enzyme is selected from the group consisting of an Aspergillus N-acylamino acid acylase, a pig N-acylamino acid acylase, and an acetylornithine deacetylase (argE).

17. The method of claim 1 , wherein the production of N-acyl-methionine is reduced by adapting the culture conditions selected among pH, oxygenation and/or temperature, or by adding a N-acyl amino acid acylase into the medium.