Method for the fermentative production of L-amino acids using improved strains of the

1. A process for the production of L-methionine or feed additive containing L-methionine comprising:

fermenting a microorganism of the Enterobacteriaceae family modified to attenuate expression of a “proton/compatible solute symporter gene (proP gene)” as compared to the parent strain of said microorganism in a medium.

2. The process of claim 1 , wherein the attenuation comprises eliminating expression of the proP gene of the microorganism.

3. The process of claim 1 , wherein expression of the proP gene of the microorganism is reduced compared to a parent strain of said microorganism, wherein expression of a proP gene of said parent strain is not attenuated.

4. The process of claim 1 , wherein production of the L-methionine by the microorganism is increased compared to a parent strain of said microorganism, wherein expression of a proP gene of said parent strain is not attenuated.

5. The process of claim 1 , wherein the L-methionine accumulates in the medium.

6. The process of claim 1 , wherein the L-methionine accumulates in cells of the microorganism.

7. The process of claim 1 , wherein the modification comprises increasing a methionine tolerance of the microorganism compared to a methionine tolerance of a parent strain of the microorganism, wherein expression of a proP gene of said parent strain is not attenuated.

8. The process of claim 1 , wherein the microorganism of the Enterobacteriaceae family comprises a bacterium chosen from the genera Escherichia, Erwinia, Providencia and Serratia.

9. The process of claim 1 , wherein the proP gene of said microorganism before attenuation comprises a polynucleotide having a sequence identity of at least 80% to the polynucleotide sequences of SEQ ID NO: 1, 3, 5 or 7.

10. The process of claim 1 , wherein the proP gene of said microorganism is a polynucleotide which has a sequence identity of at least 80% to the sequence of the polynucleotide of SEQ ID NO: 1 and wherein the polynucleotide further comprises at least one mutation over the polynucleotide of SEQ ID NO: 1 chosen from:

a. substitution of a triplet coding for L-arginine at a position corresponding to position 324 of SEQ ID NO: 2 by a triplet coding for an amino acid chosen from L-leucine, L-isoleucine and L-valine;

b. substitution of a triplet coding for L-tyrosine at a position corresponding to position 467 of SEQ ID NO: 2 by a triplet coding for an amino acid chosen from L-lysine, L-arginine and L-histidine;

c. substitution of a triplet coding for L-glutamic acid at a position corresponding to position 412 of SEQ ID NO: 2 by a triplet coding for a stop codon;

d. deletion of a nucleobase adenine at a position corresponding to position 854 of the proP gene of SEQ ID NO: 1;

e. deletion of one or more of the nucleobases from positions corresponding to position 1173 to position 1223 of the proP gene of SEQ ID NO: 1;

f. insertion of a nucleobase cytosine at a position corresponding to position 842 of the proP gene of SEQ ID NO: 1;

g. insertion of one or more nucleobase(s) at a position corresponding to position 973 of the proP gene of SEQ ID NO: 1; and

h. insertion of one or more nucleobase(s) at a position corresponding to position 183 of the proP gene of SEQ ID NO: 1.

11. The process of claim 1 , wherein the medium comprises an inorganic sulphur source.

12. The process of claim 1 , further comprising

a step chosen from isolating, collecting and/or purifying the L-methionine from a fermentation broth obtained from fermenting the microorganism in the medium, wherein the L-methionine accumulates in the fermentation broth during the fermenting the microorganism in the medium.

13. The process of claim 12 , further comprising isolating and collecting other components from the fermentation broth and/or biomass of the microorganism.