L-amino acid-containing feedstuff additive

1. A method for preparing a feed additive, comprising the following steps:

a) obtaining a fermentation broth by:

i) fermenting an L-amino acid-producing microorganism in an aqueous culture medium to produce a fermentation broth;

ii) after the fermenting step i) is complete: adding surface-active substance to the fermentation broth to a final concentration of 0.025 to 20% by weight; and

b) drying the fermentation broth obtained in step (a) in order to convert it into said feed additive;

wherein the concentrations of biomass and surface-active substance in the fermentation broth are such that the feed additive of step b) is a particulate composition with a particle density of at least 1.138 g/cm 3 .

2. The method of claim 1 , wherein the amount of surface-active substance present prior to drying is sufficient to produce a dried feed additive with a particle density of 1.138 to 1.160 g/cm 3 .

3. The method of claim 1 , wherein, prior to drying, the fermentation broth comprises a surface-active substance selected from the group consisting of: corn steep liquor, lipids, antifoaming agents, surfactants and mixtures thereof.

4. The method of claim 1 , wherein, prior to drying, the fermentation broth comprises an antifoaming agent selected from the group consisting of: polysiloxanes, mono- and polyglycols, phospholipids and fatty acid glycerides.

5. The method of claim 1 , wherein, prior to adding the surface-active substance in step a)ii), the water content of the fermentation broth is adjusted to a value of 35 to 50% by weight.

6. The method of claim 1 , wherein, prior to drying, the surface-active substance is present in the fermentation broth in an amount of 0.3 to 10% by weight.

7. The method of claim 1 , wherein the L-amino acid is L-lysine, L-methionine, L-threonine, L-valine or L-tryptophan.

8. The method of claim 1 , wherein the L-amino acid is L-lysine and, after completion of the fermentation and before the start of the drying, ammonium sulphate and/or sulphuric acid is added to the fermentation broth in order to establish a sulphate/L-amino acid ratio of 0.85 to 1.2.

9. The method of claim 1 , wherein the fermentation broth used in drying comprises:

a) a biomass content of 2 to 12% by weight;

b) an L-amino acid content of 12 to 48% by weight;

c) a solids content, including biomass, of 25 to 70% by weight;

e) a percentage by weight ratio of sulphate to L-amino acid of 0.8 to 1.2;

d) a surface-active substance content of 0.1 to 20% by weight.

10. The method of claim 9 , wherein the fermentation broth used in drying comprises:

a) a biomass content of 4 to 8% by weight;

b) an L-amino acid content of 12 to 48% by weight;

c) a solids content, including biomass, of 35 to 60% by weight;

d) a surface-active substance content of 0.3 to 10% by weight.

11. The method of claim 1 , wherein the feed additive comprises bacteria of the genus Corynebacterium or the genus Escherichia and/or cell debris from these bacteria.

12. The method of claim 1 , wherein said particle density is 1.40-1.55 g/cm 3 .

13. The method of claim 1 , wherein said particle density is 1.44-1.52 g/cm 3 .

14. The method of claim 1 , wherein drying step b) is by spray granulation.

15. The method of claim 1 , wherein the feed additive is a granulate with a moisture content of, at most, 3.5% by weight.

16. The method of claim 1 , wherein the amino acid content of the dried feed additive is at least 30% by weight.

17. The method of claim 1 , wherein the amino acid content of the dried feed additive is 40% to 60% by weight.

18. The method of claim 1 , wherein the particles in the feed additive are homogeneous.

19. The feed method of claim 1 , wherein the feed additive has cavities of less than 25% by volume.

20. The feed method of claim 1 , wherein the feed additive has cavities of less than 10% by volume.