Preparation of cadaverine

1. A method for preparing cadaverine comprising:

(1) obtaining an aqueous cadaverine salt composition from a fermentation system;

(2) adjusting the pH of the aqueous cadaverine salt composition to a pH of at least about 12 by adding an inorganic base composition to provide a first composition comprising an aqueous cadaverine composition having a pH of at least about 12 and a solid composition comprising one or more alkali metal sulfates;

(3) subjecting the first composition to solid-liquid separation without organic solvent extraction to provide the aqueous cadaverine composition and the solid composition;

(4) distilling or evaporating the aqueous cadaverine composition of step (3) without organic solvent extraction to provide purified cadaverine;

(5) preparing a saturated solution of the alkali metal sulfate(s) from the solid composition of step (3) at a temperature of about 35-40° C., mixing the saturated solution with NH 4 HCO 3 , and subjecting the mixture to solid-liquid separation to provide Solution (I) comprising ammonium sulfate and alkali metal sulfate and Solid (I) comprising alkali metal bicarbonate;

(6) adjusting the temperature of Solution (I) to about 60-80° C., and obtaining Solution (II) comprising ammonium sulfate and alkali metal sulfate and Solid (II) comprising alkali metal sulfate after solid-liquid separation;

(7) concentrating Solution (II) and obtaining Solution (III) comprising alkali metal sulfate and Solid (III) comprising ammonium sulfate after solid-liquid separation; and

(8) adding Solid (III) back to the fermentation system of step (1);

wherein steps (1) to (8) are optionally repeated one or more times.

2. The method of claim 1 , wherein the inorganic base composition in step (2) comprises one or more inorganic bases selected from the group consisting of alkaline metal hydroxides, alkaline earth metal hydroxides, and alkaline metal salts.

3. The method of claim 2 , wherein the inorganic base composition comprises one or more inorganic bases selected from the group consisting of NaOH, KOH, Na 3 PO 4 , and Na 2 CO 3 .

4. The method of claim 1 , wherein the ratio of NH 4 HCO 3 to the alkali metal sulfate(s) in step (5) is in the range of about 1.8:1 to about 2.2:1 by molar.

5. The method of claim 1 , further comprising concentrating Solution (I) before adjusting the temperature thereof in step (6).

6. The method of claim 1 , further comprising step (6′) after step (6), and comprising step (7′) instead of step (7):

(6′) adjusting the temperature of Solution (II) to about 30° C. or lower, and obtaining Solution (II-1) comprising ammonium sulfate and alkali metal sulfate and Solid (II-1) comprising a double salt of alkali metal ammonium sulfate after solid-liquid separation;

(7′) concentrating Solution (II-1) and obtaining Solution (III) and Solid (III) after solid-liquid separation.

7. The method of claim 6 , wherein the temperature of Solution (II) is adjusted to about 5-30° C. in step (6′).

8. The method of claim 7 , wherein the temperature of Solution (II) is adjusted to about 15-25° C. in step (6′).

9. The method of claim 1 , further comprising combining the solid composition with Solid (II) before preparing the saturated solution of the alkali metal sulfate(s) at a temperature of about 35-40° C. in step (5), and/or combining the solid composition with Solution (III) before preparing the saturated solution of the alkali metal sulfate(s) at a temperature of about 35-40° C. in step (5).

10. The method of claim 6 , further comprising combining the solid composition with Solid (II-1) before preparing the saturated solution of the alkali metal sulfate(s) at a temperature of about 35-40° C. in step (5).

11. The method of claim 1 , wherein the solid-liquid separation in steps (3), (5), (6) and (7) is independently selected from the group consisting of centrifugation and filtration.

12. The method of claim 6 , wherein the solid-liquid separation in step (6′) is selected from the group consisting of centrifugation and filtration.