Method of isolating biomacromolecules using low pH and divalent cations

1. A method of purifying a composition containing a recombinant protein and an impurity, the method comprising:

(a) lowering the pH of the composition to a pH range of about 3.0 to about 6.5;

(b) adding a divalent cation selected from the group consisting of Co 2+ , Ni 2+ and combinations thereof to the composition to result in a divalent cation concentration of about 1 mM to about 50 mM; and

(c) separating the protein from the impurity,

wherein the protein comprises an antibody or a fusion protein comprising an Fc region, which is produced by a recombinant eukaryotic host cell,

wherein the composition comprises a harvest feed of the recombinant eukaryotic host cell,

wherein the addition of the divalent cation increases the recovery of the protein by greater than 3% compared to the amount of protein recovered without the addition of the divalent cation, and

wherein the separating of (c) is performed by subjecting the composition to centrifugation, the centrifugation forming a supernatant and a precipitate wherein the protein is substantially in the supernatant, or wherein the separating of (c) is performed by filtering the composition, the filtering forming a permeate stream and a retentate stream wherein the protein is substantially in the permeate stream, and wherein (a) and (b) are carried out sequentially in any order before (c).

2. The method of claim 1 , wherein the divalent cation is Co 2+ .

3. The method of claim 2 , wherein the addition of the divalent cation increases the recovery of the protein by greater than 10%.

4. The method of claim 1 , wherein the pH of the composition in (a) is lowered to a pH range of about 3.0 to about 5.0.

5. A method of clarifying a recombinant protein in a composition containing an impurity, the method comprising:

(a) lowering the pH of the composition to a pH of about 5.0;

(b) adding a divalent cation selected from the group consisting of Co 2+ , Ni 2+ , and combinations thereof to the composition to result in a divalent cation concentration of about 1 mM to about 100 mM; and

(c) separating the protein from the impurity,

wherein the protein comprises an antibody or a fusion protein comprising an Fc region, which is produced by a recombinant eukaryotic host cell,

wherein the composition comprises a harvest feed of the recombinant eukaryotic host cell,

wherein the addition of the divalent cation increases the recovery of the protein by greater than 3% compared to the amount of protein recovered without the addition of the divalent cation,

wherein the separating of (c) is performed by subjecting the composition to centrifugation, the centrifugation forming a supernatant and a precipitate wherein the protein is substantially in the supernatant, or wherein the separating of (c) is performed by filtering the composition, the filtering forming a permeate stream and a retentate stream wherein the protein is substantially in the permeate stream, and wherein (a) and (b) are carried out sequentially in any order before (c), and

wherein the composition comprising the harvest feed is clarified.

6. The method of claim 5 , wherein the adding the divalent cation to the composition results in a divalent cation concentration of about 2 mM to about 50 mM.

7. The method of claim 5 , wherein the separating in (c) is performed by filtering the composition, wherein the filtering results in a transmembrane pressure; and wherein the transmembrane pressure remains substantially constant during the filtering.

8. A method of isolating a recombinant protein in a composition containing an impurity, the method comprising:

(a) lowering the pH of the composition to a pH range of about 3.0 to about 6.5;

(b) adding a divalent cation selected from the group consisting of Co 2+ , Ni 2+ , and combinations thereof to the composition to result in a divalent cation concentration of about 1 mM to about 100 mM; and

(c) separating the protein from the impurity,

wherein the protein comprises an antibody or a fusion protein comprising an Fc region, which is produced by a recombinant eukaryotic host cell,

wherein the addition of the divalent cation increases the recovery of the protein by greater than 3% compared to the amount of protein recovered without the addition of the divalent cation, and

wherein the separating of (c) is performed by subjecting the composition to centrifugation, the centrifugation forming a supernatant and a precipitate wherein the protein is substantially in the supernatant, or wherein the separating of (c) is performed by filtering the composition, the filtering forming a permeate stream and a retentate stream wherein the protein is substantially in the permeate stream, and wherein (a) and (b) are carried out sequentially in any order before (c).

9. The method of claim 8 , wherein the pH of the composition in (a) is lowered at least 1 pH unit.

10. The method of claim 8 , wherein the pH of the composition in (a) is lowered to a pH range of about 3.0 to about 5.0.

11. The method of claim 10 , wherein the pH of the composition in (a) is lowered to a pH of about 5.0.

12. The method of claim 8 , wherein the adding the divalent cation to the composition results in a divalent cation concentration of about 2 mM to about 50 mM.

13. The method of claim 8 , wherein the separating in (c) is performed by filtering the composition, wherein the filtering results in a transmembrane pressure; and wherein the transmembrane pressure remains substantially constant during the filtering.

14. The method of claim 8 , wherein

(a) the pH of the composition is lowered to a pH of 4.7 to 5.5;

(b) the adding the divalent cation to the composition results in a divalent cation concentration of about 2 mM to about 50 mM; and

(c) the separating is performed by filtering the composition.

15. The method of claim 14 , wherein the divalent cation is Co 2+ .

16. The method of claim 14 , wherein the filtering is performed by a tangential-flow filter.

17. The method of claim 8 , wherein the impurity is selected from the group consisting of a protein, lipid, nucleic acid, ribonucleic acid, and combinations thereof.

18. The method of claim 8 , wherein the addition of the divalent cation increases the recovery of the protein by greater than 10%.

19. The method of claim 1 , wherein the separating in (c) is performed by filtering the composition.

20. The method of claim 1 wherein adding the divalent cation comprises adding a salt comprising the divalent cation.

21. The method of claim 5 wherein adding the divalent cation comprises adding a salt comprising the divalent cation.

22. The method of claim 8 wherein adding the divalent cation comprises adding a salt comprising the divalent cation.

23. The method of claim 14 , wherein adding the divalent cation comprises adding a salt comprising the divalent cation.

24. The method of claim 23 , wherein the salt is selected from the group consisting of CoCl 2 , NiCl 2 , and combinations thereof.