Method of purifying phycocyanin

Patent metadata

Field	Value
Publication number	US-11795194-B2
Application number	US-201816639250-A
Country	US
Kind code	B2
Filing date	Aug 2, 2018
Priority date	Aug 18, 2017
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

A method for purifying phycocyanin from a phycocyanin-containing solution is provided. The method comprises a first step of partially purifying the solution by aqueous two-phase separation (ATPS) and a second step of purifying the phycocyanin by ammonium sulfate precipitation. The purified phycocyanin product can in some cases be of a sufficiently pure grade to be used as a food or cosmetic pigment.

First claim

The invention claimed is:

1. A method for purifying phycocyanin from a phycocyanin-containing solution, the method comprising:
a) contacting the solution with an aqueous two-phase mixture which includes a polyethylene glycol (PEG)-containing phase and a carbohydrate-containing phase in which conditions are selected to permit the phycocyanin to partition to the carbohydrate-containing phase,
b) separating the carbohydrate-containing phase from the PEG-containing phase,
c) treating the carbohydrate-containing phase with ammonium sulfate to form a first precipitating solution in which the phycocyanin is precipitated,
d) recovering a precipitated phycocyanin,
e) dissolving the precipitated phycocyanin in a solution and treating the solution with ammonium sulfate to form a second precipitating solution in which the phycocyanin is re-precipitated,
f) recovering a second precipitated phycocyanin, and
g) if the second precipitated phycocyanin has a purity lower than food grade, repeating steps e) and f) to obtain a third precipitated phycocyanin,
wherein the second or third precipitated phycocyanin has a purity of food grade or higher after one round of aqueous two-phase separation and wherein no ultrafiltration step is performed on the carbohydrate-containing phase before it is treated with ammonium sulfate.

2. The method of claim 1 , wherein the concentration of ammonium sulfate in the first precipitating solution is from 14 to 36 wt %.

3. The method of claim 1 , wherein the concentration of ammonium sulfate in the second precipitating solution is from 25 to 34 wt %.

4. The method of claim 1 , further comprising re-dissolving the second precipitated phycocyanin, treating with ammonium sulfate to form a third precipitating solution in which the phycocyanin is re-precipitated, and recovering a third precipitated phycocyanin.

5. The method of claim 4 , wherein the concentration of ammonium sulfate in the third precipitating solution is from 16 to 28 wt %.

6. The method of claim 1 , wherein the PEG has an average molecular weight of at least 6000 g/mol.

7. The method of claim 6 , wherein the PEG has an average molecular weight of at least 10,000 g/mol.

8. The method of claim 1 , wherein the carbohydrate is present in the carbohydrate-containing phase at a concentration of from about 15 to 40 wt %.

9. The method of claim 1 , wherein the carbohydrate is selected from the group consisting of: maltodextrin, ficoll, dextran, starch, glucose, fructose, galactose, mannose, sucrose, cellobiose, lactose, lactulose, maltose, maltulose, arabinose, ribose, xylose, and trehalose.

10. The method of claim 1 , wherein the overall two-phase mixture includes 15-40 wt % of the carbohydrate-containing phase, 3-15 wt % of the PEG-containing phase and 45-82 wt % of the phycocyanin-containing solution.

11. The method of claim 1 , wherein the phycocyanin-containing solution is a cell extract.

12. The method of claim 11 , wherein the cell extract is prepared from wet biomass, wherein the biomass is obtained from Spirulina.

13. The method of claim 1 , wherein the phycocyanin is C-phycocyanin.

14. The method of claim 1 , wherein the first precipitated phycocyanin has a purity of cosmetic grade or higher after one aqueous two-phase separation step and without an ultrafiltration step being performed on the carbohydrate-containing phase.

15. The method of claim 1 , wherein only one aqueous two-phase separation step is performed on the phycocyanin-containing solution.

16. The method of claim 1 , wherein the carbohydrate-containing phase is treated with ammonium sulfate directly after having been separated from the PEG-containing phase.

17. The method of claim 1 , wherein:
only one aqueous two-phase separation step is performed on the phycocyanin-containing solution; and
the carbohydrate-containing phase is treated with ammonium sulfate directly after having been separated from the PEG-containing phase.

18. The method of claim 1 , wherein:
the PEG in the PEG-containing phase has an average molecular weight of at least 6,000 g/mol (PEG 6,000);
only one aqueous two-phase separation step is performed on the phycocyanin-containing solution; and
the carbohydrate-containing phase is treated with ammonium sulfate directly after having been separated from the PEG-containing phase.

Assignees

• Univ Cape Town

Inventors

• Harrison Susan Thérèse Largier
• Burke Matthew Armstrong
• Pott Robert William Mcclelland
• Fagan-Endres Marijke Antonia

Classifications

• C07K1/36 Primary

  by a combination of two or more processes of different types · CPC title

• C07K1/145

  by extraction or solubilisation · CPC title

• C07K1/303

  by salting out · CPC title

• C07K14/195 Primary

  from bacteria · CPC title

• C07K14/405 Primary

  from algae · CPC title