Method of purifying phycocyanin

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.