A novel two-step purification process for highly stable C-phycocyanin of analytical grade purity and its properties

Efficient and economic purification of phycobiliproteins can be achieved by a novel relatively simple two-step process involving foam fractionation and ion exchange chromatography. Foam fractionation, which has not previously been used to concentrate phycobiliproteins, is a low-cost and environmentally friendly method that provides a significant volume reduction prior to the chromatography step. Two C-phycocyanin fractions with purities of 4.66 and 4.25 with slightly different characteristics and an allophycocyanin fraction with a purity of 3.23 were obtained. Both C-phycocyanins contain α-subunits of 15.0 kDa and β-subunits of 16.4 kDa, whereas the molecular weight of allophycocyanin is 15.5 kDa. The resulting C-phycocyanin retains its properties at pH in the range of 3-10, whereas strong alkaline pH leads to its rapid degradation. The purified protein is completely resistant to temperature changes in the range of 4 to 50 °C and loses only about 13% of its initial concentration during a 5 h incubation at 60 °C. Interestingly, purified C-phycocyanin is relatively resistant to photochemical degradation, as the loss in concentration after 10 h exposure to light is only about 14%. The most suitable storage conditions are temperature of 4 °C and pH in the range 4-5. The final product with an analytical purity greater than 4 is suitable for use in food, biomedicine and as a therapeutic agent. KEY POINTS: • Foam fractionation and ion chromatography for the purification of phycobiliproteins. • C-phycocyanin stable over a wide temperature and pH range without a stabilizing agent. • C-phycocyanin of analytical purity for food, medical and pharmaceutical applications.