Extraction and characterisation of analytical grade C-phycocyanin from Euhalothece sp.

Abstract

C-Phycocyanin (C-PC) is a blue pigment that has great commercial value as a fluorophore in biomedical research, diagnostics therapeutics as well as sensitive fluorescent applications. However, the cost and application of C-PC is highly dependent on its purity ratio (A620nm/A280nm). In this study, freeze-thaw and precipitation are presented as relatively simple, efficient, low-cost C-PC extraction and purification methods from Euhalothece sp. Harvested biomass (0.03 g) was subjected to − 20 °C for 5 h, re-suspended in 50 mM, (pH 7) sodium phosphate buffer (containing 0.0025 mg mL−1 lysozyme), incubated at 37 °C thereafter thawed at 4 °C for 4 h. The optimised method yielded 75 mg g−1 of crude C-PC. A high purity ratio of 5 was achieved using activated charcoal and 30–60% (w/v) ammonium sulphate precipitation. SDS-PAGE of purified C-PC yielded two bands corresponding to α (17 kDa) and β (18 kDa) subunits. The purified C-PC was found to be highly stable at a pH range of 5–8 and a temperature of 45 °C. The addition of preservatives sodium azide and sodium citrate (at 4 °C) proved to be suitable for preservation of C-PC for up to 42 weeks. By following the optimised extraction and purification protocol, we were able to purify a high yield of stable analytical grade C-PC from Euhalothece sp.