Pretreatment of algal and cyanobacterial biomass for high quality phycocyanin extraction

Phycocyanin is a water-soluble, blue-colored phycobiliprotein mainly found in cyanobacteria and Rhodophyta. Major commercial interest exists on phycocyanin as an important ingredient for food, pharmaceutical and cosmetics applications. Despite the common interest from industry, there is no dedicated method for optimized extraction of phycocyanin from different species. Yet, biomass type and choice of pretreatment have major influences on the extraction yield and final purity of phycocyanin. Various impurities such as cell debris and other photosynthetic pigments also decrease the quality of extracted phycocyanin. In this study, wet and lyophilized biomass samples from several cyanobacteria (including a local isolate) and a red microalga species were harvested and pretreated with bead-beating, mortar and pestle homogenization, freeze-thaw cycling and sonication techniques. High concentration yielding phycocyanin extracted from Phormidium sp., Synechocystis sp., Desertifilum tharense, Nostoc sp., and Galdieria sulphuraria were purified by ammonium sulfate fractionation combined with acetate buffer elution method. Bead-beating was found to be the most efficient pretreatment technique for the extraction of phycocyanin from the majority of tested biomass samples. Phycocyanin from Synechocystis sp. and Phormidium sp. was further purified with anion exchange chromatography. Overall, food grade phycocyanin (purity ratio A(620)/A(280) > 0.7) extraction was achieved for all tested biomass samples except Scytonema sp. Biomass samples from Synechocystis sp. yielded analytical grade phycocyanin (purity ratio > 4), one of the highest values observed in literature.