Comparison of three methods for thermostable C-phycocyanin separation and purification

•Purification of crude extracts of C-phycocyanin of different initial purities.•First time application of foam fractionation for purification of C-phycocyanin.•Comparison of three downstream processing methods for C-phycocyanin purification.•Food, cosmetic & biomarker grade of thermostable C-phycocyanin purity was obtained.•ATPE resulted in the highest recovery yield and partitioning coefficient. The efficient separation and purification methods are the major obstacles in the production and further use of bioproducts. One such valuable bioproduct is the thermostable C-phycocyanin (C-PC). There is a great commercial need to develop C-PC production with an appropriate degree of purity. However, the selected methods and their sequences are also depended on the quality of crude extract obtained from biomass. In this paper three down-stream processing methods, such as foam fractionation (FF), which according to our knowledge has not been used for separation of C-PC, aqueous two-phase extraction (ATPE) and conventional ultrafiltration were investigated for purification of thermostable C-PC from two crude extracts with lower and higher protein concentration and purity obtained from biomass of Synechococcus sp. PCC6715. The FF process resulted in a recovery yield of 49% and a purification factor of 1.472 without the addition of surfactants or pH adjustment. The most effective ATPSystem consists of polyethylene glycol 6000 and phosphate salt with a recovery yield of 97%, partitioning coefficient of about 28 and purification factor of 1.466. Ultrafiltration gave a recovery yield of 92% and purification factor of 1.123. Two possible ways of C-PC purification depending on the crude extract purity and concentration was proposed. [Display omitted]