Separation and purification of phycobiliproteins from Thermosynechococcus PCC 6715 by foam fractionation and aqueous two-phase extraction

The use of foam fractionation (FF) followed by aqueous two-phase extraction (ATPE) has emerged as a potential alternative to traditional liquid chromatography, hitherto irreplaceable in the purification of phycobiliproteins. The crude extracts of C-phycocyanin (C-PC) and allophycocyanin were obtained after Thermosynechococcus PCC 6715 biomass disintegration. The FF process with air flow of 2.4 L<middle dot>h-1 <middle dot> h - 1 resulted in purification factors up to 1.47 and partitioning coefficients of about 39, and did not require the addition of surfactants. A temperature of 35 degrees C degrees C allowed for the highest partitioning coefficient of 67.6 and yield of 76%; however, the purity of C-PC in condensate at this temperature was lower than at 25 degrees C. degrees C. ATPE was tested in 20 different systems consisting of polyethylene glycol and phosphate or citrate salts, of which PEG1500-citrate gave the highest purification factor value of 2.31. Conversely, partitioning coefficients of 2416 and 1094 were obtained for the PEG1500-phosphate and PEG3000-phosphate systems, respectively. Interestingly, the use of FF condensate in subsequent ATPE step resulted, for the first time, in the separation of the polymer phase into two fractions, one contained C-phycocyanin and the other allophycocyanin. It can be concluded that the use of a two-step system of FF and ATPE is a viable way to separate phycobiliproteins.