Sequential recovery of C-phycocyanin and chlorophylls from Anabaena cylindrica

Abstract

Cyanobacteria are attracting the attention worldwide as a reliable and sustainable feedstock for the production of biofuels, food colorants and biochemically active compounds. Anabaena cylindrica (A. cylindrica) is a cyanobacterium with a significant widespread occurrence in Portuguese freshwaters, with C-phycocyanin and chlorophylls, compounds with a high market value, being abundantly produced by the species. This work presents the development of a sequential downstream process to obtain C-phycocyanin and chlorophyll from A. cylindrica. The C-phycocyanin extraction is carried using Na-phosphate (20 mM, pH 7) buffer, while aqueous solutions of surface-active compounds (250 mM), as well as ethanol, were screened for the extraction of the chlorophylls. After selecting the best solvents to recover both pigments from A. cylindrica, the operational conditions (solid-liquid ratio, time of extraction and temperature) were optimized, allowing the recovery of around 90% and 55% of the total content of C-phycocyanin and chlorophylls, respectively. Finally, dextran/copolymer-based ABS were applied to promote the purification of C-phycocyanin from the residual chlorophylls and other contaminant proteins, leading to an increase in the C-phycocyanin purity of 4-fold, without compromising its photostability.