Single-step purification of C-phycocyanin from Arthrospira platensis using aqueous two-phase system based on natural deep eutectic solvents

Abstract

Natural deep eutectic solvents (NADESs) are an emerging type of green ionic liquid that has been used in aqueous two-phase systems (ATPSs). C-phycocyanin (C-PC) is an important fluorescent protein found in cyanobacteria with multiple applications. In this study, NADES [choline chloride-urea, ChCl-U]-ATPS (NADES-ATPS) was screened as an optimum system for extracting C-PC from Arthrospira platensis. Under the optimal purification conditions (crude extracted C-PC, 500 μg; [ChCl-U], 3.25 g; K2HPO4, 0.90 g mL−1; extraction time, 2 h; NaCl, 2% and 25 °C), C-PC with a purity and recovery of 3.383 and 65.64%, respectively, was obtained by single-step extraction. The purity of C-PC could increase to 4.100 after four extraction steps. The purified C-PC was further analyzed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), which showed α and β subunits with molecular weights of 18.0 and 21.0 kDa, respectively. Importantly, the NADES can successfully be recycled and reused for at least five pretreatment cycles. Furthermore, no structural changes in C-PC were detected, and the aggregation phenomenon of NADES with C-PC may be the extraction mechanism. Such a green, easily synthesized, recyclable and efficient method using NADES-ATPS could hold promise for wide applications for the purification of C-PC and other proteins.