An Efficient Method for the Separation and Purification of Phycobiliproteins from a Rice-Field Cyanobacterium Nostoc sp. Strain HKAR-11

Abstract

The wide applications of phycobiliproteins (PBPs) are essentially dependent on the purity ratio for the production of quality products. In this study, we present a novel method for the separation and purification of PBPs subunits such as phycocyanin (PC) and phycoerythrin (PE) from a rice-field cyanobacterium Nostoc sp. strain HKAR-11 using gel filtration and single step hydrophobic interaction chromatography. The separation of PBPs subunits was done using cycles of gel filtration chromatography (Sephacryl-S100 HR) with the addition of 0.5 M NaCl in 50 mM phosphate buffer. The final purification of PE and PC was performed using a HiTrap Phenyl FF column and yielded a quite high purity ratio of 11.53 and 5.75 with 83 and 73 % remaining concentrations for PE and PC, respectively. The purity of PE and PC was confirmed by emission fluorescence with excitation at 563 and 615 nm, respectively. The native molecular weight of purified PE (44 kDa) and PC (34 kDa) was determined by gel filtration chromatography. The purified PE and PC were analyzed by SDS-PAGE that showed the presence of only two bands of α and β subunits in comparison to the bands of crude PBPs. To the best of our knowledge, this is the most efficient methodology for obtaining quite high purity index of PC and PE from any rice-field cyanobacterial source.