Optimizing R-phycoerythrin purification from the red algae Gracilaria verrucosa in polymer-salt aqueous two-phase system using response surface methodology

Abstract

R-Phycoerythrin (RPE) is a protein which acts as a photosynthetic accessory pigment in red algae (Rhodophyta) and cyanobacteria, it has many biotechnological applications. In this study, phycoerythrin from Gracilaria verrucosa (Rhodophyta) was extracted by enzymatic hydrolysis and centrifugation. Phycoerythrin was purified from this crude extract via an aqueous two-phase system (ATPS). Here the ATPS process was optimized using polyethylene glycol (PEG)/Magnesium sulfate (MgSO4). Six factors that affect RPE purity were studied; namely PEG’s molecular weight, PEG’s concentration, MgSO4 concentration, R-phycoerythrin loading, NaCl concentration and temperature. A detailed study was carried out using central composite design (CCD) in response surface methodology (RSM). The absorbance ratio A565/A280, a criterion for purity, was 3.5, and was predicted for a system with 19% (w/w) PEG6000, 16%(w/w) phosphate, 4.8% (w/w) RPE loading, 0.3% (w/w) NaCl loading and an optimal temperature of 22°C. Analysis of variance exhibited a high coefficient of determination (R2) value of 0.80 and ensured that the quadratic model in tandem with the experimental data was a satisfactory one. This is the first report on RPE purification by aqueous two phase system using statistical experimental design and RSM