Potential Aqueous Two-Phase Processes for the Primary Recovery of Colored Protein from Microbial Origin

Abstract

The primary recovery of c-phycocyanin and b-phycoerythrin from Spirulina maxima and Porphyridium cruentum, respectively, using an established extraction strategy was selected as a practical model system to study the generic application of polyethylene glycol (PEG)-phosphate aqueous two-phase systems (ATPS). The generic practical implementation of ATPS extraction was evaluated for the recovery of colored proteins from microbial origin. A comparison of the influence of system parameters, such as PEG molecular mass, concentration of PEG as well as salt, system pH and volume ratio, on the partition behavior of c-phycocyanin and b-phycoerythrin was carried out to determine under which conditions target colored protein and contaminants concentrate to opposite phases. One-stage processes are proposed for the primary recovery of the colored proteins. PEG1450-phosphate ATPS extraction (volume ratio (VR) equal to 0.3, tie-line length (TLL) of 34 % w/w and system pH 7.0) for the recovery of c-phycocyanin from Spirulina maxima resulted in a primary recovery process that produced a protein purity of 2.1 ± 0.2 (defined as the relationship of 620 nm to 280 nm absorbance) and a product yield of 98 % [w/w]. PEG1000-phosphate ATPS extraction (i.e., VR = 1.0, PEG 1000, TLL 50 % w/w and system pH 7.0) was preferred for the recovery of b-phycoerythrin from Porphyridium cruentum, which resulted in a protein purity of 2.8 ± 0.2 (defined as the relationship of 545 nm to 280 nm absorbance) and a product yield of 82 % [w/w]. The purity of c-phycocyanin and b-phycoerythrin from the crude extract increased 3- and 4-fold, respectively, after ATPS. The results reported herein demonstrated the benefits of the practical generic application of ATPS for the primary recovery of colored proteins from microbial origin as a first step for the development of purification processes.