Partitioning of lysozyme in aqueous two-phase systems containing ethylene oxide-propylene oxide copolymer and potassium phosphates

Lysozyme partitioning in EO50PO50/potassium phosphate aqueous two-phase systems (ATPS) was studied. In the work, the influence of EO50PO50, potassium phosphate and sodium chloride concentration in the ATPS on lysozyme partition coefficient and separation yield was examined. In addition, the influence of the pH of potassium phosphate solution was also investigated. A Box–Behnken design was defined, and response surface models for the partition coefficient K and percentage yield of the enzyme in the top phase Y were calculated. Among the examined factors, the NaCl concentration had the highest influence on lysozyme separation parameters. This influence can be explained mainly by the hydrophobic interactions between the protein and the phase-forming components. A maximum partition coefficient KL1, yield YL1 and YL2 were predicted for EO50PO50, potassium phosphate and NaCl concentrations of 17.40, 22.67% and 0.85 mol/l, respectively, and for pH 9.0. A good agreement was obtained between the experimental and the predicted results.