Partitioning of bovine serum albumin in an aqueous two-phase system: optimization of partition coefficient.

Partitioning of proteins in aqueous two-phase systems has been shown to provide a powerful method for separating and purifying mixtures of biomolecules by extraction. There are many factors which influence the partition coefficient K, the ratio of biomolecule concentration in top phase to that in the bottom phase, in aqueous two-phase systems. In this work, the partition behavior of pure bovine serum albumin in aqueous two-phase systems was investigated in order to see the effects of changes in phase properties on the partition coefficient K. pH and concentration of NaCl salt were found to be the factors having influence on K. Optimal conditions of these factors were obtained using the Box-Wilson experimental design. The optimum value of K was found as 0.018 when NaCl concentration, and pH were 0.0195 M and 8.9, respectively, for a phase system composed of 8% (w/w) polyethylene glycol 3350-6% (w/w) dextran 37 500-0.05 M phosphate at 20 degrees C.