Transport between an aqueous phase and a CTAB/hexanol-octane reversed micellar phase

Abstract

Using bovine serum albumin (BSA) as a model protein, protein transport between an aqueous phase and a reversed micellar organic phase was examined. From near-infrared spectra and UV absorption spectra, it was confirmed that CTAB (cetyl trimethyl ammonium bromide)/hexanol octane reversed micellar solution is a suitable medium for BSA solubilization. It seems that the forward transfer efficiency depends not only on the parameters of the two phases (for example: the pH value, the concentration and species of ions in the aqueous phase, the content of surfactant and co-solvent in reversed micellar solution), but also the titration behaviour and the concentration of the protein in aqueous phase. The experimental results lead to the conclusion that the major driving force in the protein extraction is electrostatic interaction. A modified phenomenological thermodynamic model for reversed micellar extraction was presented, and shown to correlate the data on extraction efficiency of BSA with both pH value and surfactant concentration. The effects of various factors, such as pH, and the type and concentration of salt in stripping solution, on BSA back transfer were also studied. It was found that the backward transfer efficiency of BSA is strongly influenced by the type of ions in stripping solution. When the operation runs under optimized conditions and with suitable phase ratio, the recovery and concentration of protein were successfully obtained. In addition, the problems how long the reversed micellar solutions can be recycled and how much of the surfactant will be lost to the aqueous phase have been examined.