Study of the simultaneous partitioning of proteins and surfactant in reverse micellar two-phase systems - Potential impact upon purification efficiency

The recovery of four proteins by means of the classical reverse micellar two-phase system consisting of brine, AOT (Aerosol OT, sodium di-2-ethyl-1-hexyl sulfosuccinate), and iso-octane has been studied. A complete cycle of extraction - forward and backward - was performed each time in order to optimize the AOT concentration with respect to the overall protein yield. These experiments have shown that maximum global yields can be obtained at quite low surfactant concentrations in the range of 2-20 mM AOT. These low surfactant concentrations were beneficial for the operation of the extraction process owing to facile phase separation. In addition, the partitioning of surfactants in the reverse micellar two-phase system, as well as the association of surfactants with proteins in the aqueous phase, have been studied because they are of primary importance for assessing the feasability of reverse micellar protein extraction. The question of the fate of the surfactant has been addressed by using radioactively labeled AOT. By varying the initial AOT concentration in the nonpolar phase, optimum surfactant concentrations were obtained with respect to minimal AOT contamination of proteins after a complete cycle of extraction. The partitioning of AOT was studied in the absence, as well as in the presence, of proteins. Lowering the salt concentration favoured the partitioning of AOT in the aqueous phase. Therefore, most of the surfactant losses occurred during forward extraction. A simple dialysis was effective for eliminating AOT.