Study On The Extraction Of Bovine Serum Albumin Using Reverse Micelles

Reverse micelles, which are made from a surfactant, an organic solvent, water, and occasionally a cosurfactant, are thermodynamically stable systems. Characteristics of reverse micelles and its extraction principle were introduced. And the influential factors of extraction have been investigated, while reversed micellar extraction research situation was summarized.The thermodynamically stable reversed micellar system was prepared by dissolving CTAC in isooctane containing n-octanol as cosurfactant. Bovine serum albumin which was excelent heat stability has been extracted by the reversed micellar system. Forward extraction process parameters such as contact time, the surfactant concentration, co-solvent concentration, pH, ionic strength and species of the initial aqueous phase were investigated. And these parameters were varied to optimize the extraction efficiency. It was shown that the extraction equilibrium of BSA has reached the equilibrium after 4 minutes using the CTAC reversed micellar systems. Cosurfactant can increase the stability of reverse micelles, and when the cosurfactant concentration was too high, extraction efficiency decreased as the concentration was increased. Extraction efficiency increased with increasing surfactant concentration first and then decreased slightly. BSA extraction efficiency increased with an increase in aqueous phase pH or temperature. Extraction efficiency decreased with the increase of ionic strength. We found that extraction of BSA was controlled by entropy changes from the viewpoint of thermodynamics. Under the optimized conditions, maximum forward extraction efficiencies of BSA can reach practically 99.55%.We used two methods in the backward extraction experiments:one was adding short chain alcohol stripping method. For backward extraction of BSA, adding amount of ethanol to the fresh aqueous phase could improve back extraction efficiency. First, the influence of ethanol concentration, salt concentration and pH of fresh aqueous phase on the backward extraction efficiencies was studied. Under the optimized conditions, backward extraction efficiencies of BSA could reach 85.16%, and the equilibrium could be reached after 50 minutes. Second, the CD spectra of BSA indicated the maintenance of the structural integrity of BSA during reverse micelles extraction. Therefore, the backward extraction method could protect of the activity of BSA. At last, we found that the extraction efficiency slightly decreased after two cyclic operations of forward and back extraction. Another was adding the opposite ionic surfactant stripping method. Adding AOT reverse micelles to CTAC reversed micellar system could improve backward extraction speed and efficiency. Under the optimized conditions, maximum backward extraction efficiencies of BSA could reach 88.72%, and the equilibrium could be reached after 8 minutes. The influence of AOT concentration, salt concentration and pH of fresh aqueous phase on the backward extraction efficiencies has been investigated. We found that backward extraction efficiency increased with increasing AOT concentration first and then decreased.