Protein extraction using sugar ester reverse micelles

In protein extraction, using the nonionic surfactant sugar ester DK-F-110, the critical micelle concentration (CMC) of a DK-F-110/isopropyl alcohol(IP A)/hexane system was found to be at a DK-F-110 concentration of 0.5 g dm(-3 ), indicating that the sugar ester reverse micelles could be formed in hexa ne. At concentrations higher than the CMC, cytochrome c was extracted into the DK-F-110 reverse micelles as judged from UV spectra of the DK-F-110/IPA /hexane solution after it was contacted with the aqueous protein solution. In extraction of cytochrome c using this system, forward extraction was fou nd to be pH-dependent, with high extraction percentage being obtained at pH 8. The forward extraction percentage was reduced by an increase in the buff er concentration, and at a buffer concentration of 0.5 mol dm(-3) was ca 25 % as high as that of sodium bis(2-ethylhexyl) sulfosuccinate(AOT) systems. An optimal DK-F-110 concentration was found to give the maximum forward ext raction percentage. Addition of alcohol, especially IPA, to the micellar or ganic phase enabled the highly backward extraction of cytochrome c to be ac hieved without the formation of insoluble aggregates. The esterification re action rate by Rhizopus delemar lipase in the DK-F-110 reverse micellar sys tem had a higher maximum value than that of AOT and lecithin systems. (C) 1 999 Society of Chemical Industry.