SEPARATION OF ALPHA-LACTALBUMIN AND BETA-LACTOGLOBULIN USING SURFACE NET AND LOCAL HYDROPHOBICITIES IN AQUEOUS 2-PHASE PARTITIONING SYSTEMS

The surface net hydrohobicities and local hydrophobicities of alpha-La ctalbumin (alpha-LA) and beta-Lactoglobulin (beta-LG), major proteins in cheese whey, were evaluated by examining their partitioning behavio rs in aqueous two-phase systems such as polyethylene glycol (PEG)/dext ran (Dex), PEG/Dex spiked with a non-ionic surfactant, Triton, and Tri ton/salt two-phase systems. Based on the resulting surface properties for both holo- (Ca2+ bound) and apostates (Ca2+ removed), two effectiv e separation systems were presented. The first utilized the difference in surface net hydrophobicity in the hole-state, where comparatively hydrophobic alpha-LA could be separated in the top PEG rich phase whil e beta-LG could be concentrated in the bottom phase. The second utiliz ed the difference in local hydrophobicity in the apo-state, where Ca2 was removed by addition of EDTA. In this case alpha-LA could be parti tioned to the top phase containing Triton to which alpha-LA in the apo -state strongly bound. alpha-LA, partitioned to the top PEG phase in b oth systems, could be back-extracted and recovered in the bottom salt phase of the PEG/salt system in more than 90% purity.