Partition of proteins in the aqueous guar/dextran two-phase system

The partition of proteins (bovine serum albumin, beta -lactoglobulin, micel lar casein) has been examined in the guar/dextran aqueous two-phase system. The influence of parameters like pH, ionic strength (NaCl), and polymer co ncentration has been investigated while the protein concentration was incre ased up to 2% w/w. For globular proteins (bovine serum albumin, P-lactoglob ulin) the general trends of partitioning established in the literature with other systems like polyethyleneoxide/dextran were nearly verified. The dex tran-rich bottom phase was found to be slightly more concentrated in protei n than the guar-enriched top one. However, micellar casein displayed a diff erent behavior, giving a more uneven partition and phase separation phenome na at concentrations above 0.5% w/w. This difference has been attributed to the larger size of the particle. Meanwhile, the modifications of the guar/ dextran phase diagram have been investigated. It was shown that the additio n of globular protein or micellar casein up to 2% w/w did not affect the th ermodynamic features of this system. (C) 2000 Elsevier Science Ltd. All rig hts reserved.