Extraction of ß-Lactoglobulin from Bovine Milk by Affinity Counter-Current Distribution in Aqueous Two-Phase System

¹ Facultad de Veterinaria, Miguel Servet 177 50013, Zaragoza, Spain

The counter-current distribution pattern of milk and whey -lactalbumin and ß-lactoglobulin in a two-phase system containing 7% (wt/wt) Dextran T-500 and 5% (wt/wt) polyethylene glycol 6000 was investigated. Both proteins showed similar distribution profiles and were clearly separated from the main bulk of milk protein. The use of polyethylene glycol bound to a hydrophobic ligand (palmitate polyethylene glycol) enhanced the affinity of both proteins for the upper phase rich in polyethylene glycol when assayed in the presence of 5 mM EDTA. This hydrophobic binding ability of -lactalbumin, but not of ß-lactoglobulin, was strongly sensitive to the presence of Ca²⁺. Thus, a counter-current distribution of whey in the presence of palmitate-polyethylene glycol and Ca²⁺ allowed a single extraction of ß-lactoglobulin, which was apparently free of detectable contamination, as assessed by SDS-PAGE.

Key Words: partitioning • aqueous two-phase • ßbeta;-lactoglobulin • -lactalbumin

Submitted on July 15, 1991
Accepted on October 15, 1991