A combination of Sephadexes for the milk whey protein fractions isolation

Abstract

Whey proteins perform important biological functions. They can also be a source of numerous natural bioactive peptides that have a positive effect on various physiological systems of the body. For research and usage of this phenomenon, the question of these proteins isolating with saving of their structure and biological functions is relevant. Considering the significant difference in molecular weights, gel filtration is a promising method. The purpose of the study was the fractionation of milk whey proteins using gel filtration with a combination of different dextran gels. We used in the work milk whey proteins after isoelectric precipitation of casein and isolation of low molecular weight peptides by gel filtration on Sephadex G-25. The first gel filtration of the whey protein preparation was performed on a column with Sephadex G-150. For further fractionation were used three sectors from the first two chromatographic peaks obtained by gel filtration on Sephadex G-150. The first peak contains high molecular fractions of proteins eluting with a volume close to the free volume of the chromatographic column. The second asymmetric peak consists mainly of β-lactoglobulin and α-lactalbumin mixture. The third peak includes low molecular weight polypeptides and peptides that are not fixed in a polyacrylamide gel. The combined chromatographic fractions of three sectors from the first two chromatographic peaks were re-fractionated on a G-100 column. Electrophoretic analysis of chromatographic fractions after repeated chromatography of milk whey proteins confirmed the feasibility of choosing a certain sequence of sephadex. At the same time, the yield of β-lactoglobulin fraction increases by 12 ± 1 %, and α-lactalbumin by 9 ± 1 % compared to the results obtained by repeated gel filtration on one Sephadex (G-100). The degree of purification of β-lactoglobulin and α-lactalbumin, according to the densitometry, was 93 ± 5 % and 77 ± 4 %, respectively.