Purification and characterization of two porcine β-lactoglobulin variants by NaCl salting-out and reversed phase-HPLC

Summary - Porcine whey proteins have been separated by reversed-phase HPLC and the different eluted fractions were analysed by SD5-PAGE. Two protein fractions lately eluted from HPLC, with an apparent molecular weight of approximately 18 800 had an amino acid composition corresponding to that of porcine ~-Iactoglobulin. These 2 fractions differed only in their AlaNal content and consequently may be genetic variants of porcine ~-Iactoglobulin. In order to obtain larger amounts of ~-Iactoglobulin, we attempted to adapt to porcine whey a previously published method used for bovine ~-Iactoglobulin and based on NaCI salting-out at low pH. Each step of purification was monitored by RP-HPLC. After precipitation (14% NaCI), solubilisation in 7% NaCI and dialysis against distilled water, ~-Iactoglobulin was obtained with a purity of 94%. Final separation of ~-Iactoglobulin variants can be rapidly achieved by RP-HPLC on a semi-preparative column. ~-Iactoglobulin 1sow milk 1purification