Obtaining of β-LG, α-LA and BSA protein fractions from milk whey

Introduction. The purpose of the work is to obtain the protein fractions beta-LG, alpha-LA and BSA from the milk whey by preparative disc-electrophoresis. Materials and methods. The whey was obtained from the fresh cow's milk after isoelectric precipitation of casein complex proteins. The concentration of whey proteins was determined on a spectrophotometer by the absorption at lambda = 280 inn. Gel filtration was carried out on liquid chromatography columns. Sephadexes G-25 and G-100 were used for the gel filtration. The fractional composition and homogeneity of whey proteins were analyzed by disc-electrophoresis in the polyacrylamide gel slabs. Results and discussion. A system of disc-electrophoresis in native conditions for acidic and neutral proteins has been selected for the preparative isolation of homogeneous fractions of bioactive peptides proteins-precursors from milk whey taking into account the effectivety and existence of denaturation factors. A sample of whey proteins, for preparative fractionation purified, from low molecular weight compounds had been obtained at the result of the gel filtration. An optimal whey proteins sample amount should not exceed 10 ml to provide an effective separation in a modified electrophoretic chamber of Studier type apparatus. Too large sample amount does not allow to separate the whey proteins effectively and obtain the homogeneous fractions extraction. The duration of the extraction process of individual protein fractions after preparative disc-electrophoresis was about 55-60 min. The degree of homogeneity of the obtained protein fractions was established with the help of analytical disc-electrophoresis. It was 95-97% for beta-LG and BSA fractions and 89-91% for alpha-LA fractions. It has been calculated that the total yield of homogeneous milk whey protein fractions was nearly 49-61% (from milk whey proteins taken for separation). Conclusions. The proposed variant of the disc-electrophoresis allows to isolate from milk whey the electrophoretically homogeneous fractions of beta-LG, alpha-LA and BSA in native conditions. The duration of electrophoresis and proteins extraction is about 4 hours. The average yield of homogeneous fractions from whey proteins is 55 +/- 6%.