Fractionation of α-Lactalbumin and β-Lactoglobulin from Whey Protein Isolate Using Selective Thermal Aggregation, an Optimized Membrane Separation Procedure and Resolubilization Techniques at Pilot Plant Scale

An optimized fractionation method in the pilot scale for production of isolated alpha-lactalbumin (alpha-La) and beta-lactoglobulin (beta-Lg) was developed. The method comprises following steps: (1) selective thermal precipitation of alpha-La, (2) aging of the formed particles, (3) separation of native beta-Lg from the precipitate via microfiltration and ultrafiltration, (4) purification of beta-Lg, (5) resolubilization of the precipitate, and (6) purification of alpha-La. The native status of the isolated fractions was confirmed by reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and differential scanning calorimetry (DSC). Protein fractions with a purity of 91.3% for alpha-La and 97.2% for beta-Lg were produced. These values were based on the native protein detectable in RP-HPLC. High overall yields for alpha-La between 60.7% and 80.4% and for beta-Lg between 80.2% and 97.3%, depending on membrane operation parameters, were achieved. The method offers potential for pilot plant scale and possibly industrial application to produce pure native fractions of alpha-La and/or beta-Lg.