Direct separation and purification of α-lactalbumin from cow milk whey by aqueous two-phase flotation of thermo-sensitive polymer/phosphate

BACKGROUND α -lactalbumin ( α -La) is of great interest to the industry as a result of its excellent functional properties and nutritional value. Aqueous two-phase flotation (ATPF) of thermo-sensitive polymer poly (ethylene glycol-ran-propylene glycol) monobutyl ether (UCON) and KH 2 PO 4 was applied to directly separate and purify α -La from milk whey, which was purposed to simplify the production process and reduced cost of production. RESULTS The effect of ATPF composition and operating parameters on the flotation efficiency ( E ) and purity of α -La were investigated. The optimal conditions included 2 min of premixing time, 30 mL min −1 flow velocity and 20 min of flotation time, whereas the composition conditions comprised 35.0 mL 0.18 g mL −1 phosphate solution (containing 10% (cow milk whey/salt solution, v/v) cow milk whey, 50 ppm defoamer and 2 g NaCl) and 5.0 mL of 40% ( w/w ) UCON solution. Under the optimal conditions, E of α -La was 95.67 ± 1.04% and purity of α -La was 98.78 ± 1.19%. UCON was recovered by a thermally-induced phase separation and reused in next ATPF process without reducing E of α -La. Purified α -La was characterized by several key technologies. The results indicated that α -La in cow milk whey could be directly separated and purified by the ATPF and the purity was satisfactory. Moreover, it was suggested there was no obvious structure difference between the α -La separated by ATPF and the α -La standard. CONCLUSION The present study enabled the recycling of UCON, providing an effective, economically viable and environmentally friendly approach for the separation and purification of protein. © 2021 Society of Chemical Industry