Environmentally-friendly strategy for separation of α-lactalbumin from whey by aqueous two phase flotation

Aqueous two-phase flotation (ATPF) consisting of 1000 g/mol polyethylene glycol (PEG 1000)/trisodium citrate was developed for the separation of α -Lactalbumin ( α -La) from whey. The flotation efficiency ( E ) and purification factor ( PF ) of α -La were evaluated using the reversed-phase high-performance liquid chromatography (RP-HPLC). The effects of pH, concentration of trisodium citrate, flow velocity, flotation time and whey loading on the E and PF of α -La were investigated. An efficient separation of α -La from whey was achieved using ATPF with pH of 8.20, 5 mL of 0.50 g/mL PEG 1000 solution, 35 mL of 0.40 g/mL trisodium citrate solution and whey (20%, v/v), 30 mL/min of flow velocity and 42 min of flotation time. Under the optimal conditions, E and PF of α -La could reach 87.54% and 5.33, respectively. In addition, the kinetic process of the separation of α -La by ATPF of PEG 1000/trisodium citrate was investigated. The results showed that there were two stages in the separation process. Both stages obeyed the first-order kinetic equation, and the first stage was faster than the second one.