A novel method for hydrophobin extraction using CO2 foam fractionation system

► CO2 foam fractionation system was successfully used to increase the concentration of HFBII. ► Different parameters of CO2 foam fractionation were optimized. ► Pure HFBII with the MW equal to the complete molecule minus the last amino acid was obtained. ► No gushing was observed when the amount of HFBII was very high. ► 100 nm as the critical diameter of CO2 nanobubbles covered by HFBII at 1 atm was obtained.