PROTEIN RECOVERY USING GAS-LIQUID DISPERSIONS

Two separation techniques, foam separation and colloidal gas aphrons ( CGAs), both of which are based on gas-liquid dispersions, are compared as potential applications for protein recovery in downstream processi ng. The potential advantages of each method are described and the conc entration and selectivity achieved with each method, for a range of pr oteins is discussed. The physical basis of foam separation is the pref erential adsorption of surface active species at a gas-liquid interfac e, with surface inactive species remaining in bulk solution. When a so lution containing surface active species is sparged with gas, a foam i s produced at the surface: this foam can be collected, and upon collap se contains surface active species in a concentrated form. CGAs are mi crobubble dispersions (bubble diameters 10-100 IJ-m) with high gas hol d ups (>50%) and relatively high stability, which are formed by stirri ng a surfactant solution at speeds above a critical value (typically a round 5000 rpm). It is expected that when proteins are brought into co ntact with aphrons, protein adsorbs to the surfactant through electros tatic and/or hydrophobic forces. The aphron phase can be separated eas ily from the bulk solution due to its buoyancy, thus allowing separati on of protein in a concentrated form. (C) 1998 Elsevier Science B.V. ( C) rights reserved.