Concentration and purification of proteins by means of two-phase systems: membraneless osmosis process

A new approach to the biotechnological application of biopolymer incompatibility is proposed. The phenomenon of thermodynamic incompatibility of proteins with other proteins and with polysaccharides in aqueous media has been discovered and studied on more than a. hundred systems. All the protein-polysaccharide mixtures show a lower compatibility and a higher asymmetry of phase diagrams compared to that of different proteins. The asymmetry of phase diagrams shows up in the fact that mixtures of the protein and polysaccharide solution break down into two liquid phases which differ greatly in the concentrations of the macromolecular components. The highly concentrated protein phase is usually in equilibrium with the diluted polysaccharide phase. These phenomena underlie a new method for concentrating a protein solution, as well as the protein's purification and fractionation, called membraneless osmosis.