Aqueous Two-Phase Partitioning for Bioseparations

Aqueous two-phase systems are routinely used for enzyme purification. Walter and Johansson7 edited a comprehensive book on the subject entitled Aqueous Two-Phase Systems as Vol. 228 of the series Methods in Enzy-mology published by Academic Press. Another very useful book is the one edited by Walter, Brooks, and Fisher6 entitled Partitioning in Aqueous Two-Phase Systems Theory, Methods, Uses, and Applications to Biotechnology which deals with separations of a variety of biomolecules and bioparticles. 

The most popular aqueous two-phase systems in use today are the PEG-dextran-water system and the PEG-potassium phosphate-water system.4 Both PEG and dextran are fully water soluble, yet the two polymers are incompatible and separate into two aqueous phases in certain concentration ranges. Table 7 is a list of various aqueous two-phase partitioning systems compiled recently by Zaslavsky.8 

Nonionic polymer-nonionic polymer-water Polypropylene glycol Methoxypolyethylene glycol 

Polyethylene glycol Polyethylene glycol Polyvinyl alcohol Hydroxypropyldextran Dextran Polyvinyl alcohol Polyvinylpyrrolidone Dextran Arabinogalactan Hydroxypropyl starch Ficoll 

Polymer-low molecular weight component-water Polypropylene glycol Potassium phosphate 

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