Temperature-Induced Phase Partitioning for Protein Purification

Ethylene oxide (EO)-propylene oxide (PO) random copolymers are watersoluble and separate into two phases above a lower critical solution temperature (LCST), i.e., the cloud point, a polymer-rich phase, and a water phase depleted of polymer. Traditionally, the removal of polymer from protein in an aqueous two-phase separation requires either back extraction into a saltrich phase, ultrafiltration, diafiltration, or a chromatographic step, e.g., ion exchange (see Chapter 32). Thermo separating polymers can be used in place of the commonly used polyethylene glycol in polymer-polymer two-phase systems and, therefore, offer an obvious advantage for the cost-effective purification of target protein into a “clean” water phase and for the recycling of polymer (1 ),(2 ).