Purification of recombinant protein A by aqueous two‐phase extraction integrated with affinity precipitation

Aqueous two‐phase extraction incorporated affinity precipitation was examined as a technique for protein purification. An enteric coating polymer, Eudragit S100, was employed as a ligand carrier. Eudragit was specifically partitioned to the top phase in the aqueous two‐phase systems. For application of this method to purification of recombinant protein A using human IgG coupled to Eudragit in an aqueous two‐phase system, 80% of protein A added was recovered with 81% purity. The purity was enhanced 26‐fold by thid method. The IgG‐Eudragit could be used repeatedly for the purification process. This seperation method should be applicable to industrial‐scale purification as a new purification procedure combining the advantages and compensating for the disadvantages of the aqueous two‐phase method and affinity precipitation method. © 1992 John Wiley & Sons, Inc.