Emerging Trends in Designing Short and Efficient Protein Purification Protocols

Protein purification is carried out in both academic and industrial sectors. Both non-chromatographic approaches (precipitation, crystallization, partitioning) and chromatographic methods are used. When recombinant proteins are over expressed in foreign hosts, inclusion bodies are obtained. Many purification methods can be used to refold proteins. Many strategies allow one to avoid formation of inclusion bodies. The concept of affinity based separation extends to non-chromatographic methods as well. Affinity precipitation and Macro-(affinity ligand) Facilitated Three Phase Partitioning (MLFTPP) are two examples of this. Produced as fusion proteins, most of the proteins are purified via interaction of their affinity tag coupled to a solid matrix. Nanotechnology has made magnetic based methods even more powerful. Expanded bed chromatography, aqueous two phase systems and MLFTPP allow one to deal directly with feed containing particulate matter. Membrane based separations are another powerful option. Finally crystallization at the industrial level has further evolved to reoccupy an important place in protein purification. Overall, the main trends are: integrate upstream and downstream phases and reduce the number of steps required for purifying a protein. This has become possible by adopting variety of non-chromatographic methods. More important, bringing affinity based steps earlier in the purification have helped achieving this.