New methods of protein purification. Expanded bed chromatography.

This review considers a new method of protein purification--expanded bed chromatography. The method is based on pumping of the mobile phase upwards through the column bed. The bed starts to expand at liquid flow rate above a critical value, and the gaps between the sorbent beads expand. The controlled distribution of bead size and weight results in a stable expanded bed, where separate beads are not completely immobile, but oscillate about some steady position. The mobile phase flow through such a column is similar to plug flow. The main advantage of expanded bed chromatography is that it enables protein recovery directly from particulate-containing feed stocks like cell homogenates or even fermentation broth, when extracellular proteins are purified. The successful examples of protein purification by expanded bed chromatography and the available commercial systems are presented. The standard equipment for liquid protein chromatography can be used in the expanded bed mode.