Impact of Continuous Affinity—Recycle Extraction (CARE) in Downstream Processing

Abstract

As commercialization of products derived from recombinant DNA technology intensifies, the development of manufacturing and large scale processing technology has become a major challenge for the biotechnology industry. Nowhere is the challenge more evident, and yet most lacking, than in the protein recovery and isolation stage. We have attempted to address this challenge, through the development of a continuous, scaleable and integrateable protein purification system. Rather than packing conventional adsorbent particles in a fixed bed (column), solid/liquid contact is carried out in well-mixed reactors. Continuous operation is achieved by recirculation of the adsorbent particles between two or more contactors. Using a lab scale prototype unit, two continuous protein purification examples were developed; one based on affinity (biospecific) interactions and the second on ion-exchange adsorption. In an attempt to place CARE in the greater context of downstream processing, two sets of simulations were performed. The first involves early introduction of an adsorptive purification step in a purification train. Pilot plant data for cell debris removal in a continuous centrifuge was contrasted with simulated performance of the CARE system. The second involves a direct comparison of CARE to column chromatography. Adsorptive purification, utilizing the CARE process, can be introduced into a process, at a location where column chromatography is not possible (with solid contaminants and viscous material). This early introduction of a high resolution purification step should positively influence the remaining steps in the process, and lower overall purification costs. For feed streams that do not require clarification or viscosity reduction, the benefits of column operation (high capacity, high purification factor) make it an attractive and in some cases, preferred alternative to CARE.