Continuous radial flow chromatography of proteins
A continuous radial flow chromatography (CRFC) system consisting of an annular packed bed between two rotating concentric porous stainless steel cylinders was constructed and tested. The protein feed, wash buffer and elution buffer are applied simultaneously at different fixed angular positions at the periphery of the rotating bed and flow radially inwards. The target protein is bound in the feed zone and eluted in the elution zone while unbound protein flows through the feed zone. Continuity equations for fixed bed radial flow chromatography were extended to model the CRFC by including angular displacement terms, and solved using finite difference methods. Film diffusion at the resin particle boundary and pore diffusion within the resin particle was described by an overall mass transfer coefficient and a multicomponent Langmuir isotherm was used to describe protein absorption onto the resin particle. To verify the model, a solution containing 0.53 mg ml21 lactoferrin and 1.6 mg ml21 bovine serum albumin (BSA) was applied at 5 ml min21 to a 220-ml CRFC system packed with DEAE Sepharose Fast Flow ion exchange resin, with abed speed of 0.02 rpm. The proteins were separated into lactoferrin of 68% purity (74% recovery) and BSA of 94%purity (85% recovery). Experimental data were used to find values for the parameters in the model proposed.