High Performance Countercurrent Membrane Purification for protein separations

Although pressure-driven membrane filtration is used extensively in bioprocessing, protein purification is currently performed by chromatographic separations due to the difficulty in achieving high selectivity for similarly sized species using commercially available ultrafiltration membranes in the absence of fouling. This work examines a novel approach for protein separations based on High Performance Countercurrent Membrane Purification (HPCMP), which exploits highly selective diffusive transport across the thin walls of a hollow fiber membrane. Experiments were performed using commercially available hemodialysis membranes using both polydisperse dextrans and a model protein mixture of bovine serum albumin (BSA) and myoglobin (Mb). Dextran transport data obtained using diffusive transport showed significantly greater selectivity than that for pressure-driven filtration. The HPCMP system was then used to separate BSA and Mb, achieving greater than 98% yield of both proteins with purification factors greater than 100-fold. The Mb product obtained in the draw (dialysate) solution had undetectable levels of BSA. Stable operation was achieved for 96 h without any evidence of membrane fouling due to the absence of any significant pressure-driven flow. These results demonstrate the feasibility of using HPCMP for high resolution separations in the preparation of biopharmaceuticals and natural protein products. • Dextran data demonstrate enhanced selectivity for diffusive membrane transport. • Model calculations confirm enhanced diffusive selectivity versus filtration. • BSA and myoglobin separated using countercurrent diffusive contacting. • Myoglobin product obtained with >98% yield and >300-fold purification. • Protein separation performed continuously for 96 h without membrane cleaning.