Application of commercial ultrafiltration membranes for protein purification by high performance countercurrent membrane purification (HPCMP).

High performance countercurrent membrane purification (HPCMP) has emerged as a promising diffusive separation strategy for the purification of recombinant proteins and monoclonal antibodies (mAbs). However, prior studies employed dialysis membranes, which are designed for diffusive separations but have not been validated for biopharmaceutical manufacturing. This study evaluates the ability of commercial ultrafiltration (UF) membranes, engineered for pressure-driven filtration, to support highly selective diffusive separations. Scanning electron microscopy (SEM) analysis of the membrane cross-sections revealed marked morphological differences between UF and dialysis membranes. Yet, transport studies using polydisperse dextrans and model proteins demonstrated that UF membranes can deliver exceptional diffusive separation selectivity. In particular, a 100 kDa polysulfone membrane (Cytiva) provided >150-fold diffusive selectivity between bovine serum albumin (BSA) and immunoglobulin G (IgG). When utilized for mAb separation from a clarified CHO cell culture fluid, this membrane achieved >98% product yield, near-complete removal of low molecular weight species, and significant reduction in both DNA and host cell protein (HCP) levels. These results demonstrate that commercial UF membranes that are validated for bioprocessing applications can be repurposed for HPCMP, enabling scalable, continuous downstream processing of biotherapeutics.