Hydrophobic Membrane Adsorbers for Large-Scale Downstream Processing

This alternative to column chromatography is suitable for flow-through as well as bind-and-elute purification operations.
Oct 01, 2009

ABSTRACT

Ion exchange–based membrane chromatography has already proven to be a powerful alternative to polishing columns in flow-through mode for contaminant removal. More recently, new membrane adsorbers have been designed for use in other applications. This article discusses a Sartobind phenyl membrane adsorber that has been developed for the manufacturing-scale production of biomolecules based on hydrophobic interaction chromatography (HIC) principles. The new adsorptive membrane combines the advantages of membrane chromatography with a high binding capacity for proteins comparable to that of conventional HIC resins. It represents a new tool for downstream processing, applicable for both bind-and-elute and flow-through operations.


Sartorius Stedim Biotech
In the past decade, there has been a trend in the biopharmaceutical industry toward higher upstream productivity, i.e., higher cell culture titers, to meet the ever-growing clinical and commercial demand.1 This trend poses a challenge for the industry—to develop and scale-up downstream purification processes capable of purifying multiple kilograms per batch. Although downstream processing faces significant bottlenecks because of heavy reliance on traditional bead-based chromatography.2,3 For example, although Protein A chromatography has undergone great optimization for throughput in the past five years, the expected rise in cell culture titers, combined with the need for larger masses of antibodies, indicates a need for further improvement of the existing Protein A resin to accommodate the demand for high-throughput production.4 Therefore, there has been significant interest in the development of new technologies that facilitate the processing of multikilogram batches at the lowest possible cost.2,5 Among the novel technologies developed, membrane chromatography has a high potential, particularly for process-scale monoclonal antibody (MAb) purification.

Membranes feature a more open structure than resins, so there is virtually no diffusion limitation, and as a result they offer many technical advantages that have been well described in the literature.6–9 Several applications have been discussed for MAb purification. Because of the generally high isoelectric points of MAbs, anion exchange (AEX) resins are typically used as a polishing step in a flow-through mode (i.e., the product does not bind while the trace impurities such as DNA, viruses, endotoxins, and host cell proteins are retained).10 Although the amount of impurities to bind is very low in such operations, conventional polishing scale-up leads to column oversizing because of the pressure and diffusion limitations associated with conventional bead-based chromatography. In contrast, a disposable membrane chromatography device has a convective mode of mass transport, which allows operation at significantly higher linear flow-rates (shorter residence times) than columns. As a result, disposable membrane chromatography device can have a much smaller volume than that of a conventional column when used in flow-through mode. This significantly reduces buffer consumption, processing time, and floor space requirements.11 Sartobind ion exchange capsules, for example, have been successfully implemented in various downstream processes for the removal of negatively charged contaminants.12–15 It is well documented in the literature that AEX membrane adsorbers are a powerful alternative to columns and can facilitate the development of new purification strategies for downstream processing.

In addition to positively charged membranes, hydrophobic interaction membrane chromatography (HIC) has been described for the purification of a humanized MAb.16 Hydrophobic interaction is listed among the most commonly used chromatography methods for protein purification. For MAb purification, HIC is also often operated in flow-through mode.10 It is used to separate molecules based on their difference in hydrophobicity, and the technique has been presented as an efficient mode to remove dimers and high molecular weight (HMW) aggregates as a polishing step in a MAb purification process.17 In this article, we describe the use of an HIC membrane adsorber for the purification of a monoclonal IgG1 expressed using the PER.C6 human cell line. The hydrophobic membrane adsorber is based on hydrophilic regenerated stabilized cellulose with hydrophobic phenyl groups covalently attached to the base matrix.