often used as the primary recovery step to reduce the batch
volume, provide separation and purification.
Column chromatography requires molecular diffusion to
transport the target molecular species through the sub-micro-porous structure of the resin beads to internal binding sites.
Flow-through chromatographic polishing steps operate at flow
rates measured in centimeters/hour. The slower flow demands
larger diameters columns, upward of 1.0 meter or more, to
achieve reasonable flow rates. At these diameters, fill volumes
require upwards of a hundred liters of resin beads, at high cost.
Much of the columns adsorptive capacity may not be maximized in order to reach acceptable flow rates. There are also
difficulties when purifying large molecular weight molecules,
such as host cell proteins, DNA, viruses, endotoxins and large
proteins. These species present challenges due to their size and
restriction to move freely into the micropores of resin beads.1
These drawbacks to anionic exchange columns promoted the
development and use of membrane adsorber (MA) chromatography, one potential technology to achieve high dynamic capacity
and high throughput in affinity ion-exchange chromatography
processes. As a result, there is a trend towards studies of adsorptive membrane technology for antibody purification. 2
Initially promoted by filter manufacturers for contaminant
reduction/removal of HCP DNA, endotoxin and viruses, these
were first applications for membrane adsorbers. Subsequently,
it was applied to the protein purification applications. The
contaminants are directly bound to the membrane by positively
charged ligands, thus forgoing the diffusive migration into resin
beads. The higher flow rates of MAs results from the open pore
structure of the membrane, which typically range from 5-8 µm.
This feature provides little restriction for very high molecular
weight molecules to the binding sites. The higher flow rates,
measured in ml/minute, significantly decrease processing
times, improving throughput. The need for high volume buffer
rinses to flush high value product is eliminated.1
The major drawback is the reduced adsorptive performance
in higher salt concentrations. The competition from salt ions
results in greater passage of contaminates. Newer membrane
adsorbers using strong AEX ligand or hydrogel technologies in
hybrid purifiers offer higher performing product technologies
over a range of salt concentrations. These developments allow
Bioprocess suppliers offer an ever expanding portfolio of dis-
posable products that have moved into downstream processes,
such as chromatography. The use of Single-Use-Systems (SUS)
disposables is a qualified and validated technology in the manu-
facture of drugs in all aspects of biopharm manufacturing.
SUS can replace stainless steel/glassware components with
disposable polymeric equivalents in most upstream and many
downstream applications. Chromatography, as one of the
crucial and costly process step, is a bottleneck in scale-up
and speed of the purifications processes. Recent advances in
disposable chromatography systems has made it possible to
incorporate SUS disposable chromatography purification at
reasonable costs with higher throughputs and flux rates.
A choice of ion exchange technologies, ligand formulations,
device configuration and construction coupled with performance scale-up techniques, disposable and single-use chromatographic purification processes are feasible and economical
to implement. The biopharma market is being exposed to this
technology in through a growing product selection.
Chromatography is a standard process used in biopharma
for the downstream purification of protein therapeutics. It is
■ By A. Mark Trotter, Marketing Development Manager, 3M Purification, Inc. Life Science Process Technologies
A review of chromatography products and processes in biopharma applications