Membrane chromatography: Protein purification from E. coli lysate using newly designed and commercial anion-exchange stationary phases

Separation Technologies for Whey Protein Fractionation

Whey is a by-product of cheese, casein, and yogurt manufacture. It contains a mixture of proteins that need to be isolated and purified to fully exploit their nutritional and functional characteristics. Protein-enriched fractions and highly purified proteins derived from whey have led to the production of valuable ingredients for many important food and pharmaceutical applications. This article provides a review on the separation principles behind both the commercial and emerging techniques used for whey protein fractionation, as well as the efficacy and limitations of these techniques in isolating and purifying individual whey proteins. The fractionation of whey proteins has mainly been achieved at commercial scale using membrane filtration, resin-based chromatography, and the integration of multiple technologies (e.g., precipitation, membrane filtration, and chromatography). Electromembrane separation and membrane chromatography are two main emerging techniques that have been developed substantially in recent years. Other new techniques such as aqueous two-phase separation and magnetic fishing are also discussed, but only a limited number of studies have reported their application in whey protein fractionation. This review offers useful insights into research directions and technology screening for academic researchers and dairy processors for the production of whey protein fractions with desired nutritional and functional properties.

Nonwoven Ion-Exchange Membranes with High Protein Binding Capacity for Bioseparations

This study presents the preparation and characterization of UV-grafted polybutylene terepthalate (PBT) ion exchange nonwoven membranes for chromatographic purification of biomolecules. The PBT nonwoven was functionalized with sulfonate and secondary amine for cation and anion exchange (CEX and AEX), respectively. The anion exchange membrane showed an equilibrium static binding capacity of 1300 mg BSA/g of membrane, while the cationic membranes achieved a maximum equilibrium binding capacity of over 700 mg hIgG/g of membrane. The CEX and AEX membranes resulted in dynamic binding capacities under flow conditions, with a residence time of 0.1 min, of 200 mg hIgG/mL of membrane and 55 mg BSA/mL of membrane, respectively. The selectivity of the PBT-CEX membranes was demonstrated by purifying antibodies and antibody fragments (hIgG and scFv) from CHO cell culture supernatants in a bind-an-elute mode. The purity of the eluted samples exceeded 97%, with good log removal values (LRV) for both host cell proteins (HCPs) and DNA. The PBT-AEX nonwoven membranes exhibited a DNA LRV of 2.6 from hIgG solutions in a flow-through mode with little loss of product. These results indicate that these membranes have significant potential for use in downstream purification of biologics.

High-capacity multimodal anion-exchange membranes for polishing of therapeutic proteins

This contribution reports on a study using Purexa™-MQ multimodal anion-exchange (AEX) membranes for protein polishing at elevated solution conductivities. Dynamic binding capacities (DBC₁₀ ) of bovine serum albumin (BSA), human immunoglobulins, and salmon sperm DNA (ss-DNA) are reported for various salt types, salt concentrations, flowrates, and pH. Using 1 mg/ml BSA, DBC₁₀ values for Purexa™-MQ were >90 mg/ml at conductivities up to 15 mS/cm. The membranes maintained a high, salt-tolerant BSA DBC₁₀ of 89.8 ± 2.7 (SD) over the course of 100 bind-elute cycles. Polishing studies with acidic and basic monoclonal antibodies at >2 kg/L loads showed that Purexa™-MQ had higher clearance of host cell proteins and aggregate species at high conductivity (13 mS/cm) and in the presence of phosphate than other commercial AEX media. Purexa™-MQ also had a high ss-DNA DBC₁₀ of 50 mg/ml at conductivities up to 15 mS/cm, markedly outperforming other commercial products. In addition to the effectiveness of Purexa™-MQ for protein polishing at elevated solution conductivities, its unusually high binding capacity for ss-DNA indicates potential applications for plasmid DNA purification.

Downstream Processing Technologies/Capturing and Final Purification : Opportunities for Innovation, Change, and Improvement. A Review of Downstream Processing Developments in Protein Purification

Increased pressure on upstream processes to maximize productivity has been crowned with great success, although at the cost of shifting the bottleneck to purification. As drivers were economical, focus is on now on debottlenecking downstream processes as the main drivers of high manufacturing cost. Devising a holistically efficient and economical process remains a key challenge. Traditional and emerging protein purification strategies with particular emphasis on methodologies implemented for the production of recombinant proteins of biopharmaceutical importance are reviewed. The breadth of innovation is addressed, as well as the challenges the industry faces today, with an eye to remaining impartial, fair, and balanced. In addition, the scope encompasses both chromatographic and non-chromatographic separations directed at the purification of proteins, with a strong emphasis on antibodies. Complete solutions such as integrated USP/DSP strategies (i.e., continuous processing) are discussed as well as gains in data quantity and quality arising from automation and high-throughput screening (HTS). Best practices and advantages through design of experiments (DOE) to access a complex design space such as multi-modal chromatography are reviewed with an outlook on potential future trends. A discussion of single-use technology, its impact and opportunities for further growth, and the exciting developments in modeling and simulation of DSP rounds out the overview. Lastly, emerging trends such as 3D printing and nanotechnology are covered. Graphical Abstract Workflow of high-throughput screening, design of experiments, and high-throughput analytics to understand design space and design space boundaries quickly. (Reproduced with permission from Gregory Barker, Process Development, Bristol-Myers Squibb).

Nanofiber Ion-Exchange Membranes for the Rapid Uptake and Recovery of Heavy Metals from Water

An evaluation of the performance of polyelectrolyte-modified nanofiber membranes was undertaken to determine their efficacy in the rapid uptake and recovery of heavy metals from impaired waters. The membranes were prepared by grafting poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) to cellulose nanofiber mats. Performance measurements quantified the dynamic ion-exchange capacity for cadmium (Cd), productivity, and recovery of Cd(II) from the membranes by regeneration. The dynamic binding capacities of Cd(II) on both types of nanofiber membrane were independent of the linear flow velocity, with a residence time of as low as 2 s. Analysis of breakthrough curves indicated that the mass flow rate increased rapidly at constant applied pressure after membranes approached equilibrium load capacity for Cd(II), apparently due to a collapse of the polymer chains on the membrane surface, leading to an increased porosity. This mechanism is supported by hydrodynamic radius (R_h) measurements for PAA and PIA obtained from dynamic light scattering, which show that R_h values decrease upon Cd(II) binding. Volumetric productivity was high for the nanofiber membranes, and reached 0.55 mg Cd/g/min. The use of ethylenediaminetetraacetic acid as regeneration reagent was effective in fully recovering Cd(II) from the membranes. Ion-exchange capacities were constant over five cycles of binding-regeneration.

Directing membrane chromatography to manufacture α1-antitrypsin from human plasma fraction IV

The surging demand for plasma proteins, mainly driven by the growing market and the development of new therapeutic indications, is promoting manufacturers to improve the throughput of plasma proteins. Due to the inherent convective mass transfer, membrane chromatography has been proved to be an efficient approach for extracting a small amount of target proteins from large-volume feed. In this study, α1-antitrypsin (AAT) was extracted from human plasma fraction IV by a two-step membrane chromatography. An anion-exchange membrane chromatography (AEMC) was used to capture the plasma proteins in bind/elute mode, and the obtained effluent was further polished by a hydrophobic interaction membrane chromatography (HIMC) in flow-through mode. Under optimal conditions, the recovery and purity of AAT achieved 87.0% and 0.58 AAT/protein (g/g) by AEMC, respectively. After the precise polishing by HIMC, the purity of AAT was 1.22 AAT/protein (g/g). The comparison results showed that membrane chromatography outperformed column chromatography in both steps because of its high throughput. This two-step membrane chromatography could obtain an AAT recovery of 83.3% and an activity recovery of 91.4%. The outcome of this work not only offers an alternative process for protein purification from plasma, but also provides guidelines for manufacturing product from a large-volume feed with multi-components by membrane chromatography.

Functionalizing Microporous Membranes for Protein Purification and Protein Digestion

This review examines advances in the functionalization of microporous membranes for protein purification and the development of protease-containing membranes for controlled protein digestion prior to mass spectrometry analysis. Recent studies confirm that membranes are superior to bead-based columns for rapid protein capture, presumably because convective mass transport in membrane pores rapidly brings proteins to binding sites. Modification of porous membranes with functional polymeric films or TiO₂ nanoparticles yields materials that selectively capture species ranging from phosphopeptides to His-tagged proteins, and protein-binding capacities often exceed those of commercial beads. Thin membranes also provide a convenient framework for creating enzyme-containing reactors that afford control over residence times. With millisecond residence times, reactors with immobilized proteases limit protein digestion to increase sequence coverage in mass spectrometry analysis and facilitate elucidation of protein structures. This review emphasizes the advantages of membrane-based techniques and concludes with some challenges for their practical application.

Amylosucrase-mediated synthesis and self-assembly of amylose magnetic microparticles

Magnetic separation and purification of MBP-tagged protein using AMB.

Membrane adsorbers comprising grafted glycopolymers for targeted lectin binding

This work details the design and testing of affinity membrane adsorbers for lectin purifications that incorporate glucose-containing glycopolymers. It is the selective interaction between the sugar residues of the glycopolymer and the complementary carbohydrate-binding domain of the lectin that provides the basis for the isolation and purification of lectins from complex biological media. The design approach used in these studies was to graft glycopolymer 'tentacles' from macroporous regenerated cellulose membranes by atom transfer radical polymerization. As shown in earlier studies, this design approach can be used to prepare high-productivity membrane adsorbers. The model lectin, concanavalin A (conA), was used to evaluate membrane performance in bind-and-elute purification, using a low molecular weight sugar for elution. The membrane capacity for binding conA was measured at equilibrium and under dynamic conditions using flow rates of 0.1 and 1.0 mL/min. The first Damkohler number was estimated to relate the adsorption rate to the convective mass transport rate through the membrane bed. It was used to assess whether adsorption kinetics or mass transport contributed the primary limitation to conA binding. Analyses indicate that this system is not limited by the accessibility of the binding sites, but by the inherent rate of adsorption of conA onto the glycopolymer.

Preparative purification of recombinant proteins: current status and future trends

Advances in fermentation technologies have resulted in the production of increased yields of proteins of economic, biopharmaceutical, and medicinal importance. Consequently, there is an absolute requirement for the development of rapid, cost-effective methodologies which facilitate the purification of such products in the absence of contaminants, such as superfluous proteins and endotoxins. Here, we provide a comprehensive overview of a selection of key purification methodologies currently being applied in both academic and industrial settings and discuss how innovative and effective protocols such as aqueous two-phase partitioning, membrane chromatography, and high-performance tangential flow filtration may be applied independently of or in conjunction with more traditional protocols for downstream processing applications.

Development of high-productivity, strong cation-exchange adsorbers for protein capture by graft polymerization from membranes with different pore sizes

This paper describes the surface modification of macroporous membranes using ATRP (atom transfer radical polymerization) to create cation-exchange adsorbers with high protein binding capacity at high product throughput. The work is motivated by the need for a more economical and rapid capture step in downstream processing of protein therapeutics. Membranes with three reported nominal pore sizes (0.2, 0.45, 1.0 μm) were modified with poly(3-sulfopropyl methacrylate, potassium salt) tentacles, to create a high density of protein binding sites. A special formulation was used in which the monomer was protected by a crown ether to enable surface-initiated ATRP of this cationic polyelectrolyte. Success with modification was supported by chemical analysis using Fourier-transform infrared spectroscopy and indirectly by measurement of pure water flux as a function of polymerization time. Uniformity of modification within the membranes was visualized with confocal laser scanning microscopy. Static and dynamic binding capacities were measured using lysozyme protein to allow comparisons with reported performance data for commercial cation-exchange materials. Dynamic binding capacities were measured for flow rates ranging from 13 to 109 column volumes (CV)/min. Results show that this unique ATRP formulation can be used to fabricate cation-exchange membrane adsorbers with dynamic binding capacities as high as 70 mg/mL at a throughput of 100 CV/min and unprecedented productivity of 300 mg/mL/min.

An all-aqueous route to polymer brush-modified membranes with remarkable permeabilites and protein capture rates

Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm(3) of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, they capture 85 mg/cm(3) of histidine(6)-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni(2+)-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins.