Routine manufacture of recombinant proteins using expanded bed adsorption chromatography

Selective Protein Separation Based on Charge Anisotropy by Spherical Polyelectrolyte Brushes

Protein purification is of vital importance in the food industry, drug discovery, and other related fields. Among many separation methods, polyelectrolyte (PE)-based phase separation was developed and recognized as a low-cost purification technique. In this work, spherical polyelectrolyte brushes (SPBs) with a high specific surface area were utilized to study the protein accessibility and selective protein binding on highly charged nanoparticles (NPs) as well as the selective phase separation of proteins. The correlation between charge anisotropy, protein binding, and phase separation was investigated on various protein systems including those proteins with similar isoelectric points (pI) such as bovine serum albumin (BSA) and β-lactoglobulin (BLG), proteins with similar molecular weights such as BSA and hemoglobin (HB), and even protein variants (BLG-A and -B) with a tiny difference of amino acids. The nonspecific electrostatic interaction studied by turbidimetric titrations and isothermal calorimetry titration (ITC) indicates a specific binding between proteins and SPBs arising from the charge anisotropy of proteins. An optimized output based on selective protein binding on SPBs could be correlated for efficient protein separation through tuning external conditions including pH and ionic strength. These findings, therefore, proved that phase separation based on selective protein adsorption by SPBs was an efficient alternative for protein separation compared with the traditional practice.

Selective protein complexation and coacervation by polyelectrolytes

This review discusses the possible relationship between protein charge anisotropy, protein binding affinity, polymer structure, and selective phase separation. We hope that a fundamental understanding of primarily electrostatically driven protein-polyelectrolyte (PE) interactions can enable the prediction of selective protein binding, and hence selective coacervation through non-specific electrostatics. Such research will partially challenge the assumption that specific binding has to be realized through specific binding sites with a variety of short-range interactions and some geometric match. More specifically, the recent studies on selective binding of proteins by polyelectrolytes were examined from different assemblies in addition to the electrostatic features of proteins and PEs. At the end, the optimization of phase separation based on binding affinity for selective coacervation and some considerations relevant to using PEs for protein purification were also overviewed.

Antibody Capture from Corn Endosperm Extracts by Packed Bed and Expanded Bed Adsorption

Topical treatments of chronic infections with monoclonal antibodies will require large quantities of antibodies. Because plants have been proven capable of producing multisubunit antibodies and provide for large-scale production, they are likely hosts to enable such applications. Recovery costs must also be low because of the relatively high dosages required. Hence, we have examined the purification of a human secretory antibody from corn endosperm extracts by processing alternatives of packed bed and expanded bed adsorption (EBA). Because of the limited availability of the transgenic corn host, the system was modeled by adding the antibody to extracts of nontransgenic corn endosperm. Complete clarification of a crude extract followed by packed bed adsorption provided antibody product in 75% yield with 2.3-fold purification (with antibody accounting for 24% of total protein). The small size of the packed bed, cation-exchange resin SP-Sepharose FF and the absence of a dense core (present in EBA resins) allowed for more favorable breakthrough performance compared to EBA resins evaluated. Four adsorbents specifically designed for EBA operation, with different physical properties (size and density), chemical properties (ligand), and base matrices were tested: SP-steel core resin (UpFront Chromatography), Streamline SP and Streamline DEAE (Amersham Biosciences), and CM Hyper-Z (BioSepra/Ciphergen Biosystems). Of these, the small hyperdiffuse-style resin from BioSepra had the most favorable adsorption characteristics. However, it could not be utilized with crude feeds due to severe interactions with corn endosperm solids that led to bed collapse. UpFront SP-steel core resin, because of its relatively smaller size and hence lower internal mass transfer resistance, was superior to the Streamline resins and operated successfully with application of a crude corn extract filtered to remove all solids of >44 microm. However, the EBA performance with this adsorbent provided a yield of only 61% and purification factor of 2.1 (with antibody being 22% of total protein). Process simulation showed that capital costs were roughly equal between packed and expanded bed processes, but the EBA design required four times greater operating expenditures. The use of corn endosperm as the starting tissue proved advantageous as the amount of contaminating protein was reduced approximately 80 times compared to corn germ and approximately 600 times compared to canola. Finally, three different inlet designs (mesh, glass beads, and mechanical mixing) were evaluated on the basis of their ability to produce efficient flow distribution as measured by residence time distribution analysis. All three provided adequate distribution (axial mixing was not as limiting as mass transfer to the adsorption process), while resins with different physical properties did not influence flow distribution efficiency values (i.e., Peclet number and HETP) when operated with the same inlet design.

The economics of inclusion body processing

Many recombinant proteins are often over-expressed in host cells, such as Escherichia coli, and are found as insoluble and inactive protein aggregates known as inclusion bodies (IBs). Recently, a novel process for IB extraction and solubilisation, based on chemical extraction, has been reported. While this method has the potential to radically intensify traditional IB processing, the process economics of the new technique have yet to be reported. This study focuses on the evaluation of process economics for several IB processing schemes based on chemical extraction and/or traditional techniques. Simulations and economic analysis were conducted at various processing conditions using granulocyte macrophage-colony stimulating factor, expressed as IBs in E. coli, as a model protein. In most cases, IB processing schemes based on chemical extraction having a shorter downstream cascade demonstrated a competitive economic edge over the conventional route, validating the new process as an economically more viable alternative for IB processing.

InterfacingPichia pastoris cultivation with expanded bed adsorption

For improved interfacing of the Pichia pastoris fed-batch cultivation process with expanded bed adsorption (EBA) technique, a modified cultivation technique was developed. The modification included the reduction of the medium salt concentration, which was then kept constant by regulating the medium conductivity at low value (about 8 mS/cm) by salt feeding. Before loading, the low conductivity culture broth was diluted only to reduce viscosity, caused by high cell density. The concept was applied to a one-step recovery and purification procedure for a fusion protein composed of a cellulose-binding module (CBM) from Neocallimastix patriciarum cellulase 6A fused to lipase B from Candida antarctica (CALB). The modified cultivation technique resulted in lower cell death and consequently lower concentration of proteases and other contaminating proteins in the culture broth. Flow cytometry analysis showed 1% dead (propidium-stained) cells compared to 3.5% in the reference process. During the whole process of cultivation and recovery, no proteolysis was detected and in the end of the cultivation, the product constituted 87% of the total supernatant protein. The lipase activity in the culture supernatant increased at an almost constant rate up to a value corresponding to 2.2 g/L of CBM-CALB. In the EBA process, no cell-adsorbent interaction was detected but the cell density had to be reduced by a two-times dilution to keep a proper bed expansion. At flow velocity of 400 cm/h, the breakthrough capacity was 12.4 g/L, the product yield 98%, the concentration factor 3.6 times, the purity about 90%, and the productivity 2.1 g/L x h.

Single step purification of a series of wheat recombinant proteins with expanded bed absorption chromatography

Expanded bed absorption chromatography (EBA) was used to improve and simplify the purification of several wheat recombinant proteins. Binding and elution conditions were set to allow the purification of the over expressed protein in a single step. In comparison with our previous multi step protocol, same purity was obtained while EBA required less time (one day instead of five) and gave a higher yield (63% instead of 10%). This new procedure was then used for the successful purification of five other wheat ns-LTP. Despite their important polymorphism (identity from 44 to 97 %-pHi from 8 to 10), the EBA protocol allowed their purification in a single step.

Process chromatography: current constraints and future options for the adsorptive recovery of bioproducts

A contemporary review of adsorption chromatography must embrace aspects of fixed-bed, batch suspension and fluidised-bed contacting of complex feedstocks with adsorbents chemically derivatised with ligands with binding specificities for target bioproducts. Advances in the design of adsorbents, ligands and contactors have facilitated opportunities for integrated processing of unclarified feedstocks to benefit purity and yield of macromolecular products. In the face of competition from apparently simpler, yet productive, technologies (e.g. precipitation, crystallisation and aqueous solvent extraction), further advances in chromatographic purification of macromolecules and nanoparticulates demand close collaboration between inventors and/or manufacturers of new products and the suppliers of chromatographic hardware and consumables.