A new fluid distribution system for scale-flexible expanded bed adsorption

Vortex flow reactor assessment for the purification of monoclonal antibodies from unclarified broths

The vortex flow reactor (VFR) can be used in many chemical engineering applications. This paper assesses its novel use in the purification of monoclonal antibodies from cell broth. To this end, the IgG2a antibody was purified from the unclarified fermentation broth of transgenic mouse 55/6 hybridoma cells. Visual experiments showed that the VFR worked in the laminar vortices flow regime and the vortices displaced slightly faster than the axial flow. The VFR has the advantage of creating two sorts of flows: axial flow to produce the expanded bed and an extra vortex flow to avoid channeling and stabilize the expanded bed, the hydrodynamic behavior of which is plug flow with an experimental Pèclet number higher than 20. The pH was adjusted in the untreated fermentation broth, which was directly introduced into the reactor thus reducing the number of stages. The IgG2a purification was carried out in a single device via two steps: antibody adsorption in the expanded bed and antibody elution in the settled bed using Streamline rProtein A. A thirty-fold increase in the high-purity antibody concentration was achieved at the top of the pH5 elution peak with a total recovery of 93.1% (w/w) between elution peaks pH 5 and 3.

Purification of lysozyme from chicken egg white by high-density cation exchange adsorbents in stirred fluidized bed adsorption system

Lysozyme from crude chicken egg white (CEW) feedstock was successfully purified using a stirred fluidized bed adsorption system ion exchange chromatography where STREAMLINE SP and SP-XL high density adsorbents were selected as the adsorption carrier. The thermodynamic and kinetic studies were carried out to understand the characteristics of lysozyme adsorption by adsorbents under various conditions, including adsorption pH, temperature, lysozyme concentration and salt concentrations. Results showed that SP and SP-XL adsorbents achieved optimum lysozyme adsorption at pH 9 with capacity of ~139.77 and ~251.26 mg/mL, respectively. The optimal conditions obtained from batch studies were directly employed to operate in SFBA process. For SP-XL adsorbent, the recovery yield and purification factor of lysozyme were 93.78% and ~40 folds, respectively. For SP adsorbent, lysozyme can be eluted ~100% with purification factor of ~26 folds. These two adsorbents are highly suitable for use in direct recovery of lysozyme from crude CEW.

Mathematical modelling of expanded bed adsorption - a perspective on in silico process design

Expanded bed adsorption (EBA) emerged in the early 1990s in an attempt to integrate the clarification, capture and initial product concentration/purification process. Several mathematical models have been put forward to describe its operation. However, none of the models developed specifically for EBA allows simultaneous prediction of bed hydrodynamics, mass transfer/adsorption and (unwanted) interactions and fouling. This currently limits the development and early optimization of EBA-based separation processes. In multiphase reactor engineering, the use of multiphase computational fluid dynamics has been shown to improve fundamental understanding of fluidized beds. To advance EBA technology, a combination of particle, equipment and process scale models should be used. By employing a cascade of multiscale simulations, the various challenges EBA currently faces can be addressed. This allows for optimal design and selection of equipment, materials and process conditions, and reduces risks and development times of downstream processes involving EBA. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Expanded bed adsorption as a primary recovery step for the isolation of the insulin precursor MI3 process development and scale up

Expanded bed adsorption (EBA) was evaluated for the isolation of the human insulin precursor MI3, expressed and secreted by the yeast Saccharomyces cerevisiae. The isoelectric point of the insulin precursor (pH 5.3) makes cation exchange a prime candidate for direct adsorption. In order to find a suitable window of operation for the process the adsorption equilibrium was analysed in a wide range of operating conditions (pH and conductivity) and for three different stationary phases. The same array of operating conditions was examined with regard to stable fluidisation of the adsorbents in S. cerevisiae suspensions. Interactions of the yeast with the fluidised stationary phase were investigated by a pulse response technique and the hydrodynamics of the fluidised bed under process conditions by residence time distribution analysis. The case study demonstrates that by parallel examination of product binding and fluidisation quality a window of operation can be found. Analysis of the binding kinetics by breakthrough experiments and modelling led to the definition of a set of operating conditions, which yield a compromise between optimal use of the equilibrium capacity provided by the adsorbent and high throughput required for an industrial separation. After initial experiments on the bench scale the protocol was transferred successfully to pilot scale demonstrating the design of a reliable operation.

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.

Compatibility of column inlet and adsorbent designs for processing of corn endosperm extract by expanded bed adsorption

Corn has emerged as a viable host for expression of recombinant proteins; targeted expression to the endosperm has received particular attention. The protein extracts from corn endosperm differ from those of traditional hosts in regard to the nature of residual solids and extracted matrix contaminants. Each of these differences presents reasons for considering expanded bed adsorption for product capture and new considerations for limitations of the method. In this work three inlet-flow distribution devices (mesh, glass ballotini, and localized mixing) and six adsorbents with different physical (size and density), chemical (ligand), and base matrix properties were evaluated to determine conditions compatible with processing of crude corn endosperm extract by expanded bed adsorption. Of the inlet devices evaluated, the design with localized mixing at the inlet (as produced commercially by UpFront Chromatography A/S, Copenhagen, DK) allowed solids up to 550 microm into the column without clogging for all flow rates evaluated. A mesh at the inlet with size restriction of either 50 microm or 80 microm became clogged with very small corn particles (< 44 microm). When glass ballotini was used, large particles (550 microm) passed through for high flow rates (570 cm/h), but even small (< 44 microm) particles became trapped at a lower flow rate (180 cm/h). The physical and chemical properties of the resin determined whether solids could be eluted. The denser UpFront adsorbents allowed for complete elution of larger and more concentrated corn solids than the currently available Amersham Streamline adsorbents (Amersham Biosciences, Piscataway, NJ) as a result of the former's higher flow rate for the desired 2x expansion (570 cm/h for UpFront vs. 180 cm/h for Streamline). All corn solids < 162 microm eluted through nonderivatized UpFront resin. Larger corn solids began to accumulate due to their elevated sedimentation velocities. Feeds of < 44 microm solids at 0.45% and 2.0% dry weight successfully eluted through ion exchange adsorbents (DEAE and SP) from UpFront. However, significant accumulation occurred when the solids size increased to a feed of < 96 microm solids, thus indicating a weak interaction between corn solids and both forms of ion exchange ligands. Expanded beds operated with Streamline ion exchange adsorbents (DEAE and SP) did not allow full elution of corn solids of < 44 microm. A hyperdiffuse style EBA resin produced by Biosepra (Ciphergen Biosystems, Fremont, CA) with CM functionality showed a severe interaction with corn solids that collapsed the expanded bed and could not be eliminated with elevated flow rates or higher salt concentration.