Single-pass Tangential Flow Filtration Research Articles

Development of a local wall concentration model for the design of single pass tangential flow filtration (SPTFF) systems with viral vector surrogates

Recent advances in the use of viral vectors for gene therapy has created a need for efficient downstream processing of these novel therapeutics. Single-pass tangential flow filtration (SPTFF) can potentially improve final product quality via reductions in shear, and it can increase manufacturing productivity via simple implementation into continuous/intensified processes. This study investigated the impact of variations in pressure and flow rate along the length of the membrane on overall SPTFF performance. Constant-flux filtration experiments at feed fluxes from 14 to 420 L/m2/h (Reynolds numbers <20) were performed using Pellicon® 3 TFF cassettes with fluorescent nanoparticles as model viral vectors. The location of nanoparticle accumulation shifted towards the filter outlet at high conversion and was also a function of the permeate flow configuration. These phenomena were explained using a newly developed concentration polarization model that predicts the distribution in local wall concentration over the length of the membrane. The model accurately captured the observed nanoparticle accumulation trends, including the effects of the permeate flow profile (co-current, divergent, or convergent flow) on nanoparticle accumulation within the SPTFF module. Nanoparticle accumulation at moderate conversion was more uniform using convergent flow, but nanoparticle accumulation at 80 % conversion (5x concentration factor) can be minimized using a divergent flow configuration. The local wall concentration model was also used to evaluate the critical flux by assuming that fouling occurs when the nanoparticle concentration at any point along the membrane surface exceeds 15 % by volume. These results provide important insights for the design and operation of SPTFF technology for inline concentration of viral vectors.

Concentration of clarified pool by single-pass tangential flow filtration to improve productivity of protein A capture step: Impact of clarification strategies.

Protein A capture chromatography remains a high-cost and relatively low-productivity step for downstream processing of monoclonal antibodies. As bioprocessing transitions towardintensified processes, maximizing the efficiency of individual steps is key to achieving economic targets. This study was performed to assess the impact of inline concentration of clarified cell culture fluid (CCF), using single-pass tangential flow filtration, on protein A chromatography purification productivity. CCF with varying levels of impurities and turbidity were obtained dependent upon the clarification method. These CCFs were concentrated and processed over a protein A capture step. Productivity increases of 1.8- to 2.6-fold were achieved as compared to a protein A capture step with no CCF concentration. Achieving such targeted improvements requires careful consideration of the multiple components in the clarification strategy before implementation.

Predictive modeling of single pass tangential flow filtration for continuous biomanufacturing.

Opportunities for process intensification have made continuous biomanufacturing an area of active research. While tangential flow filtration (TFF) is typically employed within the biologics purification train to increase drug substance concentration, single-pass TFF (SPTFF) modifies its format by enabling continuity of this process and achieving a multifold concentration factor through a single-pass over the filtration membranes. In continuous processes feed concentration and flow rate are determined by the preceding unit operations. Therefore, tight control of SPTFF output concentration must be achieved through precise design of the membrane configuration, unlike TFF. However, predictive modeling can be utilized to identify configurations that achieve a desired target concentration across ranges of possible feed conditions with minimal experimental data, hence enabling accelerated process development and design flexibility. We hereby describe the development of a mechanistic model predicting SPTFF performance across a wide design space using the well-established stagnant film model, which we demonstrate is more accurate at higher feed flow rates. The flux excursion dataset was generated within time constraints and with minimal material consumption, showing the method's ability to be quickly adapted. While this approach eliminates characterizing complex physicochemical model variables or the need for users with specialized training, the model and its assumptions become inaccurate at low flow rates, below 25 L/m2 /h, and high conversions, above 0.9. As this low flow rate, high conversion operating regime is relevant for continuous biomanufacturing, we explore the assumptions and challenges involved in predicting and modeling SPTFF processes, while suggesting added characterization to gain further process insight.

Single-Pass Tangential Flow Filtration (SPTFF) of Nanoparticles: Achieving Sustainable Operation with Dilute Colloidal Suspensions for Gene Therapy Applications.

Recent approval of several viral-vector-based therapeutics has led to renewed interest in the development of more efficient bioprocessing strategies for gene therapy products. Single-Pass Tangential Flow Filtration (SPTFF) can potentially provide inline concentration and final formulation of viral vectors with enhanced product quality due. In this study, SPTFF performance was evaluated using a suspension of 100 nm nanoparticles that mimics a typical lentivirus system. Data were obtained with flat-sheet cassettes having 300 kDa nominal molecular weight cutoff, either in full recirculation or single-pass mode. Flux-stepping experiments identified two critical fluxes, one based on boundary-layer particle accumulation (Jbl) and one based on membrane fouling (Jfoul). The critical fluxes were well-described using a modified concentration polarization model that captures the observed dependence on feed flow rate and feed concentration. Long-duration filtration experiments were conducted under stable SPTFF conditions, with the results suggesting that sustainable performance could potentially be achieved for as much as 6 weeks of continuous operation. These results provide important insights into the potential application of SPTFF for the concentration of viral vectors in the downstream processing of gene therapy agents.

Design of a process development workflow and control strategy for single-pass tangential flow filtration and implementation for integrated and continuous biomanufacturing

Integrated and continuous biomanufacturing (ICB) offers several advantages compared to traditional batch methods, prompting the development of novel technologies and infrastructure for the implementation of ICB in the biopharmaceutical sector. However, most of the advancements have been in the early stages of the purification process, with relatively fewer advancements in the final filtration steps. This work focuses on some of the last major unit operations of a traditional bioprocess: ultrafiltration and diafiltration. Our proposed technological solution involves robust control algorithms for (1) precisely maintaining consistent protein concentration in single-pass ultrafiltration (SP-UF) and (2) achieving the targeted buffer exchange in single-pass diafiltration (SP-DF). Specifically, we adopted an integrated experimental, modeling, and simulation approach to develop a robust process understanding of SP-UF/SP-DF operations via semi-empirical maximum permeate flux models. These models were employed in the optimization of key design variables such as the filter area and the development of control strategies. Finally, we demonstrate the applicability of our proposed solution by operating a single-pass tangential flow filtration (SP-TFF) system in an integrated and continuous manner for six days. We believe that this work is instrumental for the successful realization of SP-UF/SP-DF operations in both batch and ICB processes.

Integrated double flow-through purification of monoclonal antibodies using membrane adsorbers and single-pass tangential flow filtration

A flow-through process for monoclonal antibody (mAb) purification has been created by integrating two different membrane adsorbers (MAs) with single-pass tangential flow filtration (SPTFF) for continuous buffer exchange. First, a design of experiments (DoE) was carried out to investigate the influence of pH and conductivity on the removal of desoxyribonucleic acid (DNA) and host cell proteins (HCP), and to select buffer conditions for mAb flow-through mode operation for four different MAs. As next, breakthrough curve experiments were performed with the selected buffer conditions for each MA to analyze the binding behavior of mAb, DNA, and HCP. Then, the influence of the MA sequence in the double flow-through process on the mAb yield and DNA and HCP removal was studied in batch mode. The best sequence of MAs was used for the final integrated double flow-through polishing process, where the MAs were directly connected via SPTFF. The flow-through of the first (anion exchange) MA was continuously diafiltrated via SPTFF to buffer conditions for the second (cation exchange) MA. In this way, DNA (< 2 ppm) and HCP (< 29 ppm) were removed with simultaneously high mAb yield. Moreover, 36 times higher throughput was obtained than with a standard process that combines a packed-bed column with CEX resin in a bind and elute mode with an AEX MA in flow-through mode.

Refractive index as a process analytical technology to measure real time protein concentration for monitoring and control of commercial scale tangential flow filtration operations

AbstractBiological therapeutics are increasingly being formulated to high protein concentrations to decrease drug substance storage space and increase the flexibility of administration to patients. With the higher protein concentration targets comes added challenges to the downstream purification manufacturing process. Tangential flow filtration (TFF) operations are typically performed to reach target protein concentration. TFF operations for a given drug substance may include an Ultrafiltration and Diafiltration (UFDF) step, or a UFDF step followed by a single pass tangential flow filtration (SPTFF) step. Whether a TFF step achieves a target protein concentration is determined by at‐line protein concentration measurements performed at the completion of a process step. If the measured protein concentration is outside the specified range, the unit operation may need to be restarted, reprocessing may need to be performed, or a batch may need to be terminated. Out of specification protein concentration measurements may be a result of the TFF operation or sample measurement. Increased viscosities associated with high concentration TFF operations pose added challenges to the TFF process and sample measurement. Implementation of an inline process analytical technology (PAT) to monitor real‐time protein concentration during TFF operations has the potential to improve the accuracy of the operations in achieving target protein concentrations. This will result in improved process consistency and efficiency, increased operator confidence and decreased likelihood of batch failures. This paper studies the performance of a K‐Patents PR‐23 refractometer (Vaisala) as a PAT to monitor and control the UFDF and SPTFF unit operations of a commercial scale monoclonal antibody purification process.

Process design of a fully integrated continuous biopharmaceutical process using economic and ecological impact assessment.

Continuous biomanufacturing is a promising alternative to current batch operation as it offers benefits in terms of improved productivity, product quality, and reduced footprint. This study aims to build a fully integrated continuous platform for monoclonal antibody (mAb) production incorporating novel technologies (like intensified seed expansion and continuous high cell density perfusion operations, single-pass tangential flow filtration, and single-use technologies) as well as media and buffer preparation steps. Economic assessment is performed on the basis of the total cost of goods (COGs), which is $102.2/g in the base-case scenario with a bioreactor scale of 500 L. E-factor is used as an environmental indicator and the result shows that 4865.6kg of process water and 11.1 kg of consumables are required to produce 1 kg mAbs. After the development and analysis of the benchmark process, scenario analysis is performed to assess the impacts of the bioreactor scale (60-2000 L) and upstream titers (1.12-2.08 g/L) on the process economics as well as on the environmental footprint. With the increase of bioreactor scale and mAb titer, the operating COGs per unit product decrease. Moreover, increasing the mAb titer is more favorable in terms of the ecological impacts. To investigate the production capacity, the upstream production is increased and the downstream bottlenecks are determined. It is found that only the multicolumn chromatographic (MCC) operations become the process bottleneck and the order of the MCC unit operation that becomes the process bottleneck depends on capacity utilization for that step. Finally, a new platform is built with the integration of membrane chromatography and the two designed processes are compared in terms of economic and ecological impacts.

Defining the optimal operating conditions and configuration of a single-pass tangential flow filtration (SPTFF) system via CFD modelling

Single-pass tangential flow filtration (SPTFF) is used in biopharmaceutical manufacturing to reduce volumes and concentrate products. The staging of multiple membrane cassettes makes it possible to achieve high concentration factors in one pass, but at the same time increases the system’s complexity. This work aims to provide comprehensive understanding of SPTFF at both membrane cassette level and at equipment level by evaluating the impact of different operating conditions and different filter designs on the filtration performance. An experimentally validated computational fluid dynamics (CFD) model of a commercial ultrafiltration membrane cassette was developed and first used to study the impact of operating conditions on the volumetric concentration factor (VCF). The results show that both the feed flux and the retentate pressure have a substantial impact on the VCF. At low pressures (0.0–0.4 bar) a VCF of 1.2–2.9 is achieved for feed fluxes of 137–394 Lm−2h−1, while at high pressures (0.6–1.0 bar) a VCF of up to 10.5 is achieved. The model was subsequently applied to study concentration-dependent effects and the spatial distribution of relevant physical properties. The simulation results help select suitable operating conditions and evaluate the cassette design with respect to product accumulation. Finally, a systematic comparison of different multi-stage filter designs was performed. The results show clear advantages of mixed filter designs over serial filter designs in terms of TMP and VCF, and serve as a guidance to select a suitable filter design for given concentration targets and pressure limits. An advantage of the presented modelling approach is its applicability to the evaluation of other membrane systems with different geometric dimensions and different membrane properties.

Simulation-based evaluation of single pass continuous diafiltration with alternating permeate flow direction

Abstract In the framework of modern bioprocessing continuous ultrafiltration/diafiltration (UF/DF) is getting increasingly popular. However, while continuous UF can be easily implemented using a so-called single pass tangential flow filtration (SPTFF) module, continuous DF requires a more complicated setup including several SPTFF modules and intermittent dilution steps. Recently, we introduced a novel module design for continuous DF allowing simultaneous delivery of fresh buffer while withdrawing the permeate, thus achieving high degrees of buffer exchange within a single unit. In addition, the system allows to cyclically switch the flow direction of DF buffer through the membranes. Those uncommon features, however, also make it more difficult to determine an operation optimum experimentally by means of trial and error. Therefore, here a detailed finite element model of the physical processes within the module is presented, predicting key figures such as the obtained diafiltration efficiency and the resulting pressures. Because within the module all flow channels are filled by a 3D-printed porous grid supporting the membranes from both sides, the modified Brinkman equation was used to simulate the hydrodynamics, while common mass balance differential equations including accumulation, convection, and an anisotropic dispersion term were used for the simulation of concentration profiles of dissolved species. The predicted key figures are in good agreement with experimental results, obtained for feed solutions including up to 50 g/L of protein and being operated with and without switching the flow direction of the diafiltration buffer. A thorough parameter study reveals that the module shows the best performance for unidirectional flow of the diafiltration buffer, reaching diafiltration efficiencies independence to the applied diavolumes which are comparable to the ones of a conventional multi-stage setup using three SPTFF modules. Therefore, the simulation-based evaluation of optimum operation conditions reveals that the new module design has the potential to realize truly continuous diafiltration setups with high efficiency, requiring only one unit and no extra external piping for returning diafiltration in counterflow. Such simplified setups should be especially useful in small, flexible processing plants as they are increasingly demanded in the biopharmaceutical industry.

Design and optimization of Single Pass Tangential Flow Filtration for inline concentration of monoclonal antibodies

A number of Single Pass Tangential Flow Filtration (SPTFF) systems have recently been commercialized for inline concentration of monoclonal antibodies and other biotherapeutics, both to resolve bottlenecks in existing processes and as part of the development of integrated continuous downstream processes. The objective of this study was to examine the design and optimization of SPTFF modules using a previously developed mathematical model for the filtrate flux and pressure drop that specifically accounts for the concentration dependence of the antibody viscosity and osmotic pressure as well as the variation of the flow rate and antibody concentration with the position in the long pathlength SPTFF device. Model simulations were performed to examine the effects of channel width, length, and cassette staging (number of parallel cassettes in each stage) on SPTFF performance. The concentration factor (conversion) was greatest for a long thin channel configuration, but this also caused very large feed-side pressure drops. The use of cascade configurations, with a greater number of parallel channels near the feed inlet, significantly reduced the pressure drop but with a corresponding increase in total membrane area. A key factor governing the SPTFF performance was the increase in viscosity of the antibody solution at high conversion. These results provide important insights into the design and optimization of SPTFF systems for monoclonal antibody processing.

Process steps for the fractionation of immunoglobulin (Ig) G depleted of IgA, isoagglutinins, and devoid of in vitro thrombogenicity.

Plasma-derived immunoglobulins (IgG) are essential medicines that are in worldwide shortage, especially in low- and middle-income countries. Optimised manufacturing processes can increase supply. We evaluated various new process steps for IgG fractionation. A crude, worst-case, IgG intermediate obtained by caprylic acid fractionation of cryoprecipitate-poor plasma was used as starting experimental material. It was processed inline by Fractogel® (Merck) TMAE anion-exchanger to deplete IgA and IgM, Eshmuno® P (Merck) anti-A and anti-B affinity chromatography to remove anti-A and anti-B isoagglutinins, 0.3% TnBP-1% Triton X-100 (S/D) treatment, C18 chromatography for removal of S/D agents, and single-pass tangential flow filtration (SPTFF) concentration to 20%. Quality, safety, and recovery were evaluated at small and pilot scales to assess purity, removal of IgA, IgM isoagglutinins, S/D agents, thrombogenic factors, and lack of toxicity in a cell model. The starting IgG intermediate contained approximately 90% IgG, IgA, and IgM and 10% albumin. Fractogel® TMAE, equilibrated in 25 mM sodium acetate-pH 6.0 and loaded with up to 225 mg of IgG/mL, could remove IgA and IgM, with over 94% IgG recovery with preserved sub-class distribution in the flow-through. Sequential Eshmuno®-P anti-A and anti-B columns efficiently removed isoagglutinins. The C18 packing, used at up to 17 mL of S/D-IgG solution per mL, removed TnBP and Triton X-100 to less than 1 and 2 ppm, respectively. The 20% purified IgG was devoid of activated factor XI and thrombin generation activity. This purification sequence yields a >99% pure, 20% (v/v) IgG product, depleted of IgA, isoagglutinins, and thrombogenic markers, and should be implementable on various IgG intermediates to help improve the supply of immunoglobulins.

Modelling and optimization of single-pass tangential flow ultrafiltration for continuous manufacturing of monoclonal antibodies

Formulation of biotherapeutics using single pass tangential-flow filtration (SPTFF) is a critical step in continuous manufacturing processes for many drugs including monoclonal antibodies (mAbs). The concentration of the mAb in the final formulation is a critical quality attribute which affects safety and efficacy and is determined by the concentration factor achieved by the process material stream in a single pass through an SPTFF module. Modern SPTFF modules consist of multiple smaller membranes connected in different series and parallel configurations to increase the overall membrane area and residence time of the process material in order to achieve high concentration factors in a single pass. The present work leverages the gel polarization model of protein ultrafiltration to develop a model for the permeate flux vs. time profile of a single membrane inside an SPTFF module based on three key resistances, namely the boundary layer resistance, resistance of the deposited protein layer over time, and intrinsic membrane resistance. Correlations are developed to predict the key mechanistic parameters across the typical operating range of flow rate, bulk concentration and transmembrane pressure in downstream mAb processing steps. The single membrane model is then used as a building block to model complex SPTFF configurations with diverse tree structures, and to facilitate in-silico design of customized SPTFF configurations based on operating targets.

Single Pass Tangential Flow Filtration (SPTFF) of monoclonal antibodies: Experimental studies and theoretical analysis

Single Pass Tangential Flow Filtration (SPTFF) enables continuous ultrafiltration and diafiltration for inline concentration and buffer exchange in downstream bioprocessing of monoclonal antibody (mAb) products. However, the high conversion in SPTFF modules leads to large variations in local flow rate, protein concentration, and transmembrane pressure drop, significantly complicating the design of effective SPTFF modules/processes. In this study, a recent concentration polarization model for the filtrate flux in protein ultrafiltration that accounts for protein-protein interactions has been extended to the analysis of SPTFF, specifically including the effects of the mAb and membrane properties as well as the long path-length. Model calculations are in good agreement with experimental data for the filtrate flux and pressure drop in two commercial SPTFF systems with very different module geometries. The model was then used to analyze the design of SPTFF processes for inline mAb concentration, providing additional insights into the underlying physical phenomena governing the performance and optimization of SPTFF modules for bioprocessing.

Hybrid modeling reduces experimental effort to predict performance of serial and parallel single-pass tangential flow filtration

Single-pass tangential flow filtration (SPTFF) is a promising and increasingly important tool for continuous biomanufacturing and intensified bioprocessing. SPTFF operates at high product concentrations often limiting the number of process development experiments and therefore process understanding.We developed hybrid model structures to predict the concentration performance of SPTFF in serial and parallel mode with up to three membranes at various pressures, feed flows and protein concentrations. A single experiment to gather the training data for the model was performed in batch mode, significantly reducing the required amount of protein to set up the ideal process design. The hybrid model's excellent interpolation properties further reduce the duration of the training experiments. A set of mass balances controls the model variation of the two SPTFF modes as part of the hybrid model requiring only one training set for both modes. The hybrid model can be used as a Digital Twin to perform in-silico process simulations to gain in-depth process knowledge and enable model-based process control. The Digital Twin facilitates faster process transfer from batch to continuous and gives predictions on how different SPTFF modes perform under changing process conditions. This renders it a valuable tool for efficient process development and process transfer.

An Alternative to Process Integration: Clarification and First Step of Monoclonal Antibodies Purification Using Flocculation, Adsorption and Filtration

Background: New strategies for up and downstream integration process are being required for end-to-end continuous process for recombinant protein. Single-use materials as well as low cost and easy processing are very welcome for this development. Monoclonal antibodies are largely produced in biopharmaceutical industry what makes it a good protein model to be used in this process. Objective: A new strategy for integrating up and downstream processes for monoclonal antibodies was developed as a three-step process: flocculation of the cell culture harvest (batch mode); followed by anion-exchange chromatography for impurities adsorption in a slurry, and single-pass tangential flow filtration (both semi-continuous mode). Methodology: To develop this integrated process, separated studies of flocculation and adsorptions conditions with anion-exchange beads were performed. After defining the optimal conditions, flocculation was performed, and the supernatant was pumped in a vessel along with beads suspension for adsorption. The adsorption was carried out in a residence time determined in the previous studies. Then, the suspension with supernatant was filtered where the antibodies were recovered in the permeate. Results: Under the adsorption conditions applied (pH 6.5 and 250 mM NaCl), the purer antibodies were recovered in the permeate, whereas the beads with adsorbed impurities remained in the retentate. Steady state profile was obtained during adsorption and filtration for all conditions studied, where no loss of product was obtained. Differently, when the overall process was considered, global yields varied between 61% and 90% due to the void volumes of the runs. Additionally, higher concentration of beads (sample/beads ratio of 41) enabled high amount of impurities removal: 98.9% of DNA and approximately 70% of host cell proteins. Regarding the retention devices studied, depth filter yielded lower void volumes when compared to lamella settler (higher than 5-fold), begetting a global antibodies recovery of 90.4% in 20% higher productivity. Conclusion: Combining both clarification and impurities removal protocols into a single one proved to be a simple, efficient and fast alternative, which improvement could be obtained by its fully automatization.

Enhancing protein A productivity and resin utilization within integrated or intensified processes.

Recent interest in continuous manufacturing of biologics has driven the development and evaluation of multicolumn chromatography systems to drive down resin costs by increasing productivity and maximizing resin utilization, especially for the expensive protein A capture step. Single-pass tangential flow filtration can be used to reduce the volume of perfusion harvest, enabling a further increase in the productivity of the capture step by up to fivefold. However, there are expected to be practical limits for the productivity of the capture step, which must be determined based on the manufacturing batch size, duration, and frequency, especially as it relates to efficient utilization of the column lifetime. For short fed-batch manufacturing campaigns, intensified capture processes may result in up to 82% lower resin consumption, while avoiding the long-term storage of used resin. For perfusion processes and longer fed-batch campaigns, it may be more efficient to operate at a lower productivity that enables the column lifetime to be routinely achieved and achieves the desired resin and buffer savings without introducing unnecessary process risk or complexity. An intensified batch capture process, "super-batch," will be compared as an alternative to multicolumn chromatography processes to achieve high productivity and resin utilization with a potentially simpler process.

Adapting virus filtration to enable intensified and continuous monoclonal antibody processing.

Ongoing efforts in the biopharmaceutical industry to enhance productivity and reduce manufacturing costs include development of intensified, linked, and/or continuous processes. One approach to improve productivity and process economics of the polishing step (i.e., anion exchange chromatography) is to preconcentrate the product intermediate using a single-pass tangential flow filtration step before loading on the resin. This intensification of the polishing step consequently leads to changes in product intermediate concentration for subsequent virus filtration operations, potentially impacting filter performance and methods for evaluating viral clearance. The filtrate flux performance of a virus filtration operation was evaluated with monoclonal antibody (mAb) solutions of varying concentrations. These data were used to evaluate the effect on filter sizing for a hypothetical mAb perfusion process. The optimum mAb concentration to minimize the area of the virus filter was a function of the filtration step duration and reflected the competing effects of increasing concentration and decreasing volumetric flux on the membrane productivity. mAb solutions at high and low concentrations were used to evaluate viral clearance with extended filtration times (e.g., 24-72 h) simulating continuous processing conditions. Modifications to more traditional filtration viral clearance study methods were required to avoid experimental artifacts associated with the extended filtration time. No virus passage through the filter was observed under these conditions, similar to previous results for batch processes. These data demonstrate the feasibility of obtaining effective virus removal even when mAb concentration and filtrations times are increased by up to an order of magnitude from current common practices.

Improved protein A resin for antibody capture in a continuous countercurrent tangential chromatography system.

Continuous countercurrent tangential chromatography (CCTC) enables steady-state continuous bioprocessing with low-pressure operation and high productivity. CCTC has been applied to initial capture of monoclonal antibodies (mAb) from clarified cell culture harvest and postcapture polishing of mAb; however, these studies were performed with commercial chromatography resins designed for conventional column chromatography. In this study, a small particle size prototype agarose resin (20-25 µm) with lower cross-linking was co-developed with industrial partner Purolite and tested with CCTC. Due to increased binding capacity and faster kinetics, the resulting CCTC process showed more than a 2X increase in productivity, and a 2X reduction in buffer consumption over commercial protein A resins used in previous CCTC studies, as well as more than a 10X productivity increase versus conventional column operation. Single-pass tangential flow filtration was integrated with the CCTC system, enabling simple control of eluate concentration. A scale-up exercise was conducted to provide a quantitative comparison of CCTC and batch column chromatography. These results clearly demonstrate opportunities for using otherwise unpackable soft small particle size resins with CCTC as the core of a continuous bioprocessing platform.

Model Validation and Process Design of Continuous Single Pass Tangential Flow Filtration Focusing on Continuous Bioprocessing for High Protein Concentrations

In this study, the continuous Single-Pass Tangential Flow Filtration (SPTFF) concept is adapted for high protein concentrations. The work is based on the previously validated physico-chemical model for low concentrations and high viscosities. The model contains the Stagnant Film Model for concentration polarization, as well as the Boundary Layer Model for the mass transfer through the membrane. The pressure drop is calculated as a function of the Reynolds number. By performing preliminary experiments with a single ultrafiltration (UF) cassette, the model parameter are determined. The presented model is validated for a multi-step Single-Pass Tangential Flow Filtration. With subsequent simulation studies, an optimized process is found and confirmed by experiments. The outcome of this work shows the potential to optimize this multi-parameter dependent unit operation. This is reached by a model-based optimization allowing significant reduction of experimental efforts and applying the Quality by Design approach consistently. Furthermore, a comparison between the experimental setup and a commercial module is examined.