Overcoming downstream bottlenecks with single-pass tangential flow filtration

SPTFF case study—Introduction/challenge

Continuous increases in upstream productivity mean many manufacturers are finding downstream processes have become the new bottleneck. Higher product titers are placing increased pressure on filtration and chromatography steps, driving the need for more efficient downstream process strategies.

For AGC Biologics, the challenge was clear: How do you handle growing process demands while improving manufacturing efficiency, supporting process intensification strategies, and reducing cost of goods (COGs)?

To overcome these challenges, AGC Biologics evaluated single-pass tangential flow filtration (SPTFF), a technology that minimizes operational volumes and optimizes process time by concentrating product in-line in a single pass. By eliminating recirculation, SPTFF can reduce processing time, minimize operational volumes, and simplify integration between upstream and downstream operations. These capabilities make it a promising approach for organizations looking to intensify manufacturing and enable more continuous processing strategies.

Solution: Evaluating SPTFF for in-line concentration

To address downstream concentration challenges, AGC Biologics evaluated a four-in-series SPTFF technology based on our SPTFF modular kit, Centramate™ filter holder, and seven T-series Centramate cassettes with a 30 kDa Omega™ PES membrane.

The team wanted to determine whether SPTFF could deliver the concentration factors required for intensified manufacturing while maintaining process throughput, product recovery, and product quality.

Using a model monoclonal antibody (mAb1), AGC Biologics evaluated the impact of:

• Feed concentration
• Feed flow rate
• Feed pressure
• Retentate pressure

The goal was to identify operating conditions that would support high in-line concentration performance while remaining compatible with continuous downstream processing (Table 1).

Table 1. Summary of selected SPTFF experimental runs with mAb1

Results: High concentration factors with high recovery

The study demonstrated that SPTFF can effectively address one of the key challenges associated with intensified manufacturing, that is, achieving significant in-line concentration without sacrificing productivity or product quality.

Across all conditions tested, concentration performance increased predictably with retentate pressure, providing a straightforward way to control process outcomes. This near-linear response was consistent for all feed concentrations evaluated (Fig 1).

Fig 1. Concentration response to retentate pressure at different feed concentrations. (A) Total protein concentration achieved with different feed concentrations at varying retentate pressures. (B) Concentration factor achieved under these same conditions.

Depending on the starting feed concentration, AGC Biologics achieved concentration factors ranging from 10× to 40× while operating at feed fluxes compatible with in-line processing between chromatographic steps.

For lower-concentration feeds (~ 1.0 g/L), the team achieved concentration factors of approximately 40× at a retentate pressure of 0.6 bar (8.7 psi, 0.06 MPa). Concentrations of 10× were also easily achieved without applying back pressure. Higher-concentration feeds (~ 5.0 g/L) were concentrated to more than 60 g/L, resulting in up to 13× in a single pass.

In-line concentration occurred at competitive feed flows (92 to 138 LMH), ensuring short processing times compatible between chromatographic steps. Feed flow is conditioned directly by feed concentration; higher concentrations increase viscosity and system feed pressures.

Overall process performance met expectations across all runs, with a summary of two representative runs provided in Table 2. Both feeds (1 g/L and 5 g/L) maintained a stable concentration factor of approx. 10× and achieved high total recoveries comparable to traditional TFF, consistently reaching ≥ 95%.

Table 2. Summary of performance of selected SPTFF runs with mAb1

Fig 2. Size exclusion chromatography (SEC) data from mAb1 subjected to different SPTFF conditions. (A) Data from a run with feed at 1 g/L. (B) Data from a run with feed at 5 g/L.

Utilizing a single-pass approach maintained high product quality, with no increase in high molecular weight (HMW) or low molecular weight (LMW) species. This confirms that the reduced shear stress of SPTFF protects critical quality attributes (CQAs).

As shown in Figure 2, neither feed concentration (1 g/L or 5 g/L) exhibited significant increases in HMW species in concentration factors of 10×, with the 1 g/L feed concentrated up to 40× without negative impacts on product quality as assessed by SEC.

Conclusion

For manufacturers seeking to intensify operations and for continuous bioprocessing, downstream concentration can become a critical challenge.

Through implementation of in-line SPTFF, AGC Biologics demonstrated a practical approach to overcoming this bottleneck. The technology enabled in-line concentration factors of 10× and 40× in-line while maintaining product recoveries greater than 95% and preserving product quality.

By reducing reliance on recirculation-based concentration, SPTFF helped minimize processing volumes, shorten processing time, and support integration between unit operations. These benefits make SPTFF a valuable option for organizations looking to improve manufacturing efficiency, reduce COGs, and support increasingly high-titer processes.

While this case study focused on a mAb, the approach can also be applied to emerging modalities including mRNA, viral vectors, and other complex biologics, thereby facilitating a smoother transition to high-titer, continuous manufacturing.

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