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BioProcess Filtration

Filtration steps are included on many levels in the purification of biomolecules—from clarification of crude cell culture broth all the way to concentration of the final product. Different filtration steps require different techniques and solutions.

The purification of biomolecules generally involves several crossflow filtration (CFF or TFF) and/or normal flow (NFF or dead-end) filtration steps combined with chromatographic separations. Both CFF and NFF separations can be carried out with reusable as well as single-use products.

Membrane Filtration Crossflow Filtration Normal Flow Filtration Single-Use Filtration

Filtration-based separations are frequently required in the bioprocess workflow as well as in agricultural, environmental, and pharmaceutical applications. The nature and type of filtration membrane used is crucial for successful recovery or purification.

Choose your pore size

Membrane filters retain matter primarily due to differences between the size of the molecules you wish to recover and the size of the membrane filter pores. Filtration processes are thus classified according to the size ranges of the target molecules, e.g., microfiltration and ultrafiltration.

The picture to the right shows relative sizes of biological materials and common materials along with the suitable separation processes (click to enlarge).


Choose your flow type

Filtration membranes can also be of different types depending on the flow directions of the feed stream relative to the purified liquid that passes through the membrane, the permeate. Both crossflow filtration (CFF or TFF) and normal flow filtration (NFF) are positive barrier separations allowing optimal performance with a wide variety of feed stream conditions and constituents.

Both crossflow and normal flow filtration technologies purify bioprocess solutions by removing contaminants with a fixed, porous medium, yet each format has its own unique advantages. Read more about crossflow filtration, normal flow filtration, and single-use filtration technologies on the adjacent tabs.


In crossflow (or tangential flow) filtration, the feed stream moves in parallel to the membrane surface. Purified liquid (permeate or filtrate) passes through the membrane, while most of the particulates and aggregates are carried away by the crossflow.

Unlike normal flow/dead-end/single pass filtration, crossflow filtration continuously sweeps the membrane surface by circulating the feed stream across it. This circulation minimizes blinding of the membrane, where particles fill the membrane pores, and promotes consistent, long-term productivity. It also allows filter units to be cleaned, stored, and re-used as needed.
Crossflow filtration (CFF or TFF) is best suited for:

  • Higher solid streams
  • More viscous feed solutions
  • Concentrating or purifying cells or target molecules
  • Continuous processes

For further information on when to select crossflow or normal flow filtration, respectively, please contact your local GE Healthcare representative who can help you find the optimum configuration for your specific operation needs.

In normal flow filtration, the feed stream moves perpendicular to the membrane surface and purified liquid, permeate or filtrate, passes through the membrane. Particulates and aggregates remain behind as a “filter cake”. When particles fill the membrane pores, the membrane is blinded, reducing flow and/or increasing pressure over time.

In general, normal flow filtration (NFF) is used for:

  • Clarification and/or bio-burden reduction in relatively low solid streams
  • Protecting or enhancing downstream operations
  • Final polishing to achieve sterility
  • Batch runs

For further information on when to select crossflow or normal flow filtration, respectively, please contact your local GE Healthcare representative who can help you find the optimum configuration for your specific operation needs.

Disposable filtration devices are widely used throughout the bioprocessing workflow. Eliminating the need for cleaning, single-use products save you time and money while minimizing contamination.

Learn more about single-use filtration

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