Why we all divide between ATF and TFF

Both concepts – ATF and TFF mode of operation - see broad use in the pharma industry. These are the conceptual differences.

Alternating-Tangential-Flow – ATF - a method for perfusion mode operation for continues cultivation under semi-steady-state conditions. Sequentially a broth portion (feed solution) is taken from the bioreactor and alternating (reciprocating) pass the porous membrane. The membrane insure cells in the broth is kept inside the broth (bioreactor) allowing the product to pass the membrane. Most of the broth is circulated back to the feed SUB, STR as retentate.

ATF mode of operation benefit from a Laser controlled alternating diaphragm pump such as the scalable Thalia from www.perfusecell.com able to keep the HFF clean.

Tangential-Flow-Filtration – TFF - a separation method based on range of devices, which allow selected components under pressure to pass (tangentially) from one liquid volume into another liquid volume crossing the “membrane” (cross-flow-filter). In Tangential-Flow-Filtration, a pump drives the feed solution to constantly flow parallel to the surface of the porous membrane. Driven by pressure, some of the feed solution passes through the membrane filter as permeate. Most of the broth is circulated back to the feed SUB, STR as retentate.

TFF mode of operation benefit from the scalable Clio Laser controlled diaphragm O-SUP able to keep the HFF clean.

LowRider vessels bottom broth outlet supports efficient connections to Single-Use-Pumps, which are not able to suck broth up via a deep-tube through the headplate. Thus forced into the TTF mode of operation.

Retention Filters in general

Several concepts, products, manufactures exist for upstream cell retention purposes. The use of mammalian cell lines for expression of mAbs is huge and in general serving the same purpose - lower the cost of product. Two methods are well established:

• Alternating Flow Filtration (AFF) involves broth alternating along the surface of the membrane. 
• Tangential Flow Filtration (TFF) involves one direction flow of the broth along the surface of the membrane. 

Cross-Flow-Filter (CFF) is a broad covering technology involving a porous membrane, which allow selectable components under some pressure difference to pass from one liquid volume into another liquid volume crossing the membrane, the porous barrier restricting other components from passing the membrane.

Hollow-Fiber-Filter (HFF) modules is a popular membrane product based on multiple of in parallel arranged extruded hollow straw, lumen arranged inside a plastic tube creating the cartridge. A pump force broth flow inside and along the porous wall lumen from inlet to outlet. Product harvest is transverse to the lumen wall.