Continuous mAb: perfusion bioreactor into TFF concentration

The upstream and downstream halves of a biologics process on one canvas. A perfusion bioreactor produces a cell-free harvest, and the antibody in it is then concentrated by tangential-flow filtration — the step every biologics process ends with.

The membrane is a per-species rejection, which is what makes UF/DF a genuine steady-state unit rather than something that has to be pretended into one: the antibody is fully retained while the spent substrate and lactate pass freely into the permeate. The split is not asserted — it follows from the concentration target, and the flux the membrane can actually deliver at the resulting wall concentration is what sets the area.

The polarization is the point. Retained protein piles up at the membrane wall far above the bulk, and it is the wall concentration that sets the osmotic back-pressure — which is why ultrafiltration flux plateaus with pressure instead of rising with it, and why a specified-recovery membrane model cannot represent this step at all.

Bounded, and inherited from the underlying model: no fouling or time-dependent resistance growth, and the virial coefficients that set a protein's osmotic pressure are caller inputs because they are measured per protein per formulation — no protein databank ships with this.