(611b) Tangential Flow Filtration for Bioreactor Clarification of Cell Lysates for Recovery of Adeno Associated Virus (AAV)

Tangential flow filtration has many advantages for bioreactor clarification as the product stream could be introduced directly to the subsequent capture step. However direct harvest of cell lysates by tangential flow filtration is challenging as cell lysates are particularly fouling. Further clarification of cell lysates is sometimes unavoidable as is the case here for recovery of adeno associated virus (AAV) the majority of which is intracellular. Previous studies have investigated the use of integrated processes such as tangential flow filtration and depth filtration, tangential flow filtration and centrifugation etc. Here we have investigated the use of reverse asymmetric membranes used in the Asahi Kasei Bioprocess BioOptimal MF-SL filter. These asymmetric membrane have a more open pore structure that face the feed stream (pore size up to 40 mm ) whereas the tighter barrier layer (pore size ~ 0.4 mm) faces the permeate. We show that successful operation (recovery of AAV and minimizing turbidity of the permeate) depends on ensuring the rejected cell debris forms a porous cake within the more open membrane structure that faces the feed. This involves operating at below the critical flux and at low transmembrane pressures. Our results suggest that by carefully controlling operating conditions, direct filtration of cell lysates may be feasible.