Renewed interest in perfusion technology has grown in recent years as the drive for higher product yields and faster process development continues to push the boundaries of what is achievable by today’s fed-batch processes. Robust and scalable cell retention device remains a challenge in perfusion systems. Of the two filtration systems commonly used, Tangential Flow Filtration (TFF) systems often have inferior performance compared to Alternating Flow Filtration (ATF) systems. This study demonstrates that the pump shear, and not the alternating flow, is largely responsible for the performance difference.<br/><br/>A TFF system is an attractive perfusion option due to its scalability and relatively low complexity; however, TFF systems often suffer from poor product sieving and membrane fouling. Refine Technology’s Alternating Tangential Flow (ATF) perfusion system utilizing a low shear diaphragm pump offers an alternative to traditional unidirectional TFF systems. The ATF retention system and controller are, however, more complex. In direct comparisons against an ATF, the TFF with a peristaltic pump saw worse cell growth and product recovery, which was attributed to higher rates of cell lysis. An experimental model of product sieving utilizing different sized cellular debris identified a specific particle size range that contributed to the product sieving phenomenon. The particle concentration was up to 4.4 times higher and the cell lysis as measured by LDH levels was up to 7.3 times higher in TFF systems compared to ATF systems. The peristaltic pump was demonstrated to be the single major contributor to shear stress and cell lysis in a TFF setup. A centrifugal pump was subsequently identified as being a viable low shear replacement for the peristaltic pump. Using such a pump, cell growth, cell lysis, particle concentration, and product sieving were then comparable between the TFF and the ATF systems. These results provide a correlation where poor product sieving can be partly explained by high shear in perfusion systems. Low shear TFF systems are a feasible alternative to ATF systems.

Shear contributions to cell culture performance and product recovery in ATF and TFF perfusion systems

249th National Meeting (2015)

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