Performance of small-scale CHO perfusion cultures using an acoustic cell filtration device for cell retention: Characterization of separation efficiency and impact of perfusion on product quality

Several small-scale Chinese hamster ovary (CHO) suspension cultures were gr own in perfusion mode using a new acoustic filtration system. The separatio n performance was evaluated at different cell concentrations and perfusion rates for two different CHO cell lines. It was found that the separation pe rformance depends inversely on the cell concentration and perfusion rate. H igh media flow Fates as well as high cell concentrations resulted in a sign ificant drop in the separation performance, which limited the maximal cell concentration achievable. However, packed cell volumes of 10% to 16% (corre sponding to 3 to 6 . 10(7) cells/mL) could be reached and were maintained w ithout additional bleeding after shifting the temperature to 33 degrees C. Perfusion, up to 50 days, did not harm the cells and did not result in a lo ss of performance of the acoustic filter as often seen with other perfusion systems. Volumetric productivities in perfusion mode were 2- to 12-fold hi gher for two cell lines producing two different glycoproteins when compared to fed-batch or batch processes using the same cell lines. Product concent rations were in the range of 20% to 80% of batch or fed-batch culture, resp ectively. In addition, using the protease-sensitive product rhesus thrombop oietin, we could show that cultivation in perfusion mode drastically reduce d proteolysis when compared to a batch culture without addition of protease inhibitors such as leupeptin. (C) 2000 John Wiley & Sons, Inc.