EVALUATION OF MEMBRANES FOR USE IN ONLINE CELL-SEPARATION DURING MAMMALIAN-CELL PERFUSION PROCESSES

In this study two microporous hollow fibre membranes were evaluated fo r their use as cell retention device in continuous perfusion systems. A chemically modified permanent hydrophillic PTFE membrane and a hydro philized PP membrane were tested. To investigate the filtration charac teristic under process conditions each membrane was tested during a lo ng term perfusion cultivation of a hybridoma cell line. In both cultiv ations the conditions influencing membrane filtration (e.g. transmembr ane flux) were kept constant. Filtration behaviour was investigated by monitoring transmembrane pressure and protein permeability. Transmemb rane pressure was measured on-line with an autoclavable piezo-resistiv e pressure sensor. Protein permeability was determined by quantitative evaluation of unreduced, Coomassie stained SDS-PAGE. The membrane fou ling process influences the filtration characteristic of both membrane s in a different way. After fermentation the PP membrane was blocked b y a thick gel layer located in the big outer pores of the asymmetric m embrane structure. The hydraulic resistance was higher but the protein permeability was slightly better than of the PTFE membrane. For this reason the PP membrane should be preferred. On the other hand, transme mbrane pressure decreases slower when the PTFE membrane is used, which favours this membrane for long term cultivations, especially when low molecular weight proteins (<30 KD) are produced.