High cell density continuous culture of anchorage-dependent animal cells in a cylindrical depth filter perfusion system

Abstract

A depth filter perfusion system (DFPS) equipped with cylindrical depth filter was applied to high cell density continuous culture of anchorage-dependent animal cells. Whole cell enzyme immobilization using a depth filter was also investigated as an application of the DFPS. Cylindrical depth filters are widely used in industries handling fluids containing solid particles. Many household water purification systems also use these cylindrical depth filters which are disposable and inexpensive, and have good filtration performances. An important feature of depth filters is that captured particles are distributed homogeneously in the filter matrix, which improves particle removal efficiency and makes long-term operation possible without filter clogging. The DFPS filter units are available commercially in large quantities at a reasonable price and they are also uniform in quality. In addition, the DFPS provides advantages of high surface-to-volume ratio of 450-600 ㎠/㎤, low cost set-up, easy operation and scale-up. To identify the basic characteristics of the DFPS, residence time distributions, surface modifications by coating various materials and oxygen transfer properties by bubble aeration were investigated. From the analysis of residence time distributions, the DFPS exhibits a plug flow behavior with some dispersion. In the 20 and 40 ㎛ filter, increase of the circulation rate did not affect significantly to the mixing patterns. However, in the 70 ㎛ filter, dispersion of the fluid decreased as increasing the circulation rate. Surface modification by gelatin coating increased the cation and anion exchange capacities of the depth filter and promoted the attachment rate of the cells tested onto the filter surfaces. Pluronic F-68 containing medium and sparging with the micron-size filter could supply enough oxygen to support a cell concentration in the order of $10^8$ cells/ml, theoretically. Vero cells and recombinant CHO cells were cultivated in the DFPS to test the ...