GROWTH-KINETICS OF ANIMAL-CELLS IMMOBILIZED WITHIN POROUS SUPPORT PARTICLES IN A PERFUSION CULTURE

The growth kinetics of anchorage-independent animal cells [mouse myelo ma MPC-11 (ATCC CCL 167)] immobilized within porous polyvinyl formal r esin biomass support particles (BSPs; 3 x 3 x 3 mm cubes; mean pore di ameter, 60 mu m) was analyzed by measuring intracellular and extracell ular lactate dehydrogenase (LDH) activities in a perfusion culture. Fi rst, the intracellular LDH content of cells immobilized within the BSP s was assayed in a shake-flask culture and found to remain almost comp arable to that of nonimmobilized cells in the exponential growth phase under static culture. Then, cells inoculated in the BSPs were grown i n a continuous stirred-tank bioreactor. Using the LDH content of non-i mmobilized cells, the density of immobilized cells and the numbers of leaked and dead cells were evaluated, respectively, by the intracellul ar LDH activity of immobilized and leaked cells and the LDH activity i n cell-free culture supernatant. In the initial period, immobilized ce lls exhibited exponential growth at a constant apparent specific growt h rate; however, the actual specific growth rate, which takes into con sideration cell death and cell leakage, decreased significantly. In th e stationary phase, the actual specific growth rate maintained a const ant but markedly lower value than during exponential growth.