Continuous production of tissue plasminogen activator (t-PA) by human embryonic lung diploid fibroblast, IMR-90 cells, using a ceramic bed reactor

Abstract

Ceramic pieces composed of 99.5% Al₂O₃, 3 to 6 mm long, were found to be a good matrix for growth of the human embryonic lung diploid fibroblast, IMR-90 cells. The tissue plasminogen activator (t-PA) was secreted in DME medium containing proteose peptone as a t-PA inducer. In addition, production of t-PA was enhanced by increasing extracellular CaCl₂, from 3.6 to 5.4 mM. In order to eliminate negative feed-back control caused by t-PA produced and thus raise productivity, perfusion cultivation was performed using a ceramic-packed bed column, with a recirculating vessel. The recirculating vessel was used to mix fresh medium with spent medium, and to control dissolved oxygen concentrations in the extracellular environment by stirring. In continuous production using the packed bed column with 2 kg of ceramics (Ø=H=150 mm), increasing dilution rate to 0.5 day^-1 could reduce product inhibition at 3–4×10⁵cells/ml. Cellular productivity of 560 IU/10⁶cells/day was obtained over 40 days and corresponded to the volumetric productivity of 183 IU/ml/day.