Figure 4.

Schematic illustration of the bioreactor perfusion circuit.

Notes: The tubing system contains two independent pumps for medium recirculation through the bioreactor and fresh medium feed, respectively, while rinsing out of used medium is driven by hydrostatic pressure increase (red, bioreactor-inflow tubing; blue, bioreactor-outflow tubing). The bioreactor disposes of two medium-perfusion capillary systems, which are countercurrently perfused to enhance mass exchange. Each capillary layer consists of alternating medium and oxygen capillaries, with cells being cultured in the space between the capillaries. Cells are inoculated via a separate tube line. An electronically controlled gas-mixing unit provides defined flow rates of air and CO₂ and allows for regulation of gas concentrations in the supplied gas mixture (gray lines). The temperature in the bioreactor chamber is constantly kept at 37°C via an electronically controlled heating unit.