split airlift bioreactor for continuous culture of Glycyrrhiza inflata cell suspensions

In this study, we established a perfusion split airlift bioreactor coupled with a cell retention device (CRD) and tested for the production of Glycyrrhiza inflata cell suspension cultures. The main components of the CRD were two steel membrane filters and a bidirectional-pump. The results indicated that cells could effectively be separated from the medium by using 200-μm-pore membrane filters. When the bioreactor was operational, liquid was rotated in both the reaction column and the CRD. The frequency with which the direction of liquid circulation changed in the CRD was a key factor for ensuring that the membrane was clean and the filter remained unclogged. This was achieved even at high cell densities, when the direction of liquid circulation in the CRD changed every 5 min. Nevertheless, liquid circulation mode in the reaction column was disturbed to some extent by the fast rotation of the bidirectional-pump, which worked against mass transfer and cell growth. Under appropriate conditions the bioreactor system operated smoothly and the maximum cell concentration of 27.2 g L⁻¹dry weight was attained.