2007

Cuperus, S.; Eibl, R.; Rischer, Heiko; Oksman-Caldentey, Kirsi-Marja; Cusidó, R. M.; Pinol, M. T.; Eibl, D.

The superiority of low-cost and disposable bioreactors with a gas-permeable cultivation bag of plastic film was effectively proven in a number of plant cell cultivations. The single-use cultivation bags are partially filled with medium, inoculated with cells, and discarded after harvest. This makes cleaning and sterilization in place unnecessary and guarantees high flexibility as well as process security with contamination levels below 1%. The BioWave reactor being the first mechanically driven, scalable bag reactor has a leading position among disposable bioreactors. Due to the rocking movement of the platform the surface of the medium is continuously renewed and bubble free surface aeration takes place. In the BioWave we found that the modified Reynolds number, the mixing time, the residence time distribution, the oxygen transfer efficiency and the specific power input is dependent of the rocking angle, the rocking rate, the culture bag type (CultiBag) and its geometry, as well as the filling level. Mixing times between 10 and 1400 s were determined. Experiments which focused on residence time distribution have demonstrated that a continuously operating BioWave in perfusion mode can be described by the ideally mixed stirred tank model. Oxygen transfer coefficients achieved in the BioWave reached comparable or even higher values than those which have been reported for stirred, bubble-free aerated or surface aerated bioreactors. Moreover, our studies reveal the potential of the BioWave for cultivating tobacco, grape, apple and yew suspension cell cultures as well as hairy root cultures of devil's claw, Egyptian henbane and Asian ginseng. We worked with culture volumes from 0.4 to 10 L (suspension cultures) and 0.5 to 5 L (hairy root cultures). For secondary metabolite-producing or protein-expressing plant suspension cells, we achieved maximum biomass productivities of 40 g fw L-1 d-1 and excellent doubling times of 2 days. Finally, the paclitaxel productivity accomplished in BioWave with immobilized Taxus suspension cells is one of the highest reported so far by academic researchers for Taxus species cultures in bioreactors. Encouraging results were also obtained for hairy roots cultivated in ebb-and-flow mode. We regularly achieved biomass productivities and product yields of specific hairy root clones in the BioWave operating with a 2 L CultiBag specific which were two to three times higher than in tested spray reactors.