(582bf) Effect of Heterogeneous Cultivation Conditions On Mammalian Cell Productivity and Product Quality

The demand of therapeutic proteins like monoclonal antibodies (mAb) to treat cancer or chronicle diseases is increasing from year to year. Due to the required post translational modifications like glycosylation, mammalian cells are used exclusively to produce all currently approved mAbs. To fulfill the demand of the market, large-scale cell cultures up to 20000 L became industrial standard. Up scaling to those volumes becomes therefore a fundamental necessity to guarantee process performance, product amount and product quality. Apart from regular process parameters like temperature, pH or dissolved oxygen, it is of outmost importance to be aware of scale dependent parameters influencing the process. Reactor geometry, shear stress distribution, dissolved O₂ and CO₂distribution and gas mass transfer rates can be very different in between scales, resulting in non-desired variations of process performance when changing scales.

To study these parameters an experimental two zone model, capable of simulating such scale dependent parameters individually or in combination, was developed. The device consists of two fully controlled interconnected bioreactors capable of simulating shear heterogeneity, dissolved oxygen and carbon dioxid oscillations as well as pH perturbations. Parameters can be controlled individually with frequency, magnitude and exposure time adjusted to the condition of the desired large scale reactor. To demonstrate the capability of the system several case studies will be presented including the effect of i) different aeration strategies, applying different bubble sizes, oxygen fractions and gas flow rates, ii) the combined effect of DO oscillation and elevated hydrodynamic stress and iii) the heterogeneity of  pH via acid and base addition. Culture performance, the amount of produced mAb and its quality were monitored using state of the art analytical methods.

The obtained results indicate limitations of currently used lab scale bioreactors for process development and the influence of scale dependent parameters on productivity and product quality. In contrast the proposed system can be used to test the operating window of various process parameters under quasi production scale conditions and therefore provide better understanding on the effect of these parameters on the mammalian cell cultivation.