A novel scale-up strategy for cultivation of BHK-21 cells based on similar hydrodynamic environments in the bioreactors

The scale-up of animal cell cultivation is important but remains complex and challenging. In the present study, we propose a novel scale-up strategy for baby hamster Syrian kidney-21 (BHK-21) cell cultivation based on similar hydrodynamic environments. The hydrodynamic characteristics of the different scale bioreactors were determined by computational fluid dynamics (CFD) and further correlated with the agitation speed. The optimal hydrodynamic environment for cell cultivation and vaccine production was determined from the cultivation experiments of BHK-21 cells in 5-L laboratory-scale bioreactors equipped with different impellers at various agitation speeds. BHK-21 cell cultivation was scaled up from 5-L to 42-, 350-, and 1000-L bioreactors by adjusting the agitation speed to make the hydrodynamic features similar to those in the 5-L bioreactor, especially for the shear rate in the impeller zone (gamma(imp)) and energy dissipation rate in the tank bulk zone (epsilon(tan)). The maximum cell density and cell aggregation rate in these scaled-up bioreactors were in the range of 4.6 x 10(6) similar to 4.8 x 10(6) cells/mL and 16 similar to 20%, which are comparable to or even better than those observed in the 5-L bioreactor (maximum cell density 4.8 x 10(6) cells/mL, cell aggregation rate 21%). The maximum virus titer of 10(8.0) LD50/mL achieved in the 1000-L bioreactor was close to 10(8.3) LD50/mL that obtained in the 5-L bioreactor. Hence, the scale-up strategy proposed in this study is feasible and can efficiently facilitate the scale-up processes of animal cell cultivation.