Scale-up of a monoclonal antibody CHO fed-batch production in stirred tank bioreactors: Effect of hydrodynamic conditions and feeding regimen.

Key hydrodynamic-related parameters such as volumetric power input (P/V), impeller configuration, aeration strategy, and maximum gas sparge rate, as well as an appropriate feeding strategy, must be carefully selected to improve production yields in bioreactor. In this study, the feeding regimen was found to have an important impact on cell growth and productivity of a cumate-inducible CHO fed-batch cell culture. A low-volume feeding regimen avoided a rapid increase in osmolality, allowing for prolonged cell viability and a 33% increase in volumetric titer compared to the high-volume feeding regimen. Both sparged air and oxygen were used for dissolved oxygen (DO) control, utilizing three levels of airflow rates. An optimum airflow rate of 0.0031 vvm was found to improve cell growth, longevity, and thus final titer. A larger air cap required increased gas flow rates, which led to an earlier cell mortality. Scale-up from 1-L to 10-L bioreactor using constant P/V and air cap volumetric gas flow rate (vvm) allowed for comparable cell growth and productivity. Further investigation of the effect of mixing and aeration was done by maintaining P/V and vvm constant throughout the cell culture, which further improved product titers at 11 days after induction. Our study also demonstrates that keeping a constant volume by removing a culture amount equal to the feed volume added at each sampling event can significantly improve the final volumetric titer. This finding shows the benefit of developing a concentrated feed to reduce the volume increase, which in turn could greatly ease the scale-up task.