Animal cell lines (the dominant expression systems in biopharmaceutical production processes) are mostly cultivated in stirred bioreactors (1). Although such bioreactors are widely accepted and applicable over a wide range of scales, engineering data for these systems are still lacking. Nevertheless, studies have shown that the correct choice of key parameters (e.g., power input, tip speed, mixing time, and oxygen mass transfer) can influence the growth of animal cell cultures (2). Therefore, detailed characterization is essential. It enables reliable scaling…