Dynamic mixing protocol for mixing enhancement in unbaffled bioreactor with eccentric bottom-mounted impeller

• Periodically reversing impeller direction reduces vortex mixing time by up to 93%. • Dynamic mixing protocol (DMP) does not increase the risks for shear-sensitive batch. • Optimized DMP improves mixing characteristics at reduced power demands. • CFD model is capable to characterize the effects of DMP on mixing characteristics. The study introduces a novel mixing approach for industries requiring sterility, easy cleanability, and low shearing . It aims at an ultrapure mixing configuration comprising an unbaffled cylindrical vessel with an asymmetrically placed levitating impeller . However, that solution may be prone to forming a poorly mixed central vortex region worsening its overall mixing characteristics. To eliminate these adverse effects, a dynamic mixing protocol consisting of periodic changes in the impeller speed and direction is developed. Experiments conducted in a pilot-scale vessel (60L) confirm that this method eliminates the poorly mixed zone and reduces homogenization time by more than 50 % compared to a fixed-speed impeller. Additionally, numerical simulations reveal no excessive shearing due to speed and direction changes. It is shown that dynamic mixing protocol allows for significant improvement in vessel mixing characteristics while maintaining gentle handling of shear-sensitive materials.