Background
Currently, stirred tank reactors (STR) represent the gold standard for the large scale growth of suspension cell lines. Culture performance is strongly influenced by the efficiency of mixing, as measured by the mass transfer coefficient and mixing time. The success of traditional stainless steel or glass STR systems lies in their impeller driven agitation that efficiently mixes large volumes of culture fluid. However, the transition from stainless and glass STR vessels to single use STR systems still remains a challenge, particularly in terms of replicating efficient mixing. Many single use STRs use magnetically coupled driving mechanism to eliminate the risks of biocontainer leaks from rotating mechanical seals. While this design mitigates the risks of compromising sterility, insufficient magnet strength limits the power that can be transmitted to the culture fluid, and often results in poor mixing and mass transfer performance.