MRI hydrodynamic characterization of an ambr15® bioreactor

Abstract

This work presents the first use of magnetic resonance imaging (MRI) velocimetry to study the flow field inside an ambr® microscale bioreactor. Scale-down bioreactor systems have become popular in order to meet the key biopharmaceutical development goals of reduced costs, accelerated process development timelines and increased productivity. Scalable cell growth characteristics have been reported for the 15 mL ambr®; however, the vessel configuration is dissimilar to that of large scale bioreactors. This results in different fluid dynamics and flow properties, which will influence both mixing and mass transfer. Investigations into the hydrodynamics of the ambr® system and its variation throughout a cell culture run are therefore of interest. MRI provides a non-invasive method for the highly accurate visualisation of these hydrodynamics. Through the use of MRI velocimetry it is shown that the asymmetric vessel geometry and positioning of the impeller and gas sparge tube appear to reduce vortex formation and create flow profiles more typical of larger scale, baffled, cylindrical bioreactors. Volumetric changes and impeller pumping direction are found to have a greater influence on the flow pattern than impeller speed and aeration. At increased suspension densities, dead zones and surface effects are seen.