A novel centrifugal impeller bioreactor. I. Fluid circulation, mixing, and liquid velocity profiles

A novel centrifugal impeller bioreactor for shear-sensitive biological systems was designed by installing a centrifugal-pumplike impeller in a stirred vessel. The fluid circulation, mixing, and liquid velocity profiles in the new bioreactor (5-L) were assessed as functions of the principal impeller designing and bioreactor operating parameters. The performances of the centrifugal impeller bioreactor were compared with those of a widely used cell-lift bioreactor. The newly developed bioreactor showed higher liquid lift capacity and shorter mixing time than the cell lift with comparable dimensions. Furthermore, the experiments of the liquid velocity profiles around an impeller region indicated that the centrifugal impeller bioreactor produced lower shear stress than the cell lift. This conclusion was also supported by evaluating the changes in size distributions of granulated agar particles that were sheared with those two types of impeller.