Hydrodynamics in a disposable rectangular parallelepiped stirred bioreactor with elliptic pendulum motion paddle

Abstract

Stainless steel bioreactors increasingly give way to their disposable counterparts in pharma research as no cleaning or sterilisation is required. This led company ATMI LifeSciences to develop the "Nucleo TM ". Original in design, this disposable bioreactor comprises a rectangular parallelepiped plastic bag stirred by a paddle revolving in elliptic pendulum motion. Studies covering this bioreactor showed good homogeneity of culture medium as well as good productivity for animal cell cultures. To further explain these good performances, the flow inside the "Nucleo TM " must be resolved. This paper focuses on the mean flow description, computed from stereo-PIV measurements performed in 20 vertical covering the whole volume of a 50 dm³ Nucleo TM bioreactor. As the flow is already turbulent in the chosen agitation conditions, its dimensionless mean velocity field does not vary with the paddle rotational speed. Mean flow pattern exhibits an axial symmetry -same flow is observed in opposite quarters of the tank -and can be described as a three-dimensional helix coiled on itself to form a distorted horizontal torus which covers the whole tank volume. Mean velocity is on average twice higher in the cone swept by the paddle and its two horizontal components are twice the vertical one. However, mean velocity remains significant everywhere and, in particular, no stagnant area is observed in tank corners. Above outcomes thus confirm previous studies observations.