Application Of Computational Fluid Dynamics In Bioreactor Scale-Up

Computational Fluid Dynamics (CFD) was introduced to investigate the scale-up process of bioreactor and its optimization, for the purpose of combining the engineering factor and biological factor. This approach was focused on issues as oxygen dissolving, shear stress and mixing efficiency related to bioprocessing.CFD method was applied to study hydrodynamic properties of a54m3stirring tank. The simulation result was obtained, which represent the mid-stage fermentation with non-Newtonian behavior. For solving such problem as weak axial flow, a cutting-edge impeller was come out. The principal style of the impeller was the asymmetric design, with upper blades slightly longer than lower blades. This new type of impeller could coerced the liquid-gas flow down forward at the center part near the axial, thus enhance the axial flow as well as improving the flow pattern in the bottom of fermenters.In this paper, a novel airlift bioreactor was also designed. A cylindrical airlift bioreactor was constructed of transparent Plexiglas that contained a vertical cylinder as the draft tube and porous spargers underneath the bioreactors for air supply. Stainless steel brackets were fixed in the cylinder as sustainable frame for fiber nets, which serve as immobilizing substrates for Rhizopus. With densely covered with Rhizopus., fiber nets formed baffle that played a deflector role in the liquid-gas flow. With CFD simulated optimization, the spacing between baffles was50mm, the cut height of baffle was25%and the orientation between layers was180°. Then the operating parameters were investigated, as the optimum aeration rate was0.9VVM. Comparative validation of overall gas holdup and average bubble residence time between experimental and simulated value showed that CFD simulations would correspond with the real situation.