Scale-up of aerated bioreactors: CFD validation and application to the enzyme production by Trichoderma reesei

Abstract

The application of Computational Fluid Dynamics to aerobic fermentations faces several issues, such as validation of multiphase models at high gas holdup and with complex liquids under turbulent condition. In this work, the Eulerian two-fluid model framework was adapted to simulate the enzyme production by the filamentous fungi T. reesei. Due to scarcity of data on turbulent mixing in complex fluids, every aspect of the numerical model (turbulence model, drag force law, rheology model, etc.) needed to be validated. First, the adequacy of the model was evaluated by the mean of comparison with new and previous experimental data in non-Newtonian aerated systems. Once coupled with an apparent oxygen and substrate uptake kinetics, the model was used to investigate the effect of scale-up on the enzyme productivity from biomass. Fully predictive results highlighted complex behaviors, such as: possible substrate heterogeneities, yield loss, and non-obvious interactions between mixing and oxygen transfer limitations.