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.

Gas Dispersion in Non-Newtonian Fluids with Mechanically Agitated Systems: A Review

“…Sliding mesh is a transient approach and usually predicts the fluid flow with the best agreement against experimental data, requiring a higher computational effort. Nevertheless, the prediction of global hydrodynamics variables is not significantly sensitive to the approach employed for the modeling of the impeller rotation, so that MRF is more computationally efficient as reported by Cappello et al [16].…”

“…It is worth mentioning that the CFD simulations need to be validated using experimental data because of the assumptions and closure models [7]. The accuracy of the model for lab-scale gas-liquid mixing systems is often evaluated in terms of the measured gas holdup and power consumption [16,29,33]. Once it is validated using the experimental data, other process conditions and design parameters can be simulated.…”

“…The relative power demand was predicted with an accuracy of approximately 10%, whereas the accuracy of the volumetric mass transfer coefficient correlation was approximately 20%. Computational fluid dynamics simulations can also be used to analyze the effect of the vessel size on the design variables [16]. In fact, the comprehensive analysis of the hydrodynamic behavior throughout the vessel in different scales is highly desired to have a better understanding of the fluid flow upon scaling-up.…”

“…Although fewer studies refer to the aeration of non-Newtonian fluids, a broad range of industrial applicability can still be observed in food, chemical, biochemical, pulp and paper, and painting industries [11]. More specifically, gas dispersion in non-Newtonian fluids with shear-thinning characteristics can be encountered in antibiotic and polysaccharide production, fungal fermentation, wastewater treatment, and cell culture [12][13][14][15][16].…”

Influence of Interfacial Force Models and Population Balance Models on the kLa Value in Stirred Bioreactors

“…The most commonly used bioreactors in both process development and commercial production are stirred bioreactors with forced aeration. Both computational fluid dynamics (CFD) and classical process engineering approaches are used for optimization and scaling-up of stirred bioreactor processes [3][4][5][6]. CFD is based on the laws of conservation of energy, mass, and momentum.…”