Bioreactor Performance and Design of Large Scale Packed-Bed Solid-State Fermentation

Abstract

Bioreactor performance and design was investigated by simulating a transient two-dimensional heat transfer model. The model was able to describe the microbial growth and death kinetics and the energy balance in both axial and radial directions at any location in packed-bed solid-state fermentation. The emphasis of heat conduction, convection and the effect of evaporation made the model particularly useful and practical for large-scale investigation in which the overheating is critical. The system was simplified by assuming pseudo- omogeneous and constant values of bed physical and thermal properties. Orthogonal collocation technique was applied to solve the equations. The characteristic of temporal temperature and biomass concentration profiles in two dimensions were predicted. The effects of various design and operating variables on the performance of the 10 m³ were explored, with the aim of identifying strategies to minimize overheating at the top of the bed. Superficial velocity and inlet air temperature were found to have significant effects on the bioreactor performance. Superficial velocities of 0.08 to 0.1 m/s are required for effective convective heat removal. A low inlet air temperature (308 to 312 K) leads to overheating after 10-20 h which cause all organisms to die. The geometric ratios of 1.0 and below minimized overheating problems and lead to high growth rates.