A model-based strategy for scaling-up traditional packed-bed bioreactors for solid-state fermentation based on measurement of O2 uptake rates

Abstract

• O 2 uptake profiles are used to obtain the kinetics of metabolic heat generation. • The kinetics are incorporated in a two-phase heat and mass transfer model. • The model is validated with temperature profiles in a pilot-scale bioreactor. • The model is then used to explore packed-bed design and operation at large scale. • The approach is superior to previously published scale-up strategies for packed-beds. Model-based strategies for scaling up traditional packed-bed bioreactors used in solid-state fermentation have been available for over two decades. However, these strategies are theoretical, not being based on experimental data. A recently proposed strategy did use experimental data; however, it was based on data from a slow-growing fungus and also considered heat transfer in both the axial and radial directions, ignoring the fact that radial heat transfer is negligible in large-scale packed-bed bioreactors. The current work demonstrates a scale-up strategy based on a model describing heat transfer only in the axial direction. The strategy is demonstrated for the cultivation of Aspergillus niger , a fast-growing filamentous fungus. In the model, the kinetics of production of metabolic heat are based on an experimental time-course profile for the O 2 uptake rate. The model is validated by comparing its predictions for temperature profiles in the bed with temperatures measured experimentally in a pilot-scale bioreactor. Finally, the validated model is used to explore strategies for optimizing the performance of large-scale traditional packed-bed bioreactors. We conclude that a key strategy is to decrease the temperature of the inlet air during periods of peak heat generation.