INCORPORATION OF DEATH KINETICS INTO A 2-DIMENSIONAL DYNAMIC HEAT-TRANSFER MODEL FOR SOLID-STATE FERMENTATION

Dynamic two-dimensional modelling was used in a theoretical analysis of the overheating problem in solid-state fermentation within a packed-bed bioreactor. The model described the growth and death of the fungus Rhizopus oligosporus as functions of temperature; the generation of metabolic heat; and the transfer of heat within the packed-bed by conduction and convection. The model predicted that convection was the dominant heat transfer mechanism under the design and operational parameters applied. Significant death occurred in the upper region of the bed where the highest temperatures were reached. The temperature rise at the top of the bed could be minimised by using high superficial air velocities or low inlet air temperatures. The most effective strategy for a column with a bed height:bed diameter ratio of 1:1 or less was to use a high superficial air velocity.