MODELING SUBSTRATE PARTICLE DEGRADATION BY BACILLUS-COAGULANS BIOFILM

A mathematical model for solid particle degradation by an aerobic biof ilm of Bacillus coagulans is developed. A moving biofilm is assumed to be present on the surface of the solid particle. Oxygen and glucose a re assumed to be growth limiting. The depleting glucose concentration in the solid particle is tracked as a function of time and it is found that the time taken for degradation of the particle is a function of particle size. Comparison with the experimental results found in liter ature on the particle size reduction by the action of Bacillus coagula ns (Nandakumar et al., 1996) indicates that the model is able to predi ct the general trends of experimental data well. It is suggested that the diffusion of the enzyme glucoamylase plays a crucial role and is a more dominant determining factor than the variation of the compositio n of particles with size as suggested previously (Nandakumar et al., 1 996) for the experimental observation that larger particles rook more time to degrade than smaller particles, It is hoped that the results o btained will lead to a better understanding of the mechanism of partic le degradation by aerobic biofilms and help in better design of biofil m reactors. (C) 1997 Published by Elsevier Science Ltd.