Simulation of the cellular anabolic activity within biofilms: Where a new immobilized cell will preferably be born?

A mathematical model, based on structured growth kinetics, is presented to simulate the profile of assimilated radioactive sulphur by a biofilm, after the release of calculated amounts of 35SO42− in the biofilm environment. The radiolabelled sulphur (35S) stands as a biomass growth indicator, thus allowing the estimation of the cellular anabolic activity (growth) profile inside the biofilm. The model predicts that the maximum rate of biomass synthesis occurs at the external layer of the biofilm. A good correlation between the model predictions and previously published experimental data is reported, indicating the applicability of the structured model to describe microbial growth in immobilized cell systems.