Modeling Substrate Transport into Biofilms: Role of Multiple Ions and pH Effects

Abstract

Steady‐state substrate utilization in biofilms has traditionally been modeled by coupling Fickian diffusion with Monod reaction kinetics. An inherent assumption in most of the previous models was that the pH remains constant within the biofilm. Experiments have shown differences between the pH in the bulk solution and in the biofilm. Since the rate of substrate utilization in biological systems can be affected severely by changes in pH, recent models have tried to account for the pH variations within the biofilm. However, these models neglected ionic interactions during mass transport. A fundamental approach incorporating the effects of pH in any chemical or biological system involving diffusion with reaction is presented. The approach is applied to a steady‐state model of substrate utilization in carbon‐limited algal biofilms.