Combined effect of substrate concentration and flow velocity on effective diffusivity in biofilms

We have evaluated the influence of glucose concentration and flow velocity at which biofilms were grown on the distribution of effective diffusivity in biofilms consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae. From the local diffusivity profiles, measured by a novel microelectrode, the surface averaged relative effective diffusivities (Ds) were calculated at different depths in the biofilms. The Ds decreased toward the bottom of the biofilms and the Ds profiles were affected by growth conditions. The Ds was higher in biofilms grown at high glucose concentrations and at low flow velocities; and it was influenced by the glucose concentration to a much larger extent than by the flow velocity.