title: Diffusion coefficients of metabolites in active biofilms.
abstract: Diffusion coefficients of actual metabolites in completely active biofilms can be determined by applying a new concept that is based on a constant local activity in the entire biofilm. In that case, a concentration step will be transmitted unattenuated. Subsequently, the diffusion coefficient can be calculated from the response monitored with a microelectrode positioned in the biofilm without quantitative knowledge of the local microbial kinetics. The conditions required for such a constant microbial biofilm activity were formulated in terms of the Thiele modulus and the substrate concentration in the bulk liquid. This proposed method was successfully applied to determine diffusion coefficients of oxygen and glucose in agar gels containing various fractions of active immobilized microorganisms. The values obtained were compared to experimental results from well-defined inert systems. The transient response of oxygen was far more affected by the presence of the immobilized cells than glucose. This can be explained by partition of the diffusing solute between the microbial cells and the aqueous phase.
authors.affiliation: Department of Chemical Engineering, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
authors.forename: E E
authors.initials: EE
authors.lastname: Beuling
authors.forename: J C
authors.initials: JC
authors.lastname: van Den Heuvel
authors.forename: S P
authors.initials: SP
authors.lastname: Ottengraf
mesh_terms: D018441:Biofilms; D004058:Diffusion; D005947:Glucose / Q000378:metabolism; D016982:Micrococcus luteus / Q000378:metabolism; D008954:Models, Biological; D010101:Oxygen Consumption
chemical_list: D005947:Glucose