A model for multicomponent biosensing and its application to a dead cell-based BOD biosensor

Abstract

The sensor response of a biofilm-modified dissolved oxygen probe in a multicomponent organic solution was described mathematically with respect to the mass transfer and biooxidation rate processes of the organic solutes and the dissolved oxygen in the biosensor. The model was used to interpret and define mathematically the biochemical oxygen demand (BOD 5) of an organic solution with respect to the universally accepted BOD check solutions containing equal mass concentrations of glucose and glutamic acid. The model was also extended to describe the effect of cell population immobilized in the biofilm and substrate temperature on the BOD-sensing sensitivity. The model showed that the sensing characteristics for a given solute in a solution depends on the stoichiometric ratio of its diffusivity to that of oxygen in the biofilm. This parameter was determined for a number of single organic solutes using a BOD biosensor with immobilized thermally killed Bacillus subtilis cells. The single solute parameters were used to verify the application of the model to the sensing of multicomponent organic mixtures with respect to their compositions and their biochemical oxygen demand. The model’s description of the sensor response for multicomponent organic mixture and its interpretation and description of its biochemical oxygen demand were well substantiated experimentally. The model is useful for the characterization, design and fabrication of a bio-oxidation-based biosensor for monitoring multicomponent organic solutions and their biochemical oxygen demands.