Development of quantitative biofilm simulation models considering mass transfer at the liquid-biofilm interface

Two quantitative biofilm simulation models, a deterministic model and a stochastic model with adding the stochastic term for sloughing events, were developed in the present study. Both models considered the effect of mass transfer at the liquid-biofilm interface during biofilm development. Model parameters were estimated experimentally by creating Pseudomonas oleovorans biofilms in polystyrene tubes under different nutrient levels (5%, 2% and 1%) at 5°C. Both models were shown to be well-fitted with time-course changes in bioilm quantity. The stochastic model was especially well-itted with the distribution of bioilm quantity under each culture condition. Moreover, the model parameters reflected properties of the biofilm, such as concentration of nutrients using extracellular polysaccharide, improvement of bioilm forming ability at low substrate concentrations and decrease of the bioilm growth rate. Thus, the models are adequate for bioilm simulations. The models presented are expected to be able to predict time-course changes in bioilm quantity and to enable analysis of experimental data. Additionally, the stochastic model has the potential to estimate not only the distribution of bioilm quantity but also sloughing events, an important concept in food safety.