Net growth rate of continuum heterogeneous biofilms with inhibition kinetics

WUERTZ, STEFAN; RAJAL, VERONICA B.; GONZO, ELIO EMILIO

npj Biofilms and Microbiomes

Springer Nature

Año: 2018 vol. 4 p. 1 - 8

Biofilm systems can be modeled using a variety of analytical and numerical approaches, usually by making simplifying assumptionsregarding biofilm heterogeneity and activity as well as effective diffusivity. Inhibition kinetics, albeit common in experimentalsystems, are rarely considered and analytical approaches are either lacking or consider effective diffusivity of the substrate and thebiofilm density to remain constant. To address this obvious knowledge gap an analytical procedure to estimate the effectivenessfactor (dimensionless substrate mass flux at the biofilm-fluid interface) was developed for a continuum heterogeneous biofilm withmultiple limiting-substrate Monod kinetics to different types of inhibition kinetics. The simple perturbation technique, previouslyvalidated to quantify biofilm activity, was applied to systems where either the substrate or the inhibitor is the limiting component,and cases where the inhibitor is a reaction product or the substrate also acts as the inhibitor. Explicit analytical equations arepresented for the effectiveness factor estimation and, therefore, the calculation of biomass growth rate or limiting substrate/inhibitor consumption rate, for a given biofilm thickness. The robustness of the new biofilm model was tested using kineticparameters experimentally determined for the growth of Pseudomonas putida CCRC 14365 on phenol. Several additional cases havebeen analyzed, including examples where the effectiveness factor can reach values greater than unity, characteristic of systemswith inhibition kinetics. Criteria to establish when the effectiveness factor can reach values greater than unity in each of the casesstudied are also presented.