The Physical Mechanisms of Microbiological Cellular Transport, Storage, and Metabolism of Aromatic Hydrocarbon-Degrading Soil Microbiota

Abstract

The Monod bioreaction equation, though justified from extensive practical use, has been found to have limited mechanistic basis (Enouy, Walton, et al., 2021). To attempt to gain a biological mechanistic representation of the equation, Enouy, Walton, et al. (2021) created a three-stage serial process by deriving Monod as a special case of aquifer phase diffusive transport rate of a substrate onto the surface of microbe, uptake rate across the microbial membrane, and the subsequent interior biodegradation rate. The derivation was parameterised with single-substrate depletion of benzene, phenol, and toluene, and biomass (Pseudomonas putida F1) growth data from Reardon et al. (2000). Though this derivation of Monod can fit the data adequately, it is simplistic, and sometimes deviates from the data. It is proposed that a detailed understanding of the biological processes involved in the biodegradation of aromatic hydrocarbons is necessary to begin to provide a meaningful mechanistic basis to the Monod coefficients, 𝐾! and μ"#$, and to support and embellish this derivation for the purpose of improving the fit of the data, and of future experimental data sets. To this purpose, a literature review of the four major steps in the biological degradation of aromatic hydrocarbons was undertaken. The processes studied are as follows: a) cellular transport; b) energy storage; c) metabolism of aromatic hydrocarbons (both aerobically and anaerobically); and d) cellular growth. The contributions of these processes are discussed alongside the fits of the Reardon et al. (2000) data to propose embellishments to the Monod derivation for improving the data fit, and future biological investigations for improving mechanistic understanding and contributing to biological systematic modelling.