Experimental Results and Integrated Modeling of Bacterial Growth on an Insoluble Hydrophobic Substrate (Phenanthrene)

Abstract

Metabolism of a low-solubility substrate is limited by dissolution and availability and can hardly be determined. We developed a numerical model for simultaneously calculating dissolution kinetics of such substrates and their metabolism and microbial growth (Monod kinetics with decay) and tested it with three aerobic phenanthrene (PHE) degraders: Novosphingobium pentaromativorans US6-1, Sphingomonas sp. EPA505, and Sphingobium yanoikuyae B1. PHE was present as microcrystals, providing non-limiting conditions for growth. Total PHE and protein concentration were tracked over 6–12 days. The model was fitted to the test results for the rates of dissolution, metabolism, and growth. The strains showed similar efficiency, with v max values of 12–18 g dw g–1 d–1, yields of 0.21 g g–1, maximum growth rates of 2.5–3.8 d–1, and decay rates of 0.04–0.05 d–1. Sensitivity analysis with the model shows that (i) retention in crystals or NAPLs or by sequestration competes with biodegradation, (ii) bacterial growth conditions (dissolution flux and resulting chemical activity of substrate) are more relevant for the final state of the system than the initial biomass, and (iii) the desorption flux regulates the turnover in the presence of solid-state, sequestered (aged), or NAPL substrate sources.

Using a Bayesian approach to improve and calibrate a dynamic model of polycyclic aromatic hydrocarbons degradation in an industrial contaminated soil

“…Finally, the model predicts that the metabolites production would be less than 1%, and that the contribution of the biogenic non-extractible residues to the total extractible residues could be neglected at such short time scale. This finding would be in agreement with results indicating that sorption occurs more rapidly than the biodegradation in the soil (Adam et al, 2014).…”

A Model Framework to Describe Growth-Linked Biodegradation of Trace-Level Pollutants in the Presence of Coincidental Carbon Substrates and Microbes

“…Hence, the framework is not sufficient to describe the biodegradation of compounds with low aqueous solubility in environmental matrices, where partitioning across different domains (e.g., gas, solid, liquid) would demand explicit inclusion of mass transfer kinetics. 32 Such processes could be added in extended models using established formulations. 33 Here, for the first time, we separate the coincidental carbon in two fractions: the fraction that can be utilized by the degrader strain (X B,Z ) termed S AOC,Z , and the remaining fraction, termed S AOC,other .…”

Impact of bacterial activity on turnover of insoluble hydrophobic substrates (phenanthrene and pyrene)—Model simulations for prediction of bioremediation success

“…PAH are metabolised by several bacteria, fungi, algae and also by cytochrome P-450 monooxygenases of higher eukaryotic cells [3], but undergo no or slow decomposition in the environment [4]. Full mineralisation with productive growth is only known for bacteria [5]. However, reports about full mineralisation of PAH with > 5 rings are relatively rare [6].…”

“…Recently a modelling approach for integrated mass transfer, biodegradation (parameter determination: v max , K M and yield) and residual concentration assessment was developed and applied for the turnover of non-water soluble substrates like PAH under mass transfer limitations [5,12]. The model equations imply that below a certain substrate concentration, or more exactly below a certain substrate flux to the microorganisms, bacterial growth ceases and bacterial populations start to decline which in turn leads to non-degraded residues.…”