Kinetic evaluation of anthracene biodegradation by Bacillus velezensis and mathematical model fitting under substrate inhibition conditions.

Abstract

Polycyclic aromatic hydrocarbons (PAHs) such as anthracene are persistent environmental pollutants that accumulate in ecosystems and contribute to harmful air pollution, posing risks to human health. Due to its significance, anthracene must be removed using nontoxic methods such as bioremediation. This study focuses on degrading anthracene with Bacillus velezensis and investigating the kinetics of this process. The bioremediation potential of B. velezensis in degrading anthracene under aerobic conditions was explored through batch experiments conducted at varying anthracene concentrations (100–600 ppm). The bacterium exhibited rapid biomass growth and efficient degradation at 100 ppm, while growth was inhibited at higher concentrations due to substrate toxicity. GC-MS analysis identified 9,10-anthracenedione as the primary intermediate, which was further broken down into carbon dioxide and water at 100 ppm. Phytotoxicity assays confirmed this intermediate was nontoxic to the bacterium and phyllosphere. The degradation kinetics deviated from the Michaelis–Menten model at high concentrations, indicating the influence of substrate inhibition. Among several models evaluated, the Wayman and Tseng model showed the best statistical fit, with a high adjusted R2 value (0.95191) and a low RMSE (0.0019), indicating accurate predictions. Data interpolation improved model performance, providing a more reliable framework for predicting anthracene degradation by B. velezensis.