Biodegradation of benzene by a novel Rhodococcus sp. MKS26 isolated from petroleum refinery wastewater for remediation of hydrocarbon-contaminated environments

Abstract

Petroleum refinery activities are major sources of benzene contamination that contribute to the degradation of industrial soils and water resources, posing significant environmental and ecological risks. Biological remediation using indigenous microorganisms represents a sustainable alternative to conventional physicochemical treatments for restoring hydrocarbon-contaminated environments. This study aimed to isolate and characterize an efficient indigenous benzene-degrading bacterium from petroleum refinery wastewater and evaluate its biodegradation performance under different environmental and nutritional conditions. The isolate, designated Rhodococcus sp. MKS26, was identified by morphological characterization and 16S rRNA gene sequence analysis. Benzene degradation was evaluated under varying substrate concentrations, pH, temperature, nutrient composition, oxygen availability, and metal ion supplementation, while biodegradation kinetics were analyzed using the Michaelis–Menten model. Phylogenetic analysis placed strain MKS26 within the Rhodococcus erythropolis clade. Under optimal conditions (50 mg/L benzene, pH 7.0, and 30 °C), strain MKS26 removed 95.8 ± 1.2% of benzene within 72 h. Benzene degradation followed Michaelis–Menten kinetics, with a maximum specific degradation rate (Vmax) of 1.2 mg/mg/h and a half-saturation constant (Ks) of 8-12 mg/L. Benzene removal was enhanced by succinate, inorganic nitrogen, adequate oxygen, and Fe²+. The strain also maintained stable activity in non-sterile refinery wastewater. These findings demonstrate the potential of Rhodococcus sp. MKS26 as an indigenous bioaugmentation agent for benzene-contaminated wastewater and hydrocarbon-polluted industrial environments.