Effect of metal ions on chlorobenzene degradation by Burkholderia sp. in a co-contamination system

Co-contamination of heavy metals and chlorobenzenes (CBs) presents a significant environmental challenge, yet the impact of metal ions on CB biodegradation remains unclear. This study investigates the effects of Cd²⁺, Hg²⁺, Zn²⁺, and Fe³⁺ on the CB degradation ability of Burkholderia strain TF-2. The results indicate that metal ions inhibit CB biodegradation, with the most pronounced inhibitory effects observed at concentrations of 10.0 mg/L (Zn²⁺), 50.0 mg/L (Fe³⁺), 2.5 mg/L (Cd²⁺), and 3.0 mg/L (Hg²⁺). Han-Levenspiel modelling identified critical inhibitory concentrations for Zn²⁺, Cd²⁺, and Hg²⁺ as 9.198, 2.891, and 2.234 mg/L, respectively, while Fe³⁺ was not applicable to this model. Toxicity assessments, expressed as EC50 values, ranked the metal ions as follows: Hg²⁺ (0.451 mg/L) > Cd²⁺ (0.505 mg/L) > Zn²⁺ (5.531 mg/L) > Fe³⁺ (10.37 mg/L). These findings identify Hg²⁺ and Cd²⁺ as the strongest inhibitors of CB degradation by Burkholderia TF-2 and offer insights to optimise bioremediation strategies for heavy metal-organic co-contaminated sites.