Biochar enhances the remediation of fluorene and Cd(II) co-contamination by Burkholderia sp. FM-2

This study investigated the fluorene degradation ability and metabolic pathway of Burkholderia sp. FM-2. The FM-2 demonstrated a 72.16 % degradation rate of 300 mg/L fluorene over a period of three days. HPLC-MS analysis identified major metabolites including 9-fluorenol, 9-fluorenone, and phthalate. The impact of heavy metals on fluorene degradation was also assessed. FM-2 exhibited strong tolerance to heavy metals, with a minimum inhibitory concentration (MIC) of 1000 mg/L for Cd(II). The study found that the removal rate of 100 mg/L Cd(II) was 70.42 %, and it was observed that this concentration had a slightly enhancing effect on fluorene degradation. Proteomic analysis revealed that multicopper oxidases and proteins involved in metabolic pathways for instance glutathione metabolism, sulfur metabolism were up-regulated under Cd(II) stress, suggesting potential mechanisms for Cd(II) tolerance and co-metabolism. Moreover, the effect of biochar on FM-2 for the remediation of co-contamination with fluorene and Cd(II) was evaluated. After immobilizing FM-2 with modified biochar (BC-BW), the degradation efficiency of fluorene significantly increased from 72.58 % to 84.93 % and the removal efficiency of Cd(II) increased from 70.42 % to 84.50 %. In the contaminated soil remediation experiment, the removal rates of fluorene and Cd(II) by the immobilized bacteria were 72.59 % and 66.67 %, respectively. These findings demonstrate that modified biochar enhances the remediation efficiency of FM-2 in co-contaminated soils. This study provides theoretical support and practical guidance for the application of biochar-based immobilization techniques in microbial remediation of complex polluted environments.