Bioremediation of Dicofol-Contaminated Wastewater: Evaluating the Efficiency of Freely Suspended Cells and Immobilized Cells of Methylobacterium sp. TMN

This study investigates the biodegradation of dicofol (DCF) by Methylobacterium sp. TMN, a bacterial strain isolated from pesticide-contaminated soil and enriched with DCF as the sole carbon and energy source. The strain was characterized through morphological, biochemical, and phylogenetic analyses, with its identity confirmed by 16S rRNA gene sequencing. Optimal degradation conditions were identified at pH 7 and 30 °C, achieving complete degradation of 10 mg/L DCF within 96 h, as confirmed by HPLC analysis. Metabolite identification using TLC, HPLC, GC–MS, and FT-IR revealed 4,4’-dichlorobenzophenone as a key intermediate. The cell-free extract of the strain demonstrated dehalogenase activity, with the release of chloride ions from DCF confirming its dechlorination capability. To enhance degradation efficiency, Methylobacterium sp. TMN was immobilized in polyurethane foam (PUF), sodium alginate (SA), and sodium alginate-polyvinyl alcohol (SA-PVA). PUF-immobilized cells exhibited the highest efficiency, achieving complete degradation of 50 mg/L and 100 mg/L DCF within 42 and 144 h, respectively. Furthermore, PUF-immobilized cells retained their degradation potential for over 35 cycles in semi-continuous operation and remained active for 60 days at 4 °C. These results demonstrate the potential of immobilized Methylobacterium sp. TMN, particularly in PUF-based systems, for bioremediating environments contaminated with organochlorine pesticides.