Bio-electrodegradation of chlorpyrifos by Streptomyces pactum AR-8: A sustainable approach for efficient degradation and ecotoxicity reduction in earthworm (Eisenia fetida)

Chlorpyrifos (CPF), a widely used organophosphate pesticide, poses considerable environmental and health risks due to its persistence and toxicity. This study investigates the potential of a bio-electrochemical system (BES) employing Streptomyces pactum (AR-8) for CPF degradation in artificially contaminated soil. Comparative analysis revealed that bio-electrodegradation achieved a degradation efficiency of 80.15% (pre-optimization experiments), which was markedly higher than that observed with biodegradation (59.87%) and electrodegradation alone (3.44%). Enzymatic assays demonstrated enhanced esterase and organophosphorus hydrolase (OPH) activity under bio-electrodegradation, corroborating the improved degradation efficiency. Optimization of key operational parameters - Initial CPF concentration (100 mg/kg), pH (6.5), temperature (28 °C), inoculum dose (2% v/w), and applied potential (1.4 mV) resulted in maximum CPF removal of 98.54%. HPLC-MS/MS analysis elucidated the degradation pathway, indicating the progressive breakdown of CPF into less toxic intermediates, signifying near-complete mineralization. Toxicity assessments using earthworm (Eisenia fetida) demonstrated significantly reduced lethality, growth inhibition, and CPF bioaccumulation in BES-treated soil compared to CPF-contaminated soil. Biomarker and gut microbiome analyses confirmed effective CPF detoxification in BES-treated soil, showing no adverse effects on earthworm physiology or gut microbial composition. Collectively, these findings highlight the potential of BES as an efficient and sustainable approach for on-site CPF remediation in pesticide contaminated environments.