Screening, Molecular Identification and Degradation Characteristics of a Diflufenican-Degrading Bacterial Strain

This study aims to identify microbial strain resources capable of degrading diflufenican and elucidate their degradation characteristics, with the goal of mitigating the phytotoxicity hazards associated with the prolonged use of this persistent herbicide. A degradation strain was isolated, purified, and screened from wheat field soils that had been subjected to diflufenican treatment using an enrichment culture method. The taxonomic classification of the strain was determined through a comprehensive analysis of its morphology, physiology, biochemistry, as well as its 16S rRNA gene sequence. The results demonstrated that the screened bacterial strain 88-1 could utilize diflufenican as its metabolic carbon source and was identified as Enterobacter hormaechei, a facultative anaerobe. The degradation efficiency of strain 88-1 on diflufenican was closely associated with cultivation time, the initial concentration of the herbicide, temperature, pH, and inoculation amount of the strain. Additionally, the degradation rate exhibits a positive correlation with the biomass of the strain. Under optimal conditions (40 mg/L diflufenican, 30 °C, pH 8.0, 10% inoculum), the highest observed degradation efficiency and viable cell density over the 120 h incubation period were 55.11% and 8.05 × 10⁶ CFU/mL, respectively. Furthermore, rapid biotransformation commenced within 24 h, yielding a cascade of metabolites, with 2-(3-(trifluoromethyl)phenoxy)pyridine-3-carboxamide identified as the primary metabolite. These findings suggest that strain 88-1 holds promise for the bioremediation of soils contaminated with diflufenican.