Bioremediation potential of bacterial isolates for diamide pesticides: Enzymatic activity, tolerance, biofilm formation, and degradation efficiency

This study investigates the bioremediation potential of six bacterial strains isolated from pesticide-contaminated soils for the degradation of two widely used diamide pesticides: chlorantraniliprole (CAP) and flubendiamide (FBD). The strains were evaluated for their enzymatic activities, tolerance to pesticide mixtures, biodegradation efficiency (as measured by 2,6-dichlorophenol-indophenol (DCPIP) decolorization and biomass accumulation), and their ability to form biofilms under pesticide-induced stress. Significant enzymatic activities were recorded, with dehydrogenase activity ranging from 510 to 560 µg triphenyl formazan (TPF) mL^-1 (n = 3, mean ± SD: 535 ± 25 µg TPF mL^-1) and catalase activity from 40.13 to 40.88 µmoles H₂O₂ min⁻¹ mg⁻¹ protein (n = 3, mean ± SD: 40.51 ± 0.38 µmoles H₂O₂ min⁻¹ mg⁻¹ protein). All strains exhibited considerable tolerance to CAP-FBD pesticide mixtures, with optical density (OD₆₀₀) values ranging from 0.201 to 2.212 across the tested concentration range (50-3000 mg L^-1) after 24 h of incubation. Biodegradation assays revealed efficient breakdown of CAP and FBD, with decolorization times ranging from 18 to 62 h. Notably, all strains formed robust biofilms, suggesting enhanced resilience to environmental stressors. High-performance liquid chromatography (HPLC) analysis confirmed that the bacterial consortium T3 (n = 3) achieved the highest FBD degradation rate of 98.23 % of 60 mg kg^-1 FBD after 20 days, with only 1.77 % residues, compared to C1 (native bacteria, FBD, without NPK, which gave 29.4 % degradation) and C2 (native bacteria, FBD, with NPK, which gave 31.70 %), indicating that nearly the entire pesticide loss was due to biological activity of T3 consortia rather than native bacteria. These findings highlight the adaptive capabilities of these bacterial isolates and their potential for environmentally sustainable pesticide remediation. The novelty of this study lies in its integrative assessment of enzymatic function, pesticide tolerance, and biofilm formation, offering a comprehensive understanding of microbial strategies for diamide pesticide bioremediation.