Efficient sulfoxaflor removal via cell-immobilized nitrile hydratase from Ensifer adhaerens: Biodegradation kinetics, catalytic characteristics, and ecotoxicological evaluation

Sulfoxaflor (SUL, [ N -[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl] ethyl]-λ4-sulfanylidene] cyanamide]), a widely used neonicotinoid insecticide (NENI) with documented ecological risks, currently lacks effective microbial remediation strategies and comprehensive assessment of metabolite toxicity. Here, we demonstrate that the nitrogen-fixing bacterium Ensifer adhaerens CGMCC 6315 mediates SUL degradation via nitrile hydratase (NHase)-catalyzed hydration, yielding the amide product N -(methyl(oxo){1-[6-(trifluoromethyl)pyridin-3-yl]ethyl}-λ4-sulfinyl)urea (designated X11719474). Resting cells of E. adhaerens CGMCC 6315 degraded 77.91% of 0.89 mmol/L SUL within 3 h (half-life 46.21 min). Calcium alginate-immobilized cells exhibited extremely high degradation efficiency (78.57% removal in 2 h), achieving near-complete SUL elimination from surface water within 3 h, while immobilized recombinant Escherichia coli pET28a-PnhA showed significantly improved NHase acid tolerance, storage stability and reusability. Crucially, we provide the first evidence that the metabolite X11719474 exhibits greater toxicity than the parent SUL to Synechocystis sp. PCC 6803, inducing distinct oxidative stress responses (transient activation followed by collapse of (superoxide dismutase) T-SOD/catalase (CAT) activities with sustained malondialdehyde (MDA) accumulation). These findings establish an efficient immobilized-cell bioremediation platform for SUL contamination while revealing previously underestimated ecological risks of pesticide metabolites, underscoring the imperative to incorporate transformation products in neonicotinoid environmental risk assessments. • Ensifer adhaerens CGMCC 6315 degrades SUL via hydration to form X11719474 • Immobilized cells achieve 78.57% SUL removal in 2 h • Recombinant E. coli enhances NHase tolerance and reusability • X11719474 shows greater toxicity to cyanobacteria Synechocystis sp. PCC 6803 than SUL