Biodegradation of sulfoxaflor by Pseudomonas stutzeri CGMCC 22915 and characterization of the nitrile hydratase involved

Abstract

Sulfoxaflor (SUL), a novel sulfoximine insecticide, causes environmental contamination and poses potential risks to animals. However, there are few reports of SUL degradation by pure microbes. In this study, a novel isolated bacterium, Pseudomonas stutzeri CGMCC 22915, rapidly degraded SUL to SUL-amide via hydration. P. stutzeri CGMCC 22915 degraded 58.2% of SUL (814.28 μmol/L) within 2 h with a half-life of 1.6 h. P. stutzeri CGMCC 22915 effectively facilitated SUL degradation in soil and surface water. The nitrile hydratase PsNHase with a different gene orientation of <β-subunit> <α-subunit> <accessory protein> was responsible for the formation of SUL-amide from SUL and transformed other nitrile-containing insecticides thiacloprid and acetamiprid to their amides. Nitrile hydratases with this gene orientation have never been reported to degrade nitrile-containing insecticides. E. coli expressing PsNHase degraded 90.4% of SUL (798.29 μmol/L) within 5 min with a half-life of just 0.59 min. PsNHase showed the highest activity in SUL degradation among reported NHases (Vmax 21.69 U/mg, Km 1.62 mmol/L). Modeling of PsNHase suggested that β-His62 was important for its highest enzymatic activity toward SUL. P. stutzeri CGMCC 22915 is promising for application in the bioremediation of SUL in contaminated soil and surface water.