Biodegradation of the nitrile-containing insecticides sulfoxaflor, flonicamid, thiacloprid, and acetamiprid by immobilized Escherichia coli harboring genes of nitrile hydratase and a cobalt transporter

Abstract

The nitrile-containing insecticides sulfoxaflor, flonicamid, thiacloprid, and acetamiprid are used widely in agriculture, polluting the environment and harming animals. The Co2+-dependent enzyme nitrile hydratase (NHase) is a powerful tool for the degradation of nitrile-containing insecticides. Here, the NHase activities of Escherichia coli pET28a-PsNHase, harboring Pseudomonas stutzeri CGMCC 22915 (Ps) NHase gene, and E. coli pET28a-PsNHase-PsCbiM, harboring genes of PsNHase and a cobalt transporter PsCbiM, were compared. The presence of PsCbiM promoted PsNHase activity. E. coli pET28a-PsNHase-PsCbiM was immobilized using calcium alginate, which increased the tolerance of its NHase to acidic, alkaline, and high-temperature environments. Immobilized E. coli pET28a-PsNHase-PsCbiM was applied to degrade sulfoxaflor, flonicamid, thiacloprid, and acetamiprid. These insecticides were both substrates and inhibitors of immobilized E. coli pET28a-PsNHase-PsCbiM. Substrate inhibition model assays showed that the optimum initial concentrations of sulfoxaflor, flonicamid, thiacloprid, and acetamiprid for degradation by immobilized cells were 455.01, 195.50, 139.20, and 410.26 μmol/L, respectively. Degradation of nitrile-containing insecticides by immobilized engineered E. coli cells was reported here for the first time. This study provides a novel and excellent bioremediation agent for treatment of wastewater contaminated with nitrile-containing insecticides.