Enantioselective degradation of the organophosphorus insecticide isocarbophos in Cupriavidus nantongensis X1T: Characteristics, enantioselective regulation, degradation pathways, and toxicity assessment

The chiral pesticide enantiomers often show selective efficacy and non-target toxicity. In this study, the enantioselective degradation characteristics of the chiral organophosphorus insecticide isocarbophos (ICP) by Cupriavidus nantongensis X1(T) were investigated systematically. Strain X1(T) preferentially degraded the ICP R isomer (R-ICP) over the S isomer (S-ICP). The degradation rate constant of R-ICP was 42-fold greater than S-ICP, while the former is less bioactive against pest insects but more toxic to humans than the latter. The concentration ratio of S-ICP to R-ICP determines whether S-ICP can be degraded by strain X1(T). S-ICP started to degrade only when the ratio (CS-ICP/CR-ICP) was greater than 62. Divalent metal cations could improve the degradation ability of strain X1(T). The detected metabolites that were identified suggested a novel hydrolysis pathway, while the hydrolytic metabolites were less toxic to fish and green algae than those from P-O bond breakage. The crude enzyme degraded both R-ICP and S-ICP in a similar rate, indicating that enantioselective degradation was due to the transportation of strain X1(T). The strain X1(T) also enantioselectively degraded the chiral organophosphorus insecticides isofenphos-methyl and profenofos. The enantioselective degradation characteristics of strain X1(T) make it suitable for remediation of chiral organophosphorus insecticide contaminated soil and water.

Automated summary

The study found that the strain Cupriavidus nantongensis X1(T) has enantioselective degradation characteristics towards the chiral organophosphorus insecticide isocarbophos, preferentially degrading the R isomer over the S isomer. S isomer only starts to degrade when the concentration ratio relative to R is greater than 62, and divalent metal cations can enhance the degradation ability of the strain.