Isolation of the Novel Chiral Insecticide Paichongding (IPP) Degrading Strains and Biodegradation Pathways of RR/SS-IPP and SR/RS-IPP in an Aqueous System

Chiral insecticide paichongding (IPP) is a member of cis-nitromethylene neonicotinoid insecticides used in China. IPP was the promising replacement for imidacloprid as a result of its higher activity against imidacloprid-resistant insects. Two pairs of enantiomers, RR/SS-IPP and SR/RS-IPP, were separated by preparative high-performance liquid chromatography and employed in an aqueous system to investigate their biodegradation process. In this study, the strains G1-13/G1-14 and G2-19 with effective IPP degrading capability were isolated from agricultural soils. G1-14 was mutated from G1-13 by ultraviolet light exposure. Sequence alignment of 16S rRNA proved that these three strains belonged to the genus of Sphingobacterium. The degradation rate of RR/SS-IPP by Sphingobacterium sp. G1-13 and G1-14 reached 13 and 30% within 6 and 4 days, respectively. The degradation rate of SR/RS-IPP by Sphingobacterium sp. G2-19 could reach 35% within 5 days. Degradation intermediates (I1-I6) of enantiomers were detected, and two possible biodegradation pathways were proposed on the basis of the identification of metabolites.