Assessment of Biodegradation of Lambda-Cyhalothrin by Bacterium Isolated from Agricultural Soil in Elemere, Kwara State, Nigeria

Abstract

A synthetic pyrethroid (SP), lambda-cyhalothrin (LC) has been used as an insecticide to control a variety of insect pests. Despite being thought to be potentially hazardous, LC is nevertheless used in horticulture, forestry, and agriculture to control a wide variety of insect pests. Another strategy for reducing pesticide residues is biodegradation, which is both economical and environmentally benign. Utilizing an enrichment approach in the mineral salt medium, LC-degrading bacteria were isolated for this investigation. Their morphology and certain biochemical tests were used to characterize them. For 25 days, the most powerful isolate's growth and biodegradation in an LC-enriched mineral salt medium were monitored at various intervals using optical density as a metric. Gas Chromatography-Mass Spectrometry (GC-MS) analysis was used to confirm the biodegradation of LC. The LC-degrader was molecularly identified using the 16S RNA analysis. The results from the optical density showed an increase in the growth of the isolate from the 5th day up to the 15th day before it gradually decreased till the 25th day. The results from identifying metabolites using GC-MS analysis revealed different retention times at different peak areas indicating different metabolites after the biodegradation. The study of the metabolites showed new compounds were formed after the degradation of LC.  The metabolites identified include; 3-phenoxyphenyl acetonitrile, Cyclopropane-1-carboxylic acid, N-(Hydroxymethyl)-acetamide, Phenol, Phenoxy-benzoate, 3-phenoxy-acetic acid, and Phosphonoacetic acid. The bacterial isolate with the best potential for LC degradation was identified as Klebsiella pneumoniae strain ABS1 and can be explored for bioremediation of LC-contaminated agricultural soils and other synthetic pyrethroids.