Biodegradation of λ-cyhalothrin by Bacillus sp. isolated from pesticide-polluted site: Isolation, identification, and optimization of its growth parameters

Abstract

λ-cyhalothrin (LC), a frequently used synthetic pyrethroid insecticide, poses a substantial risk to human health and the environment due to its prolonged presence in plants, soil, and water. This study aimed to identify and characterize bacteria with the ability to degrade and utilize λ-cyhalothrin as their sole carbon and energy source. The bacteria were isolated by employing an enrichment technique on mineral salt media through a series of dilution steps. Strain isolated underwent identification through morphological, biochemical, and molecular analyses, specifically employing 16S rRNA and phylogenetic analysis, which disclosed its classification as Bacillus sp. With the accession number OR133746. Physio-cultural conditions, including temperature, initial substrate concentration, pH, incubation time and inoculum size affecting the strain's activity were investigated in MSM using a one-variable-at-a-time approach. The optimal conditions for bacterial growth and λ-cyhalothrin degradation was found to be a substrate concentration of 6 g/L, a temperature of 30 °C, a pH of 6.5, and an incubation time of 96 hours. The results of Gravimetric analysis revealed that the selected isolate exhibited notable degradation rates of 75.4 % and 100 % after 72 hours and 96 hours of incubation, respectively. These findings highlight the exceptional efficiency of the strain in degrading λ-cyhalothrin. Consequently, this strain emerges as a promising candidate for tackling pollution attributed to λ-cyhalothrin through bioremediation processes.