[Isolation, identification and characterization of cypermethrin-degrading strain L12]

To isolate and characterize bacteria to degrade cypermethrin (CP).

We used enrichment culture to isolate and characterize bacterial strains based on the observation of morphological and biochemical characters and analysis of 16S rRNA gene sequences. We determined the concentration of CP, metabolite, densities of strain cells and cell surface hydrophobicity (CSH) in pure culture liquid.

We isolated a bacterium able to effectively degrade CP from polluted wastes of pesticide plant and assigned it as strain L12. Phylogenetic analysis based on 16S rRNA gene showed the similarity of 99% between strain L12 and Bacillus cereus. In pure culture with CP as the sole carbon and energy source, 85.6% of CP at initial concentration of 50 mg /L was degraded in 5 days. Thin layer chromatography (TLC) analysis of the culture extracts revealed presence of a metabolite (R(f)0.13), and HPLC analysis confirmed the retention time of the metabolite (2.26 min) corresponded with 3-phenoxybenzoic acid (3-PBA) standard. The method of microorganism adhering to hydrocarbon (MATH) was used to analyze strain L12 of the highest CSH of 68.91%.

The results showed that strain L12 belonged to Bacillus cereus, which showed CSH and capacity to degrade CP to 3-PBA.