Isolation,identification,degradation characteristics and pathway of a pyrethroid-degrading bacterial strain

A bacterial strain named P-01 was newly isolated by enrichment culture from the activated sludge in the wastewater of a pyrethroid-manufacturer in Zhongshan.Based on the morphology,physio-biochemical characteristics,and 16S rDNA sequence analysis,strain P-01 was temporarily identified as Achromobacter sp.P-01.Response surface methodology(RSM) was used to optimize degradation conditions.The optimal conditions for biodegradation were obtained as follows:31.4℃,pH 7.6 and inoculum biomass 0.4 g · L-1.Under the optimal degradation conditions,strain P-01 could effectively degrade deltamethrin,fenvalerate,beta-cypermethrin,beta-cyfluthrin and cyhalothrin with degradation rates of 98.9%,92.2%,91.0%,85.1% and 77.3%,respectively,within 7 days of incubation.Strain P-01 not only could utilize deltamethrin as the sole carbon source and energy for growth in mineral salt medium(MSM),but also could tolerate and efficiently degrade high concentrations of deltamethrin(100~500 mg · L-1).Furthermore,the degradation reaction followed first-order kinetics and half lives(T1/2) were 1.3,1.8,2.0,2.5 and 3.0 d,respectively.Studies on the degradation pathway showed that deltamethrin was degraded by hydrolysis of the carboxylester linkage to yield alpha-hydroxy-3-phenoxy-benzeneacetonitrile and 3-phenoxy benzaldehyde,and then the intermediates were further degraded by oxygenolysis to form 2-hydroxy-4-methoxy benzophenone and 1,2-benzenedicarboxylic acid,mono ester,finally resulting in complete detoxification.