Study On Isolation And Degrading Characteristics Of Deltamethrin-degrading Bacteria

Bioremediation is an environmentally-benign method for degrading insecticides from contaminated substrates.Bacteria that can effectively degrade pesticide compound had been isolated from natural environment,they can be pour into contaminated system and obviously enhanced the effect,therefore,they have extraordinary potential in bioremediation.Pyrethroids are neural toxicum substance and is very harmful to human health.Its origin existed wildly in our life.Synthetic Pyrethroid insecticides is the third largest class of insecticides.The residue of this kind of insecticides has become one of the most dominant insecticide residues in farm produce.And microorganism has important function on degrading pesticide residues.Therefore, the technology of microbial degradation has turned into the organic production technology to remove pesticide residues.In this text,our goal was to find bacteria that could degrade the Pyrethroids that are used in agriculture production.We isolated bacteria from pesticide-treated contaminated soil from vegetable garden.Initial screening was on enrichment media,which subsequent sequential isolation on minimal media containing the pesticides as sole C source.As a result,two strains which grew particularly well(designated X09 and X20) was Enterobacter cloacae and Pseudomonas fluorescens respectively,identified with the Biolog whole-auto-microbial analysis system.We then used gas chromatography HP6890 to measure the rates of disappearance of the deltamethrin from pH 7.0,liquid cultures maintained aerobically at 30℃.Other than 50mg/L of the pesticides,the media were carbon flee.Seven days after inoculation with X09 and X20the concentrations of the deltamethrin decreased was 62.82%and 43.25%respectively.The optimal conditions for the aerobic degradation of deltamethrin by two strains should be Nutrition Agar substrate with the content of 50mg/L Deltamathrin,at 30℃,with pH 7.0 and 96 hours and inoculation 25%.Growth measured as optical density measured the rate of disappearance of other pesticides,we showed that two strains also degrade the Cypermethrin, Fenpropathrin and Fenvalerate,53.9%,49.9%and56.7%being average degraded respectively, after 7 days.Preliminary observation of the stains,they were all grew negative reaction,we further indentify the physiological and biochemical of the strains.Since X09 Enterobacter cloacae and X20 Pseudomonas fluorescens can degrade a broad spectrum pesticides,it should be able to use it in a bioremediation process to minimize contamination of the product and the environment during primary products cultivation.From the pot-culture orthogonal experiment statistical analysis result,we can see the optimal conditions for the degradation of deltamethrin were that,strain-X20,each plant was sprayed 10mg/L Deltamethrin,5mL culture liquid,spraying bacteria culture liquid mixed with deltamethrin and kept for 7 days.In this paper,through nearly two years of laboratory work,we isolated Deltamethrin-degrading bacteria.Study on its degrading characteristics,then we simulated environmental conditions,explore they degradation effect.We work for microbial remediation of pesticide residues,then provide data basis.