Screening, Identification Of Chlorpyrifos-degrading Strains And Their Uses In The Bioremediation Of Chlorpyrifos-contaminated Soil By Composting

The degradation of chlopyrifos in soil was been concerned by people for its efficient and low toxicity as an broad-spectrum organic phosphorus insecticides. Microbial degradation was considered to the most reliable and efficient way, for microorganism playing a key role in the degradation process of organic phosphorus pesticide in envionment. Isolation and screening of effective chlopyrifos-degrading microorganism was an effective measure to chlorpyrifos pollution control and the bioremediation of contaminated soil. Bioremediation technology of composting for its low cost but high efficiency was widely used to the treatment of persistent organic pollutants such as chlopyrifos.In this paper, the feasibility of bioremediation of chlopyrifos contaminated soil by composting with inoculating screened chlopyrifos degradating microorganism was discussed. Also the strains isolating and screening from organophosphorus pesticides contaminated soil were identified and studied on their degradation characteristics, for whose effect on the degradation of chlorpyrifos were better.Cultured by enrichment culture and impressed by high concentration chlopyrifos,12 strains were isolated from the soil contaminated by organophosphorus pesticides for a long time, which could utilize chlopyrifos as the sole carbon source. In the liquid pure culture conditions, the degradation of chlorpyrifos studies showed that when the concentration of chlorpyrifos was 50mg/L, the degradation effect of three isolated chlorpyrifos-degrading strains were much better, and the results of degradation kinetics studies also made the following sort about the degradation characteristic of chlorpyrifos:X1>Y>Y3. Strain X1 could be applied to bioremediation of chlorpyrifos contaminated soil at normal tempeature because it was the best screening strain for degradation of chlopyrifos when the culture tempeature was 30℃, which. Strain Y3 was the most suitable strain to inoculating in composting for bioremediation of chlorpyrifos contaminated soil because of its degradation ability on chlorpyrifos and adaptation to high temperature.The species of X1 and Y3 were identified by the 16SrDNA sequencing with phylogenetic analysis methods and the Biolog automated microbial analysis system, respectively. The results showed that Strain X1 was identified as Methylobacterium sp. Strain X1 for 100% homology about its 16SrDNA sequence with that of Methylobacterium sp. Strain, while Strain Y3 was identified as Aspergillus fumigatus Fresen-Y3 with 100% probability by matching with the microbial species database of Biolog automated microbial analysis system.Mature Index of Composting and degradation of chlopyrifos in composting of chlopyrifos contaminated soil with an inoculum of Strain Y3 were investitaged in this paper. The results found that the residues time of chlopyrifos in soil reduced by 12d, efficiency of composting was improved, and the time to maturity of the compost also was shortened for the reason of inoculating Strain Y3 in composting. Chlopyrifos with the concentration of 50mg/kg in siol was confirmed to affect the process of composting with the maturity time extended of composting, but the inoculation of Strain Y3 could significantly offset the impact on composting process.All studies above indicated that a large number of microorganism utilizing chlopyrifos as the sole carbon source were discovered in organophosphorus pesticides contaminated soil for a long time, which could efficiently biodegrade chlopyrifos after isolated and acclimated. The method for bioremediation of chlorpyrifos-contaminated soil by composting with inoculating the screening chlopyrifos degrading-strain Y3 was absolutely practical, which also was applied to the bioremediation of persistent organic pollutants by composting.