| Di-(2-ethylhexyl) phthalate(DEHP) is a high molecular weight phthalate esters(PAEs), which has been widely used in polyvinyl chloride(PVC) manufacturing as a plasticizer. Because of biological toxic, teratogenic and mutagenic to human, DEHP has been listed as a priority pollutant by the United States Environmental Protection Agency and by China National Environmental Monitoring. Remediation of DEHP-contaminated sites has been a continuous concern both at home and abroad. Since microbial remediation has the merits of lower cost, environmentally responsible and high-effect, it is the potential and promising techniques in site remediation.In our study, strain JQ-1 which could degrade DEHP efficiently was isolated from an abandoned greenhouse soil in Harbin. The strain was identified by colony morphology, physiological and biochemical tests and gene sequences comparison. The growth and degradation characteristics of strain JQ-1 were also studied. Moreover, the repairing effects of strain JQ-1 by simulating the restoration of DEHP contaminated soil were investigated. The main results are as follows:(1) The strain was named JQ-1 and identified as Arthrobacter(Arthrobacter sp.). It formed a yellow colony, with neat edges and wet and shiny surface. It was Gram-positive and could use DEHP as sole carbon and energy source. Strain JQ-1 was short rod-shaped when observed under transmission electron microscope which was 2.1 μm long and 0.6 μm wide with no flagella.(2) The growth(OD600) of the DEHP-degrading strain was used as an investigation target when single factor tests(temperature, p H, rotation speed, amount of inoculation and different initial concentrations of DEHP) were carried out. The results showed that JQ-1 had good tolerance to alkaline conditions and high concentration of DEHP. On this basis, an orthogonal test with five factors and five levels L25(56) was carried out to optimize the culture conditions. According to analysis of the orthogonal tests, the optimum growth conditions of strain JQ-1 are as follows: the initial concentration of DEHP was 2000 mg!L-1, optimum temperature was 30℃, the p H was 9, the inoculation amount was 4% and the rotation speed was 150 rpm!min-1.(3) The DEHP degradation rate of the strain JQ-1 under liquid medium was 98.86% after 84 h cultivation. Besides the strain JQ-1 showed strong substrate specificity by broad spectrum tests.(4) The degradation effect of strain JQ-1 in DEHP polluted soil was investigated. The concentration of DEHP in the soil decreased from 50 mg kg-1 to 9.88 mg!kg-1 after 42 days remediation. While, the residual concentration of DEHP in contaminated soil without inoculation of the strain still remained at a high level(25.33±0.29 mg!kg-1). The results showed that addition of strain JQ-1 could accelerate the degradation of DEHP in contaminated soil. Meanwhile, chloroform fumigation extraction technology was adopted to determine the variation of microbial biomass C, N and P over time in the contaminated soil. The results showed that, during the experiment, addition of strain JQ-1 could effectively alleviate the toxic effects of DEHP on soil microbial activity.(5) Studies have shown that addtion of strain JQ-1 strain could repair the DEHP contaminated soil efficiently and reduce the hazards of DEHP to soil microorganisms. This result will provide some theoretical bases and technical supports for the removal of PAEs in contaminated soil. |
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