| Dibutyl phthalate phthalate(DBP) is a kind of refractory organic compounds, which is widely used as plasticizers in PVC plastics. DBP attracts more and more attention, because of the widespread use, the ubiquity in environments, as well as the neural and reproductive toxicity, and the damage caused to the flora, fauna and the human body. In nature, biodegradation is the only way to effectively reduce the concentration of PAEs, which is not effectively decomposed in the water or in the light.In the experiment, the bacterial strain DNB-S1, which is capable of degrading DBP effectively, is extracted from a derelict contaminated soil, with DBP as the sole source of carbon for energy. And its physiological and biochemical index, growth characteristic and degradation characteristic, as well as degrading enzyme extraction and preliminary applications are studied and discussed. The main results are as follows:1. A DBP degradation bacteria strain, isolated and identified as Pseudomonas sp, was named DNB-S1. Under the electron microscope, the strains, which was 1721 nm long and 709 nm wide,showed straight rods, with polar flagella movement, no nuclei. In the treadmill test, we found that,the colonies are white and opaque, with jagged edges, a raised center, and no spores. And the colonies, a class of strict oxygen fungus, were Gram-negative, with DBP as the sole carbon and energy source for growth.2. The optimum growth conditions for DNB-S1 are that : The DBP concentration of500mg/L,temperature 35 C 7 for p H,inoculation amount was 3%,shaker speed is set to 125r/min.Determination of the discovery and training of strain 48 h,under this condition, the degradation ofthe500mg/LDBP rate of DNB-S1 was 90%.Analysis of selected 12-33 h degradation kinetic equation, get the DNB-S1 first-order kinetic equation,(R2=0.9837),the degradation half-life of approximately 20.9 hours.At the same time, the growth characteristics also shows that high concentrations of DBP(2000mg/L)has certain inhibitory effect on the DNB-S1 growth.3. Through the comparison of enzymatic degradation capacity, DNB-S1, the degradation bacteria of DBP, is proved to be the induced intracellular enzymes. In the condition that, with a ratio of 1:10, the crude enzymes with 90ug/ml concentration of soluble protein is mixed withphosphate buffer, in which the initial concentration of DBP is 500mg/L, after 24 hours, the degradation rate of DBP achieves 85.6% in optimal conditions( 35℃, p H=7.0).4. The sodium alginate is chosen as immobilized material for immobilized treatment of DNB-S1 intracellular enzymes, as well as doing the single factor experiment and orthogonal experiment. The four factors, including Sodium alginate mass fraction,mass fraction of Ca Cl2 solution,the embedding ratio,fixedtime,can be screened.To get the optimum immobilization conditions for:18m L immobilized crude enzyme system in optimum adding amount of 900ug(the concentration of soluble protein was 50ug/m L),mass fraction of sodium alginate as embedding ratio 1%,1:2,Ca Cl2 solution mass fraction is 2%. Within the 24 h immobilized enzyme pellets can degrade DBP500mg/L to only 98.5mg/h,the degradation rate can reach 80.3%。(5) Respectively set blank processing repair treatment,free enzyme,immobilized enzyme repair 3 experimental groups of soil in the repair test, adding 500mg/kg DBP in soil sample,respectively,finally found in 0,7,14,21,28 day sampling to detect residual DBP content, compared with blank treatment, after adding the degrading enzyme the content of DBP was obviously decreased,and after 28 days of treatment response, free enzyme DBP can be degraded to only9.192kg/mg, the degradation rate was 63.2%, the effect is remarkable. The immobilized enzyme effect is better,the degradation of DBP within 28 days of the rate of 91.01%,the final DBP content of only2.2215mg/kg,slightly higher than the provisions of the United States environmental standards,lower than the average content of detection DBP Harbin agricultural soils,preliminary reach the aim of repair. |
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