Study On PAHs-degrading Enzyme Preparation And Remediation Of PAHs Contaminated Soil

With the increasing consumption of fossil fuels, polycyclic aromatic hydrocarbons(PAHs), poisonous to humankind, accumulate continually in the environmental. Microbialdegradation is the main way of PAHs removal in the soil.In this study, Acinetobacter calcoaceticus21#, which can degrade PAHs efficiently, wasisolated and intracellular enzyme was extracted with ultrasonic from its fermentation liquid.Then the immobilization materials were selected and the crude enzyme was immobilized.Finally, preparation of PAHs degrading enzyme and process optimization was studied. Thispaper has also studied the bioremediation of immobilized enzyme on PAHs contaminated soil.The main research results are as following:1. The highly efficient degradation bacterium, Acinetobacter calcoaceticus, was screenedwhen PAHs as the sole carbon. The degradation regular pattern of phenanthrene and pyreneby Acinetobacter calcoaceticus was similar with a lag period of5days and was quicklydegraded from the6thday. The degradation rate of phenanthrene was45.9%and pyrene49.3%after10days.2. The optimum medium for Acinetobacter calcoaceticus determined through responsesurface methodology was yeast extract12.6g/L, tryptone5.8g/L, NaCl5.0g/L. The thallusyield was16.4g/L when cultured at30℃with rotate speed at150r/min.3. The optimum conditions for PAHs depredating-enzymes extraction fromAcinetobacter calcoaceticus were determined through box-benhnken center combinationexperimental design and response surface method were duration of radiation each time2s(with a2s interval), ultrasonic power320W, total irradiation time17min, cell dilutionmultiple12.5. The PAHs-depredating enzymes activity was190.48U/g under the optimumcondition. Culture of Acinetobacter calcoaceticus reaches the maximum biomass at27h andreached the maximum enzyme activity at24h.4. Diatomite was chose as the carrier to immobilize the enzyme. It is showed that whenthe load of enzyme was2-5mg·g-1, especially when2-3mg·g-1, the activity of theimmobilized enzyme was biggest.5. The optimized immobilization process showed that the activity of the immobilized enzyme reached the peak after immobilizing6hours under the condition of glutaraldehydeconcentration was3%as cross linking agent, immobilization temperature was4℃, pH was7.0.6. Soil remediation process with immobilized enzyme was carried out and it was showedthat when the moisture content was20%, temperature was20℃and stirred on random couldreach a better result with a degradation rate of49.5%after handled for2days.