| At the same time when petroleum brings great economic benefits, it poses seriousthreat to the environment. During the process of reconnaissance, exploitation,transportation and deposit, a large area around the oil field suffered from seriouspollution.Oil pollution makes the Physical and Chemical properties of the soil change,which does harm for the crop.The poly aromatic hydrocarbons (PAHs) of petroleumcome into human and animal bodies through respiration, skin contact, eating and soon, which influences the normal functions of organs like liver and kidney, etc., andeven causes cancer. The petroleum substances constitute a menace to layers of humansurviving surroundings by the pollution of groundwater and the transfer of pollution.Therefore, it is very significant to solve the problem of oil pollution.The present disposal ways of oil pollution includes physical technique, chemicaltechnique and biological restoration, among which, biological restoration has distinctadvantages because the microbiological technique in it attracts people's attention dueto its economy, high efficiency and no second contamination.This thesis discusses about the research development of petroleum degradingbacteria. Some physical and chemical properties of the polluted soil on Shengli oilfield are investigated, and the influence of the physical and chemical factors on themicroorganisms is analyzed. The result indicates that the pH index and water contentof the soil on Shengli oil field are comparatively good for the degradation ofpetroleum, however, the content of nitrogen and phosphor is deficient. The amount ofbacteria in the polluted soil on Shengli field is positively correlated with the degree ofoil polution, which shows that oil pollution stimulates the growth and reproduction ofbacteria, many of which are oil-degrading ones. Trying to increase the amount ofoil-degrading bacteria can improve the oil degrading velocity to some extent.Forty eight hydrocarbon-degrading bacteria are isolated from the polluted soil.They can grow on the culture with oil as the sole carbon source. Their degradingcapacity is determined by weighing it. One of them named 227# had the betterdegrading capacity. It reached 43%.The identification of this bacterium onphysiological biochemical and molecular biological level illustrates that it isPseudomonas aeruginosa.Many factors govern the process of degrading. Firstly, every factor was analyzed.Then an orthogonal experiment was done. After optimization, pH was 7.5, initial oilconcentration was 0.8%, the volume of medium was 100ml/500ml, inoculum size was2.5%. Under such condition, cultivating in the shaking flask at 35℃ for 10 days, wecarried out an experiment finding that the biodegradation rate reached 53.7%.Contrastof petroleum between biodegraded and unbiodegraded by using gas chromatographyindicates that some component of the crude oil was obviously reduced or disappeared.This strain can use crude oil, lubricating oil, diesel oil and hexadecane as the solecarbon sources. The activity of dehydrogenase which correlated with alkanedegradation was measured. The result shows that the activity of dehydrogenase in theoil medium was much higher than that without oil, which proves that the activity ofdehydrogenase was improved in the medium which contains hydrocarbons. So it isinferred that this enzyme has some relationship with hydrocarbon degradation. Theeffective expression of the coding gene needs the inducement of hydrocarbons.This strain can also use naphthalene and phenanthrene as the carbon sources. Theactivity of catechol 2,3-dioxygenase which is correlated with aromatic hydrocarbonsdegradation was measured. It is found that activity of the ferment liquid is muchlower than that of the broken cell, which proves that this enzyme is in the cell.Moreover, this strain has high lipase activity.The plasmid of 227# is extracted by alkali lysis. It is detected by electrophoresis.The result shows that this strain had a plasmid of 4 kb, which may carry degradinggenes. |
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