Screening Of Petroleum Degrading Strains And Studying On The Mechanisms Of Bioremediation Of Petroleum Contaminated Soil

Petroleum is the important energy source in human`s life and productive. Petroleum is akinds of complex compound which consisited of alkanes, polycyclic aromatichydrocarbons,asphaltene and resins.The polycyclic aromatic hydrocarbons which are one partof petroleum are toxcitity to human beings and animals.With the wide use of petroleum,petroleum-polluted soils became progreesively worse. Therefore, how to remediationpetroleum polluted soils is the focus problem.In this paper,16strains were isolated from three different petroleum-contaiminated soilsby enrichment culture using Bush-hass medium.Their physiological-biochemicalcharacteristics, degrading genes, and total petroleum hydrocarbon (TPH) removal efficiencywere studied by using16sRNA sequece and PCR-agarose electrophoresis.And petroleumpolluted soils were bioremediated with different treatments by using the degrading strains.During bioremediated, the changes of physical and chemical characteristics of soils, TPHdegrading genes, the number of degrading strains, the bacteria community diversity and theTPH components were studied. The results have shown as follows: The results of our analysisand investigation have shown as follows:16strains of bacteria have been isolated from three different petroleum-contaminatedsoils through cultural enrichment via the Bush-hass medium. These strains have beenidentified as Pseudomonas，Pseudomonas aeruginosa，Pseudomonas stutzeri，Acinetobacter，Bacillus， Flavobacteriaceae，Escherichia, Achromobacter, etc.Among the16strains，7strains showed good degradation ability to TPH, whichTPH-removing rates were from31.5%to54.7%after20days’ inoculation.There is a clear correlation between the degaration genes of strains and the TPH removal rates. Those strainswho contained both the genes of dioxygenase and monooxygenase showed high degradationability toward TPH.Different threatments showed different bioremediation effects towards petroleumpolluted soils.The best treament was biostimulation which added N and P nutrients to soils,and bioaugmentation(adding degrading bacteria to soils) the better and and naturalremediation the worst one.There exists both positive correlations between catalase/degrading genes and the TPHremoval capabilites in bioremediation soil. The more degrading genes, the betterbioremediation effect. The number of TPH and alkanes degrading strains is more thanaromatic degrading strains in petroleum-polluted soils.PCR-DGGE profiles of soil bacteria community were analyzed. When strain SZ-1wereadded to soils, the diversity of soil bacterial community increased, the Shannon and Simpsonindex of soil bacterial community were determined, and there is a certain correlation betweenthe baterial community diversity and the TPH degradation effciency.In the later period of bioremediation, TPH removal efficiency decreased and TPHbiodegradation showed lag phase. There is no noticeable degradation effects when continue toadd nutrition(N and P) or degrading strains to soils, but TPH biodegradation effects are betterwhen glucose substrate were added to soils which were in lag phase.The different compinent of TPH in one stage bioremediation(for the first eight weeks)were analyzed by using GC-FID. The results shown that the degrading efficiency of saturatedhydrocarbons in5#threatment(which added N/P nutrions) were the best. The degrading rateof saturated hydrocarbons with C14~30are both higher than70%.The different componet of TPH in third stage bioremediation(for the third six weeks)were analyzed by using GC-FID. The results shown degrading effciency of saturatedhydrocarbons in the4#-1treatment (which added glucose substrate to the soil) and the6#-2(which added glucose substrate and N/P nutrition to the soil) were both good. In the6#-2threatment, the saturates hydrocarbon with C14~C30were all fully degraded. However, in4#-1threatment, the degradation rate of saturated hydrocarbon with C14~C19is mainlyhigher than50%.