Isolation Of Efficient Crude Oil Degrading Strains And Study Of Their Degrading Performance

Dalian University of Technology panjin campus was located in Panjin city,it is the home of Liaohe Oilfield.The crude oil contamination of soil is becoming a serious environmental issue,due to the intensive and continuous uses in recent decades.The pollution status of petroleum hydrocarbons and accompanied heavy metals in local soil environment was studied first.Novel bioremediation methods get more attention to solve the current environmental challenges due to their green,cost-effective and sustainable.Functional wild strains were highly efficient to degrading the crude oil.Therefore,present research have isolated indigenous strains from local contaminated soil and study their degradation performance in liquid media and artificially contaminated soil.The degradation performance was evaluated through Gas Chromatography and UV spectrophotometry methods.In parallel,we have studied the degradation of a typical single-ring aromatic hydrocarbon BTEX?benzene,toluene,ethylene,and xylene?.As we know,BTEX could penetrate into the deeper location of soil which would further contaminated the groundwater.So that,it is worth to study the biodegradation of BTEX,which could benefit from the bioremediation of contaminated groundwater.In this study,we have found that the pollution degree was inversely proportional to the distance from the sampling point to the oil well.The content of petroleum hydrocarbons in the soil within 40 m from the oil well was exceeded the national standard limit(500 mg·kg^-1).Soil heavy metal pollution caused by the migration of crude oil components were often overlooked.From the detailed soil contaminant analysis,the total content and distribution of various forms of heavy metals in the soil sample were found that the Cd and Pb were significantly correlated with the petroleum hydrocarbons?P<0.01?.Besides that,38.54%of Cd contained in oil-polluted soil existed in an exchangeable form which could make it highly bioavailable and high in toxicity.Functional microbes is the key factor of bioremediation.Two indigenous strains that metabolize strictly depend on crude oil were screened out from the local crude oil contaminated soil and identified as Pseudomonas aeruginosa and Rhodococcus erythropolis,respectively through 16s rDNA sequencing and biochemical test.Oil spreading and thin layer chromatographic analysis implied that both strains could produce glycolipid bio-surfactants,which was quite beneficial for enhancing the bio-degradability of crude oil.Monitoring the degradation of crude oil in liquid media leading us to determine that the multiple strains have higher bio-degradations efficiency compare to the single strain,the oil degradation rate can reach up to 92%?crude oil inoculation for 2%,V/V?within 20 days.Further study on the bioremediation of in-vitro contaminated soil showed that exogenous carbon source could promote the degradation of crude oil components.25%(crude oil inoculation for 5.0 g·kg^-1)were degraded within 30 days when excluding the effect of natural evaporation on the content change of petroleum hydrocarbons.In addition,Cd²⁺has a minor impact on the microbial metabolism of petroleum hydrocarbons in soil under experimental concentration(10 mg·kg^-1).When took BTEX mixture as a sole carbon source,all the four aromatic substrates conform to the Monod first-order degradation kinetic model,the degradation capacity of Pseudomonas aeruginosa strain Dut-lxm0725 were higher than that of Rhodococcus erythropolis strain Dut-lxm1018.The degradation rate constant of Benzene,Toluene,Ethylene,o-Xylene were 0.0257h^-1,0.0351 h^-1,0.0391 h^-1 and 0.0353 h^-1 respectively.