The Structure Of Highly Efficient Hydrocarbon-Degrading Complex Bacterium And The Research Of Degradation Characteristics

Petroleum pollution has become serious day by day worsening,which not only cause serious damage to the environment,but also poses a great threat to human health.Efficient management of oil pollution has become one of the hot spots of environmental science,and bioremediation has known as an effective and environmental friendly approach for the decontamination of petroleum pollution.To improve the degradation efficiency of oil pollutant through bioremediation,one key point is the construction of microbial flora with high degradation performance.In this study,three kinds of petroleum hydrocarbons were selected as the sole carbon source and seven highly efficiently hydrocarbon degrading strains were isolated from the oily sludge in the SBR tank with high-salinity from the Weizhou terminal wastewater treatment plant.Through physiological and 16s rDNA phylogenetic analysis,the n-hexadecane degrading strains of A14 and B45 were identified as Leclercia adecarboxylata,strains of C28 and A27 were identified as Enterobacter xiangfangensis and Enterobacter cloacae,respectively.while the phenanthrene degrading strain F7 also belonged to Enterobacter cloacae,the cyclohexane degrading strains of HJ1 and HJ5were identified as Stenotrophomonas maltophilia and Pseudomonas aeruginosa,respectively.All hydrocarbon degrading strains mentioned above are Oxidase negative.Four n-hexadecane degrading strains were isolated,and they could use n-hexadecane as the sole carbon source under the following conditions:n-hexadecane concentration of 0.05-1%（v/v）,salinity of 5-150g/L,and pH of 5.0-9.0.In addition,under the optimal conditions:salinity of 15-25g/L,pH of 6.0-7.0,inoculum rate of 10%,37℃,160r/min,the hexadecane（initial concentration of 0.3%,v/v）degradation rate could reach as high as 93.7%,87.8%,73.3%,and 65.7%,respectively,after incubation for 16 days,while,the degrading ratio of complex flora Z-9 reach 99.1%.The growth of strains followed the Logistic model,with specific growth rate of 0.137,0.066,0.145 and0.254d^-1,respectively.Meanwhile,the hexadecane utilization followed the first order reaction kinetics model,with the half value period of 5.87,6.73,7.97and 10.0d,respectively.Under the metabolism of degrading n-hexadecane,phospholipids-type biosurfactant were produced by strains,meanwhile the yield reached as 0.657g/l,oil diameter was 4.2cm,emulsification index was 70%,Rf value was 0.33,surface tension was 46.6 mN/m,respectively.The degrading ratio of Z-9 was 99.1%,nearly degrade completely.Phenanthrene degrading strain F7 could use phenanthrene as the sole carbon source under the following conditions:pH of 5.0-9.0,salinity of 10-30g/L,inoculum rate of10-30%（v/v）,substrate concentration of 60-140mg/l,30℃,160r/min.In addition,under the optimal conditions:pH of 7.0,salinity of 25g/L,inoculum rate of 15%,the substrate（initial concentration of 100mg/l）degradation ratio could reach as high as 59.3%.The most effect of single factor:pH>salinity>substrate concentration>inoculum rate,the optimal conditions designed by RSM:pH of 7.23,substrate concentration of 80.36mg/l,salinity of 19.79g/l,inoculum of 18.33%,predicted the degradation rate could reached to 64.69%,however,measured in experiment was 63.4%.The addition of 0.8g/l phospholipid surfactants produced by strain B45 could accelerate the degradation,the phenanthrene utilization followed the first order reaction kinetics model,degration ratio reach as high as 81.6%,the rate was 1.72 times compared to no adding.The optimum growth substrate concentration of cyclohexane degrading strains HJ1and HJ5 were 1.5%and 3%（v/v）,the degradation rates of HJ1 and HJ5 could reached95.4%and 97.7%.The strains could growed at the substrate concentration of 5%,HJ1performance than HJ5 in the degradation of cyclohexane shonwed better was better than HJ5 in the degrading cyclohexane with degradation rate were 88.7%and 69.9%,respectively,The complex flora consist of HJ1 and HJ5 showed better degradation than single strain,probably due to the synergistic effect,with maximum degradation rate of90.5%in 5d.The best petroleum degradation efficiency of the compound petroleum degrading bacteria consist of strain A14,F7 and HJ1,with the degrading rate of 88.3%in 72h.GC-MS analysis showed that the compound bacteria had a better efficiency in the medium and long chain petroleum bydrocarbon as C14 to C34.