The Isolation And Identification Of Naphthalene And Phenanthrene Degrading Bacteria From Coal Bed Water And The Study Of Their Degradation Capability

Coal is a kind of important fossil energy,and it is solid-combustible minerals formed by ancient plant remains which were trapped in the ground after a long period of geological process,which can cause serious pollutions to the atmosphere,soil and water environment in the process of using.Because of its highly complex structural components,making it become the direct source of the high-molecular-refractory-organic pollutants such as PAHs,PCB,BTEX and cycloaliphatic polymer.PAHs are common organic pollutants which are made up of two or more aromatic rings fused together,and they are volatile organic compounds being formed by incomplete combustion of the coal,oil and other organic materials under high temperature,and also they are carcinogenic,teratogenesis,mutugenic potentially.Their stable chemical structures and strong hydrophobic properties determine that they have characteristics of degradation-resistance and the accumulation,so they can exist in the environment for a long time stably.They are difficult to control with conventional methods,therefore,the microorganisms involved in PAHs degradation studies have increasingly become the focus.Microbial degradation of PAHs is that PAHs are degraded into harmless or less harm small molecular compounds with the action of microorganisms,which is economic,high efficiency and no secondary pollutions,etc.In this article,we mainly have used the coal seam water of Sihe mine and Zhaozhuang mine in the southern of Qinshui basin to enrich and screen out the degrading bacteria with the PY medium containing naphthalene and LB medium by microbiological method.We have done a comprehensive identification for all the degrading bacteria through the morphological,physiological and biochemical characteristics and 16 S rDNA homologous sequence analysis methods or so and isolated out seven aerobic degrading strains finally,that was one strain Bacillus and six strains Pseudomonas,respectively named the strain 2,strain 3,strain 4,strain 5,strain 6,strain 7 and strain 8.The strain 2 belonged to the Bacillus,the rest of the strains belonged to the Pseudomonas.We have analyzed the naphthalene and phenanthrene degradation capability for the seven degrading bacteria using HPLC technology finally,and drawed some conclusions as follows:(1)The seven degrading bacteria could utilize many soluble sugars such as glucose,lactose,maltose and so on for growth as their carbon source,the methyl red test was negative other than strain 2,the V-P test was negative,the catalase test and the oxidase test were both positive,no indoles,the nitrate reduction reaction was positive and the nitrite reduction reaction was negative,which could produce yellow-green fluorescent pigments except strain 5 and strain 8.(2)Most degrading bacteria had faster degradation rate within the logarithmic phase and then slowed down.Strain 2 had better degradation effect for low concentration of naphthalene and phenanthrene comparing to other Pseudomonas,the degradation rate was74.01%,69.84% respectively within 7 days for initial concentration of 50 mg/L of naphthalene and 500 mg/L of phenanthrene,whereas it did not present high efficient degrading rate for high concentrations of naphthalene and phenanthrene.(3)Strain 4 had a degradation rate reaching up to 69.34%,40.69% respectively for concentration of 500 mg/L and 1000 mg/L of naphthalene within a week,whereas the degradation rate was as high as 72.9%,66.27% respectively for concentration of 50 mg/L and 500 mg/L of phenanthrene.While strain 7 had a degradation rate reaching 74.66%,41.32% respectively for initial concentration of 500 mg/L and 1000 mg/L of naphthalene within a week,whereas the degradation rate was as high as 65.34%,53.57% respectively for initial concentration of 50 mg/L and 500 mg/L of phenanthrene,and they showed a remarkable degradation effection.(4)With the increase of the concentration of naphthalene and phenanthrene,the degradation capability of degrading bacteria presented a downward trend,and the degradation of difficulty of degrading bacteria increased as the increase of the number of benzene rings in PAHs.