| With the development of industry and agriculture,a large number of toxic and harmful substances discharged into the soil.The soil quality decreased and the biological activity of the soil was suppressed.Polycyclic aromatic hydrocarbons are ubiquitous persistent organic pollutants in the environment,which are widely concerned because of their carcinogenic,mutagenic and mutagenic effects.The low water solubility and transfer rate of PAHs in soil are the limiting factors of bioremediation.In this study,we isolated a bio-surfactant producing bacterium,and studied the effects of remediation on PAHs contaminated soil by the strain,finally combined the strain with the plant to remediate the PAHs contaminated soil.The aim of the present study was to isolate a biosurfactant-producing bacterium,The selected strain was identified as Pseudomonas aeruginosa 147 by physiological,biochemical characteristics and16S rDNA sequencing.The fermentation products were assigned to glycolipid by Thin Layer Chromatography(TLC)and Fourier Transform Infared kSpectroscopy(FT-IR)analysis.The optimal conditions for the strain to produce biosurfactants were under the initial carbon source of peanut oil,nitrogen source of(NH4)2SO4,carbon nitrogen ratio of 25:1,pH 8,temperature 30? and 5%NaCl.Under these conditions,the surface tension of the fermentation broths could be reduced by 42.08mN/m compare with the control,then kept stable for 144 hours.At the 108 hours of incubation,the bacteria achieved the maximum biomass(2.63g/L)and has the maximum fermentation product(2.02g/L).The solubilization of different polycyclic aromatic hydrocarbons(fluoranthene,pyrene,benzene[a]pyrene)were tested after the addition of the fermentation product The solubilization of polycyclic aromatic hydrocarbons was increased with the increment of the fermentation product added.Under the same concentration of the fermatation product added,the higher weighted polycyclic aromatic hydrocarbons(benzene[?]pyrene)showed the less solubilization compared with the lower weighted polycyclic aromatic hydrocarbons(fluoranthene,pyrene).We set sterilization and non-sterilization treatment of the PAHs contaminated soil with the addition of different concentrations of Pseudomonas aeruginosa 147 strain and incubated with different period.After 15 or 75 days of the incubation under the sterilized treatment,the PAHs concentration were promoted under the treatment with the addtion of the bacteria,and the PAHs concentration increased with the increment of the bacteria.IThese might due to the external bacteria which could produce biosurfactant and increase the solubilization of soil PAHs,finally increase the total PAHs concentration.However,under the non-sterilized soil treatment,the PAHs concerntration decreased,which may due to the strain which can increase the content of PAHs,at the same time promote the growth of indigenous microorganisms with PAH-RHD a GP and PAH-RHDaGN gene,and accelerate the PAHs removal in the soil.When we combined the plant and the bacteria to remediate the PAHs contaminated soil,we found that singly applying the bacteria did not enhance the remediation of the PAHs in the soil,,and plants can effectively promote the soil PAHs removal.The combination of the plant and the strain can further improve the removal efficiency,although it was statistically significant.The accumulation of the PAHs was different between different plants,and the PAHs concentration was higher in the ryegrass than that in the Alfalfa,but with the addition of the bacteria,the opposite result emerged.The removal of PAHs in soil was negatively correlated with the amount of PAHs in the plants,the copy number of fungal genes,PPO and POD enzyme activities in the soil environment.The accumulation of PAHs in plant was positively correlated with the PAHs concentration in vivo,the copy number of bacterial gene,PAH-RHD a GP and PAH-RHDaGN gene copy number,PPO,POD activities and plant biomass. |
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