Development And Application Of PAHs Phenanthrene-Degrading Bacteria In Engineering

Polycyclic aromatic hydrocarbon(PAHs), a kind of toxic pollutants, is accumulated and widely existed in the environment. Phenanthrene, as a special tricyclic aromatic, has the typical structure with a “Bayregion” and a “Kregion”, which are major causes of carcinogenic PAHs. By virtue of its chemical composition, it has become the representative of PAHs in the research.By microbial metabolism, the natural attenuation of some toxic pollutant can be prompted. Bioremediation technology has many advantages such as low costs, high efficiency, no secondary pollution, therefore it’s a most competitive method to repair phenanthrene. Although high concentration of PAHs causes serious pollution, studies of microbial degradation in this substrate environment are rarely reported now. Other factors like some human activities in industry, mining, agriculture and high values in soil background also intensified the problem. Consequently, it’s more valuable to screen high efficient phenanthrene-degrading strains in high concentrations.In this study, twenty strains, which use phenanthrene as carbon source, with great degradability were screened from activated sludge in aeration tank of Shenyang northern sewage treatment plant, then investigated their ability to degrade phenanthrene. The results showed that six strains, W2, W6, W9, W12, W16 and W20 respectively, had great degradability of phenanthrene and the rates were all above 50%. Through rescreening, W12 was assessed as the best efficiency degradation bacterium with optimal degradability and growth performance.According to character analysis of morphological, physiological and biochemical and 16 S r DNA sequence, strain W12 was identified as Pseudomonas otitidis, a new type.The research on its degradation of phenanthrene was rarely reported. And the draft genome sequence of it was the genome of such strains for reference.The degradation character tests of strain W12 showed that the optimum temperature for biodegradation of phenanthrene was 30℃, p H was about 7.0, and inoculum was 10%; when salinity was 2%, the degradation rate and growth of the strain showed significant downward trend, so the optimum salinity was 0.5%; When peptone and yeast extract were added as additional organic, the degradation rate were increased to 75.65% and 70.85% respectively, while with the addition of glucose the degradation was inhibited; With different inorganic nitrogen sources, the fluctuation of strains growth status was smooth, with diammonium phosphate, the growth and phenanthrene degradation were all in the best condition, then, ammonium sulfate. However, the effect of sodium nitrate was not very obvious; When each environmental factor were in the most suitable scope, concocted the sample with 1000mg/L phenanthrene concentration, the degradation rate of phenanthrene reached to 65.80% after 96 hours and the tolerance of concentration was up to 2000mg/L.Under the 500mg/L concentration conditions, phenanthrene degradation rate and constant of it were both high, and the stain W12 degradation kinetics of phenanthrene followed the Monod equation model, the parameters were as follows: vm=0.7710, ks=170.3315, ?m=0.0540; While under the 1000mg/L concentration conditions, the degradation process almost matched Haldane equation, the parameters were as follows: vm =2.66, ks =603.25, ki =1059.06, ?m=0.0400.