| Polycyclic Aromatic Hydrocarbons (PAHs) may cause serious threats to biological growth and ecological environment. Micro-biological degradation is a common and widely used method among some migration or eliminate ways of PAHs. This paper targeted Bacillus. Y2 strains which has efficient degradation of Phenanthrene and filtrated from Dianchi, used Phenanthrene as pattern material of PAHs, and studied the characteristics of some enzymes as well as the degradation ability of Y2 strain under different phenanthrene concentrations. The main conclusions of this paper show as follows:(1) Y2 strain had strong tolerance ability and wide tolerance range of phenanthrene, it could grow well in 50-5000 μg/L phenanthrene. Both the concentration of phenanthrene and incubation time had significant effects on bacteria growth. Adding 5%LB culture medium, the bacteria grew rapidly (OD600) on the first day and remained stable on the second day. The bacterioprotein accumulated rapidly within 48h, bacteria gradually decline and concentration of bacterioprotein gradually reduced between 48-72h.5000 μg/L phenanthrene could promote bacteria growth, but 500μg/L and 50μg/L phenanthrene restrained it. Using phenanthrene as sole carbon source, within 24 h, bacteria almost had no growth indication in the concentration of 0 μg/L,50 μg/L,500μg/L, only 5000μg/L phenanthrene promoted bacteria growth obviously. The bacteria grew rapidly within 24-48h, the acceleration to bacteria of 5000 μg/L phenanthrene reached 379.45%. within 48-72h, protein accumulated slightly, the higher of phenanthrene concentration, the weakest acceleration to increases.(2)Phenanthrene could intensify the oxidative stress of bacteria (the oxygen anion and MDA content increased), but it may induce the defensive system of bacteria (including super oxygen anion, superoxide dismutase(SOD), catalase(CAT) and total antioxidant capacity(T-AOC). glutathione transferase (GST)) at the same time. In the concentration of phenanthrene, Adding 5% LB culture medium may promote the defensive system of bacteria. Bacteria feeled the stimulus from phenanthrene, which induced cells peroxide and produced more superoxide anion and MDA which damaged to cells and mitigated damage by producing SOD, GST, CAT to eliminate the superoxide anion. oxygen radicals, MDA and so on. But high phenanthrene concentrations damaged to bacteria severely, which result in cells cannot induce much detoxified substances. Without 5% LB culture medium, cells sustained double stimulation of phenanthrene and hunger, so the ability of resist adverse environment was weak relatively. and actuated its defensive system slowly(3)Phenanthrene could stimulate bacteria enhance the activity of phenanthrene degradation enzyme. In the concentration of 50 μg/L,500μg/L phenanthrene, bacteria could produce more degrading enzyme such as C23O, PPO, salicylate hydroxylase in the presence of initial carbon source. These enzymes helped bacteria open cycles of phenanthrene and use of intermediates, increasing the ability of phenanthrene degradation; in 5000 μg/L phenanthrene, bacteria produced less C23O, PPO salicylate hydroxylase compare to bacteria in the situations without initial carbon source.(4) Y2 strain had strong degradation ability of phenanthrene. Adding 5% LB culture medium, the phenanthrene degradation rate of bacteria reached 74.25%, 84.23% and 69.29% respectively in the concentration of 5000 μg/L,500 μg/L,50 μg/L on the third day; Without 5% LB culture medium, the degradation rate of bacteria on phenanthrene reached 75.93% ,72.98% and 69.84% respectively in the concentration of 5000 μg/L,500 μg/L,50 μg/L at the same time. The bacteria accumulated phenanthrene and stored in the body in 24h, then began to degrade it in 24-48h. The bacteria degraded more quickly in high concentration of phenanthrene.This study reflects that Y2 strain (indigenous microorganisms of Dianchi) has strong tolerance and strong degradation ability of phenanthrene, which can provide foundation of the government of PAHs contamination. |
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