Study On Solation,Screening And Degradation Mechanism Of Nitrobenzene Degrading Bacteria At Low Temperature

Nitrobenzene is a yellowish organic substance of bitter almond flavor.It is highly toxic,volatile,dense and water stable,and difficult to degrade once it enters the environment.Nitrobenzene is a common chemical raw materials,with industrial wastewater emissions,a serious threat to human health and water environment,has been listed nitrobenzene in many countries or organizations in the list of priority pollutants in water,so the use of the appropriate treatment of nitrobenzene degradation,or reduce the concentration to the country the prescribed emission standards is one of the environmental problems we need to solve.In this experiment,nitrobenzene as the target pollutant,the bacteria mixed microbial caotan section of Weihe city of Xi'an in the sediment as strain source,using nitrobenzene as sole carbon source at low temperature?12??condition,the pH value is 7,the bacteria anaerobic acclimation by gradually increasing concentrations of nitrobenzene,purified four nitrobenzene degrading strains isolated from domesticated domestication and mature in the liquid?named W1,W2,W3,W4?.The screening experiments of 4 nitrobenzene degrading strains showed that the degradation rate was 84.26%,89.78%,81.66% and 93.82% at nitrobenzene concentration of 20mg/L and 9 days after degradation.Through screening experiments,W4 strain was found to be a dominant strain of nitrobenzene.According to morphological characteristics,Gram staining,physiological and biochemical test results,combined with the manual of identification of the Earl of bacteria,W4 as Corynebacterium rods.At the temperature of 12? under anaerobic conditions,the pH value,the initial concentration of nitrobenzene,microbial inoculation,different carbon source and nitrogen source for the influencing factors of degradation characteristics of strain W4 showed that the strain degradation of nitrobenzene in the optimal condition is: pH 7,microbial inoculation amount was 15 ml,the initial concentration of nitrobenzene 16.93mg/L;under the optimal conditions of anaerobic degradation of nitrobenzene at low temperature for 9 days,the degradation rate can reach 97.91%.At the same time by GC-MS analysis of degradation products,the main product was aniline,aldehydes,ketones and alcohols,speculated that the degradation pathway may is first generated through reduction of nitrobenzene Nitrosobenzene and aniline by microbial degradation of the enzyme synthesis of aromatic ring opening,generating low toxic or nontoxic alcohols,organic acids and ketones,and finally mineralized to CO₂ and H₂ O.