Study On Isolation And Characterization Of An Efficient Nitrobenzene-degrading Bacterium Strain

Nitrobenzene,also known as dense-patches oil or bitter almond oil,isa colorless or slightly yellow oily liquid with bitter almond flavor.It is widely used indyes,perfumes,explosives,pesticides and other chemical industries for the organicsynthesis intermediates and the raw materials of the aniline production.It havefeatures such as chemically stable,refractory and high toxicity,so it can bring aboutserious environmental pollution once enter into the environment,therefore it wasincluded in the list of Environmental priority control toxic or organic pollutants.Theauthor screen and separate a strain which can use nitrobenzene as the sole carbonsource and degrade it efficiently from nitrobenzene swage treatment pond,and namedit as NB-K strain.Firstly,16S rDNA sequencing comparison was done to the NB-K strain.Sequence analysis showed that it had99%similarity to the16S rDNA of klebsiellavariicola,and combined with the main physiological and biochemical characteristicsof NB-K strain,it could be identified as klebsiella.sp(The GenBank accessionnumber is KC354804).Secondly,do some research on strain NB-K characteristics of degradingnitrobenzene.The results show that when the strain use nitrobenzene as the solecarbon source,The optimum condition is the temperature35℃,pH7.0,inoculumsize5%,and the orthogonal experiment at the late stage aslo test and verify thecombination of these conditions is the best degradation combination.Under thiscombination,the degradation rate of600mg/L nitrobenzene is about to reach98%,closed to the national emission standards.Experiments show that if plus acertain amount of glucose,the degradation time can be effectively reduced,and thestrain has strong adaptability to the external environment:the highest toleratednitrobenzene concentration was close to1500mg/L；could maintain more than90%degradation rate at the pH5.0～9.0Under the above conditions and less than3%saltconcentrations have no effect on the strain degradation.It has the potential to beapplied to the actual sewage treatment，and can be used as the biological repair strainsof the polluted environment by nitrobenzene. Finally,a preliminary study on the kinetics of the degradation process wasconducted.As The research shown,the zero-order reaction equation could betterdescribe the degradation process when the nitrobenzene concentration below1000mg/L,it degraded nitrobenzene at a relatively constant rate.When thenitrobenzene concentration was600mg/L,the maximum degradation rate was12.74mg/(L·h),and this data was the highest in recent years reported.Higher or lowerthan this concentration,the degradation rate had different degrees of decline.Whenthe nitrobenzene concentration exceeded1000mg/L,the inhibition to the straindegradation is obvious.