Isolation Of Nitrobenzene Degrading Bacteria And Study On Its Enzymatic Degradation Charateristics

As an important chemical raw material,nitrobenzene has a huge production volume and is increasing year by year.It is a highly toxic environmental organic pollutant.When discharged into a water body,it can cause damage to the ecological environment,destroy water resources,and enter the human body through drinking water or food chain,which can cause various diseases to human beings.Because of its"three-dimensional"characteristics,it has been listed as"environmental priority control pollutants"by many countries.The development of biotechnology provides technical support for the effective use of biological enzymes for the treatment of organic pollutants.The speciality,high efficiency and low cost of microorganisms and their biological enzymes provide new ideas and methods for the degradation of nitrobenzene by microorganisms and their biological enzymes.In this paper,microbes in the mixture of sediment and river water of the Weihe River were used as research objects,and nitrobenzene was used as the target pollutant.By enriching,acclimating and separating,a nitrobenzene dominant degrading bacterium was screened and identified by microbial physiological and biochemical identification.Methods,combined with the"Common Bacterial System Identification Manual"and"Berger's Bacterial Identification Manual"to preliminarily identify the strain as Acinetobacter;the initial concentration,pH value and temperature of nitrobenzene as the influencing factors to study the nitrobenzene dominant degradation bacteria The optimum conditions for degradation characteristics showed that when the initial concentration of nitrobenzene was 50 mg/L,the pH was 7.0,and the temperature was 30°C,the degradation rate of nitrobenzene was the best,which was 99.68%.The intracellular and extracellular enzymes of the nitrobenzene dominant degradation strain were extracted by salting out method,and the degradation characteristics of nitrobenzene were studied.The results showed that the intracellular enzyme played a major role in the degradation of nitrobenzene.The external enzyme plays an auxiliary role;the initial concentration,pH value,temperature and metal ion of nitrobenzene were used as the influencing factors,and the intracellular,extracellular and intracellular+extracellular enzymes of the strain were used as the research object to investigate the dominant degradation of the nitrobenzene.The optimal conditions for enzymatic degradation of the strains showed that the intracellular,extracellular and intracellular+extracellular enzymes had the same degradation characteristics.When the initial concentration of nitrobenzene was 50 mg/L,the pH was 7.0,and the temperature was 30°C.The enzymatic degradation rate of this strain was optimized.The effect of metal ions on enzyme activity showed that the metal ions Fe³⁺and Cu²⁺inhibited the activity of the enzyme,while the metal ions Na⁺,K⁺,Mg²⁺and Ca²⁺responded to the enzymatic reaction no effect,but had some activation;by studying the enzymatic reaction rate of different nitrobenzene concentrations,it was found that the intracellular,extracellular and intracellular+extracellular degradation of nitrobenzene by the nitrobenzene dominant degradation strain obeys the Mie equation;The double-reciprocal mapping method was used to determine the intracellular enzyme Vmax=1.3387mg/L?h,Km=173.73mg/L,extracellular enzyme Vmax=0.7531mg/L?h,Km=119.54mg/L,intracellular+outer enzyme Vmax=1.5038mg/L?h,Km=160.56mg/L;by p-nitrobenzene in the dominant degradation strain and its intracellular enzymes,extracellular enzymes and intracellular enzymes plus extracellular enzymes The qualitative analysis of the degradation products under good degradation shows that the degradation products are mainly amines,alcohols,carboxylic acids,ketones,aldehydes and the like.Based on the results and conclusions of this study,it is suggested that S-1,a predominant strain of nitrobenzene isolated in this study,could be used to degrade nitrobenzene in case of a similar pollution event of nitrobenzene in Songhua River in 2005.