Research On The Isolation And Degradation Characteristics Of Nitrobenzene Cold-adapted Bacteria

The nitrobenzene (nitrobenzene) is faint yellow, with bitter almond taste poisonous substance, which is hardly biodegraded. It is widely used in chemical industry, dye, pharmacy and so on. The emission of nitrobenzene brings serious threat to the environment. Therefore, the treatment of this toxic organic pollutants has been the focus of research.The common technology in removal nitrobenzene includes physical methods,chemistry methods and biological methods. The biological methods can degrade pollutants greatly with low cost. Recently, the study on the biodegradation of nitrobenzene in domestic and international show that various nitrobenzene-degrading bacteria have been isolated, Such as Bacillus subilis, Streptomyces albidoflavus, Comamonas sp., Acinetobacter sp., Pseudomonas pseudoalkaligenes, Rhodotorula mucilaginosa and so on. However, the most bacteria degrade nitrobenzene under normal temperature, the research of nitrobenzene-degrading bacteria under low temperature is very rare. In our country, especially the winter, the temperature is very low when bacteria degrade nitrobezene. The metabolism of most microorganisms is restricted, thus the ability of degradation is aslo restricted. Therefore, it is significant to screen bacteria that can effectively degrade nitrobenzene.In this paper, sixteen bacteria that can utilize nitrobenzene as sole source of carbon at low temperature, which was isolated from activated sludge of aeration tank and Cholramphenicol production wastewater collection pond in Northeast pharmaceutiocal factory. Study on degradation characteristics of sixteen bacteria show that there are six strains with high degrading ability, named as aa-1, aa-2, bb-1, cc-1, cc-2 and cc-3. Through the experiment of screening of bacteria, we find out cc-2 is effective nitrobenzene-degrading bacterium at low temperature. According to morphological characteristics,physiological and biochemical characteristics and 16SrDNA, the bacterium cc-2 is identified as Acinetobacter baumannii.The study on growth and degradation characteristics of cc-2 shows that the optimal temperature,pH and shaker rotary speed for strain cc-2 utilizing nitrobenzene are 15℃,7 and 140r/min, respectively. The degradation rate is 66.84% in 48h when the nitrobenzene concentration is 200mg/L, the temperature is 15℃, the inoculum is 10% and the pH is 7. The limit nitrobenzene concentration of bacterium cc-2 is 400mg/L with a high tolerance capacity of nitrobenzene. The addition of glucose and Sodium acetate as a secondary carbon can accelerate the nitrobenzene biodegradation of cc-2 at low temperature. The nitrobenzene degradation rate reaches 80.44% and 78.57%, respectively. The growth and nitrobenzene degradation characteristics of cc-2 provides technical support for the treatment of nitrobenzen.