| 2,6-Dinitrotoluene (2,6-DNT for short) is a kind of compound with higher toxicity, which is hardly degradated under the normal conditions. Microbial degradation method is an effective way to eliminate environmental contaminants, and gets a rapid development because of the advantages such as the high efficiency, economy, not any secondary pollution and so on. Therefore, in this we have studied the microbial degradation of 2,6-DNT, including the degradation abilities of 2,6-DNT by the activated sludge, a single strain and the mixed bacteria respectively.In this study, sludge from the sewage treatment plant was domesticated at the very beginning, which made a stronger degradation of 2,6-DNT. And meanwhile Uniform Design was also invited to gain the optimal degradation condition in order to make the most efficient degradation of 2,6-DNT(pH7.3,29℃,129r/min) via the observation of temperature, shaker rpm and pH value. It proved that under this condition, when the concentration of 2,6-DNT was 90mg/L,135mg/L and 180mg/L, the micro-organisms had a high degradation of 2,6-DNT, and the relevant degradation rate in 96h was 92.2%,90.2% and 85.8% respectively.Bacteria of the activated sludge were cultivated in the expansion culture medium after the dilution and then observed and selected. And the selected bacteria were re-cultivated in the expansion culture medium, after which the bacteria were purified again. With the help of the selected single bacteria,2,6-DNT was degradated and the concentration of 2,6-DNT in the degradated bacteria solution were detected. Results showed that the three strains of bacteria with the numbers of 6.1,48N4,7.1 had great degradation rates, and the relevant rates were 64.58%,60.17% and 70.14%. In order to check out what kind of bacteria on earth they were that had the great degradation rate, evaluations were carried on. The single bacterium was enlarged cultivated by using LB medium. Following the genome extraction Kit steps, the DNA extract of the single strain bacteria would be gained. The extract was taken to carry out the horizontal gel electrophoresis experimrent under 2000bp, from which the Marka direction range of the gene extract was gained and that was between 1000bp and 2000bp. And the PCR temperature could follow this. The single bacterial gene extract was amplified by PCR, and the product was taken to carry out the gene detection to get the base sequence. And this sequence was put into the GeneBank in order to gain the logging number GU223217. Compared with the ten kinds of bacteria gene sequence of which the similarity was 99% with MEGA 4.0, it showed that the bacteria were Pseudomonas aeruginosa.For the mixed bacteria, every two made a group. The three strains of bacteria which was domesticated and screened were grouped, following the upper grouping method. And three groups of mixed bacteria solutions. The degradation rate was observed via the degradation of 2,6-DNT by using of the gas chromatography. It showed that the degradation ability of A(6.1, 48N4) was greater than 6.1 and 48N4; B(6.1,7.1) greater than 6.1, weaker than 7.1; C(6.1, 48N4) greater than 6.1 and 48N4. It was also to say that the single bacteria in the mixed bacteria A(6.1,48N4) and C(6.1,48N4) mutual synergy effects and the degradation rates were 67.44% and 73.45%.In order to know much about the mechanism of the degradation of 2,6-DNT, every single bacterium was observed and detected. The excellent single bacterium was taken to degradate 2,6-DNT. Samples were collected at 2,4,10,24,36,48,72,96,120,144,168,192h, when treated, they were detected and identified through GC-MS. From it, we could see that the intermediate products were 2-nitro-6-amino-toluene and 2,6-diamino toluene and the degradation pathway was The toxicity of the former and degradated bacteria solution had a initial investigation by MTT method and the result showed that the toxicity of 2,6-DNT degradated by the single bacterium decreased.
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