Selection Of Degradeting Bacteria Of Azo Dye And Studies On Its Mechanisms

Along with the rapid development of the dyestuff production and textile industry, gradually increased the amount of dye waste water. Azo dyes as a broad categories in the dye, Which becomes one of the principal pollutants in the dye wastewater. Dye wastewater discharging into the environment, both for the environment and for humans are poisonous. Thus,dye wastewater containing azo dyes must be treated before released into the environment. Microorganisms in the dye waste water treatment process has high cost performance, environmental friendly etc, in recent years which becomes a research hotpot in the dye wastewater treatment method. This paper is use of Reactive Black 5 dye as a model to systematically study of the process of microbiological methods in treating dye wastewaterReactive Black 5 degrading strains selected from waste water and sludge. In this study,57 strains were screened out which have better degradation efficiency. Among them,JY-51 strain and JY-52 strain have best degradation capacity. The JY-51 strain and JY-52 strain could degrade 100 mg/L Reactive Black 5 respectively reach to 43.2% and 96.3% within 16h. Show that they have high ability of degradation. On the basis of the configuration、 physiological and biochemical characteristics and 16S rDNA identification of the strains, the strain JY-51 and JY-52 are primarily identified as Bacillus cereus strain and Paenibacillus sp.We researched the relationship between growth and dye degradation rate of strain JY-51 and JY-52. The result shows that the degradation rate of reactive black 5 and bacteria content of the degradation process were positively correlated in the process of degradation. The degradation efficiency synchronously increased with the increase of bacteria content. From degradation studies of the strain JY-51 and JY-52,we have found that the two strains exhibited a good degradation ability in the ranges of temperature from 25-37 ℃,pH from 5-9, salinity from 0.5-30 g/L,and glucose concen -tration from 0-2 g/L.The degradation rate of the two strains in stationary culture is significantly higher than the 160 r/min shaking culture.Optimal conditions were initial pH 9 and temperature at 37℃. The salt tolerance of Bacillus cereus strain JY-51 is higher. It can reach 53.56%-68.52% degradation rate at salt concentration from 1-30g/L in 60 h. Paenibacillus sp. JY-52 completed 67.53%-66.44% degrada- tion at salt concentration from 10-15g/L in 10h. When the concentration of NaCl con- centration exceeded 15g/L, dyes degradation rate of JY-52 was restrained. Adding a small amount of glucose can enhance the degradation rate of the two strains.Response surface experiments infered optimal degradation conditions of JY-51 which was 37℃, pH 8.37,15g/L NaCl,2 g/L glucose. And the optimal degradating conditions of JY-52 was 36.36℃, pH 7,1.44g/L NaCl,1.5 g/L glucose. The late small experimental reactor showed that the degradation efficiency of reactor same as a conical flask cultu-re. The small experimental reactor preliminary evidenced that the two strains were feasible for dye wastewater treatment in the natural environment.We used HPLC to study the degradation products of reactive black 5.With the extension of time, the peak of reactive black 5 gradually reduced and even disappear-ed.And along with new chromatographic peak produced and disappeared.For the rese-arch of the structure of production in degradation process, we used liquid phase mass spectrum analysis to test the molecular mass of new production.lt was concluded that the possible intermediate were 2-(4-aminobenzenesulphonyl) ethanol and 4-(ethane-sulfonyl) aniline. We hypothesized that the degradation of azo dye reactive black 5 started from the reduction of azo double bond cracking, then took off sulfonic group、 alkyl and amino group,and further product aromatic ring compounds.Next aromatic ring compounds cracking to production lower toxicity and small molecule compound-s.Finely,we studied microorganism flora richness and structure change in the pro-cess of bacteria domestication by high-throughput sequencing technologies.As the extension of domestication time, the proportion of common bacteria increased. Throu-gh analysis the difference of the flora composition, we found that Atopococcus, Bacteroides, Arcobacter and Acinetobacter dominant gradually in the process of domestication.They are likely to work on the degradation of dye.At the late of sludge domestication, the content of Proteobacteria, Clostridia were the highest, becoming the phylum which advantaged growth in the process of dye degradation.Results also showed that the bacteria abundance and content in the sludge in the degradation proce -ss of reactive black 5 were greatly influenced by external environment factors.The tolerance of bacteria from outside world in culture medium contained reactive black 5 were low. And survival time of some bacteria were shorter, and flora changes greatly.