Isolation Of Bacteria For Azo Dye Decolorization And Optimization Of Production Of Azoreductase Medium

In this study, we have isolated a bacterium which was grown in Luria-Bertani (LB) medium supplementing with50mg/L methyl red and can decolorize different azo dyes under aerobic conditions from the disposal site of a textile-dyeing industry located in Haicheng, China. Identification of the strain by16S rDNA technique and morphology observation showed that the strain belonged to Escherichia, and clustered within Escherichia coli. So we renamed the strain as E. coli CD2.Single factor test was used for initial optimization of production of azoreductase medium of E. coli CD2. Three significant factors:MgCl2、Na2HPO4、pH value were screened out by Plackett-Burman design on the basis of results of single factor test, Three variables were selected for further optimization studies using Box-Behnken design of design expert7.0soft. Optimization of medium were mannitol2g/L, NH4Cl3g/L, pH value6.5, KH2PO42g/L, Na2HPO46g/L, MgCl20.99g/L, inoculation amount5%. The optimization by response surface methodology resulted in a nearly three-fold increase in the production of azoreductase.Under aerobic conditions, optimization of disruption of cells, cultures supplementing with0.1%β-mercaptoethanol at the beginning of cells were disrupted by sonication can increase production of azoreductase effectively. The optimal disruption of power and times were85%output and50×. Escherichia coli CD2could decolorize azo dyes effectively at high salt concentration (1%-4%NaCl), pH(3.0-11.0) and temperature (30℃-42℃). Escherichia coli CD2could decolorize different azo dyes effectively after16hours. The decolorization of methyl red, Congo red, eriochrome black T, and eriochrome red B were97.15%,86.03%,56.92%and81.14%, respectively. Different concentration of methyl red was employed for the model dye to evaluate influence of the decolorization efficiency. Under conditions of optimization in our study, Over80%of the methyl red was decolorized within10min when the methyl red concentration was below100mg/L. After a50min cultivition, about95%of methyl red was finally degraded by Escherichia coli CD2. Nearly50%of the methyl red was decolorized within10min when the methyl red concentration was150mg/L. After a50min cultivition, about73.5%of methyl red was finally degraded by Escherichia coli CD2.The result showed that optimization of production for azoreductase medium of Escherichia coli CD2by Response surface methodology can increase decolorization efficiency of azo dyes effectively. The decolorization potential increased the application of Escherichia coli CD2for the wastewater treatment.