Isolation, Identification And Decolorization Study Of The Strain For Congo Red Decolorization

Azo dyes, which are molecules with one or several azo bridges (-N=N-) linking substituted aromatic structures, are the most important and largest class of synthetic dyes used in commercial applications. These dyes are extensively used in the paper, food, leather, cosmetics, pharmaceutical and textile dyeing industries. Sulfonated azo dyes and their metabolites in aqueous ecosystems leads to a reduction in sunlight penetration, which in turn decreases photosynthetic activity, dissolved oxygen concentration and so on, and results in acute toxic effects on aquatic flora and fauna, causing severe environmental problems worldwide. The widely used of microorganism on azo dyes biodegradation are fungus and anaerobic bacteria, but there just a few reports are about the aerobic bacteria. It is need to screen aerobic strains which could degrade azo dyes efficiently and be used in dye wastewater treatment. In this study, with an integration of microbiology, molecular biology and biochemistry, the degradation conditions of aerobic strains and advantages and disadvantages of this method were studied with the provision of corresponding theoretical data and technical support for the application of biological treatment of dyeing wastewater. The main contents in this study include:1. A strict aerobic bacterium YNWH226, isolated from an activated sludge process in a textile plant, was able to successfully decolorize Congo red as the sole carbon source under aerobic conditions. Their identification were based on standard morphological and physiological properties, and nucleotide sequence analysis of enzymatic amplified16S ribosomal deoxyribonucleic acid. Strain named YNWH226was isolated and identified as acinetobacter baumannii YNWH226which was the first representative of acinetobacter baumannii able to degrade Congo red very fast at high experimental concentration.2. The effects of Congo red concentrations and environmental parameters (i.e., pH, temperature, agitation speed) on the biodegradation of Congo red in aqueous phase were studied and evaluated using response surface methodology (RSM). The results indicated that the optimal degradation concentration was100mg/L and the optimal decolorization conditions were as follows:37℃, pH7.0,180rpm. The final degradation efficiency at490nm,344nm and240nm were99.1%,100%and94.69%, respectively, and the TOC removal efficiency was93.72%。3. Investigate the biodegradation kinetics of Congo red with different hydrogen donor by the strain acinetobacter baumannii YNWH226. The second-order equation-dS/dt=K2S2+K1S+K0, proposed by Quiroga and Sales was applied to the experimental data obtained from the biodegradation test of Congo red. It showed that Ethanol, soluble starch and glucose had no significant impact on the Congo red biodegradation, while the N-(1-naphthyl) ethylenediamine dihydrochloride had a negative impact, However, Citric acid, riboflavin and vitamin C can promote the Congo red biodegradation. Congo red biodegradation of YNWH226enhanced with the increase of riboflavin concentration (0-0.25mmol·L-1), the optimum riboflavin concentration was0.25mmol·L-1.Whereas no obvious improvement was observed for Congo red biodegradation with the riboflavin concentration over0.25mmol·L-1.