| In recent years,with the rapid development of the textile industry and dye production,preparation and use of dyes has also been a rapid development.However,Large number of wastewater generated by it has become one of most difficult waste water to treat at the present time.The printing and dyeing wastewater results in contamination of natural water bodies,aquatic plants and animals died,ecological imbalance,directly or indirectly,cause harm to humans.Therefore,discoloration and degradation of dyes has become a key element of treating wastewater.At present,the physical and chemical methods of dye wastewater treatment at home and abroad are mostly used,these two methods is not only costly,but also incomplete treatment will cause secondary pollution to the environment,however biological dye wastewater treatment is low cost,high efficiencye low sludge production,and environmentally-friendly,therefore it become a hot topie of dye wastewater treatment technology.The most important contaminants are azo dyes.Currently,decolorization and degradation of azo dyes mainly including yeast,algae,filamentous fungi,bacteria and mixed bacteria.The mechanism of microbial decolorization of dye wastewater occurs from adsorption,enzymatic degradation or a combination of both two,reductases and oxidases are involved in the process of microbial degradation.The ultimate goal of microbial treatment of dye wastewater is to decolorize and detoxify of azo dyes and their degradation products.Therefore screening strains from the soil and research on dye with efficient decolorization is very necessary,and the significance of the dye used in practical engineering of large-scale biological wastewater treatment far-reaching.Therefore,this paper means by using microorganisms,molecular biology and biochemistry,get a fungal strain which can decolorize azo dye Reactive Black 5 efficiently and the conditions and mechanism of fungal degradation of azo dye were studied.The main results are as follows:(1)The microorganism used in this study was isolated from soil which was polluted by azo dye-contaminated effluents has high efficient decolorization of Reactive Black 5.The strain was identified as Geotrichum candidum,named NAU-16.Its colonies is dense,the surface of bacteria is flat,it was short fiber-shaped,creamy white,opaque,with mycelium and diaphragm,the edge is radial growth,easy to provoke.(2)The optimization of experimental conditions decoloration experiments showed that pH=4 or 10,the salinity of 1%,liquid volume was 50 mL,the strain NAU-16 showed best decolorization of Reactive Black 5,96.8%decolorization rate in 24h.And the maximum tolerated concentation of the fongus on Reactive Black 5 can reach 4000 mg/L,and it also can decolorize difilerent dyes such as methyl orange,methyl red,Acid Orange 7,it has a broad spectrum.(3)To investigate the possible mechanism and the degradation products during methyl orange decolorization by Geotrichum candidum NAU-16,FTIR and LC-MS analyses were carried out.The azo reductase,laccase and manganese peroxidase showed their key role in the Reactive Black 5 decolorization.In addition,the degraded Reactive Black 5 showed less toxicity to agricultural crops than before,and it provides the experimental basis for the practical agricultural irrigation.The results show that the strain Geotrichum candidum NAU-16 has a great value and potential of the dye degradation of pollutants,the study to better and more effectively applied to actual bioremediation environmental biotechnology field work laid a good foundation. |
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