Screening Identification,Decolorization Conditions And Machanisms Of Isolated Strain For The Degradation Of Azo Dye Methyl Orange

The textile printing and dyeing industry is a substantial consumer of water and produce large amounts of dye wastewater.The most important contaminants are azo dyes.At present,most treatment of dye wastewater by physical method and chemic al method which have disadvantages such as high cost,processing incomplete,seco n-dary pollution and so on.However,microbial treatment of dye wastewater has a lot of advantages,such as low cost and high efficiency and low sludge production and environmentally friendly.The mechanism of microbial decolorization of dye wa stewater occurs from adsorption,enzymatic degradation or a combination of both t wo,reductases and oxidases are involved in the process of microbial degradation.The ultimate goal of microbial treatment of dye wastewater is to decolorize and de toxify of azo dyes and their degradation products.Recent studies about the decolori zation or degradation of azo dyes mainly using yeast,algae,filamentous fungi and bacteria,However,these studies have the following questions:(1)Biomass from y east,algae,fungi has been used to remove dyes by biosorption.After microorgani sms died,the cells rupture,dyes will be released and it cannot remove the dyes c ompletely.(2)For the printing and dyeing wastewater,it contains high salt,many microorganisms' growth will be inhibited when the salt concentration reaches a cert ain range,it will affect the microbial decolorization of printing and dyeing wastew ater.(3)In present,although the strains used in the degradation of dyes have certa in decolorization ability,the decolorization efficiency is not so good,the decoloriz ation effect of azo dyes with different structures is different and the spectrum is p oor.In this paper,with the integration of microbiology,molecular biology and bioc hemistry,get a strain can tolerate the high salinity and decolorize different azo dye s,then the conditions and mechanism of bacterial degradation of azo dye were stu died.The main results are as follows:(1)The microorganism used in this study was isolated from the soil which was polluted by azo dye-contaminated effluents has high efficiency decolorization of me thyl orange.The strain was identified as Paenibacillus polymyxa,named YP-5.It w as a long rod cell morphology and has small,round,pale yellow and neat edge col onies.The surface of this strain is raised,glossy,smooth,moist,semilucent,and vis cous.It is the kind of gram positive bacteria.(2)The bacteria YP-5 showed 98.9%decolorization of methyl orange within 30 h,at pH 7.0,salinity 1%,liquid volume 50mL under static conditions.In the prese nt study the strain YP-5 showed a good performance with the initial concentration o f 2000mg/L of methyl orange and it also can decolorize different azo dyes like Aci d Orange 7,Congo Red and Reactive Black 5.(3)To investigate the possible mechanism and the degradation products during methyl orange decolorization by Paenibacillus polymyxa YP-5,FTIR and LC-MS an alyses were carried out.The four products are 4-methyl aminoazobenzene-4-sulfonic acid,2,4-Diaminotoluene,N,N-dimethyl-p-phenylenediamine,4-aminophenol.The azo reductase,laccase and manganese peroxidase showed their key role in the methyl or ange decolorization.In addition,the degraded methyl orange showed less toxicity to agricultural crops than before,and it provides the experimental basis for the practic al agricultural irrigation.