| Dissimilated metal reducing bacteria(DMRB),as a kind of bacteria with special extracellular electron transfer(EET)mechanism,can transfer electrons which generated in metabolic process to a variety of extracellular electron receptors under anaerobic conditions,thus reducing a variety of metals and organic pollutants.Therefore,this kind of bacteria is widely used in ecological management and environmental restoration.With the rapid development of industry,the discharge of wastewater is continuously increasing.salinity wastewater has always been a difficult link in wastewater treatment.If it is not effectively treated,it will bring great impact to the natural environment.Among various treatment methods,the biological treatment method is uses the metabolic process of bacteria to bioabsorb,degrade and reduce pollutants in wastewater.Biological treatment method has the advantages of high efficiency,wide application range,easy operation,economy and harmlessness,and can complete in situ bioremediation.It is one of the most widely used methods in wastewater treatment at present.However,for high salinity wastewater,the salinity will affect the growth activity and inhibit the growth and metabolism of microorganisms,thus the treatment effect is reduced.In addition to dilution pretreatment of high salinity wastewater,how to screen out salt-tolerant strains with stronger performance is an important problem that engineers need to face.In order to solve the above problems,this paper screened out a dissimilated metal reducing bacteria with good salt tolerance from seawater environment,The strain was identified,and its related characteristics and pollutant reduction performance were explored.Then the strain was modified by molecular biological methods to further optimize the electron transfer performance of the strain.The main contents are as follows:(1)A salt tolerace and high eficiency electrogenic bacterium was screened and isolated from sediments in Xiamen Bay by microbial fuel cell(MFC)device,named XMS-1.The shape of the bacterium is short rod,the surface is smooth,and the size of the bacterium is about 0.5 ? m × 1.5 ? m.The results of 16 S r RNA gene sequencing were compared in NCBI database,Strain XMS-1 and Shewanella aquimarina SAH7W001 belong to the same branch with 99.86% homology.(2)The optimum growth conditions of Strain XMS-1 were studied by single factortest.The optimum growth p H,temperature and Na Cl concentration were ph=7,30?and 1% ~ 4% respectively.The strain could grow at 0% ~ 6% Na Cl concentration,but when the salt concentration was higher than 5%,the growth of the strain was delayed to a certain extent.In addition the strain XMS-1 can use sodium lactate,glucose and starch as carbon source.(3)The strain XMS-1 has good performance in Cr(?)reduction and methyl orange decolorization,and can complete the reduction and decolorization process under a wide range of p H and Na Cl concentration conditions.The strain can reduce Cr(?)and methyl orange in the range of Na Cl concentration 6% ~ 7% or p H=6~9.(4)The strain was modified by molecular biology.The amount of flavin secreted by the engineering strain was 4.3 times higher than wild strain,thus improving the efficiency of extracellular electron transfer.Through pollutant reduction and electrochemical experiments,it is confirmed that compared with wild strains,the engineering strains have greatly improved in pollutant reduction and electricity generation performance.(5)Graphene oxide was used to construct 3D hybrid biofilm electrode in MFC anode,the extracellular electron transfer efficiency of the strain in MFC was further improved.Compared with the maximum current density 243 m A/m2 of wild strain,the maximum current density of engineering strain increased 2.6 times to 650 mA/m~2. |
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