The Impact Of Iron Oxides To The Microorganisms Extracellular Polymers Of Electrochemical Activity Microorganisms

Iron oxide can affect the generation of methane through affecting the type and abundance of the microbial flora in anaerobic environment.The electron transfer between the methane-producing bacteria and Iron reduction bacteria can be done by conductivity minerals such as hematite and magnetite.Iron reducing bacteria have the ability to transfer electrons to iron oxide,but how methanogens get electrons from iron oxide is not clear now.At present many studies indicate that the extracellular polymer of microorganisms with electron transfer ability plays an important role in the interaction of mineral-microorganisms,extracellular electronic transfer process is associated with humus and other extracellular polymers microorganisms with electrochemical activity also participate in this process..However,the composition of metabolites produced by microorganisms with electrochemical activity and whether it is regulated by conductive iron oxides need to be clarified.Therefore,this article selects the typical electrochemical active microorganism Bacillus subtilis(B.subtilis CGMCC 1.4255)and typical iron reduction microorganisms Shewanella oneidensis MR-1(S.oneidensis MR-1)as the research object,explore the effect of semiconductor iron oxide minerals(Goethite and Hematite)to the extracellular polymeric substances(EPS)of electrochemical activity microorganisms.Study the methanogenesis with iron oxides in anaerobic environment to reveal the relationship between methanogenes and EPS.This study can provide certain theoretical basis and deeply understanding of interaction relationship between microbes and minerals and also improve the efficiency of organic matter in anaerobic digestion to produce methane.(1)Goethite and hematite are promoting B.subtilis CGMCC 1.4255 microbial protein content increased by 6.4% and 6.4%,microbial polysaccharides content increased by 1.59% and 2.86%,respectively.While for S.oneidensis MR-1,goethite and hematite respectively promote S.oneidensis MR-1 microbial protein content increased by 7.94% and 7.94%,which polysaccharide content was reduced by 0.17%and 0.17%,respectively.The results of three dimensional fluorescence spectrum showed that iron oxides promoted the production of fulvic acid in the extracellular polymers(EPS)of B.subtilis CGMCC 1.4255,for S.oneidensis MR-1 role in promoting its extracellular polymers in humus and class of fulvic acid;The results of electrochemical testing showed that the capability to accept electrons of extracellular polymers of microbial strains was enhanced with iron oxides.(2)Experimental results showed that goethite and hematite respectively promote extracellular polymer protein content increased by 4.56% and 3.73%.In addition,the two minerals respectively make polysaccharide content in the extracellular polymer decrease by 0.39% and 0.87%.Electrochemical testing results showed that goethite and hematite respectively increased the ability of extracellular polymers to accept electrons by 58% and 63% in the anaerobic system.The results of three dimensional fluorescence spectrum showed that the iron oxides could promote the formation of humic acid in extracellular polymers,which hematite promoted the production of fulvic acid in ultraviolet region.