The Research On Expansion Of Carbon Source Spectrum And Enhanced Electrochemical Performance Of Shewanella Oneidensis

Microbial fuel cell(MFC)can convert chemical energy in organic substrates into electrical energy,which enabled wide applications in environmental treatment and new energy development.However,low power density output of MFC limited its practical applications.Enhancing the extracellular electron transfer(EET)efficiency of exoelectrogens is an important strategy in enhancing the energy output of MFCs.In this study,Shewanella oneidensis MR-1 is taken as the main research object,I aimed to genetically engineer S.oneidensis and improve its EET efficiency by focusing on two key issues:i)S.oneidensis could only use very limited carbon sources,which significantly restricted its practical applications;ii)The EET efficiency of S.oneidensis is low,and there are few genetic manipulation tools.In order to solve the issues abuout the limited carbon source of S.oneidensis,this study successfully constructed a S.oneidensis-Saccharomyces cerevisiae microbial consortium guided by the principle of division of labor.We optimized the co-culturing conditions of the microbial consortium,such as the ration of OD₆₀₀,carbon source concentration,to achieve an optimal coordination between carbon source metabolism of the fermenter and extracellular electron transfer of the exoelectrogen.Furthermore,the transformation of S.oneidensis by porin and electron carrier flavins respectively promoted the formation of biofilm,and the maximum power density of the microbial consortium reached 123.4 and 238.4 m W/m²,respectively.Our design strategy of synthetic microbial consortia was highly scalable to empower the possibility of a wide range of carbon sources being used in MFCs,e.g.,cellulosic biomass,recalcitrant wastes.Aiming to improve the EET efficiency of S.oneidensis,this investigation studies both the direct electron transfer(DET)and the electron flavins-mediated electron transfer(MET).Firstly,the promoters available in S.oneidensis were systematically studied,and the optimal promoter Ptet was ligated to the exogenous gene rib ADEHC of the synthetic electron carrier flavins,which effectively increased the content of the flavins to 39.7?M.Secondly,to increase permeability of cell membrane by flavins,which could increase electron transfer rate,a porin protein Opr F was introduced in S.oneidensis.I optimized the ribosomal binding site(RBS)to control the expression level of Opr F and significantly promoted the EET rate.In addition,a highly hydrophobic S.oneidensis mutant CP2-1-S1 was used as the chassis cell,which further improved the EET efficiency.Finally,graphene oxide(GO)was added to the anolyte,S.oneidensis and GO self-assembled to form a three-dimensional biohybrid biofilm of S.oneidensis-flavins-reduced graphene(r GO).In this process,the r GO sheets in the biohybrid could further absorb flavins to enhance the?-?interaction,to increase the local concentration of flavins to facilitate flavins-mediated MET,and to promote the DET between cells and anodes,to improve the coulombic efficiency,and produces the highest power density to 2.63 W/m²,the so far highest record of the electricity output of MFCs inoculated with S.oneidensis.