Analysis Of Self-Mediated Interfacial Electron Transfer On Pseudomonas Aeruginosa Anode Based On Cavity Microelectrode

Microbial fuel cell(MFC)is a kind of battery device that utilizes bacterium as a catalyst to convert the chemical energy of organic matter into electrical energy.It combines wastewater treatment with electricity production,which provides new ideas and approaches to energy and environmental issues.MFCs use microorganisms as catalysts rather than the precious metal catalyst.Considering the controllable metabolite pathways of microorganisms,they can catalyze the degradation of all kinds of organic matter and even some inorganic materials to produce energy in theory.In this case,the MFC is a low-cost,high efficiency and environment friendly power source,which has a huge application prospects on the sewage treatment,ecological restoration and portable energy.At the present stage,MFC’s power density is relatively low,which is mainly due to the activation loss caused by bacterial metabolism.More importantthings are the inefficient electron transfer ratio(Coulomb efficiency)and the low electron transfer rate(Current yield).To improve the power generation of the MFCs,it is necessary to understand the extracellular detail mechanism behind the interfacial electron transfer.On the other hand,biofilm formation has a critical effect on current generation of the MFCs.However,it is hard to investigate the relationship between the biofilm formation and the current generation as well as the electron mediators excretion.The function of biofilm in the interfacial electron transfer for those exoelectrogens rely on the electron shuttles is still unclear.It is urgent to develop a new method for real-time analysis of electron shuttles’ excretion in the anode during the MFC operation and the effect of biofilm formation on the electron shuttles distribution.In this study,cavity microelectrode is used for real-time monitoring of electron mediator(phenazine)in anolyte and sodium houttuyfonate is used to inhibit biofilm formation.The extracellular electron transport mechanisms of Pseudomonas aeruginosa(P.aeruginosa)are systymatically investigated with electrochemical methods.The main contents and results are as follows:1.Phenazines are a kind of metabolites that can mediate extracellular P.aeruginosa cells in microbial fuel cells(MFCs).However,it is still not clear that whether and how the excretion profile of phenazines is affected by the operating MFC.Here,we report a real time analysis approach based on a cavity microelectrode electrochemical sensor to investigate the phenazines excretion behavior of P.aeruginosa during MFC operation.The phenazine concentration increases at first 72 h,reaches a plateau and decreases after 120 h and also shows local dependent variation.It is dependent on the MFC current generation profile but also affect by the biofilm formation.Accordingly,a mechanism about phenazines excretion in MFC anode and the phenazines mediated extracellular electron transfer of the P.aeruginosa anode is proposed.This work provides a novel strategy for self-mediated extracellular electron transfer analysis in the operating MFCs.2.Bacteria biofilm plays a key role in current generation of MFCs especially for the start-up stage.However,the detailed mechanism of the biofilm promote the power generation is not very clear so far,especially for those exoelectrogens who rely on the self-excreted electron mediators for extracellular electron transfer.In this work,a biofilm formation inhibitor--sodium houttuyfonate(SH)is used to build a “non-biofilm” anode of P.aeruginosa without affecting the bacteria growth during the MFC operation.According to the comparison results of the “non-biofilm” anode and biofilm covered anode on current generation,phenazines concentration variation and anodic electrocatalysis,the biofilm covered anode could greatly improve the current generation of the MFC.The reason is that the biofilm on the anode not only provides lots of bacterial cells for catalysis but also promotes the interfacial phenazine redox reaction through accumulating the self-generated mediators on anode for fast interfacial electron transfer.At the same time,the phenazine concentration variation in the anolyte could be used as an indicator to evaluate the status of the biofilm formation at the early stage of the MFC operation.This work proves that the biofilm assisted electron mediator accumulation will benefit such kind of exoelectrogens to sustain sufficient electron mediators for extracellular electron transfer.