Study On Microbial Metabolism And Microbial Community Structure In Microbial Fuel Cell

Microbial fuel cell(MFC)is a electrochemical system of integrating sewage treatment and energy regeneration,and a device of translating organic chemical energy into electrical energy by biological microbes using the electron transfer mechanism.The development and application of the technology meet the demand of easing the global energy crisis and the sustainable development about economy and environment.Yet actually demanding maximum output voltage and current are still low, it is difficult to meet the actual needs. There are many more theoretical and technical problems needed to be solved to achieve practical application of MFC in large scale. Electrogenesis microorganism is the most key elements in MFC system, organic matter as the substrate by fermentation bacteria and Electrogenesis bacteria generate electricity in the process of organic waste treatment, the community structure of anode biofilm and population types has a great impact for degradating organic matter and generating electricity, so the study of electrogenesis microorganism metabolism mechanism and the community structure analysis of anode chamber is particularly important.The relationship between microbial fermentation and electricity production was explored by analyzing the bacterium and fermentation products using two bottles of microbial fuel cell(MFC)with glucose as substrate.And the community structure of the inoculum sludge, biological membrane of electrodes and anode liquid microbial was parsed, finally the producing electricity mechanism of MFC was analysed.The study results showed that:(1)Using years of highly active anaerobic sludge as the inoculums, cathode with 50 m M of potassium ferricyanide as electron acceptor, the reactors MFC was quickly started after about 20 days and the maximum output voltage reaches 570 m V.And 1000 mg·L-1 of substrate COD concentration,35℃ of the temperature is the optimal condition of the reactor.(2)Glucose is mainly fermented to three kinds of carboxylic acid,acetic acid, propionic acid and lactic acid in the MFC.Acetic acid and propionic acid can be directly used to produce electricity,in which acetic acid is more easily oxidized to generate higher voltage by electricigens.Lactic acid needs to be decomposed to butyrate acid,propionic acid and acetic acid,and then butyrate acid to a mixture of metabolites including acetic acid and propionic acid, which these products are used to produce electricity.(3)Oxidation reduction potential(ORP)of anolyte had three stages: first, when the ORP began to decline, the content of microbes metabolism is not high and the voltage at the initial stage;Second,ORP began to rise, voltage also began to rise, fermentation metabolic product is much more, and the electrogenesis microorganism used volatile organic acids to make voltage also to rise;Third, ORP continued to rise, voltage began to decline, volatile organic acids is reduced.(4)The surface of anode is adhered by a large number of bacillus in form of biofilm,in which mainly includes Klebsiella sp.,Citrobacter sp.,Lactococcus sp.,Enterobacter sp.,and Proteobacterium.Predominant bacteria are Yokenella sp.,Eubacterium limosum,Firmicutes bacterium in anode chamber sludge.Predominant bacteria are Lactococcus sp., Peptostreptococcaceae, Clostridiales and Salmonella sp. in seed sludge.(5)It is considered that the electricity generation in the MFC is the results of cooperated metabolism of electricigens and fermentation bacteria via decomposing substrate and utilizing products step by step.The optimum combination between electricigens and non-electricigens can provide a direction for improving to produce electricity of MFC. Lactococcus sp. as predominant bacteria was included in anode biofilm and seed sludge. To reveal the difference of the bacteria’s respiratory way will help people to understand it in the MFC system or not.(6)Electron shuttle including soluble microbial metabolites, humic acid which was secreted by bacteria can improve the efficiency of the electron transfer between biological membrane and the electrode in anode chamber with three-dimensional fluorescence(3DEEM).And the general trend has certain relevance with the voltage total trend.Humic acid can promote electronic which was release by the substrate oxidized transfer to the anode electrode in the system.