Study On Electrical Properties Producing Enterococcus Faecalis (Enterococcus Faecalis)

In recent years, because of energy shortage and the needs of sustainable development of society, the development and utilization of new energy has aroused extensive attention all over the world. Recently, the microbial fuel cell (microbial fuel cell, MFC) was a new technology that can degrade organic substrate and transform chemical energy into electrical energy. Organic matter can be used as mater source, from which can get power directly. Consequently, MFCs cause people’s extensive concern. In this paper, a series of experiments to study on the characteristics of electricity generation by Enterococcus faecalis was carried out in microbial fuel cell. Experimental results are shown below:Part one:Characteristics of Enterococcus faecalis producing electricityThis chapter were mainly studied the Enterococcus faecalis produced electrical properties and optimized growing conditions. Enterococcus faecalis grows fast and produced acidic material in the process of our growth. Glucose as electron donor, play an important role in the process of bacteria to produce electricity. Lack of yeast powder, bacteria does not grow without electricity, which showed that the yeast powder contains substances essential for bacterial growth and the interface necessary to produce electricity. Tryptone as electron donor can prolong the discharge time and improve the battery performance. At the same time, optimum growth temperature of Enterococcus faecalis is40℃and the best growth potential (V vs SCE) is zero.Part two:Foreign electronic media affects the output voltage of Enterococcus faecalisRiboflavin and pyocyanine could as electron mediator affects the output voltage of the MFCs by the mature biofilm attached to electrode. We found that Enterococcus faecalis cannot produce riboflavin, but it can improve the output voltage of the cells, which be confirmed by cyclic voltammograms and control potential, etc in anaerobic cells.But when bacteria and electrode is separated, the output current of the MFCs is almost zero. From this we can draw that bacteria contacting with the electrodes and the electron media exists are the necessary conditions to produce electricity. We also found that riboflavin has influence on cell suspension of electricity production, but which less than the effect of biofilm produced electricity. Otherwise, pyocyanin produced P. aeruginosa BTE-1can also improve the production performance of microbial fuel cells.Part three:Conductive material affects the output voltage of Enterococcus faecalis Collection of Enterococcus faecalis cells in single improved chamber microbial fuel cells was studied, which can be faster to form a thick biofilms in the anode surface. At the same time conductive material (conductive carbon black, multi-walled carbon nanotubes) was added to the anode chamber. The experimental results show that, conductive carbon black to promote the effect of the MFCs is not obvious. When multi-walled carbon nanotubes (MWCNT) dispersed in water, it can obviously increase the production performance of microbial fuel cells, which is due to the conductive material and bacteria on the electrode surface. With three kinds of multi-walled carbon nanotubes dispersed in anhydrous ethanol are used to modify electrodes. The results showed that effect of multi-walled carbon nanotubes containing hydroxyl is better than the others. When using0.5mg (0.377mg/cm2) of multi-walled carbon nanotubes modified electrodes can be obtained the maximum output current.We collect a large nember of Enterococcus faecalis cells to the anode chamber change anode liquid constantly. With replacing the anode fluid, the output current of microbial fuel cells was gradually reduced. This does not agree with previous experimental results. The SEM shows that this electrode surface covered with a thick layer of dead cells, which can affect the electron transfer from the cells to the electrode surface. On the contrary, collection a large nember of Shewanella、Geobacter sulfurreducens cells can increase the output current of microbial fuel cells and shorten the start-up time. This is due to the two strains of bacteria have longer growth cycle than Enterococcus faecalis.