 I'm Dan Tsang, Apple Store in Bruce Logan's app, and this is my partner in this project. I'm Doug Caul, I'm also a postdoc, and today we're going to share some results on our paper in biotechnology and bioengineering. As we know, microbial fuel cell is a system that converts chemical energy in substrates to electrical energy by the catalytic reactions of microorganisms. Many different substrates have been used in MFCs. One substrate of particular interest is formic acid, which is produced during the glucose fermentation. Based on the standard thermodynamic calculations, it should theoretically produce the highest cell voltage of fermentation and products. However, our previous results showed that the maximum of poor density produced with formic acid is only 60 million words per square meter, which is much lower than the poor density of 800 million words per square meter obtained with acidic acid or lactic acid. So now we're just going to show you a couple of slides to talk about some of our results. So one reason for the low power densities that we see with formic acid could be that most exo-electrogens cannot use formic acid as a carbon source, such as geobacter cell produces. Two centrophic processes could lead to current generation using formic acid, which are hydrogen generation and acetogenesis. The hydrogen generation pathway is that formic acid was used by paracoccus to generate hydrogen, and then the hydrogen was used by geobacter to generate current. The second possible centrophic interaction is based on generation of acetic acid. Formate can be converted to acetate by bacteria such as acetylbacterium. Acetic acid can then be used by geobacter cell produces. This centrophic relationship is more thermodynamically favorable and results in acetate, which is a favorite substrate for geobacter cell produces. It's recently shown that different microbial communities can be developed on an anode by controlling the anode potential. In order to improve the performance of MFC's fed formic acid, we hypothesized that effective centrophic communities could be developed by controlling the anode potential. Three different anode potentials, minus 0.3, minus 0.15, and positive 0.15 volts versus standard hydrogen electrode were used in this study. Setting the anode potential at minus 0.3 volts, we can bypass the acetate oxidation pathway and only allow formic acid to be reduced. Minus 0.15 volts was used because it is the midpoint potential for geobacter cell produces when oxidizing acetic acid in MFC's. Positive 0.15 volts was used because it allows oxidation of all possible intermediates and may produce more diverse communities than lower potentials. 30 days after inoculation with wastewater, no current was generated at minus 0.3 volts, suggesting a lack of direct formic acid oxidation. More positive potentials, minus 0.15 and positive 0.15 volts that allowed for acetic acid utilization all produced current, and the best performance was obtained at minus 0.15 volts. The anode community and the minus 0.15 volt reactor was about 60% geobacter cell produces and about 20% aceto bacterium. Lower proportions of the genre were found in the positive 0.15 volt reactor and the control MFC with a thousand ohm external resistance. More of our acetic acid was detected in all MFC's. This suggested that current generation by geobacter cell produces was dependent on acetic acid production by aceto bacterium. In order to see if these centrophic interactions could be maintained over time, all MFC's were then examined in longer-term operation. In that way, all reactors were disconnected from the potential stat and operated in external resistance for maximum power production. At this mode, they produced similar power densities and exhibited the same midpoint potential of minus 0.15 volts in first derivative cyclic voltammetry scans. All of the mixed communities converged to similar proportions of the two prominent genre, 50% geobacter cell produces and 25% aceto bacterium. These results show that centrophic interactions can be enhanced through setting certain anode potentials.