Power output and columbic efficiencies from biofilms of Geobacter sulfurreducens comparable to mixed community microbial fuel cells

Abstract

It has been previously noted that mixed communities typically produce more power in microbial fuel cells than pure cultures. If true, this has important implications for the design of microbial fuel cells and for studying the process of electron transfer on anode biofilms. To further evaluate this, Geobacter sulfurreducens was grown with acetate as fuel in a continuous flow 'ministack' system in which the carbon cloth anode and cathode were positioned in close proximity, and the cation-selective membrane surface area was maximized in order to overcome some of the electrochemical limitations that were inherent in fuel cells previously employed for the study of pure cultures. Reducing the size of the anode in order to eliminate cathode limitation resulted in maximum current and power densities per m(2) of anode surface of 4.56 A m(-2) and 1.88 W m(-2) respectively. Electron recovery as current from acetate oxidation was c. 100% when oxygen diffusion into the system was minimized. This performance is comparable to the highest levels previously reported for mixed communities in similar microbial fuel cells and slightly higher than the power output of an anaerobic sludge inoculum in the same ministack system. Minimizing the volume of the anode chamber yielded a volumetric power density of 2.15 kW m(-3), which is the highest power density per volume yet reported for a microbial fuel cell. Geobacter sulfurreducens formed relatively uniform biofilms 3-18 mum thick on the carbon cloth anodes. When graphite sticks served as the anode, the current density (3.10 A m(-2)) was somewhat less than with the carbon cloth anodes, but the biofilms were thicker (c. 50 mum) with a more complex pillar and channel structure. These results suggest that the previously observed disparity in power production in pure and mixed culture microbial fuel cell systems can be attributed more to differences in the fuel cell designs than to any inherent superior capability of mixed cultures to produce more power than pure cultures.

Probing single- to multi-cell level charge transport in Geobacter sulfurreducens DL-1

“…DL-1 was grown from frozen 50% dimethyl sulfoxide stocks (generated from cultures provided by D. Lovley, UMass Amherst) in sterile sealed tubes containing 10 ml of freshwater media degassed with a N 2 / CO 2 (80/20) gas mixture 22,39 . All transfers were performed in the 80/20 gas mix.…”

Quantitative population dynamics of microbial communities in plankton-fed microbial fuel cells

“…However, these studies examined bacterial diversity from 16S rDNA clone libraries, which reflect bacterial diversity at a single point in time, typically at the end of the incubations. More recent studies have shown qualitative changes in diversity do occur over time, and that power output from mixed microbial assemblages may be greater than pure cultures (Rabaey and Verstraete, 2005;Nevin et al, 2008). Quantitative changes in microbial processes in relation to MFC performance, however, have not been examined.…”

Microbial Fuel Cells, A Current Review

“…Studies are demonstrating that any compound degradable by bacteria can be converted into electricity [20]. The range of compounds include, but by no means limited to, acetate [21,22], glucose [23], starch [24], cellulose [25], wheat straw [26], pyridine [27], phenol [28], p-nitrophenol [29] and complex solutions such as domestic waste water [30,31], brewery waste [32], land file leachate [33], chocolate industry waste [34], mixed fatty acids [35] and petroleum contaminates [36]. Within these systems less biomass is also generally produced then their equivalent aerobic processes and without the need for an energy intensive aeration process less energy is required [7].…”