Abstract
BackgroundWe previously reversed methanogenesis in microbial fuel cells (MFCs) to produce electricity for the first time from methane by combining an engineered archaeal strain that produces methyl-coenzyme M reductase from unculturable anaerobic methanotrophs (to capture methane and secrete acetate) with Geobacter sulfurreducens (to produce electrons from the generated acetate) and methane-acclimated sludge (to provide electron shuttles).ResultsHere, the power density in MFCs was increased 77-fold to 5216 mW/m2 and the current density in MFCs was increased 73-fold to 7.3 A/m2 by reducing the surface area of the cathode (to make reasonable comparisons to other MFCs), by changing the order the strains of the consortium were added to the anode compartment, and by adding additional electron carriers (e.g., humic acids and cytochrome C).ConclusionsThis power density and current density are comparable to the best for any MFC, including those with Shewanella and Geobacter spp. that utilize non-gaseous substrates. In addition, we demonstrate the methane MFC may be used to power a fan by storing the energy in a capacitor. Hence, MFCs that convert methane to electricity are limited by electron carriers.
Highlights
We previously reversed methanogenesis in microbial fuel cells (MFCs) to produce electricity for the first time from methane by combining an engineered archaeal strain that produces methyl-coenzyme M reductase from unculturable anaerobic methanotrophs with Geobacter sulfurreducens and methane-acclimated sludge
Medium variation and pH To determine if any medium component was limiting electricity production, we varied the composition of the MFC medium, HSNR (Additional file 1: Table S1), which includes trace elements, vitamins, cysteine–HCl (3.2 mM), and Na2S (1 mM)
The pH of the anode chamber of the MFC reactor was measured for the MFC medium and for two reactors for the base case #2 reactor set with 3.3% humic acids (Table 2) and found to not vary
Summary
We previously reversed methanogenesis in microbial fuel cells (MFCs) to produce electricity for the first time from methane by combining an engineered archaeal strain that produces methyl-coenzyme M reductase from unculturable anaerobic methanotrophs (to capture methane and secrete acetate) with Geobacter sulfurreducens (to produce electrons from the generated acetate) and methane-acclimated sludge (to provide electron shuttles). The microbial fuel cell (MFC) is a device that utilizes microorganisms to convert the chemical energy of organic matter into electric energy [1]. MFCs do not produce sufficient power for many applications [7] and typically, a power density of around 1240–2800 mW/m2 is obtained [9], power densities as high as 7200 mW/m2 may be obtained (current density of 15 A/m2) [11].
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