A Microbial Fuel Cell Coupling Anaerobic Degradation of Agricultural Lignocellulose Wastes to Electricity Generation

Microbial fuel cells (MFCs) are bio-electro-chemical reactors in which renewable biomass resources are used as fuels to generate electricity. The objectives of this study were (i) to evaluate electricity generation from cellulose in an MFC with rumen microbes as biocatalysts, and (ii) to analyze the microbial diversity that developed in the MFC. The anode was inoculated with rumen microorganisms, and suspended cellulose powder was the sole substrate in the anodic chamber. Power density reached 55.3 mW·m-2 without the addition of external redox mediators. Electricity generation involved anode-attached and suspended microorganisms working in a concert to link cellulose hydrolysis to anaerobic respiration and electrode reduction. The results also demonstrate that the current could be sustained for over 1440 hours with cellulose as the sole substrate. Denaturing gradient gel electrophoresis of PCR amplified 16s rDNA revealed that microbial communities changed when different substrates were used as fuel in MFCs. Results suggested that microbial consortia composed of both anode-biofilm and suspended microbes could evolve within an MFC’s environment. Phylogenetic analysis by the use of rDNA clone libraries, showed differences between the two communities in the cellulose- MFC. This study demonstrates that rumen microbes are capable of hydrolyzing cellulose with concomitant transfer of electrons to an electrode. In addition it adds to the diversity of microorganisms that have been shown to produce electricity in MFCs, and expands the range of suitable substrates to include cellulose, a most abundant plant biomass component readily available as a waste material in many parts of the world.