Engineering Geobacter sulfurreducens to produce a highly cohesive conductive matrix with enhanced capacity for current production

Ching Leang, Nikhil S. Malvankar, Ashley E. Franks, Kelly P. Nevin, Derek R. Lovley
2013 Energy & Environmental Science  
The conductive biofilms of Geobacter sulfurreducens have potential applications in renewable energy, bioremediation, and bioelectronics. In an attempt to alter biofilm properties, genes encoding proteins with a PilZ domain were deleted from the G. sulfurreducens genome. A strain, in which the gene GSU1240 was deleted, designated strain CL-1, formed biofilms much more effectively than did the wildtype strain. Increased production of pili and exopolysaccharide were associated with the enhanced
more » ... ith the enhanced biofilm production. When grown with an electrode as the electron acceptor CL-1 produced biofilms that were 6-fold more conductive than wild-type biofilms. The greater conductivity lowered the potential losses in microbial fuel cells, decreasing the charge transfer resistance at the biofilm-anode surface by ca. 60% and lowering the formal potential by 50 mV. These lower potential losses increased the potential energy of electrons reaching the biofilm-anode interface and enabled strain CL-1 to produce 70% higher power densities than the wild-type strain. Current-producing biofilms were highly cohesive and could be peeled off graphite electrodes intact, yielding a novel conductive biological material. This study demonstrates that simple genetic manipulation can yield improved bioelectronics materials with energy applications. Broader context Long-range electron transport through microbial biolms has applications for the conversion of organic wastes to methane in anaerobic wastewater digesters or electricity in microbial fuel cells, as well as for microbial electrosynthesis, a process in which microorganisms use electrical energy to produce fuels and other organic commodities from carbon dioxide. Geobacter sulfurreducens naturally produces biolms that are electrically conductive, but genetic engineering offers the possibility of constructing strains that are superior to what natural selection has provided. In this rst reported attempt to genetically manipulate G. sulfurreducens biolm formation we describe a strain produced via a gene deletion that generates biolms with enhanced cohesiveness, conductivity, and capacity for current production. These results demonstrate how synthetic biology may signicantly contribute to the emerging eld of electromicrobiology.
doi:10.1039/c3ee40441b fatcat:bsmclbgmhfa3jew4lo2x3rbzli