Design of biohybrid electrodes for improving bacterial energy production

DIEGO MASSAZZA; JUAN PABLO BUSALMEN; RODRIGO PARRA; HERNÁN E. ROMEO

Congreso; X Congreso Argentino de Microbiología General; 2014

Microbial fuel cells (MFCs) appear as a new and appealing possibility for both the treatment of organic waste and the generation of electric power. They are similar to conventional fuel cells but take advantage of electro-active microorganisms, especially those from the genus Geobacter, which act as bioelectrocatalysts converting the energy stored in chemical bonds of organic compounds into electric energy. In recent years this concept has triggered considerable interest among academic researchers towards environmentally safe and novel low cost biotechnologies. A MFC consists of an external electric circuit which links anodic and cathodic compartments separated by a proton or cation exchange membrane. Generally used anodes consist of non-porous graphite rods immersed in the bacterial culture medium, upon which the colony of cells can develop. Recent results have indicated that long term development of anodic bacterial biofilms does not correlate with current production, mainly due to a drop in the outside cells redox potential with the distance to the electrode; this potential decay is thought to be due to the imperfect electric conduction of the biofilm matrix and determines that cells composing outer layers of the biofilm structure cannot contribute to the power production process. Applications that make use of electro-active biofilms are not yet economically sustainable, but this situation may change if the electric connection between cells in the biofilms is improved. This work aims at developing hierarchically structured and electrically conducting ceramic supports exhibiting an open structured porosity that allows the proliferation and development of electrogenic bacterial biofilms, in which most of cells are in close contact with the conducting material. These so-called bio-Hybrid anodes are expected to produce much more current than traditionally used graphite rods. An ice-templating technique was used to produce macroporous ceramic matrices (based on electrically conducting titanium suboxides) able of being employed as alternative supports (instead of graphite) for the development of electrogenic biofilms of Geobacter sulfurreducens in conventional electrochemical reactors. Scanning electron microscopy (SEM) was employed to visualize the formation of biofilms on the surface of the new electrodes. The production of current was followed by chronoamperometry and was found to be three (3) times higher compared to conventional graphite rods. Summarizing, the proposed material appears as an interesting alternative for the replacement of graphite electrodes conventionally used in MFCs by porous ceramic anodes.