STRUCTURE AND PERFORMANCE OF ELECTRO-ACTIVE BACTERIAL COMMUNITIES IN MICROBIAL FUEL CELLS UNDER VARYING OPERATING CONDITIONS
Résumé
Microbial Fuel Cells (MFCs) are being developed as a novel biotechnology to harvest energy from dissolved organic matter with potential applications ranging from wastewater treatment to power sources for remote environmental sensors. The objective of this work was to assess the role of operating conditions on the taxonomic structure and function (i.e., electricity production) of electro-active bacterial communities developing at the surface of the electrodes. Parameters tested included substrates (domestic wastewater, starch, glucose, acetate, lactate and LB medium), organic loads, feeding mode (batch and continuous mode) electrical conductivity of the system (open and close circuits), external resistances, and electrode composition and architecture. All experiments were performed using single chamber MFCs fed with primary clarifier effluent from a municipal wastewater treatment plant. Electrical performances (voltage, power) were determined throughout the different experiments. Community structure analyses were performed using RISA and 16S-rRNAbased phylogenetic microarrays. Results show that bacterial communities responsible for electricity production are markedly different from the inoculum (wastewater) and planktonic communities and from other compartments in the MFC. Communities are influenced by operating conditions and the presence of additional carbon sources, but remain relatively stable through time under given operating conditions. Correlations between bacterial community structure and substrates (nature and concentration) were observed, as well as between substrate concentration and electricity production. Interestingly, experiments conducted with different external resistances and with close and open circuits (i.e., electrons allowed to flow or not between the electrodes) showed the structure of electro-active bacterial communities is driven by electricity production.