Microbial fuel cells (MFC) can transform the chemical energy from cheap organic compounds directly into electrical energy. The concept was known since the 70s, but with little prospect of industrial development in the short or medium term. A fundamental breakthrough occurred in 2002: the unexpected discovery of microorganisms capable of catalyzing the oxidation process at the surface of graphite electrodes. These microorganisms can attach spontaneously to the surface of materials and form a three-dimensional structure more or less organized called electro-active (EA) biofilm. The electro-active biofilms can be formed artificially in laboratory from pure culture of microorganisms or can develop spontaneously on electrodes immersed in natural environments rich in microorganisms such as sediments or sludge from wastewater treatment plants. With this new type of electro-catalysis assisted by micro-organisms, the MFC technology produce electrical energy by oxidizing a large diversity of organic compounds (acetate, volatile fatty acids, saccharides ...) contained in natural environments. These key advances have been highlighted by teams of microbiologists or environmental engineers, who use currently basic electrode materials based on carbon and conventional experimental systems, poorly adapted to the study of microbial fuel cell. In addition, the low efficiency of the cathodic compartment was rapidly reported as the main drawback of the technology. On this point, the “laboratoire de genie chimique” (LGC) and the BioCathInox project manager (B. Erable) have proposed a decisive answer to lift the problem of the cathode. They described in 2010 a marine EA bacterium (Algoriphagus sp.) colonizing the surface of stainless steel and giving to this material the property to electro-catalyze the reduction of dissolved oxygen, with kinetics comparable to those obtained on the solid platinum. This innovation on the cathodic process may be the answer saving the MFC technology, however, there are still some scientific problems and fundamental processes are not yet understood. The BioCathInox project proposes to develop the research on EA biofilms engineering beyond the current knowledge in two complementary ways: • Building the necessary basic knowledge on "Stainless Steel / electro-active biofilm” interfaces. The tools of microscopy and molecular biology will then be combined to understand how EA biofilms is structuring on the surface of stainless steels. Advanced techniques in electrochemistry at the local level (as SVET for example) will be used to pierce the mysteries of electron transfer between microorganisms and the surface of stainless steel. • Using these fundamental advances in designing optimal microbial cathodes that will lead the MFC technology to a pre-industrial development. The combination of different scales of electrodes structuring (nano- and/or micro- structuring) to promote bacterial adhesion and the electron transfer is an original approach to maximize the calatytic performance of the interfaces. Also, a strategy combining the stabilization of the reaction and the improvement of mass transport inside he biofilm structure should consistently improve the stabilitye of microbial cathodes. The final objective is to achieve a current density of about 10 A/m2 with a stainless steel based microbial cathode formed from the bacterial strain Algoriphagus sp.