Hydrogen producing microbial communities of the biocathode in a microbial electrolysis cell

摘要

In the search for alternatives for fossil fuels and the reuse of the energy from wastestreams, the microbial electrolysis cell is a promising technique. The microbialelectrolysis cell is a two electrode system in which at the anode organic substances,including waste water, are used by microorganisms that release the terminal electrons tothe electrode. These electrons are subsequently used at the cathode resulting in theproduction of a current. By addition of a small voltage, hydrogen gas can be produced bycombining electrons and protons at the cathode. To catalyse the hydrogen evolutionreaction at the cathode, expensive catalysts such as platinum are required. Recently, theuse of biocathodes has shown great potential as an alternative for platinum. The microbialcommunity responsible for the hydrogen evolution in such systems is, however, not wellunderstood. In this study we focused on the characterization of the microbialcommunities of the microbial electrolysis cell biocathode using molecular techniques.The results show that the microbial community consists of 44% Proteobacteria, 27%Firmicutes, 18% Bacteriodetes and 12% related to other phyla. Within the majorphylogenetic groups we found several clusters of uncultured species belonging to noveltaxonomic groups at genus level. These novel taxonomic groups developed underenvironmentally unusual conditions and might have properties that have not beendescribed before. Therefore it is of great interest to study those novel groups further.Within the Proteobacteria a major cluster belonged to the Deltaproteobacteria and basedon the known characteristics of the closest related cultured species, we suggest amechanism for microbial electron transfer for the production of hydrogen at the cathode.