Methanogens: biochemical background and biotechnological applications

Since fossil sources for fuel and platform chemicals will become limited in the near future, it is important to developnew concepts for energy supply and production of basic reagents for chemical industry. One alternative to crude oiland fossil natural gas could be the biological conversion of CO2or small organic molecules to methane via methanogenic archaea. This process has been known from biogas plants, but recently, new insights into the methanogenicmetabolism, technical optimizations and new technology combinations were gained, which would allow movingbeyond the mere conversion of biomass. In biogas plants, steps have been undertaken to increase yield and purity of the biogas, such as addition of hydrogen or metal granulate. Furthermore, the integration of electrodes led to thedevelopment of microbial electrosynthesis (MES). The idea behind this technique is to use CO2and electrical power to generate methane via the microbial metabolism. This review summarizes the biochemical and metabolic background of methanogenesis as well as the latest technical applications of methanogens. As a result, it shall give a sufficient overview over the topic to both, biologists and engineers handling biological or bioelectrochemical methanogenesis.