Chapter 2 - Microbe–material interactions for direct interspecies electron transfer in anaerobic digestion

Abstract

In vivo microbial consortium syntropy is used to metabolize complex organic matter into a simpler type. In this syntropy, direct interspecies electrons transfer (DIET) is involved, in which the transfer of free electrons occurs within syntrophic partners without involving redox mediators such as hydrogen or formate. Therefore, DIET helps to bypass hydrolysis, the rate-limiting step during anaerobic digestion (AD). In AD-involving DIETers, the transfer of electrons occurs between electron-donating bacteria that oxidize biodegradable matter and electron-accepting methanogenic archaea that reduce carbon dioxide into methane. This chapter presents the effect of conductive materials (CMs), including carbon nanotubes, granular activated carbon, carbon cloth, biochar, and Fe-based nanoparticles, on the DIET process. CM-mediated DIET expedites methanogenesis and is proven to be more efficient than indirect interspecies electron transfer during AD. In this work, DIET mechanisms, DIET-active microbial communities, syntrophic interactions among them with the influence of conductive materials, and DIET stimulation via conductive biofilm generation are discussed.