Availability of Hydrogen Shapes the Microbial Abundance in Biofilm Anodes based onGeobacterEnrichment

Abstract

AbstractBiofilm anodes based onGeobacterenrichment in one‐chamber and two‐chamber reactors are qualitatively and quantitatively investigated. The methanogenic community of biofilms in both types of reactors consists exclusively of hydrogenotrophs, mainly the genusMethanobacterium. As qPCR demonstrates in one‐chamber reactors, the abundance ofGeobacterand methanogens increases due to the presence of cathodically produced hydrogen. In two‐chamber reactors, the abundance of methanogens is decreased by 98 % compared to one‐chamber reactors. Adding hydrogen gas to the anodic compartment of two‐chamber reactors recovers the abundance of methanogens andGeobacter. Ratios of methanogens/bacteria are confirmed by using the cofactor F420autofluorescence of methanogens. The impact of the reactor setup for developing primary microbial electrochemical technologies is discussed, reasoning that two‐chamber reactors have to be generally favored. Yet, their use inheres a trade‐off when cultivating biofilm anodes, as the indicated syntrophic interactions between methanogens andGeobacterare reduced, but pH decrease might influence microbial processes.