Nickel Foam Promotes Syntrophic Metabolism of Propionate and Butyrate in Anaerobic Digestion

[Image: see text] Enhanced interspecies electron transfer (IET) among symbiotic microorganisms is an effective method to increase the rate of methane (CH(4)) production in anaerobic digestion. Direct interspecies electron transfer (DIET), which does not involve dissolved redox media, is considered an alternative and superior method to enhance methane production by interspecific hydrogen (H(2)) transfer (IHT). In this study, nickel foam was built into a semicontinuous anaerobic reactor to investigate its effect on the metabolism of propionate and butyrate. Both increased the average yield of CH(4) in anaerobic digestion by 18.1 and 15.9%, respectively. Analysis of bacterial and archaeal communities showed that the addition of nickel foam could increase the relative abundance of microbial communities involved in DIET and could increase the diversity of microorganisms in the reactor. Moreover, the anaerobic digestion performance of the nickel foam reactor was good at high hydrogen partial pressure.