Synergetic effects of conductive materials and bacterial population in inoculum on mixed-culture biohydrogen production

• Published in: International journal of hydrogen energy 2024-01, Vol.53, p.1293-1302
• Main Authors: Yang, Jisu, Sim, Young-Bo, Kim, Saint Moon, Joo, Hwan-Hong, Mašek, Ondřej, Kim, Sang-Hyoun
• Format: Article
• Language: English
• Subjects: Biohydrogen; Conductive materials; Dark fermentation; Exoelectrogen
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2023.12.103

This study examined the effect of conductive materials (softwood pellet biochar pyrolyzed at 550 °C and 700 °C, powdered activated carbon and stainless-steel) on the two series of batch biohydrogen production inoculated with three types of heated-treated anaerobic digester sludge. Biochar pyrolyzed at 550 °C and stainless-steel exhibited the highest enhanced hydrogen yield up to 117 % in the first and second series of experiments, respectively. Importantly, the enhancement effect by the introduction of conductive materials was significantly affected by the microbial population in inoculum, particularly the relative abundance of electroactive H2-producing Clostridium sp. Metabolic flux analysis revealed that the enhanced H2 yield was concurrent with the decrease of lactate production and the increase of H2-producing acetogenesis. Conductive materials also improved electron transport system activity and NADH/NAD+ ratio, which are related with the metabolic activity. This study shows that introducing conductive material can control intracellular redox environment, thereby reinforcing the metabolic activity selectively. [Display omitted] •Effect of conductive matter depends on the inoculum electroactive microbe abundance.•Biochar pyrolyzed at 550 °C and stainless-steel raise H2 yield up to 117.6 %.•Conductive materials increase metabolic activity as well as H2 yield.•Redox-active groups and conductivity increases microbial electroactivity.