Evaluating the feasibility of carbon fiber brush for improving biohydrogen production in acidogenic dark fermentation

Abstract

Dark fermentation is a promising technology for biohydrogen (bioH2) production. Augmenting the dark fermentation process with conductive materials has drawn significant research interests improving the bioH2 yield. This study evaluated the feasibility of using carbon fiber brush (CB) as an additive to increase the efficiency of mesophilic dark fermentation using glucose as substrate and heat-shock pretreated anaerobic sludge as inoculum. Effect of electrode packing density on bioH2 yield, soluble metabolite product formation, and substrate degradation was investigated. Maximal bioH2 yield of 334.6 mL/g-glucose was obtained using medium-sized CB with 72.5% higher than the control (194 mL/g-glucose) and butyrate-type fermentation was the dominant metabolic pathway. Further, enhanced concentrations of proteins and polysaccharides on CB biofilm suggested the critical role of extracellular polymeric substances in microbial electron transfer. This was supported via electron transport activity in CB biofilm. Finally, microbial community analysis revealed a selective enrichment of the potentially electroactive Clostridium_sensu_stricto_1 on the CB (56.6%) compared to 40.9% abundance in control. Insights gained from this study demonstrated that CB aided dark fermentation can be an economical and environmentally benign strategy for improving bioH2 yield.