Enhancement Of Interspecies Electron Transfer Research Articles

Synthetic bacterial consortium enhances hydrogen production in microbial electrolysis cells and anaerobic fermentation

Microbial electrolysis cells (MECs) provide effective approaches for hydrogen production from wastewater and renewable biomass. Improving the efficiency of energy recovery from wastes remains a challenge. Here we report the cross-feeding interactions between the hydrogen-producing Ethanoligenens harbinense and electroactive Geobacter sulfurreducens in MECs and anaerobic fermentation using glucose as electron donor. Results showed that G. sulfurreducens could oxidize acetate produced by E. harbinense and transfer electrons extracellularly to the electrode of MECs, which also enhanced hydrogen production by E. harbinense via mitigation of metabolic feedback inhibition and enhancement of interspecies electron transfer. The defined co-cultures showed 2.5–2.9 times higher hydrogen production rates compared to the mono-cultures, while the MECs further enhanced the substrate conversion efficiency and converted electrical energy into hydrogen energy. The molar ratio of ethanol to acetic acid in co-cultured MECs doubled compared to mono-cultures, indicating that G. sulfurreducens steered the fermentation products of E. harbinense towards ethanol. The co-cultures formed dense aggregates or biofilms, in which close physical interactions by intercellular pili-like nanowire structures were observed between E. harbinense and G. sulfurreducens in the co-culture biofilms of both anode and cathode. These findings provide new insight into syntrophic interactions, beyond that previously reported on fermentative hydrogen-producing bacteria with electroactive bacteria or methanogens, and offer an effective strategy to enhance H2 production and steer metabolic products of fermentative bacteria.

Methane production in a bioelectrochemistry integrated anaerobic reactor with layered nickel foam electrodes

Towards the regulation and enhancement of inter-species electron transfer in sludge anaerobic digestion system, microbial electrolysis technology has become one of the effective ways to accelerate both fermentation and methanogenesis. In this study, the reactor performances and microbial activities related to biocathode formation are evaluated when the role of biocathode is regulated by series of layered cathodes. The results show the abundance of the cathodic methanogens decreased when enlarges the cathode area due to the lower current density. The biocathode evolution is directly related to the spatial methane distribution, which can further determine 25% increase of methane production rate compared to control without biocathode. Ultimately, the maximum methane production yield of 145.79 mL·d−1 is achieved by the optimal cathode area with a current density of 5.3 mA/cm3. The spatially methanogens distribution in suspended sludge and electrodes regulated by the layered cathodes is regarded to be the key to increase methanogenesis.