Biohydrogen Production in Microbial Electrolysis Cell Operating on Designed Consortium of Denitrifying Bacteria

Abstract

Research background. This study provides insight into the use of a designed microbial community to produce biohydrogen in simple, single-chambered microbial electrolysis cells (MECs). The ability of MECs to stably produce biohydrogen relies heavily on the setup and microorganisms working inside the system. Despite having the most straightforward configuration and effectively avoiding costly membranes, single-chambered MECs are prone to competing metabolic pathways. We present in this study one possible way of avoiding this problem using characteristically defined, designed microbial consortia. In this study, we are comparing the performance of MECs inoculated with a design consortium to MECs operating with a naturally occurring soil consortium. Experimental approach. We adapted a cost-efficient and simple single-chambered MEC design. The MEC was gas-tight, 100 mL in volume, and equipped with continuous monitoring for electrical output using a digital multimeter. Microorganisms were sourced from Indonesian environmental samples, either as denitrifying bacterial isolates grouped as a design consortium or natural soil microbiome used in its entirety. The design consortium consisted of 5 species spread among the Pseudomonas and Acinetobacter genera. The headspace gas profile was followed periodically by gas chromatography. At the end of the culture, the composition of the natural soil consortium was characterized by NGS and the anodes were observed for surface-growth of the bacteria by FE-SEM imaging. Results and conclusions. We found that MEC operating on a design consortium presented a better H2 production profile, with the ability of the system to maintain headspace H2 concentration relatively stable for a long time after reaching stationary growth period. In contrast, MECs inoculated with soil microbiome exhibited a strong decline in headspace H2 profile within the same timeframe. Novelty and scientific contribution. This work utilizes a designed, denitrifying bacterial consortium isolated from Indonesian environmental samples that can survive in a nitrate-rich environment. Here we propose using a designed consortium as a biological approach to avoid methanogenesis in MECs, as a simple and environmentally friendly alternative to current chemical/physical methods. Our findings offer an alternative solution to avoid the problem of H2 loss in single-chambered MECs along with optimizing biohydrogen production through bioelectrochemical routes.