Dual cathode configuration and headspace gas recirculation for enhancing microbial electrosynthesis using Sporomusa ovata

• Published in: Chemosphere (Oxford) Vol. 287; no. Pt 3; p. 132188
• Main Authors: Bajracharya, Suman, Krige, Adolf, Matsakas, Leonidas, Rova, Ulrika, Christakopoulos, Paul
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2022
• Subjects: acetates; acetogens; Biochemical Process Engineering; Biokemisk processteknik; Bioprinting; carbon dioxide; cathodes; Dual cathode; electricity; electrosynthesis; Gas recirculation; graphene; headspace analysis; Hydrogen evolution; hydrogen production; Microbial electrosynthesis; solubility; Sporomusa ovata; Synthetic biofilm; titanium; value added; Bioprinting; Microbial electrosynthesis; Dual cathode; Synthetic biofilm; Hydrogen evolution; Gas recirculation
• DOI: 10.1016/j.chemosphere.2021.132188
• ISSN: 0045-6535; 1879-1298

High-rate production of acetate and other value-added products from the reduction of CO2 in microbial electrosynthesis (MES) using acetogens can be achieved with high reducing power where H2 appears as a key electron mediator. H2 evolution using metal cathodes can enhance the availability of H2 to support high-rate microbial reduction of CO2. Due to the low solubility of H2, the availability of H2 remains limited to the bacteria. In this study, we investigated the performances of Sporomusa ovata for CO2 reduction when dual cathodes were used together in an MES, one was regular carbon cathode, and the other was a titanium mesh that allows higher hydrogen evolution. The dual cathode configuration was investigated in two sets of MES, one set had the usual S. ovata inoculated graphite rod, and another set had a synthetic biofilm-imprinted carbon cloth. Additionally, the headspace gas in MES was recirculated to increase the H2 availability to the bacteria in suspension. High-rate CO2 reduction was observed at −0.9 V vs Ag/AgCl with dual cathode configuration as compared to single cathodes. High titers of acetate (up to ∼11 g/L) with maximum instantaneous rates of 0.68–0.7 g/L/d at −0.9 V vs Ag/AgCl were observed, which are higher than the production rates reported in the literatures for S. ovata using MES with surface modified cathodes. A high H2 availability supported the high-rate acetate production from CO2 with diminished electricity input. [Display omitted] •A simple modification with an additional Ti cathode in MES promoted H2 evolution.•Headspace gas recirculation improves the gas-liquid mass transfer of H2 and CO2.•High rates up to 0.68–0.7 g acetate/L/d from CO2 reduction by Sporomusa ovata.•Long-term stability with up to 11 g/L acetate and 80% efficiency was attained.