Search

Graphical abstract Highlights • The acetate production rate with fluidized GAC was 2.8 times that of control. • Fluidized GAC provide a high electrode surface and a favorable mass transport. • Fluidized GAC likely promoted the enrichment of electrochemically active bacteria. • Fluidized GAC electrode is a promising strategy to improve MES efficiency. Abstract The electricity-driven bioreduction of carbon dioxide to multi-carbon organic compounds, particularly acetate, has been achieved in microbial electrosynthesis (MES). MES performance can be limited by the amount of cathode surface area available for biofilm formation and slow substrate mass transfer. Here, a fluidized three-dimensional electrode, containing granular activated carbon (GAC) particles, was constructed via MES. The volumetric acetate production rate increased by 2.8 times through MES with 16 g L−1 GAC (0.14 g L−1 d-1) compared with that of the control (no GAC), and the final acetate concentration reached 3.92 g L−1 within 24 days. Electrochemical, scanning electron microscopy, and microbial community analyses suggested that GAC might improve the performance of MES by accelerating direct and indirect (via H 2) electron transfer because GAC could provide a high electrode surface and a favorable mass transport. This study attempted to improve the efficiency of MES and presented promising opportunities for MES scale-up. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal organic frameworks (MOFs) significantly promote CO 2 biomethanation with H 2. • MOFs promote direct interspecific electron transfer between microorganisms. • Hydrogenotrophic methanogens were enriched in the anaerobic reactors with MOFs. • MOFs alleviated the hydrogen competition of bacteria. • MOFs increase the abundance of functional gene for CO 2 biomethanation with H 2. In this work, metal–organic frameworks (MOFs) were prepared to evaluate its impact on carbon dioxide (CO 2) biomethanization during anaerobic degradation (AD). The results showed that MOFs significantly improved the CO 2 biomethanation efficiency, especially in the AD reactors using a concentration of 1.0 g/L MOFs. Furthermore, MOFs promoted direct interspecific electron transfer and alleviated the hydrogen competition of bacteria. Meanwhile, hydrogenotrophic methanogens were enriched in the AD reactors with MOFs. After the addition of MOFs, there was 3.28 times and 3.41 times increase in the abundance of metabolic functions related to methanogenesis by CO 2 reduction with hydrogen and dark hydrogen oxidation, respectively. There was an increased abundance of all genes that encode the key enzymes used in methane metabolism. However, functional genes involved in nitrate reduction had their expressions inhibited. The work may offer a contribution to helping the industry achieve the carbon capture and utilization policy. [ABSTRACT FROM AUTHOR]

• The synergistic biodegradation mechanisms of coal and corn straw were explored. • The synergistic biodegradation of coal is combined with straw-filled goaf. • The production of liquid-phase products is related to the coal rank. • Coal can promote the biodegradation of cellulosic substances from corn straw. • Corn straw and coal improve the microbial community structure. The mechanisms associated with the biomethane metabolism through the synergistic biodegradation of both coal and corn straw were explored to improve the utilization rate of corn straw. This applies to the filling of the goaf with corn straw and the production of biomethane using indigenous bacteria in the mine water with coal. The results showed that new macromolecular substances (e.g., Tetracosane and Pentacosane) were produced on the third day. A lower coal rank leads to a lower biodegradation rate of low-molecular-weight substances (e.g., butyric acid and valeric acid). Under the addition of coal samples, the biodegradation rate of cellulose, hemicellulose and lignin in corn straw could reached up to 29.82%, 35.79% and 6.16%, respectively. The addition of corn straw promoted the complementary advantages of archaeal genera (such as Methanosarina and Methanospirillum) and decreased the adverse bacterial genera (such as Desulfovibrio and Pseudomonas) in the fermentation system of single coal. [ABSTRACT FROM AUTHOR]