Biogas upgrading towards acetic acid production using Clostridium thailandense supplemented with granular activated carbon (GAC) and L-arginine: A genomic analysis approach

This study explores the impact of granular activated carbon (GAC) and L-arginine supplementation on biogas upgrading and acetic acid production employing Clostridium thailandense. GAC and L-arginine concentrations ranged from 0 to 20 g/L and 0 to 5 g/L, respectively, with H₂ acting as the electron donor at an H₂ to CO₂ ratio of 2:1 (v/v). Experiments were conducted at 30 °C with an agitation speed of 150 rpm. Additionally, gene annotation of the C. thailandense genome using Rapid Annotations using Subsystems Technology (RAST) identified genes involved in CO₂ to acetic acid conversion. Results indicate that adding 7.5 g/L GAC boosts CH₄ purity in biogas, elevating CO₂ and H₂ consumption efficiencies to 88.3 % and 98.7 %, respectively. This enhancement leads to a CH₄ content increase to 93.3 %, accompanied by 0.90 g/L acetic acid production. Conversely, L-arginine demonstrates no significant impact on CO₂ conversion. Leveraging RAST, the study identifies hydrogenase genes and NADH-dependent ferredoxin-NADP⁺ oxidoreductase (Nfn), as crucial for heightened H₂ consumption efficiencies and cell growth facilitated by GAC, thus enhancing biogas upgrading efficiency in C. thailandense. This research provides vital insights into optimizing sustainable biogas production through strategic GAC utilization and elucidates the roles of hydrogenase genes and Nfn.