Rates of anaerobic oxidation of methane and metabolite production from a model landfill gas using an enriched...

Anaerobic oxidation of methane (AOM) can contribute to reducing methane emissions in landfills; however, the AOM rates vary depending on the inoculum source. This study addressed the capacity of AOM of a fermentative microbial community derived from a reactor treating municipal solid wastes. First, the inoculum's autotrophic capacity was verified using a gas mixture of 75 % CO₂ and 25 % H₂. Results demonstrated that the fermentative microbial community reached a maximum CO₂ consumption rate of 22.5 ± 1.2 g CO₂/(m³·h), obtaining acetate as the main product. Then, the inoculum was grown on a gas mixture of 50 % CH₄, 35 % CO₂, and 15 % N₂, using iron (Fe³⁺) as the electron acceptor. The AOM rates increased over time and peaked at 3.1 ± 0.9 g CH₄/(m³·h) by 456 h with the simultaneous consumption of CO₂. Acetate was the main product, with a maximum concentration of 180 ± 9 mg/L. By 408 h, a bacterial cluster of indicator species correlated with the AOM rates, including to Rhodobactereceae (r = 0.80), Oceanicola (r = 0.80), Propionicicella (r = 0.77), Christensenellaceae (r = 0.58), Oscillospiraceae (r = 0.53), Mobilitalea (r = 0.66), Hungateiclostridiaceae (r = 0.46), and Izemoplasmatales (r = 0.77). Methanosarcina, Methanobacterium, and Methanoculleus correlated with the AOM and CO₂ consumption rates. A co-occurrence network analysis showed that Methanosarcina positively interacted with syntrophic bacteria like Christensenellaceae and Acinetobacter and diverse heterotrophic bacteria. This study demonstrated the feasibility of obtaining a CH₄-oxidizing microbial community in 16 days, exhibiting AOM rates higher than those reported for soils.