Identification of key steps and associated microbial populations for efficient anaerobic digestion under high ammonium or salinity conditions

• Published in: Bioresource technology Vol. 360; p. 127571
• Main Authors: Duc, Luong Van, Miyagawa, Yuta, Inoue, Daisuke, Ike, Michihiko
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2022
• Subjects: Inhibition threshold; Methane production; Propionate; Seed sludge; Syntrophic propionate-oxidizing bacteria; Propionate; Methane production; Syntrophic propionate-oxidizing bacteria; Inhibition threshold; Seed sludge
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2022.127571

[Display omitted] •CH4 production during anaerobic digestion under NH4+ or NaCl stress was explored.•Common tolerable levels of NH4+ and NaCl for CH4 production were identified.•Propionate regulates CH4 production under inhibitory conditions.•Candidatus Brevefilum is a propionate degrader enabling efficient CH4 production.•Methanothrix appeared to be tolerant to 5 g NH4-N/L and 30 g/L NaCl. Ammonium (NH4+) and salinity are major inhibitors of CH4 production in anaerobic digestion. This study evaluated their inhibitory effects on CH4 production and explored the key populations for efficient CH4 production under high NH4+ and NaCl concentrations to understand their inhibition mechanisms. Comparative batch experiments for mesophilic anaerobic digestion were conducted using three seeding sludges under different concentrations of NH4+ (1–5 gNH4-N/L) and NaCl (10–30 g/L). Although all sludges tolerated 3 gNH4-N/L and 10 g/L NaCl, NH4+ or NaCl concentrations higher than these substantially reduced CH4 production, depending on the seeding sludge, primarily by impairing the initial hydrolysis and methanogenesis steps. In addition, propionate was found to be a deterministic factor affecting CH4 production. Based on microbial community analysis, Candidatus Brevefilum was identified as a potential syntrophic propionate-oxidizing bacterium that facilitates the mitigation of propionate accumulation, allowing the maintenance of unaffected CH4 production under high inhibitory conditions.