Evaluation of Nanaerobic Digestion as a Mechanism to Explain Surplus Methane Production in Animal Rumina and Engineered Digesters

Zhuoying Wu, Duc Nguyen, Shilva Shrestha, Lutgarde Raskin, Samir Kumar Khanal, Po-Heng Lee

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
32 Downloads (Pure)


Nanaerobes are a newly described class of microorganisms that use a unique cytochrome bd oxidase to achieve nanaerobic respiration at <2 μM dissolved oxygen (∼1% of atmospheric oxygen) but are not viable above this value due to the lack of other terminal oxidases. Although sharing an overlapping ecological niche with methanogenic archaea, the role of nanaerobes in methanogenic systems has not been studied so far. To explore their occurrence and significance, we re-analyzed published meta-omic datasets from animal rumina and waste-to-energy digesters, including conventional anaerobic digesters and anaerobic digesters with ultra-low oxygenation. Results show that animal rumina share broad similarities in the microbial community and system performance with oxygenated digesters, rather than with conventional anaerobic digesters, implying that trace levels of oxygen drive the efficient digestion in ruminants. The rumen system serves as an ideal model for the newly named nanaerobic digestion, as it relies on the synergistic co-occurrence of nanaerobes and methanogens for methane yield enhancement. The most abundant ruminal bacterial family Prevotellaceae contains many nanaerobes, which perform not only anaerobic fermentation but also nanaerobic respiration using cytochrome bd oxidase. These nanaerobes generally accompany hydrogenotrophic methanogens to constitute a thermodynamically and physiologically consistent framework for efficient methane generation. Our findings provide new insights into ruminal methane emissions and strategies to enhance methane generation from biomass.

Original languageEnglish
Pages (from-to)12302-12314
Number of pages13
JournalEnvironmental Science and Technology
Issue number33
Early online date11 Aug 2023
Publication statusPublished - 22 Aug 2023


  • anaerobic digestion
  • biogas
  • cytochrome bd oxidase
  • microaeration
  • nanaerobe
  • nanaerobic respiration
  • oxygen
  • rumen

ASJC Scopus subject areas

  • General Chemistry
  • Environmental Chemistry


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