Nitrogen and oxygen isotope signatures of nitrogen compounds during anammox in the laboratory and a wastewater treatment plant

Shotoku Kotajima, Keisuke Koba*, Daisuke Ikeda, Akihiko Terada, Kazuichi Isaka, Kazuya Nishina, Yuuya Kimura, Akiko Makabe, Midori Yano, Hirotsugu Fujitani, Norisuke Ushiki, Satoshi Tsuneda, Muneoki Yoh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Isotopic fractionation factors against15N and18O during anammox (anaerobic ammonia oxidization by nitrite) are critical for evaluating the importance of this process in natural environments. We performed batch incubation experiments with an anammox-dominated biomass to investigate nitrogen (N) and oxygen (O) isotopic fractionation factors during anammox and also examined apparent isotope fractionation factors during anammox in an actual wastewater treatment plant. We conducted one incubation experiment with high δ18O of water to investigate the effects of water δ18O. The N isotopic fractionation factors estimated from incubation experiments and the wastewater treatment plant were similar to previous values. We also found that the N isotopic effect (15εNXR of –77.8 to –65.9‰ and15ΔNXR of –31.3 to –30.4‰) and possibly O isotopic effect (18εNXR of –20.6‰) for anaerobic nitrite oxidation to nitrate were inverse. We applied the estimated isotopic fractionation factors to the ordinary differential equation model to clarify whether anammox induces deviations in the δ18O vs δ15N of nitrate from a linear trajectory of 1, similar to heterotrophic denitrification. Although this deviation has been attributed to nitrite oxidation, the O isotopic fractionation factor for anammox is crucial for obtaining a more detailed understanding of the mechanisms controlling this deviation. In our model, anammox induced the trajectory of the δ18O vs δ15N of nitrate during denitrification to less than one, which strongly indicates that this deviation is evidence of nitrite oxidation by anammox under denitrifying conditions.

Original languageEnglish
Article numberME20031
Pages (from-to)1-11
Number of pages11
JournalMicrobes and Environments
Issue number4
Publication statusPublished - 2020


  • Anammox
  • Denitrification
  • Isotopic fractionation
  • Nitrite oxidation
  • Stable isotope

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Soil Science
  • Plant Science


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