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Efficient denitrification and N2O mitigation in low-C/N wastewater treatment by promoting TCA cycle anaplerosis via glyoxylate shunt regulation

Nature Water volume 3, pages 992–1002 (2025)Cite this article

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Abstract

Conventional biodenitrification for water with a low carbon-to-nitrogen ratio (C/N) demands exogenous carbon, exacerbating carbon consumption and emissions. Here we propose a metabolic reprogramming strategy leveraging Mo(VI)–Fe(III)–Cu(II) synergy to redirect carbon flux through the glyoxylate shunt (GS), enhancing tricarboxylic acid cycle anaplerosis for efficient denitrification and reduced greenhouse gases during low-C/N wastewater treatment. At a C/N of 3, Mo(VI)–Fe(III)–Cu(II) promoted carbon metabolism by the tricarboxylic acid cycle in Paracoccus denitrificans, elevating reducing power (electron carriers) production and electron transporter activity. This increased total nitrogen removal by 196.2% compared with the blank control and by approximately 32.0–146.6% compared with single- or dual-metal-supplemented controls, while reducing nitrous oxide emissions by 51.3% and approximately 26.2–85.6%, respectively. This effect originated from the inhibition of isocitrate dehydrogenase and α-ketoglutarate dehydrogenase by Mo(VI)–Fe(III)–Cu(II), causing isocitrate accumulation that activates isocitrate lyase of the glyoxylate shunt and prioritizes GS-driven anaplerosis. Finally, activated sludge validation increased 31.7% total nitrogen removal efficiency, highlighting the approach’s practical potential. This carbon-metabolism reprogramming strategy reduces organic carbon demand in denitrification, enhancing energy efficiency and advancing carbon-neutral wastewater treatment.

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Fig. 1: Schematic diagram of TCA-cycle-driven wastewater denitrification facilitated by the regulation on the GS.
Fig. 2: Effects of metal ions on denitrification of P. denitrificans.
Fig. 3: Effects of metal ions on the acetate metabolism of P. denitrificans.
Fig. 4: Potential mechanism for the GS facilitation by the associative action of metal ions with P. denitrificans.
Fig. 5: Effects of metal ions on electron transporters and denitrifying enzymes with P. denitrificans.
Fig. 6: Effects of metal ions on the denitrification performance, community structure and function contribution in activated sludge microorganisms.

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The data supporting the findings of this study are available within the paper and its Supplementary Information.

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (grant no. 52470053).

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Authors and Affiliations

  1. State Key Laboratory of Water Pollution Control and Green Resource Recycling, School of Environmental Science and Engineering, Tongji University, Shanghai, China

    Haojin Peng, Qingran Zhang, Yu Su, Shuai Wang & Yinguang Chen

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  1. Haojin Peng
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  2. Qingran Zhang
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  3. Yu Su
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  4. Shuai Wang
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  5. Yinguang Chen
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Contributions

Y.C. supervised the study. H.P. designed and performed experiments, compiled and analysed all the data, and wrote the original paper. Q.Z. and Y.S. reviewed the paper. S.W. provided feedback. All authors discussed the paper.

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Correspondence to Yinguang Chen.

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Nature Water thanks Gyucheol Choi, Rui Du and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Notes 1–7, Tables 1–6, Figs. 1–12 and References.

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Peng, H., Zhang, Q., Su, Y. et al. Efficient denitrification and N2O mitigation in low-C/N wastewater treatment by promoting TCA cycle anaplerosis via glyoxylate shunt regulation. Nat Water 3, 992–1002 (2025). https://doi.org/10.1038/s44221-025-00501-z

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