Synergism Between Electron Donors and Microbes Toward Highly Efficient Denitrification with Minimal Sludge Yield

Jing Zhao; Yunjie Liao; Yuting Wang; Qinghua Ji; Ruiping Liu; Huijuan Liu

doi:10.1016/j.eng.2026.03.014

Engineering ›› :202603014 DOI: 10.1016/j.eng.2026.03.014

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Synergism Between Electron Donors and Microbes Toward Highly Efficient Denitrification with Minimal Sludge Yield

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Abstract

Hydrogen (H₂), formate, and acetate are effective electron donors for denitrification; however, their interactions with microflora and their impacts on sludge production remain poorly understood. In this study, integrated mixed- and pure-culture experiments were conducted to systematically elucidate how these electron donors and microbes collectively regulate denitrification and sludge formation. Mechanistic insights were further elucidated using metagenomics-based metatranscriptomics methods. In mixed culture reactors, H₂ and formate share similar microbial communities, dominated by Paracoccus pantotrophus (60.4%–70.0%). In contrast, acetate-driven denitrification was primarily facilitated by Pseudomonas aeruginosa (42.3%) and Pseudomonas stutzeri (39.1%), which achieved the highest denitrification rate of 142.3 mg _N·(L·h·OD ₆₀₀) ⁻¹. Metagenomics-based metatranscriptomics identified Pseudomonas aeruginosa as the main contributor to denitrification, a finding validated by pure-culture experiments. Notably, in the pure-culture experiment, Pseudomonas aeruginosa demonstrated superior denitrification performance with lower acetate demand (0.56 g _COD·g _N ⁻¹) and lower biomass yield (OD ₆₀₀ 0.20 vs 0.54). Support vector machine analysis further indicated that Pseudomonas is widely distributed in wastewater treatment plants globally, and that acetate is the most efficient electron donor for denitrification. These results highlight that the combination of acetate and Pseudomonas aeruginosa is a promising strategy for achieving high efficiency with minimal sludge production in wastewater treatment plants.

Keywords

Pseudomonas aeruginosa / Denitrification / Electron donor / Meta-omics / Low-sludge generation

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Jing Zhao, Yunjie Liao, Yuting Wang, Qinghua Ji, Ruiping Liu, Huijuan Liu. Synergism Between Electron Donors and Microbes Toward Highly Efficient Denitrification with Minimal Sludge Yield. Engineering 202603014 DOI:10.1016/j.eng.2026.03.014

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