Related Experiment Video
Updated: Sep 13, 2025

Characterizing Electron Transport through Living Biofilms
Published on: June 1, 2018
Granular activated carbon (GAC)-driven microbial electron shuttle boosts denitrification and mitigates N2O in cold
Xiangyu Yang1,2,3,4, Mingchen Yao1,4,5, Peng Li6
1Key Laboratory of Environmental Aquatic Chemistry, State Key Laboratory of Regional Environment and Sustainability, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, P. R. China.
Background:
Denitrification in wastewater treatment is severely limited under low-temperature and low-carbon ("dual-low") conditions, hindering sustainable nitrogen removal. Biofilm systems, though energy-efficient, suffer from reduced efficiency in such environments due to impaired interspecies electron transfer (IET). Granular activated carbon (GAC), a conductive mediator, offers potential to enhance IET between electroactive microorganisms (EAMs) and denitrifiers, yet its role in dual-low systems remains underexplored. This study investigates GAC's capacity to optimize biofilm functionality and mitigate greenhouse gas (GHG) emissions under these constraints.
Results:
Under dual-low conditions (4-6°C, C/N = 4), GAC increased denitrification efficiency by 19.4-21.9% and reduced N2O emissions by 10.6-22.9%. Metatranscriptomes revealed upregulation of denitrifying genes (e.g., nosZ) and electron transport pathways (e.g., omcB in Geobacter). FISH/SEM confirmed GAC-driven coacervates of EAMs and denitrifiers, linked by nanowires, enhancing direct electron transfer. Microbial diversity decreased, but functional redundancy improved, with Pseudomonas fluorescens and Geobacter sulfurreducens dominating. TOC removal rose under low temperatures, indicating enhanced carbon utilization.
Conclusions:
GAC fosters synergistic EAM-denitrifier partnerships, enabling efficient denitrification and GHG mitigation in cold and carbon-limited ("dual-low") biofilm systems, advancing sustainable wastewater management. Video Abstract.
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