1 School of Environmental and Municipal Engineering, Tianjin Key Laboratory of Aquatic Science and Technology, Tianjin Chengjian University, Jinjing Road 26, Tianjin, 300384, China.
2 School of Environmental and Municipal Engineering, Tianjin Key Laboratory of Aquatic Science and Technology, Tianjin Chengjian University, Jinjing Road 26, Tianjin, 300384, China; Zhuhai Orbita Aerospace Science & Technology Co.,LTD, Orbita Techpark1, Baisha Road, Tangjia Dong'an, Zhuhai, China. Electronic address: lucaicai2010@163.com.
3 Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve Blvd. W, Montreal, Quebec, Canada.
4 School of Civil Engineering and Architecture, Taizhou University, Taizhou, 318000, Zhejiang, China; School of Environmental and Municipal Engineering, Tianjin Key Laboratory of Aquatic Science and Technology, Tianjin Chengjian University, Jinjing Road 26, Tianjin, 300384, China. Elect

Intrinsically conductive polymers, polyaniline and polyaniline sulfonate (PASAni) were used to explore their effect on denitrification. Denitrification was accelerated 1.90 times by 2 mM PASAni and the possible mechanisms were mainly attributed to the accelerated electron transfer and the enhanced microbial metabolism activity. Intracellular electron transfer was accelerated by PASAni and the acceleration sites were from NADH to coenzyme Q (CoQ), quinone loop, from Complex II to CoQ and from QH₂ to Cyt. c₁. Extracellular electron transfer was accelerated because PASAni promoted more secretion of redox species and PASAni embedded in extracellular polymeric substance (EPS). Moreover, PASAni may pass across cell membrane like type IV pilus, which provided more electron transfer pathways. Microbial metabolism activity was also enhanced by PASAni, which was reflected in the increased nitrate/nitrite reductase activity (236.13/155.43%), electron transfer system activity (112.49%), adenosine triphosphate level (133.41%) and EPS content (189.06%). Besides, the enriched Proteobacteria in PASAni supplement system was also conducive to denitrification. This work provided fundamental information for conductive polymers mediating microbial electron transfer and enhancing contaminants biotransformation.