Interspecies electron transfer and microbial interactions in a novel Fe(II)-mediated anammox coupled mixotrophic denitrification system

Ying Wang; Zikun Zhang; Lan Lin; Guowei Xing; Yushi Jiang; Wenzhi Cao; Yanlong Zhang

doi:10.1016/j.biortech.2024.130852

Interspecies electron transfer and microbial interactions in a novel Fe(II)-mediated anammox coupled mixotrophic denitrification system

Bioresour Technol. 2024 May 16:403:130852. doi: 10.1016/j.biortech.2024.130852. Online ahead of print.

Authors

Ying Wang¹, Zikun Zhang¹, Lan Lin¹, Guowei Xing¹, Yushi Jiang¹, Wenzhi Cao¹, Yanlong Zhang²

Affiliations

¹ Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China.
² Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China; Fujian Key Laboratory of Coastal Pollution Prevention and Control (CPPC), College of Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China; Fujian Institute for Sustainable Oceans, Xiamen University, Xiamen, Fujian 361102, China. Electronic address: ylzhang@xmu.edu.cn.

PMID: 38761867
DOI: 10.1016/j.biortech.2024.130852

Abstract

This study effectively coupled anammox and mixotrophic denitrification at a high nitrogen load rate of 6.84 g N/L/d with 40 mg/L Fe(II). Fe(II) enhanced the activity of nitrate reductase, nitrite reductase, and hydrazine dehydrogenase enzymes, facilitating accelerated ATP synthesis. Through electrochemical experiments, interspecies electron transfer processes in coupled system were explored. Fe(II) promoted flavin mononucleotide secretion, enhancing electron-donating and electron-accepting capacity by 2.8 and 1.3 times, respectively. Fe(II) triggered the enrichment of autotrophic denitrifying bacteria (Azospira and Hydrogenophaga), transitioning from single organic nutrient to mixotrophic denitrification. Meanwhile, Fe(II) increased Candidatus_Kuenenia abundance from 35.2 % to 49.0 %, establishing the competitive advantage of anammox bacteria over completed denitrifying bacteria (Comamonas). The synergistic interactions between anammox and various denitrification pathways achieved a nitrogen removal rate of 5.88 g N/L/d, with anammox contribution rate of 88.3 %. This study provides insights into broadening the application of partial denitrification /anammox and electron transfer in multi-bacterial coupling systems.

Keywords: Electron transfer mediators; Enzyme activity; Fe-N network; Microbial structure; Nitrogen removal; Partial denitrification/anammox.