Deep insights into the biofilm formation mechanism and nitrogen-transformation network in a nitrate-dependent anaerobic methane oxidation biofilm

• Published in: Environmental research 2024-07, Vol.252, p.118810-118810, Article 118810
• Main Authors: Zhao, Zhi-Cheng, Fan, Sheng-Qiang, Lu, Yang, Tan, Xin, Liu, Lu-Yao, Wang, Xiao-Wei, Liu, Bing-Feng, Xing, De-Feng, Ren, Nan-Qi, Xie, Guo-Jun
• Format: Article
• Language: English
• Subjects: ammonium; Archaea; biofilm; Biofilm formation; biosynthesis; Extracellular polymeric substance; Gene expression; Membrane aerated moving bed biofilm reactor; methane; microbial communities; nitrate reduction; Nitrate/nitrite-dependent anaerobic methane oxidation; nitrates; nitrogen; Nitrogen cycle; nitrogen fixation; oxidation; polymers; polysaccharides; wastewater treatment
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2024.118810

Nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) process offers a promising solution for simultaneously achieving methane emissions reduction and efficient nitrogen removal in wastewater treatment. Although nitrogen removal at a practical rate has been achieved by n-DAMO biofilm process, the mechanisms of biofilm formation and nitrogen transformation remain to be elucidated. In this study, n-DAMO biofilms were successfully developed in the membrane aerated moving bed biofilm reactor (MAMBBR) and removed nitrate at a rate of 159 mg NO3−-N L−1 d−1. The obvious increase in the content of extracellular polymeric substances (EPS) indicated that EPS production was important for biofilm development. n-DAMO microorganisms dominated the microbial community, and n-DAMO bacteria were the most abundant microorganisms. However, the expression of biosynthesis genes for proteins and polysaccharides encoded by n-DAMO archaea was significantly more active compared to other microorganisms, suggesting the central role of n-DAMO archaea in EPS production and biofilm formation. In addition to nitrate reduction, n-DAMO archaea were revealed to actively express dissimilatory nitrate reduction to ammonium and nitrogen fixation. The produced ammonium was putatively converted to dinitrogen gas through the joint function of n-DAMO archaea and n-DAMO bacteria. This study revealed the biofilm formation mechanism and nitrogen-transformation network in n-DAMO biofilm systems, shedding new light on promoting the application of n-DAMO process. •n-DAMO biofilms were visually developed on polyurethane sponge.•EPS production was important for the development of n-DAMO biofilm.•n-DAMO archaea may dominate the EPS biosynthesis and biofilm development.•n-DAMO archaea actively expressed DNRA and nitrogen fixation.•n-DAMO microorganisms may convert the ammonium produced to NO.