Despite the growing interest in using mixed-culture aerobic denitrifying fungal flora (mixed-CADFF) for water remediation, there is limited research on their nitrogen removal performance in low C/N polluted water bodies. To address this knowledge gap, we isolated three mixed-CADFFs from overlying water in urban lakes to evaluate their removal performance. The total nitrogen (TN) removal efficiencies were 93.60 %, 94.64 %, and 95.18 %, while the dissolved organic carbon removal efficiencies were 96.64 %, 95.12 %, and 96.70 % for mixed-CADFF LN3, LN7, and LN15, respectively in the denitrification medium under aerobic conditions at 48 h cultivation. The three mixed-CADFFs could utilize diverse types of low molecular weight carbon sources to drive the aerobic denitrification processes efficiently. The optimal C/N ratio for the mixed-CADFFs were C/N = 10, and then C/N = 15, 7, 5, and 2. The high-throughput sequencing analysis of three mixed-CADFFs indicated that Eurotiomycetes, Cystobasidiomycetes, and Sordariomycetes were the dominant class in the communities at class level. The network analysis showed that the rare fungal species, such as Scedosporium dehoogii Saitozyma, and Candida intermedia presented positively co-occurred with the TN removal and organic matter reduction capacity. Immobilization mixed-CADFFs treatment raw water experiments indicated that three mixed-CADFFs could reduce nearly 62.73 % of TN in the low C/N micro-polluted raw water treatment. Moreover, the cell density and cell metabolism indexes were also increased during the raw water treatment. This study will provides new insight into resource utilization of the mixed-culture aerobic denitrifying fungal community in field of environment restoration.

Civil and Environmental Engineering Department Utah State University Logan UT 84322 USA

Department of Applied Ecology Faculty of Environmental Sciences Czech University of Life Sciences Prague Kamýcká 129 Praha Suchdol 16500 Czech Republic

Department of Civil and Environmental Engineering the Pennsylvania State University USA

Department of Civil Engineering Queen's University Kingston Ontario K7L 3N6 Canada

Department of Oncology The 2nd Affiliated Hospital of Xi'an Jiaotong University Xi'an 710004 China

Papanin Institute for Biology of Inland Waters of Russian Academy of Sciences 109 Borok Nekouz Yaroslavl 152742 Russia

Shaanxi Key Laboratory of Environmental Engineering Key Laboratory of Northwest Water Resource Environment and Ecology MOE Xi'an University of Architecture and Technology Xi'an 710055 China; School of Environmental and Municipal Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

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