Aerobic denitrification performance and nitrate removal pathway analysis of a novel fungus Fusarium solani RADF-77

•A novel aerobic denitrification fungus was isolated and identified.•RADF-77 was capable of removing nitrogen under aerobic conditions.•The optimized conditions for denitrification of RADF-77 were obtained.•Transcriptional nitrate reduction chain was detected in aerobic nitrate removal.•Tea residue can be utilized as solid organic carbon source for RADF-77. Increasing nitrogenous contaminants have caused immense challenges to the environment and human health. As compared to physical and chemical methods, biological denitrification is considered to be an effective solution due to its environmental friendliness, high efficiency, and low cost. In the present work, a novel fungal strain identified as Fusarium solani (RADF-77) was isolated from cellulose material-supported denitrification reactor; this strain is capable of removing nitrogen under aerobic conditions. The average NO3–-N removal rate for RADF-77 were 4.43 mg/(L·h) and 4.50 mg/(L·d), when using glucose and tea residue as carbon source, respectively. The nitrogen balance revealed that 53.66% of N vanished via gaseous products. Transcriptional results revealed that respiratory and assimilative nitrate reductases may work together for nitrate removal. Our results indicate that RADF-77 could be used as a potential means of enhancing nitrate-removal performance, as well as recycling tea residue, which is the main byproduct of the manufacture of tea extracts.