Unlocking the microbial aerobic denitrification potential in reservoirs and lakes: Development of a novel aerobic denitrifying fungal medium and its practical application.

Recent studies have shown that aerobic denitrifying fungi (ADF) exhibit substantial environmental tolerance and can produce a multitude of nitrogen-transforming enzymes, giving them the potential for nitrogen removal. They can degrade multiple pollutants, making them promising microorganisms for pollution control in aquatic environments. However, conventional fungal media cannot efficiently isolate ADF, limiting their application in bioremediation. In this study, we supplemented seven conventional fungal media with specific amounts of glucose, potassium nitrate, and a trace element solution, and evaluated the ability of these modified media to isolate fungi from reservoirs using high-throughput sequencing and plate counting. Modified dichloran rose bengal chloramphenicol agar (mDRBC) was used as the basal medium. Based on the carbon source metabolic preferences of three ADF strains, we supplemented the mDRBC with d-ribose and glycerol to develop a novel aerobic denitrifying fungal medium (NDFM). The results showed that NDFM significantly increased the abundance and community diversity of the culturable colonies. In addition, it improved the isolation efficiency of ADF by 20%-40% and increased the ADF biomass by 1-2 orders of magnitude compared to mDRBC. It also recovered two low-abundance genera of potential ADF (PADF) undetectable by mDRBC, allowing the isolation of most PADF genera from surface water. Thus, this study provides a feasible approach to efficiently explore aerobic denitrifying fungal resources and theoretical support for biological nitrogen removal in surface water.