Aims: The aim of this study was to obtain cold-adapted denitrifying fungi that could be used for bioaugmentation in woodchip bioreactors to remove nitrate from agricultural subsurface drainage water. Methods and results: We isolated a total of 91 nitrate-reducing fungal strains belonging to Ascomycota and Mucoromycota from agricultural soil and a woodchip bioreactor under relatively cold conditions (5 and 15°C). When these strains were incubated with 15N-labelled nitrate, 29N2 was frequently produced, suggesting the occurrence of co-denitrification (microbially mediated nitrosation). Two strains also produced 30N2, indicating their ability to reduce N2O. Of the 91 nitrate-reducing fungal strains, fungal nitrite reductase gene (nirK) and cytochrome P450 nitric oxide reductase gene (p450nor) were detected by PCR in 34 (37%) and 11 (12%) strains, respectively. Eight strains possessed both nirK and p450nor, further verifying their denitrification capability. In addition, most strains degraded cellulose under denitrification condition. Conclusions: Diverse nitrate-reducing fungi were isolated from soil and a woodchip bioreactor. These fungi reduced nitrate to gaseous N forms at relatively low temperatures. These cold-adapted, cellulose-degrading and nitrate-reducing fungi could support themselves and other denitrifiers in woodchip bioreactors. Significance and Impact of the Study: The cold-adapted, cellulose-degrading and nitrate-reducing fungi isolated in this study could be useful to enhance nitrate removal in woodchip bioreactors under low-temperature conditions.
Bibliographical noteFunding Information:
We thank Dr. Gary Feyereisen at the USDA‐ARS for his help with collecting soil and woodchip samples and Dr. Brandy Toner at the University of Minnesota for her helpful comments and encouragement to complete this study. This research was supported by MnDRIVE Initiative of the University of Minnesota. AD was supported by the Saudi Arabian Cultural Mission Scholarship and the Minnesota Mycological Society Scholarship.
- cellulose degradation
- woodchip bioreactor
PubMed: MeSH publication types
- Journal Article