Isolation of cold‐adapted nitrate‐reducing fungi that have potential to increase nitrate removal in woodchip bioreactors

Abstract

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°C and 15°C). When these strains were incubated with 15 N labeled nitrate, 29 N 2 was frequently produced, suggesting the occurrence of co-denitrification (microbially mediated nitrosation). Two strains also produced 30 N 2 , indicating their ability to reduce N 2 O. 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.

Sulfate-reducing bioreactors subjected to high sulfate loading rate or acidity: variations in microbial consortia

“…In contrast, it prospered while other fungal groups diminished, indicating high tolerance to changing environmental conditions for this fungal genus. Aldossari and Ishii ( 2021 ) detected Cadophora in soil and woodchip bioreactors at relatively low temperatures (5–15 °C) and confirmed the nitrate-reducing capability of this genus. It is likely that Cadophora is an important contributor in the nitrogen cycle also in our BSR bioreactors, especially when the sulfate loading was gradually increased.…”

Microbiome Structure and Function in Woodchip Bioreactors for Nitrate Removal in Agricultural Drainage Water

“…So far, however, little is known about the life and ecological role of fungi in denitrifying woodchip bioreactors. Remarkably, and in addition a role in lignocellulose degradation, Aldossari and Ishii (2020) newly reported the occurrence of denitrifying fungi from a woodchip bioreactor in Minnesota (United States), where these organisms seemingly contributed directly to anaerobic N transformations, thus indicating a novel physiological and ecological role to be further examined.…”

Genome Sequence of Linnemannia hyalina Strain SCG-10, a Cold-Adapted and Nitrate-Reducing Fungus Isolated from Cornfield Soil in Minnesota, USA

“…We previously isolated 91 nitrate-reducing fungal strains from woodchip bioreactors and the adjacent cornfield soil in Minnesota, USA ( 3 ). One of the strains, Linnemannia hyalina strain SCG-10, can reduce 15 N-labeled nitrate to 30 N 2 at cold temperature (5°C) and therefore has strong potential for bioaugmentation applications.…”

“…One of the strains, Linnemannia hyalina strain SCG-10, can reduce 15 N-labeled nitrate to 30 N 2 at cold temperature (5°C) and therefore has strong potential for bioaugmentation applications. However, nirK and p450nor are not detected by PCR ( 3 ). To detect these genes and other genes important for denitrification, we sequenced the whole genome of Linnemannia hyalina strain SCG-10.…”

“…Genomic DNA was extracted from a 3-g pellet of cells grown in glycerol peptone broth supplemented with 2 g/liter of sodium nitrate ( 3 ) at 5°C for 1 week. The cells were frozen in liquid nitrogen and homogenized using a micropestle before DNA extraction using the DNeasy PowerSoil kit (Qiagen, Hilden, Germany).…”