Isolation and Characteristics of a Formaldehyde-Degrading Fungus

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Nine novel formaldehyde-resistant fungi were isolated from 170 soils and wastewater samples from Aichi prefecture. When these fungi were cultured in medium containing various concentrations of formaldehyde after being cultured in a plate of basal medium containing 1.5% agar and 0.2% formaldehyde, 0.30–0.50% formaldehyde was almost completely consumed in the medium containing glucose as the carbon source. The highest degradation activity of the 9 strains was obtained for, strain IRI017; the fungi could grow in medium containing 0.5% formaldehyde and almost all of the formaldehyde was degraded in 100 h. This was the highest formaldehyde concentration for biological direct degradation as far as we know. Strain IRI017 was identified as Paecilomyces variotii from sequence analysis of 18S rDNA. When cell-free extracts of strain IRI017 were prepared from cell suspension using medium supplemented with formaldehyde and glucose as the carbon source, high nicotinamide adenine dinucleotide (NAD)-linked, glutathione (GSH)-dependent formaldehyde dehydrogenase activity 1.68 µmol/(min·mg-protein) was detected. When strain IRI017 was suspended in buffer solution at an initial formaldehyde concentration of 0.26%, the cells degraded the formaldehyde completely in 150 h.