Isolation of Thermophilic Fungi from Self-Heated, Industrial Wood Chip Piles

SUMMARY

Thermophilic fungi isolated from self-heated wood chips stored at a paper factory included Chaetomium thermophile var. coprophile Cooney & Emerson, C. thermophile var. dissitum Cooney & Emerson, Humicola grisea var. thermoidea Cooney & Emerson, H. lanuginosa (Griffon & Maublanc) Bunce, Sporotrichum thermophile Apinis, Talaromyces emersomi Stolk, T. thermophilus Stolk, and Thermoascus aurantiacus Miehe sensu Apinis. Fewer species were present in fresh chips and in chips from unheated piles. The thermotolerant fungus Aspergillus fumigatus Fresenus was recovered from all chip samples. Incubation of whole or ground chips at 50 C on Emerson YpSs Agar (Difco), on 2% malt agar, and in damp chambers was necessary and sufficient for enrichment and detection of thermophilic species present in the samples. Use of a lower temperature or of only a single enrichment medium resulted in incomplete detection of species present. Enriching in atmospheres of tank N₂ and of CO₂-supplemented air, and plating on a variety of nutritionally restrictive media, failed to increase the number of thermophiles isolated. Dilution-streak plating was the most efficient and effective method for isolation and purification; addition of 100 units per ml of both streptomycin sulphate and penicillin G to isolation media facilitated purification. It was concluded that thermophilic fungi are abundant in self- heated wood chips, and together with thermotolerant fungi contribute to heating and biodeterioration.