Thermal resistance and viability of asexual spores of thermophilic fungi from composts.

The growth-temperature relations and thermal tolerance of the asexual spores of thermophilic fungi commonly found in composting plant materials were determined. The optimum temperature range for germination of the spores was 40 degrees - 50 degrees C. The spores of Humicola lanuginosa (GRIFFON and MAUBLANC) BUNCE were able to survive 60 min exposure to 68 degrees C while those of Mucor pusillus COONEY and EMERSON survived only 5 min exposure to 68 degrees C. A determination of the thermal death rates of the spores at 65 degrees C showed a rapid loss of viability of those of Torula thermophila COONEY and EMERSON. The thermal tolerance of the propagules of thermophilic fungi in relation to their special ecological niche is discussed.