Biodegradation of toluene by the new fungal isolates Paecilomyces variotii and Exophiala oligosperma.

Two new fungal strains, namely Paecilomyces variotii and Exophiala oligosperma, were isolated on toluene as the sole carbon and energy source, mineralizing the substrate into carbon dioxide. Fungal strains isolated so far on such a pollutant and completely degrading it are very scarce. Both fungi degraded the pollutant over the pH range 3.9-6.9 and temperature range 23-40 degrees C, but E. oligosperma was barely active at the highest temperature of 40 degrees C. Fungal growth on alkylbenzenes at 40 degrees C has not been reported before. Since the activity of the strains gradually decreased at pH values below 4.0, the use of nitrate instead of ammonium was tested. In the presence of toluene, nitrate was a suitable nitrogen source for the Exophiala strain, but not for the Paecilomyces strain. Nitrate rather than ammonium allowed the maintenance of a more constant pH.