Isolation and characterisation of fungi growing on volatile aromatic hydrocarbons as their sole carbon and energy source

Five fungal strains that are able to grow on toluene were isolated from enr ichment cultures. Three different techniques were used: solid state-like ba tches, air biofilters and liquid cultures. Fungal growth in the latter syst ems was favoured by combining low pH and low water activity. Soil and groun dwater samples from gasoline-polluted environments were used as inocula. Th e isolates were identified as deuteromycetes belonging to the genera Cladop hialophora, Exophiala and Leptodontium and the ascomycete Pseudeurotium zon atum. The previously isolated toluene-degrading fungus Cladosporium sphaero spermum was included in the present study. Results showed that fungi grew o n toluene with doubling times of about 2 to 3 days. Some of the strains als o grew on ethylbenzene and styrene. The apparent half-saturation constant ( K-m) for toluene oxidation ranged from 5 to 22 muM. Degradation activity wa s inhibited by 50% at toluene concentrations ranging from 2.4 to 4.7 mM. Th ese kinetic parameters are comparable to analogous data reported for toluen e-degrading bacteria. The ability of fungi to grow at low water activities and low pH suggest that they may be used for the purification of gas stream s containing aromatic hydrocarbons in air biofilters.