Bioremediation of BTEX hydrocarbons: effect of soil inoculation with the toluene-growing fungus Cladophialophora sp. strain T1.

The biodegradation of a mixture of benzene, toluene, ethylbenzene, xylene, (BTEX) and methyl-tert-butyl ether (MTBE) was studied in soil microcosms. Soil inoculation with the toluene-metabolising fungus Cladophialophora sp. strain T1 was evaluated in sterile and non-sterile soil. Induction of biodegradation capacity following BTEX addition was faster in the soil native microflora than in axenic soil cultures of the fungus. Toluene, ethylbenzenes, and the xylenes were metabolized by the fungus but biodegradation of benzene required the activity of the indigenous soil microorganisms. MTBE was not biodegraded under the tested environmental conditions. Biodegradation profiles were also examined under two pH conditions after a long term exposure to BTEX. At neutral conditions the presence of the fungus had little effect on the intrinsic soil biodegradation capacity. At an acidic pH, however, the activity of the indigenous degraders was inhibited and the presence of Cladophialophora sp. increased significantly the biodegradation rates of toluene and ethylbenzene. Comparison of the BTEX biodegradation rates measured in soil batches combining presence and absence of indigenous degraders and the fungal inoculum indicated that no severe antagonism occurred between the indigenous bacteria and Cladophialophora sp. The presence of the fungal inoculum at the end of the experiments was confirmed by PCR-TGGE analysis of small subunits of 18S rDNA.