Resumo

Aromatic hydrocarbons are components of oil and oil products. During its extraction, transportation and storage, spills may lead to an important contamination of diverse environments. Toluene or methylbenzene comprises a fraction of gasoline fuels, but it is also widely used as solvent. As alkylated benzene, it is known or suspected carcinogen with mobility and solubility in water, which facilitates environmental impact. It is said that only aliphatic hydrocarbons support fungal growth, but it has been proved that black fungi are able to assimilate aromatic compounds. Due to this ability and remarkable extremophily, investigations on the use of black fungi for environmental technologies like the remediation of contaminated sites have increased. This study aimed to test the ability of 50 black fungal strains to use toluene as sole C source, growing in saturated atmosphere inside desiccators. The isolates were obtained from oil contaminated soil samples. They were grown on MA 2% for 7 days, and then inoculated into 3 mL of mineral medium in tubes. Besides the treatment that exposed the inoculum to the hydrocarbon (30 mL volatilized toluene, corresponding to 0.23 g C/tube), positive (mineral medium + 4% glucose) and negative controls (inoculum in mineral medium without C source) were also performed. Desiccators were incubated at room temperature for 30 days. Biomass production was measured and expressed in dry weight. Fungal isolates were identified by ITS sequencing. Among the studied strains, two Exophiala sp. showed higher biomass values in toluene (approximately 20 mg), than the one found in the positive control with glucose. The results showed that black fungi can produce a significant amount of biomass using carbon from volatile compounds as the only carbon source, indicating the potential for its use in BTEX contaminated areas. This result is considered of great importance since bioremediation is of low cost, and allows localized treatment with reduction of the residue to acceptable levels. Acknowledgements: To Professor Dr. Roberto Naves Domingos and to PRH-05 (Formation Program of Human Resources) for providing the infrastructure used for this experiment.