Resumo

Environmental contamination with BTEX (benzene, toluene, ethylbenzene and xylenes) is a serious problem crossed nowadays. An alternative for the recovery of affected areas is the bioremediation which uses micro-organisms for removing pollutants from the environment. Recent studies highlight the potential of melanized fungi in biodegradation processes of monoaromatic hydrocarbons thanks to extremophile and oligotrophic character of these fungi. In this work, a methodology originally employed for the isolation of micro-organisms able to grow in volatile hydrocarbons, was adapted for screening a collection of black fungi with potential for degradation. Melanized fungi were inoculated in test tubes previously weighted containing 3 mL of mineral medium, covered with perforated foil and organized inside glass desiccators containing a beaker with 30 mL of toluene inside, creating a secluded atmosphere that was saturated with toluene steam, which served as the sole carbon source during the 30 days of incubation. After, the tubes were dried in an oven at 105 °C for 24 hours and weighted again to give the value of biomass produced during the test. Besides the treatment containing only toluene, it was prepared a treatment containing dibutyl, an organic solvent used to reduce the volatilization rate of toluene, a positive control (with glucose and without toluene) and a negative control (no carbon source). The results point to the efficiency of the methodology. In the test treatments containing toluene there was a production of 10 to 20 mg of biomass for most strains. Biomass values were higher (30 to 90mg) in the positive control. Although insignificant, some strains grew in the negative control highlighting the oligotrophic character of black fungi. Previously published data on the subject provided the basis for adapting this new method and its implementation proved to be an effective method for analyzing the assimilative capacity of toluene by melanized fungi. The next goal of this study will be to test the success of this method to screen other microorganisms using different volatile hydrocarbons. We would like to acknowledge to Dr. Roberto Naves and Physics Department for the infrastructure, and to Capes and Fapesp for financial support.