Habilidade degradadora de combustíveis por isolados bacterianos

Abstract

Soil and water contamination by fuels is one of the major problems on the world stage. Microorganisms are protagonists in the degradation of these contaminants, forming the basis of bioremediation processes. Therefore, recognition of the degrading ability of microorganisms can contribute to bioremediation processes, such as bioaugmentation. This study aimed to evaluate the degradation potential of fuels [diesel S10 and S500, aviation gasoline (GAV) and ethanol] by bacterial isolates obtained from an oil/water separator of an automotive wash. Biodegradability tests were performed in mineral medium containing redox indicator and fuels as the only carbon and energy sources for microbial growth, as well as experiments to determine the emulsifying capacity (IE24) and cellular hydrophobicity of the isolates. Eleven bacterial strains, named UFFS 1 to UFFS 11, were isolated. Eight strains degraded S10 diesel constituents at concentrations of 5, 10 and 15 % (v/v). Tests performed with S10 diesel generally resulted in low emulsifying capacity levels; isolates UFFS 6, 8, 9 and 11 presented IE24 from 0.94 % (UFFS 8) to 10.14 % (UFFS 10) in the presence of cells, and from 0 % (UFFS 6 and 8) to 8.18 %. (UFFS 9) in the absence of cells. Cellular hydrophobicity, evaluated on S10 diesel, ranged from 0 % to 57.9 %, with emphasis for UFFS 1 and 8 isolates (~ 56 %). Four isolates were selected (UFFS 6, 8, 9 and 11) for degradation tests using diesel S500, GAV and ethanol, at 10 %. These isolates were able to degrade diesel S500 constituents; however, they did not degrade GAV and ethanol, possibly due to toxic effects at this concentration. Isolates grown on S500 diesel and evaluated for toluene emulsifying capacity showed IE24 from 24 % (UFFS 6) to ~71 % (UFFS 8 and 11) in the presence of cells, and ~53 % in the absence of cells, indicating production of extracellular and cell-associated bioemulsifiers. Cellular hydrophobicity, assessed with toluene, ranged from 80 % to 89 %. The production of bioemulsifiers and high cellular hydrophobicities may positively affect the accessibility of diesel S500 constituents to microbial degradation. The results obtained for the four selected isolates suggest their applicability in bioaugmentation processes for the degradation of diesel oil constituents; however, this should be confirmed by subsequent studies.