Microbial removal of weathered hydrocarbons by well adapted-bacteria

The effectiveness of bioremediation processes may be limited by the physical and chemical properties of the pollutant, such as availability, recalcitrance, concentration and weathering, among others. The aim of this work was to evaluate the removal of recalcitrant oil fractions (aliphatic-aromatic and asphaltenic fractions) from a weathered soil, by two bacteria adapted to a high concentration of oil hydrocarbons, isolated from a soil with a concentration of 227,000 mg of total petroleum hydrocarbons per kg soil. Kinetics of hydrocarbons removal by Bacillus coagulans and/or Serratia liquefasciens was performed in liquid culture for 168 h; hydrocarbons from soil as sole carbon and energy source (600 mg/l) were added and each of the microorganisms was inoculated for evaluation independently or as a mixed culture. The aromatic fraction was removed by B. coagulans at 330 mg/l; by S. liquefasciens at 130 mg/l; and by both microorganisms at 360 mg/l. The asphaltenic fraction was removed by B. coagulans at 23 mg/l; by S. liquefasciens at 15 mg/l; and by both microorganisms at 34 mg/l. Chromatographic analysis of the aliphatic-aromatic fraction showed the presence of branched aliphatic C6 to C26, polyaromatic substituted compounds of two and three rings, and heteroaromatic compounds of dibenzothiphene type. The compounds that were removed from the aliphatic-aromatic fraction were of all types in the range of C6 to C13.