Abstract Accidents caused by leaks and/or spills on soils need to be addressed. Natural attenuation, biostimulation and bioaugmentation can be useful bioremediation strategies for decontamination processes in soils of diesel/biodiesel mixtures. The purpose of this study was to evaluate the degradation rate of the different fuels (B0, B20 and B100) in an ultisol under natural attenuation and biostimulation/bioaugmentation during 60 days of incubation in a controlled microcosm simulating a surface spill over soil. The degradation of different diesel/biodiesel mixtures was monitored for up to 60 days by dehydrogenase activity, respirometry by CO2 release, the most probable number of heterotrophic and degrading microorganism and gas chromatography. The bacterial inoculum employed for biostimulation/bioaugmentation strategy consisted of Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The two bioremediation strategies have showed great degradation rates. The natural attenuation was effective for B0 and B20 treatments. The addition of the bacterial consortium and macronutrients contributed to the increased degradation of pure biodiesel in relation to natural attenuation, with higher rates for CO2 release, enzymatic and degrading activity. It is suggested that the bacterial consortium has proven effective for presenting significant values for such parameters until the end of the 60-day incubation period.

The aim of this study was to evaluate the antimicrobial activity of bio-oil (obtained by pyrolysis of biomass: soybean oil, eucalyptus sawdust and coffee grounds) added to the blend B10 (diesel and biodiesel). The bio-oil is compatible to diesel oil and it contains promising compounds that can exhibit antimicrobial activity during fuel storage. We evaluated the antimicrobial activity of bio-oil added to diesel oil B10 by determining the minimum inhibitory concentration at different concentrations (0-10%) using oil-deteriorating microorganisms for 10 days at 30 °C. Bio-oil was separated from the aqueous phase by solid phase extraction using ultrapure water and sodium hydroxide. The aqueous phase containing the solubilized compounds of bio-oil was characterized by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection. Minimum inhibitory concentration in the range of 0.25% to 4% was observed for the tested inocula. The chromatographic analysis of both extracts allowed the identification of several oxygenated compounds, which the majority of the analytes consisted of phenolic compounds, followed by ketones.