Bio-removal of diesel oil through a microbial consortium isolated from a polluted environment

• Increased of inoculum and ratio C:N favored the bio-removal.
• Bio-removal in bioreactor higher than 70% of diesel oil.
• Partial detoxification of diesel oil.

Cultures were selected to form a consortium, and were submitted to essays in flasks according to a complete factorial design 2³ in order to determine temperature, inoculum concentration and C:N ratio conditions more favorable to biodegradation, which were used later in the experiment conducted in a bioreactor. The micro-organisms with the greatest potentiality to degrade diesel oil, without developing antagonistic activity, were identified as Staphylococcus saprophyticus, Serratia marcescens, Rhodotorula aurantiaca and Candida ernobii, which formed a mixed microbial consortium, consisting of bacteria and yeasts. The C:N ratio and temperature were the factors that displayed significant effect on the bioprocess. The increased C:N ratio and the amount of inoculum yielded a positive effect while the increase of the temperature caused a negative effect on biodegradation. In the seven-day trial in a bioreactor was verified an increase of biomass, decrease in surface tension, reduction of all n-alkanes belonging to the range of C9 to C21 and decreased toxicity for vegetable seeds. The tested mixed microbial consortium present high ability to degrade diesel oil constituents and the maintenance of appropriate conditions leads to transformation of this oily source into less toxic compounds.