Aerobic Biodegradation of Liquid Motor Fuels under Extreme Acidic Conditions

Abstract

Biodegradation of liquid petroleum motor fuels and fuel mixtures containing biodiesel fuel (methyl ethers of rapeseed fatty acids) by aerobic acidophilic actinobacteria Mycobacterium sp. AG_S10 was studied. Strain AG_S10 was found to be able to grow on aviation kerosene Jet A-1 as the sole carbon and energy source under highly acidic conditions. After 21 days of cultivation at 30°C and pH 2.5, bacterial numbers increased from 4.2 × 10⁶ to 7.0 × 10⁸ cells/mL, while the hexane-soluble part of the fuel was degraded by 90.4%. The strain also utilized components of the winter diesel fuel, including С₈–С₂₀n-alkanes, iso-alkanes, and aromatic compounds. Overall hydrocarbon consumption under the same conditions was 99.4%. The ratio of (iso-С₁₉ (pristane) + iso-С₂₀ (phytane))/(n-С₁₇ + n-С₁₈) changed from 1.21 in the control to 2.39 in the experiment with bacterial degradation, which indicated preferable utilization of n-alkanes, rather than isoprenoids. Over 90% of diesel fuel hydrocarbons were consumed from day 4 to day 12 of cultivation, while abundance of the bacterial population increased by three orders of magnitude. Strain AG_S10 consumed both hydrocarbons and oxygen-containing (plant-derived) components of the fuel mixtures with biodiesel fuel. Bacteria preferentially consumed hydrocarbons, and the ratio between oil diesel fuel and biodiesel fuel in the mixture changed in the course of incubation.