Biodegradation of Petroleum Hydrocarbons by Actinobacteria and Acinetobacteria Strains Producing Biosurfactant.

Environmental pollution with petroleum hydrocarbons has become one of the most urgent problems worldwide. The effectiveness of bioremediation of oil pollutions is significantly affected by the inherent capabilities of microorganisms and their specific adaptive mechanisms of hydrocarbon assimilation. In this study the hydrocarbon biodegradation efficiency and the surface-active properties of the hydrocarbon-oxidizing strains of Gordonia rubripertincta IMB Ac-5005, Rhodococcus erythropolis IMB B-7012 and Acinetobacter calcoaceticus IMB B-7013 were determined. These strains showed high efficiency of biodegradation of n-hexadecane (82.1–86.7 %), kerosene (72.5–80.3 %), diesel fuel (70.1–74.3 %) and crude oil (63.5–68.9 %). The mixed culture of these strains completely assimilated n-alkanes C9–C21 as well as iso-alkanes C8–C17 and significantly decreased (150–230 times) the amount of n-alkanes C22–C26 in the process of cleaning up water from raw oil. The utilization of hydrocarbons by G. rubripertincta IMB Ac-5005 and R. erythropolis IMB B-7012 with low initial hydrophobicity index (2.4 and 9.6 % respectively) was accompanied by the increase in cell surface hydrophobicity (4 and 25 times respectively) and by the synthesis of cell-bound biosurfactants forming stable emulsions of “oil-in-water” type. The dominating components of these biosurfactants were glycolipids: mono- and dimycolates of trehalose. The assimilation of hydrocarbons by highly hydrophobic A. calcoaceticus IMB B-7013 with the initial hydrophobicity index 99.4 % resulted in the decrease of this value by 1.4 times and the synthesis of extracellular biosurfactant forming stable emulsions of “water-in-oil” type. The biosurfactant of A. calcoaceticus IMB B-7013 is similar to emulsans according to its chemical composition and ratio of the main components (carbohydrates, proteins and lipids). The experimental data provide grounds for efficient using of these strains in the process of bioremediation of oil-polluted water and soils.