Role of microorganisms in bioremediation of oil polluted soils

The comparative analysis of microbial communities of pure and oil – polluted soils of Ukraine conducted by us has shown the considerable predominance in the latter the representatives of Rhodococcus and Gordonia genera. Among them the most part of strains belonged to the species of Rhodococcus erythropolis and Gordonia rubripertincta. Rhodococcus fascians, Rhodococcus ruber and Dietzia maris species were also characterized by active hydrocarbon – oxidizing properties. Among isolated and collection strains of hydrocarbon-oxidizing bacteria we selected the most active strains, which belong to Rhodococcus erythropolis, Gordonia rubripertincta and Acinetobacter calcoaceticus species. They don’t possess pathogenecity and phytotoxicity, that permits to use them in natural conditions. It was shown by chromato-mass-spectrometry method, that the selected strains were capable to utilize almost all oil components. In Gordonia rubripertincta, which forms only S-variants of colonies, cells hydrophobicity was increasing in 3.9 times. In contrast to Rhodococcus and Gordonia, Acinetobacter calcoaceticus cells possessed high initial hydrophobicity index – 99%, which during the growth process on hydrocarbons was reducing to 70%. Cell suspensions of Rhodococcus erythropolis and Gordonia rubripertincta have the high (51–54%) of emulsification index. And supernatants of their cultural broth have the low index of emulsification. It testifies the fact that they produce associated with cells emulgators. Presence of small quantities of biosurfactants in supernatant is explained by lipid nature of these substances. They are easily dissolved in hydrocarbons and can be extracted by them from cells. During of these strains growing process on the hydrocarbons the surface tension in the cultivation medium was slightly reduced (from 70 to 46–50 milliNewton per meter). The investigated strains differed between themselves by the type of emulsion they formed. Rhodococcus and Gordonia strains formed the stable emulsion “oil in water”, and Acinetobacter – “water in oil”. Study of chemical nature of tested strains biosurfactants has shown, that in Actinobacteria they are presented by glycolipids, identificated as trehalose monomycolate and trehalose dimycolate. They are the main glycolipid components of their walls cells. Carbohydrate and protein components prevail over in the composition of extracellular biosurfactants of Acinetobacter calcoaceticus strain. These biosurfactants contain small lipids quantity. As to the structure, these substances are close to “emulsans”, which are typical for this species. They represent heteropolysaccaride, containing fatty acids and noncovalently bound with them proteins. On the base of investigated strains we have created biopreparations RODOIL and EKOLAN for purification of soil and water from oil and oil products. The preparations include hydrocarbon-oxidizing bacteria which are immobilized on oil absorbed sorbents and mineral fertilizers.