Establishment and characterization of turbine oil-degrading bacterial consortia
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概要
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A microbial consortium capable of degrading turbine oil (TuO) consisting mainly of recalcitrant branched and polycyclic alkanes, has been established using a sludge sample collected from an oil-water separation tank of a hydraulic plant, by repeated enrichment cultivation. When this consortium, named the tank-2 consortium, was cultivated in a minimal salts medium containing 0.5% TuO, it degraded approximately 90% of TuO at 30℃ under shaking at 160 rpm in five days. During cultivation, the consortium formed cell aggregates. Fourteen bacterial species were isolated from the consortium. Although the mixtures of all of the isolated strains (IM) and predominant strains selected from the IM (PM) degraded approximately 60% of the TuO maximally in seven days after repeated enrichment, the degradation rate was not maintained. The decreased rate of TuO degradation in the PM was recovered by inoculation with a mixture (AM) consisting of isolates involved in the cell aggregate formation in the tank-2 consortium, suggesting that the formation of bacterial aggregates is an important factor for the degradation of TuO by the bacterial consortia. Interestingly, the formation of bacterial aggregates was only observed when cyclic alkanes were added to the consortium as a source of carbon. The cell surface hydrophobicity of the bacterial aggregates was significantly high (77.6%). These results suggest that the growth of bacteria with high cell hydrophobicity can be induced by the cyclic alkanes fraction of TuO, and that the formation of aggregates facilitates cells to form contact with the recalcitrant components of TuO and uptakes these components.