Uptake modes of octadecane by Pseudomonas sp. DG17 and synthesis of biosurfactant.

In order to gain more insight into the uptake modes of octadecane by bacteria. A strain that could utilize octadecane well was isolated from crude oil contaminated soil, and named as Pseudomonas sp. DG17 by 16S rDNA analysis. Culture growth result showed that Pseudomonas sp. DG17 grew well in the addition of 200 and 400 mg l(-1) of octadecane, which showed that physical contact between substrate and bacteria was important in the substrate biodegradation. Meanwhile, Pseudomonas sp. DG17 produced rhamnolipids biosurfactant that contains 10 congeners, thus causing the surface tension of the culture medium decline and facilitating the contact between hydrocarbon and bacteria. Scanning-electron-microscopy results showed that a disruption of the surface membranes in certain zones was observed in some of the cells grown in 400 mg l(-1) octadecane at 176 h compared with the cells in exponential phase at 72 h due to the production of biosurfactant-rhamnolipid. These results indicated the possibility that the direct contact with insoluble octadecane droplets occurred before the contact with pseudosolubilization smaller oil droplets. This report throws more light on the uptake mechanisms of octadecane by bacteria, and proposes the possibility that role of biosurfactant is to increase the contact between hydrocarbon and bacteria by changing the cell membrane structure which needs studied in depth. IMPACT OF STUDY: Results of this study are useful in the bioremediation of petroleum polluted soil.