The Isolation Of Biosurfactant-producing Bacteria And Their Effects On Recovery Of Oil From Oily Sludge

Biosurfactants are produced by a wide variety of microbes and amphipathic molecules with a hydrophilic and hydrophobic group. Biosurfactant has obtained international attention because of its environment friendly and broad application potentials. As the traits of the biosurfactants, biosurfactant can form micelles, enhance the solubility of poorly soluble compounds in water. Most of biosurfactants are biodegradable and less toxic than the chemically synthesized surfactants, which makes them have great potential application chance in enhancing oil recovery. The crude oil and soil samples were collected,from which some strains that can use crude oil as carbon source were screened. And, by using the surfactant tensions technique,we screened some bacteria with the capability to produce biosurfactants.The biosurfactants from screening, determining of strains and primary optimizing of cultural medium were investigated, and also distilling and makeup was analyzed in this exepriment. A bacterial strain BS-5 was studied, which could use oil as the sole carbon source. By the experimental results of the morphological structure, Biolog test and by the comparison of its whole sequence of 16S rDNA with the type strains in Genebank, it was showed that the stain BS-5 was Gram negative, short rod. By Biolog test, it was identified as Pseudomonas aeruginosa and its probability and similarity were 99 percent and 0.770. In addition, I6S rDNA of the stain and that of Pseudomonas aeruginosa was 99 percent of homology in GenBank. Therefore bacterial strain BS-5 was identified as Pseudomonas aeruginosa as well. The results of TLC and FT-IR showed that the biosurfactant produced by the strain BS-5 was a kind of glycolipid. The conditions for shaking flask fermentation of strain BS-5 which has higher productivity of biosurfactant have been studied. The influences of the nutrient and environmental factors on the fermentation are investigated through the complex orthogonal designing. The result showed that the optimal medium for the biosurfactant by this was (g·L-1): vegetable oil 10, MgSO4 0.2, K2HPO4 1.0, KH2PO4 1.0, peptone 1.0, FeSO4 0.05, CaCl2 0.02 and initial pH7.5. The optimal cultivation conditions were observed at 35℃. By using the bacterial fermentative fluid to treat oily sludge sample, oil removal rate reached 45% in 8d.