Studies On The Isolation Of Oil-Degrading Bacteria With Biosurfactant Production And Their Characteristics

With the development of petroleum industry, the pollution caused by the petroleum becomes more and more serious. At the same time when petroleum brings great economic benefits, it poses serious threat to the environment. Characters including low density, strong viscosity and poor ability to emulsify of petroleum make it easily conglutinate with soil particle, which as a result reduce the quality of soil. Meanwhile, groundwater, river and ocean may be polluted by infiltrated pollutants within the petroleum. Component of polycyclic aromatic hydrocarbons in petroleum can lead to cancer and aberration harming the health of mankind. And cycloalkane without substitute group is hard to be attacked by microorganism, therefore could exist for a long time, abiding and destroying the environment seriously. In order to get rid of the petroleum from the environment, lots of scientific researches have been carried out by scientists to seek the safe, economic and reliable techniques wiping out petroleum.This thesis has shown up some important information such as the components of petroleum contaminants, pollution and dangers of oil, degradation mechanisms of different hydrocarbons, study on bioremediation of oil pollution by biosurfactant. Based on the above information, the important thing is to obtain better strains with biosurfactant and to understand their biodegradation characteristics. Therefore, screening marine oil-degrading strains with biosurfactant from environment samples and studies on the biodegradation characteristics are the main contents of this thesis.A petroleum hydrocarbons-degrading strain named X-1 that is capable of high-producing biosurfactant was finally isolated from crude oil-contaminated soil in the vicinity of Shengli oil-field in Shandong province by hydrocarbon enrichment culture, testing its ability to produce biosurfactant and degrade diesel. Strain X-1 was identified as Bacillus sp. according to its morphological, physiological, biochemical features and 16S rDNA sequence analysis.The degradation rate of strain X-1, which had high oil-degradation capacity, reached 30.04% when natural degradation rate had been deducted from total after incubating for 6d. GC-MS was used to carry on dehydrogenase the qualitative and quantitative analysis to the degeneration effect of petroleum hydrocarbon component. The biodegradation of each chemical component was analyzed to probe the rule by GC-MS. X-1 strain could degrade aliphatic hydrocarbon of C10～C20 in crude oil, mixed bacteria of stains X-1 and A-1 could degrade aliphatic hydrocarbon of C10～C20 completely. Biosurfactant by stain X-1 had no effect on degradation of crude oil individually, had effect on stain X-1 for degradation of crude oil but not stain A-1.The biosurfactant produced by strain X-1 was extracted, purified and studied by various of methods, such as column chromatography experiment, silica gel TLC and FT-IR analysis. Results showed that the biosurfactant from strain X-1 was light yellow powdery material. By the method of silica gel TLC and FT-IR analysis, the biosurfactant was lipopeptid and lipoproteins. The optimize conditions for biosurfactant production were 32℃, pH 7.0 and 2 g·L-1 NaCl. And the best carbon source and nitrogen source were starch and peptone, respectively.20 mg·L-1 Fe2+,Mn2+ and Ca2+ could promote the growth of X-1, also promote the production of biosurfactant, but 20 mg·L-1 Cu2+ and Zn2+ could stunt growth and the production of biosurfactant.The strain X-1 showed powerful potential for bioremediation on the pollution caused by the petroleum.