Domestication Of Bacterial Flora With High Efficiency Of Oil Degradation And Study On The Activity And Structure

In recent years, the pollution caused by the leakage and spill of crude oil and itsrefined products has become so serious that it has aroused the attention of people.Many oil products have become the main contaminants of surface water and soil. Assome of them can be accumulated through food chain, thus it endangershuman-beings as well. Therefore, as a more effective, economical and green method,bio-treatment technology is now gaining more concern than ever.Machine oil is one of the most widely used petroleum products, which aremainly composed of a series of long-chain alkanes. There is few report about thebiodegradation of machine oil. For this reason, the compound bacteria was screenedfrom several samples of oil-contaminated soil. The biodegradation conditions,immobilization and biosurfactant were studied. Because of the failure of theconventional separation method for the compounded-bacteria, the molecular biologymethod was used to analyze and compare the microbial community structure of thecompounded-bacteria. The results of the study are as follows:1. The machine oil removal efficiency achieved 81.4% by 7-day-biodegradationusing the compound bacteria while the initial machine oil concentration was about2000 mg/L, the biodegradation conditions were 32℃, pH 7.2, 190 r/min(rotationspeed) and inoculum-concentration was 0.1%;2. The compound bacteria have the ability to resist the chloride ions, copper ions,SDS and other restrictive matters. The machine oil removal efficiency will decrease ifthe compound bacteria has been culturing several days in the culture medium whosecarbon resource is non-selective, such as glucose, glycerin etc.3. The second-order equation-dS/dt=k₂S²+k₁S+k₀, proposed by Quirogaand Sales was applied to the experimental data obtained from the biodegradationtest(machine oil concentration of 489, 1075, 2088 mg/L), and the correlationcoefficient values r² are all above 0.98.4. Embeding immobilization can help to resist the change of the externalcondition. The machine oil removal effectiveness of adsorption immobilization was not better than the non-adsorption unit.5. The biosurfactant secreted by the bacteria contains two kinds of matter, one isglycolipid and another is lipopeptide, which can decrease the surface tension of theculture medium from 68.5 mN/m to 35.1 mN/m and can resist the high concentrationof chloride and calcium ion and change of pH.6. The type of carbon resource of the culture medium determined the dominantstrain of the compound bacteria by using the PCR-DGGE technology. Some newstrains would be dominant under the condition of high salinity. A new kind of strainbecame dominant after a period of contious aeration culture. The machine oilbiodegradation mechanism of this kind of strain which is different from that culturedin the shake table, is direct contact mechanism.7. The sequencing results showed that most of the dominant strains were thestrains that could not be sperate cultured. This is the reason why these strains couldnot be isolated by using the spread plate method.