| Based on soil pollution of petroleum hydrocarbon in Kelamayi oil field, three strains of bacteria were isolated by crude oil as sole carbon source, and the roles of biosurfactants involved in bacterial strategies for accessing crude oil were investigated. Based on studies testing the effectiveness of environmental and biological factors on oil degradation of three stains and analysis difference of degradation for components of crude oil by three strains, we constructed high-effective microbial consortium, and it will be applied to offered theoretic reference for petroleum contaminated bioremediation.The main study results are as follows:There was a high variability of the total oil concentrations in Kelamayi oil field, ranging from less than 5200 to 20345 mg·kg-1.The level of soil pollution was 10 times of the national standard, and it is need to bioremediation of contaminated soil.Three high efficient hydrocarbon degrading bacteria named DM-1, DM-2, DM-3 were separated from the oil contaminant soil. Strains DM-1 and DM-3 both belonged to Bacillus sp. and strain DM-2 belonged to Pseudomonaa sp.identified by momhological, biological tests and and 16S rDNA.The study of fermentation characteristic of three strains indicated that the optimal cultivation parameters for temperature, pH and salinity were determined as 30℃, 7.5 and 0.5%. Based on the tests of the cell-surface hydrophobicity, oil displacement and EDTA inhibited production of biosurfactants, it was confirmed that three strains uptake crude oil emulsified with the biosurfactants produced by the cells, which increase the surface area of water-oil and enhance the bioavailability of hydrophobic compounds. The experimental results indicated that the biosurfactants were Lipopeptides and lipoproteins, and three strains released biosurfactants in its logarithmic growth period. The mode of growth correlativity of three strains releasing biosurfactant was proposed, and the highest biosurfactans production could be obtained in its stable period. The optimum conditions of biosurfactants-producing were determined as follows: temperature 30℃, pH 7.5 and salinity 0.5%.After optimum, the biosurfactants concentration of three strains can reach 1.78 g·L-1, 2.15g·L-1 and 2.75g·L-1 at 48 hour.Degradation rates of crude oil with three strains were enhanced by addition of glucose, peptone, yeast extract and biosurfactants to mineral salts medium. Compared to glucose and yeast extract, Peptone could promote the degradation of crude oil significantly by strains DM-1 and DM-3, whereas yeast extract could enhance the degradation of the crude oil remarkably by strain DM-2.Degradation rates of crude oil with three strains were impacted remarkably by the environmental and biological factors.The flask culture conditions for growth of three stains in crude oil medium were investigated and optimized. The optimal culture conditions of strain DM-1 were: temperature 30℃, pH 7.0, inoculation 10%, and shaking speed 150r/min. The optimal culture conditions of strain DM-2 were: temperature 32℃, pH 7.5, inoculation 10%, and shaking speed 150r/min. The optimal culture conditions of strain DM-3 were: temperature 30℃, pH 8.0, inoculation 10% and shaking speed 150r/min. After optimum, degradation rates of crude oil with three strains could reach 66.94%, 63.39% and 77.05%.Moreover, three strains capable of degrading certain components of crude oil were examined with respect to their degradation abilities.Strains DM-1 and DM-2 could degrade saturats and asphltenes mostly, while strain DM-3 was able to degrade saturats and resins obviously.Compared to strains DM-1 and DM-2, strain DM-3 has been shown to be capable of degrading aromatics better. According to the difference of degradation for oil components by three strains, we obtained three bacterial consortia. Using these consortia, the degradation rates reached 83.33%, 85.25% and 83.06%, respectively in 7 days.
|
PDF Full Text Request