The Study On Bioremediation Of Oil Pollution

The bioremediation of oil pollution was studied in this subject, the study included the isolation and selection of the effective oil-degradation bacterium and the mixed bacteria, mechanism of the oil-degradation, effect of biosurfactant on the bio-degradation of oil, mechanism and the best fermentation condition of biosurfactant released by bacterium, and the characteristics of biosurfactant.Five effectual oil-degrading bacteria were isolated from refinery wastewater, and were identified as Pseuomonas XD-1, Xanthomonas XD-2, Zoogloea XD-3, Bacillus XD-4 and Plesiomonas XD-5, respectively.The study showed that various growing conditions had great effect on the oil-degradation. At pH=7.0, 1% quantity of inoculation and 12h aged bacterium, Pseuomonas XD-1 had the best effect of biodegradation. Strain could degrade oil effectively when there was plenteous nitrogen and phosphorus nutrition. The strain could live in paraffin, but could not use aroma.The study showed that the mixed bacteria community could degrade oil generally and effectively. The mixed bacteria community including Xanihomonas XD-2, Zoogloea XD-3, Bacillus XD-4 and Plesiomonas XD-5 could degrade oil more effectively than each one alone. The best degrading effects would be obtained when four strains were inoculated Xanihomonas 0.1%, Zoogloea 0.1%, Bacillus 0.5%, Plesiomonas 2.0%, respectively. Strain Xanihomonas sp. and Zoogloea sp. could degrade C12~C]6 straight chain alkanes and some branched alkanes, strain Bacillus sp. and Plesiomonas sp. degrade C12~C22 straight chain alkanes. The community showed finer effect of oil-degradation.The biosurfactant played an important role in oil-degradation. Pseuomonas XD-1 could release biosurfactant, and disperse crude oil into oil droplet, then adsorbed on the oil droplet to degrade crude oil. The existence of biosurfactant decreased the inducement time of strain XD-1 degrading oil by half, and increased the rate of oil-degradation.Pseuomonas XD-1 released biosrufactants in log phase of growth and the modeof the biosurfacant release was correlated with growth. The biosurfactant was the mixture of lipo-peptide and gly-peptide. The CMC value of the biosurfactant was 50mg/L, and the lowest surface tension appeared at pH 6.0. Strain XD-1 released biosurfactant when growing, and the biosurfactant mainly accumulated in the special organelle of the cell and on the outer cell wall, in which a viscous biosurfactant film about 140nm thick was formed. The biosurfactant would be released outer of cell in growing. The strain could release the biosurfacant accumulated in cell after 6 hours of dipping in pure water.Plenteous carbon sources were propitious to produce biosurfactant. Pseuomonas XD-1 could release a mass of biosurfacant continuously when growing in a medium containing crude oil as carbon source. The results showed that the best carbon source and nitrogen source were crude oil and urea in which strain grew well to release biosurfacants, and the best fermentation condition was as follows: glucose 10g, urea 4g, postassium dihyhrogen phosphate 1g, mineral solution 4mL, water 1L, pH8.0.