Isolating, Selecting And Activity Analysis Of Superior Strains With Deemulsification Activity

Nowadays, in oil industry of our country all of the deemulsifiers used in the oil and water separating of the crude oil are chemical deemulsifiers. While the chemical deemulsifiers have many drawbacks, such as high selective activity, high oil percentage in the separated water and needing organic solvent as adjuvant. In addition, the residue of the chemical deemulsifiers in the separated water is hard to degrade and could also contaminate the environment. As the development of the biological sciences, many developed countries have already started to develop biodeemulsifiers which have higher activity and less environmental hazard than chemical deemulsifiers. In the future biodeemulsifiers will be broadly used in many fields, for example in separating and removing oil contaminations. In this study, we isolated and selected two superior strains with deemulsification activity from crude oil contaminated soil, and then studied the effects of culture conditions on the growth and the deemulsification activity of the two strains and the effects of deemulsification conditions on the deemulsification activity of the two strains.Firstly, on the base of others' studies we established a set of procedures to isolate and select superior strains with deemulsification activity and at last got two strains with high and steady deemulsification activity. One is belonging to Corynebacterium Lehmann et Neumaun family and the other is belonging to Bacillus family. The deemulsification efficiencies of the two strains were 87% and 90.5% respectively and heat-steady. It was found that the clear bacteria culture media removed of bacteria had no deemulsification activity, which indicated that the deemulsification activity was not due to any compound released from bacteria caused by split of covalent bond, but due to the compounds or radicals on the surfaces of intact bacteria.In different culture conditions the growth statuses of the superior strains are different. After comparing and analysis of the growth statuses of the two superior strains in different culture time span, temperature, pH, medium composition and ventilation . It was found that the most favorable conditions for the growth of the superior strains were: temperature 25 ~ 30℃, pH 6~8, medium volume 100ml/250ml, rotation speed 160r/min and culture time span 60~80 hours. The most favorable medium was medium + 2% glucose + 2% liquidparaffin as carbon nutrition + 0.1% yeast extract as nitrogen nutrition.The deemulsification efficiencies of the superior strains cultured in different conditions were far from the same. After comparing and analysis of the deemulsification efficiencies of the two superior strains in different culture time span, temperature, pH, medium composition and ventilation . It was found that the most favorable conditions for the deemulsification activity of the superior strains were: temperature 30°C, pH 7, medium volume 100ml/250ml, rotation speed 160r/min and culture time span 72 hours. The most favorable medium was medium + 2% glucose + 2% liquid paraffin as carbon nutrition + 0.1% yeast extract as nitrogen nutrition.The deemulsification conditions could also have effects on the deemulsification efficiency. After comparing and analysis of the deemulsification efficiencies of the biodeemulsifiers in different concentrations, temperature, rotation speed and the water percentage of the oil/water emulsion, It could be concluded that the deemulsification efficiency of the biodeemulsifier was related to biodeemulsifier concentration, rotation speed and the water percentage of the oil/water emulsion, and have no relation with temperature . Increasing the biodeemulsifier concentration or rotation speed or decreasing the concentration of the oil/water emulsion could improve the deemulsification efficiency of biodeemulsifier. As the biodeemulsifiers are heat-steady, temperature has almost no effect on the deemulsifier efficiency of biodeemulsifiers.