Screening Of Highly Effective Oil-degrading Strain And Primary Study Of Degrading Condition

Restaurant wastewater is a high-concentration oil wastewater. If it is not disposed and discharged to water directly, it will have a serious influence on the process of reoxygenation and self-purification, and jeopardizes aqueous ecosystem. Current physical and chemical technologies such flotation and sedimentation are often insufficient and remove oil in water incompletely. Biological technology is the most effective safe and reasonable method for wastewater, and does not bring secondary pollution. Therefore, all the scholars at home and abroad regard them very well.In the study, lipase-producing strain was isolated from oil-contained sewage and earth samples in cloaca of university, oil manufactory, slaughterhouse. Oil-degrading rate of a strain DC-3-2 was the highest after effectively primary and secondary screening method, which reached 67.32%. Several experiments were done: morphology observation of cell , colony, ascospore and pseudo-hyphae and so on, and physiology biochemistry, such as glucose fermentation, carbon nutriments assimilation, nitrogen nutriments assimilation, producing starch compound, urealyticum, gelatin liquefaction, growth in no-vitamin plates. According to J.Lodders yeast classification system, the yeast was identified as Candida sp. primarily.On the base of this, the original strain Candida sp. DC-3-2 was implanted by 30kev N⁺ in several doses. The results showed that the plus mutant percentage was the highest in the dose of 4×10¹⁵ion/cm².Therefore, the dose was conformed optimum and the mutant was performed in the dose. The results showed that the oil-degrading rate of the strain implanted by N⁺ ion beam was increased by 11.09%. Single factor method was used in the experiments to study the influence on oil-degrading rate. There were several factors: pH value, inoculum size, temperature, dissolved oxygen, carbon nutriments. The results indicated that the optimal culture conditions were as follow: initial pH value 9.0, inoculum size 3%, temperature 25～30°C, dissolved oxygen 180～200rpm, carbon nutriments soybean salad oil. In optimum condition, it had the highest oil-degrading rate, which was 87.7%.