Isolating And Screening Of PAH-degrading Predominant Strains And Study Of Their Metabolic Properties

Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous persistent organic pollutants in environment. PAHs which are of diversity, stability and complicated conformation, high toxicity and bio-refractory have done harm to human health by biological-chains accumulation. PAHs can hardly be central disposed for their extensive distribution. As one of the PAHs removal methods, biodegradation by the various bacteria widely exists in nature has the superiority to the other methods for its low cost, simple manipulation and no second pollution. Therefore, the study on bioremediation of PAHs is bound to be useful.This paper has shown PAH pollution on the following information: the origin, the migration and the danger, the disposal methods, the analytic detection means and the corresponding progress of study in domestic and overseas. Especially, there is more detailed information about the PAHs biodegradation method. Based on the above information collected, to removal PAHs from environment, it is clear that the important thing is to get predominant strains for PAHs degradation and further research on biodegradation properties. Based on the former research in the lab, This paper will do the following researchs: Firstly, domesticate, isolate and screen of the predominant bacteria for biodegradation of PAHs. Then, optimize the demulsification of extraction process of pyrene from the biodegradation system. Subsequently, study the influential factors of biodegradation of predominant bacteria. Finally, study the biodegradion of anthracene phenanthrene and pyrene by the predominant bacteria and its coarse endoenzyme.Four predominant strains named 2#, 5#, 7# and 9# have been domesticated, isolated and screened from the taming PAHs polluted soil. They are all effective or typical for PAHs biodegradation, for which they are selected for the experiment below. The result of demulsification of extraction process of pyrene from the biodegradation system has shown that Hg²⁺ is the most effective ionfor the demulsification process of the systems, when the concentration of Hg²⁺ is within 300～350mg/L, the emulsification layer almost does not appear within the separating funnel, and the dehydrating rate can reach 99.0% during the extraction.The extracting recovery rate of pyrene is 93.04%.The main results of influential factors effect on biodegradation of predominant bacteria have shown as follows: the initial pH has some influence on the biodegradation of pyrene by 9#, the biodegradation sestem with initial pH=6.00 or 9.02 is more effective for pyrene removal and the bacteria grow better. The temperature test has shown that the biodegradations of 2#, 5# and 9# are influenced by T. The optimum T to high-point of biodegradation is 30℃ for 2#, the degradation rate of pyrene was 23.57% after 48h' reaction. The change of reactive temperature almost has no effect on degradation of 5#, the biodegration rate is vary in the narrow range of 6.98%～12.01% within 25℃～40℃. The optimum T is 40 ℃ and the biodegradation was 28.06% after 48h' reaction. The inorganic ions test has shown that Mn²⁺ can promote the degradation velocity of 2# and 5#, while it is almost no effect on 9#; Cu²⁺was a restraining factor for biodegration of all the three strains, but its restraining degree is not the same; the effect of Zn²⁺, Co²⁺, Mo⁶⁺ and Fe³⁺on degradation vary with the sorts of strain. Additional carbon source test has shown that glucose is a beneficial substrate on the degradation of pyrene for 2#, 5# and 9# strains.The study on the biodegradability of anthracene phenanthrene and pyrene by the predominant bacteria 7# and its coarse endoenzyme has shown up: 7# and its coarse endoenzyme were capable of biodegradarion of anthracene phenanthrene and pyrene. Especially in the beginning of the bio-reaction, the effect is most obvious.7# strain and its coarse endoenzyme have the similar effect of initial pH on degradation of anthracene phenanthrene and pyrene, when initial pH is in the range of 5 to 9, the degradation can effectlively carried on. The strains are favorite of the neutral or alkalescence condition, either increasing or decreasing the initial pH will lower the biodegradation rate.