Study On The Kinetic Characteristics During The Microbial Competitive Metabolism Of Anthracene, Phenanthrene, Pyrene And Its Intermediate Products

PAHs are the obstinate and widespread pollution in the envieonment and can be released to atmosphere, soils, foods and water. It is firmly believed that increase in concentration and type of PAHs in environmental system has threatened the health of animals, including human, on the earth. Anthracene, phenanthrene and pyrene were frequently discovered in the environment sample, and human cancer has the direct relevance with PAHs. The chemical structure of PAHs possesses carcinogenic structure. Therefore, they have been taken as model compounds for studies on PAHs. Study on anthracene,phenanthrene,and pyrene biodegradation is not only beneficial to eliminate the comtamination of anthracene,phenanthrene,and pyrene, but also valuable to understand the biodegradation mechanism, path of other PAHs. This can provide evidence for prevention of PAHs pollution to the environment.This paper describes the toxicity, existing status, behavior, transfer mechanism, pollution source, and distribution and pollution status of the PAHs. This paper also mainly discussed the degradation and kinetics of PAHs by predominant microbes.Two predominant isolates screened at an early stage in our lab were used in the experiment. The biodegradability, optimization of the optimum degradable conditions and the optimum environmental factors for endoenzymic catalytic degradation were studied, also degradation kinetic characteristics of anthracene, phenanthtene , pyrene by active predominant microbe and endoenzyme, competitive metabolic laws between the intermediate products and substrate of the degradation system was researched. The results were as follows:1. CN2 and CN4, isolated from coking wastewater at an early stage in the lab, could grow well as anthracene, phenanthtene and pyrene being the sole carbon source. The two isalates possessed the best degradability to phenanthtene with 51.1% degradation rate in 120h; and the latter enjoyed the best degradability to anthracene with 48.2% degradation rate in 120h. Adding of Ca²⁺,Mg²⁺, Fe³⁺, Cu²⁺, Mn²⁺, Zn²⁺ have differ degree results for the biodegradation of CN2 and CN4.Adding of Mn2+ played a better role in the degradation of anthracene by CN2, and the degradation rate amounted to 33.2% in 24h. Adding of Mn2+ and Cu2+ into the degradation system obtained over 40% in 24h, respectively, during the degradation of phenanthtene, Mn2+-added system got a better degradation rate than that of Cu2+-added system. Adding of inorganic ions achieved little difference in the degradation rate of pyrene compared with the no metal ions-added system. Adding of Mn2+ played a better role in the degradation of anthracene, phenanthtene and pyrene by CN4, compared with the no metal ions-added system in the same condition, the degradation rateof anthracene enhance to3.4%, the degradation rateof anthracene enhance to 1.56%, the degradation rateof anthracene enhance to1.28%.This difference could be attributed to the different biological oxidase secreted by the two isolates during the process of degrading anthracene, phenanthtene , pyrene.They have higher activity for degrading anthracene and phenanthtene, pyrene in weak acid condition, and Their degradability have restrained in alkalescence condition.when pH=6,CN2 has the best degradability to anthracene, phenanthtene , pyrene,Respectively is 31.16%,44.8%,36.32%. when pH=5,CN4 has the best degradability.to anthracene,phenanthtene,pyrene,Respectively is 31.16%,44.8%, 36.32%.2. The average degradation rates CN2 and CN4 indicated: With the concentration of anthracene,phenanthtene and pyrene increasing,the degradation rates increasing,This assumes the linear relations.The degradation was restrained as concentration of anthracen e,phenanthtene and pyrene exceeded 200mg/L.3. The biggish effects of temperature on enzymatic catalysis degradation of anthracene, phenanthrene, and pyren by CN2 and CN4:The endoenzyme of CN2 have the better degradability in pH=6～7, The endoenzyme of CN2 have the better degradability in weak acid condition.When suitable temperature was 18℃～50℃, The degradation.active of endoenzyme of CN2 and CN4 have been keep. When suitable temperature was 30℃～35℃,The endoenzyme of CN2 and CN4 have the best degradability.4. Uses Eadie-Hofstee law determine michaelis constant Km and maximum degradation rates Vm..With the original concentration increasing,the kinetic character of enzymatic catalysis indicate the average original rates increasing in certain tine scope.For random original concentration of anthracene,phenanthtene and pyrene,the average rates minish in 15 , 30,60, 120min.Every curve nearly parallel.It show the nearly the same seeming reaction order of biodegradation in different time.For CN2, the average seeming reaction order of anthracene is 0.6606, the average seeming reaction order of phenanthtene is 0.7762, the average seeming reaction order of pyrene is 0.627. For CN4, the average seeming reaction order of anthracene is 0.9331, the average seeming reaction order of phenanthtene is 0.7629, the average seeming reaction order of pyrene is 0.896.5. In the degradation system of CN2 and CN4,The different period of transformed intermediates can strain the biodegradation of anthracene,phenanthtene and pyrene We combine the results of enzymatic catalysis, the reason maybe is compete metabolize. In majority situation, substrate removal rate of the intermidiate product-added degradation system was lower than that of control one.The experiment results obtained provided a research foundation for the PAHs bioremediation.