Study Of Characterization And Mechanism Of Degradation Of Polycyclic Aromatic Hydrocarbons By Pseudomonas Aeruginosa NY3 Extracellular Active Compounds

Pseudomonas aeruginosa could degrade alkanes,aromatics and chlorinated aromatics arapidly,which are commonly used in bioremediation of contaminated sites.The excellent degradation ability of Pseudomonas aeruginosa to organic contaminant is not only due to its accelerated oxidase system,but also related to its extracellular secretions.At present,the studies on the excellent degradation ability of Pseudomonas aeruginosa are mainly focused on intracellular enzymes and their extracellular secretion of rhamnolipids,while little attention has been paid to the degradation and mechanism of small molecular active substances in the process of microbial remediation.In this paper,based on the extracellular liquid of Pseudomonas aeruginosa NY3 in different growth environments,the characteristics and mechanism of the active small molecules in the degradation of PAHs were studied.In this paper,the phenanthrene was used as the degradation object.The following results were obtained by means of high performance liquid chromatography,high performance liquid chromatography-mass spectrometry,gas chromatography-mass spectrometry.?1?When NY3 strian was grown in LB medium,it could secrete high yield phenazines,such as pyocyanin?Pyo?,phenazine 1-formamide?Pcn?,phenazine1-carboxylic acid?Pca?.The cell-free fluid can degrade phenanthrene effectively through 3-phenyl lactic acid pathway.The biodegradability of phenanthrene wastewater can be improved and the growth of bacteria in phenanthrene wastewater can be promoted.?2?NY3 strian could produce pyochelin?PCH?in iron-deficient environment,such as M9 liquid medium.The M9 extracellular solution of NY3 strian rich in PCH could effectively degrade phenanthrene in combination with iron,and its degradation rate increased with the increase of PCH in extracellular solution.On the other hand,its degradation rate and iron dosage are related.The pathway of degradation of phenanthrene by M9 extracellular solution of NY3 strain is 2-vinyl-1-naphthoic acid pathway.The biodegradation of phenanthrene by extracellular fluid increased the biodegradability of solution and promoted the growth of NY3 bacteria in degradation system.?3?Common extracellular phenazine secreted by Pseudomonas aeruginosa,including Pyo,Pca,Pcn,Hpe,can cause the degradation of phenanthrene when it reacts with reductive coenzyme NADH,in which pyo's degradation efficiency is the best.The identification of intermediate products showed that,the way of degradation of phenanthrene by PHCs and NADH is 2'2-biphenyl dialdehyde pathway,which is similar to extracellular solution of NY3 bacteria contains phenazines,it is the oxidative transformation initiated by hydroxyl radicals produced by the reaction of phenazine with NADH.OPAH,such as 2,3-naphthalene diphenol,could also be degraded by free radicals produced by reaction of Pyo with nadh.?4?Without the participation of bacteria,the degradation of phenanthrene can be induced by the reaction of FeCl₃ with purified PCH,when the concentration ratio of Fe Cl₃ to PCH extracted from M9 extracellular solution of NY3 strain is 1:2:2:1,the best degradation rate of phenanthrene can reach 40%in 24 hours,and the removal rate of TOC phenanthrene increases gradually.The degradation of phenanthrene by FePCH was similar to that of extracellular solution,and the bioavailability of phenanthrene was improved.The intermediate product of phenanthrene degradation by Fe PCH was analyzed.It was found that FePCH could degrate phenanthrene through phthalate way and 2-ethyl-1-naphthalic acid pathway,which is similar to extracellular solution of NY3strain grewn in M9 liquid medium.These results indicated that PHCs and PCH,the small extracellular active compounds secreted by NY3 strain,could react with other components in the extracellular fluid to degrade PAHs pollutants.The degradation can promote NY3's uptake for PAHs and the growth of NY3 cells.The research provides a theoretical guidance for understanding the mechanism of degradation of organic pollutants by Pseudomonas aeruginosa and theoretical basis for optimizing the remediation efficiency of organic pollutants of NY3 bacteria.