Study On The Characteristics Of Polycyclic Aromatic Hydrocarbons And Oxygen-containing Polycyclic Aromatic Hydrocarbons Degradation By Arthrobacter Crystallopoietes NT16

Polycyclic aromatic hydrocarbons?PAHs?are persistent organic pollutants that are ubiquitous in the environment.They can be converted into oxygen-containing polycyclic aromatic hydrocarbons?OPAHs?with higher toxicity and easy accumulation in the biodegradation process,which is harmful to the ecological environment and human health.Arthrobacter is a type of gram-positive bacterium widely existing in the soil environment and its biodegradation function is prominent,which has been paid more and more attention by researchers.In this paper,the experimental strains of Arthrobacter crystallopoietes NT16 which was isolated and selected by our research group were used to study the characteristics and mechanism of degradation of polycyclic aromatic hydrocarbons and oxygen-containing polycyclic aromatic hydrocarbons.This paper use naphthalene,phenanthrene,pyrene,1-hydroxy-2-naphthoic acid?1H2NA?,and 1-naphthol as main research objects.Liquid-liquid extraction was used as a sample pretreatment method.The following results were obtained using liquid chromatography,TOC detector,UV spectroscopy,three-dimensional fluorescence spectroscopy,and gas chromatography-mass spectrometry.?1?NT16 bacteria can metabolize various carbon sources such as PAHs,OPAHs,sugars and various surfactants.NT16 bacteria can grow stubbornly in high toxic solutions of naphthalene,phenanthrene and pyrene up to 2000mg/L.After the secondary or tertiary growth on the PAHs carbon source,the maximum growth amount OD_600nm00nm can reach 1.22¹.42,and can continuously degrade and mineralize naphthalene,phenanthrene and pyrene with the extension of culture time.From the trend of UV and fluorescence spectra of the degradation solution,it was also confirmed that the PAHs were continuously degraded and the conversion products accumulated continuously.?2?NT16 bacteria could use 50 mg/L 1H2NA as the sole carbon source and energy source.The maximum growth OD_600nm00nm was 0.77.The cell growth was synchronized with 1H2NA degradation.The bacteria convert 1H2NA into a4?2'-carboxyphenyl?-2-oxygen-3-butenoic acid product by ring-opening cleavage.The optimization results of degradation conditions were as follows:the bacterial inoculation amount was 10%,the initial pH was 9,ammonium nitrate was a nitrogen source,and sufficient oxidizing sulfur source was needed,and 1H2NA was suitable for a growth concentration of 50 mg/L.?3?The coexistence of carbon sources of succinic acid and malonic acid can greatly improve the ability of NT16 bacteria to degrade and mineralize 1H2NA.At 120hours,the cell growth in the system can be increased by 53%and 62%,respectively,at the same time,the degradation efficiency of 1H2NA can be improved by 9%and 7%while accelerating the mineralization of the 1H2NA carbon source.?4?Although 1-naphthol is obviously toxic to the growth of NT16 cells,it can still grow under 50mg/L 1-naphthol conditions.NT16 bacterial cells contain 1H2NA hydroxylase,ortho-ring-opening lyase,decarboxylase,salicylic acid hydroxylase,catechol ring-opening lyase and other five kinds of degradation of 1H2NA oxidase.It is the hydroxylase that initiates the degradation of 1H2NA by NT16 bacteria.When only1H2NA was used as the carbon source,except for the 1H2NA decarboxylase activity that was not detected in the cells,the activity of the other four enzymes was high;coexistence of malonic acid and succinic acid increased the expression of cellular oxidase,especially in cells.14.3KDa,25KDa,45KDa,60KDa or 97.2KDa size protein expression was improved.The results of this dissertation provide a basis for understanding the regularity of degradation of polycyclic aromatic hydrocarbons by Arthrobacter,and lay the foundation for the application of these bacteria in the restoration of polluted environment.