Isolation,Identification,Characterization & Degradation Pathway Of 3-Bromocarbazole Degrading Bacteria

Polyhalogenated carbazoles(PHCs)belong to the group of heterocyclic aromatic hydrocarbons,PHCs was a group of potential persistent organic pollutants which has the similar chemical structure to polychlorinated dibenzofurans and show dioxin-like toxicity,bioaccumulation and persistance.They were firstly found in the environment in 1980 s,Up to now more than 20 PHCs have been detected in soil samples and sediments.As emerging contaminants,the study on environmental behaviors of PHCs is relatively limited.Three strains named CH-1,CH-2 and CH-3 were isolated and purified from the polluted soil of a pesticide manufacturer in Suzhou,which were capable of degrading 3-bromocarbazole.The strain CH-3 was used for further investigation due to its best performance.Physiological characteristics and analysis of 16 S rDNA gene sequence revealed that MZ-3 belonged to Stenotrophomonas sp.The optimal degradation conditions of CH-1 were pH 7.0 and 30?.Under these conditions,the highest degradation rate was approximately 70% of 3-bromocarbazole(50 mg/L)within 8 d.The activity of degradation was significantly inhibited when the pH below 5.0 or up to 9.0,The optimum temperature for the biodegradation was 30~35?,when the temperature blow 20? or higher to 40?,it is not good for the degradation.The strain could grow well at initial concentrations from 25 to 50 mg/L,and the degradation rate decreased with the substrate concentration higher than 100 mg/L.Only 40.9% of degradation rate was observed in 8 d when the initial concentration was 200 mg/L.Additional carbon source could enhance the biodegradation of 3-bromocarbazole.During the biogradation process,one main intermediate metabolite was produced by strain CH-1 and determined as(2E,4Z)-6-(2-amino-5-bromophenyl)-2-hydroxy-6-oxhexa-2,4-dienoic by gas chromatography-mass spectrometry(GC-MS)analysis.