| Tetrabromobisphenol A(TBBPA) is a kind of bromide flame retardants, and widely used in all kinds of plastic. Its pollutants are commonly found in the environment. It has a strong biological toxicity and will damage on the biological organisms, including human beings. Although it has been reported many brominated flame retardants degrading microorganisms, and Pseudomonas aeruginosa NY3 is the most promising solution to this kind of microbial contaminants.In the early study, the NY3 strain contains two alkyl oxidase genes, alk B1 and alk B2,and the mutants NB1D、NB1D and NB12 DD was constructed by knockout the alk B genes. This paper reveals the role of the alkane oxidase gene in the cell, and optimize the conditions for the degradation of TPPBA, which has a practical and theoretical significance for the remediation of contaminated environment.In this study, Pseudomonas aeruginosa NY3 and its mutant strains as tested stains,TBBPA as the object of degradation. By means of ion chromatography, GC, GC-MS,UV spectroscopy and three-dimensional fluorescence and other analytical methods, the following results were obtained:(1)The study showed that TBBPA was toxic to the strains, but as a single carbon source for growth, NY3 anti-toxicity and cell growth were maximum and the net maximum growth of OD600nm=0.577, and the double mutant strains NB12 DD bacteria metabolism ability was worst. With ammonium sulphate as nitrogen source and culture solution initial p H was adjusted to alkaline, increasing inoculation amount could improve the culture liquid in the growth of cells, thus greatly improve the strains of the debromination efficiency and degradation rate, which could make the maximum debromination rate of strain reach to the range of 26-28%.(2)The study found that the strain cell growth amount is large, under the same conditions,the metabolic efficiency of various strains without significant difference,but when cell growth amount is small, wild NY3 metabolic efficiency is generally higher than the mutants, and in the metabolism of TBBPA alkb2 gene action than alkb1 gene greater.(3)The study found the five tested co metabolic carbon sources, sodium lactate as the best in the presence of carbon source, sodium lactate coexistence than glucose, citric acid sodium, ethanol, sodium acetate as carbon source coexistence of cell biomass were increased by 1.9, 3.38, 697, 6.97 times. At the same time of TBBPA on degradation efficiency and debromination efficiency rate also significantly improve.(4)The study found that many intermediate species of the strains accumulated under the condition of coexistence of sodium lactate.The structure of the intermediate product features simultaneously by UV and fluorescence spectroscopy and mass spectrometry confirmed. Intermediate products of metabolism of TBBPA of every strain was divided into three categories: direct reductive debromination and dehydroxylation product 3,3 ’, 5 were three tetrabromobisphenol A and 2 bromo 4(isopropyl-Bromophenyl)- phenol; isopropyl fracture, oxidation, de bromine products of 2 bromo4(isovalerate)- phenol, 2,6 dibromo 4(acetic acid)- phenol, 4-(2- hydroxy-isopropanol based) 2,6 dibromo- phenol, 2,6 dibromo 4(allyl) phenol and 2 bromo 4(3- hydroxy propionic acid)- phenol; do not contain bromine single aromatic ring product catechol.The NY3 and single mutant strains NB1 D and NB2 D and at the same time, the degradation of TBBPA debromination reduction and cumene cracking in two ways promoter, and double mutant strains of bacteria NB12 DD only isopropyl fracture a way to start tetrabromo bisphenol A metabolism and metabolic ability is poor. Ny3 and single mutant strains NB1 D and NB2 D by degradation of TBBPA debromination reduction and cumene cracking in two ways promoter, and double mutant strains of bacteria NB12 DD only isopropyl fracture a way to start tetrabromo bisphenol A metabolism and metabolic ability is poor. |
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