Studies On Characteristics And Mechanism Of Aerobic Degradation Of Tetrabromobisphenol A By Co-metabolism

Tetrabromobisphenol A (TBBPA), as the world’s highest production-volume and the most widely used brominated flame retardant, has been detected in various environmental medias including air, water, soil, sediment, even in biota. Moreover, TBBPA has the characteristics of persistent organic pollutants (POPs), i. e., persistence in the environment, potential for long-range transport, bioaccumulability and high toxicity, thus its environmental behavior and fate have got extensive attention. Biodegradation is an important pathway for TBBPA transformation and removal in the environment, and present researches mainly focus on the anaerobic biodegradation of TBBPA, whereas the studies on the aerobic biodegradation for TBBPA are limited.In order to investigate the characteristics of microbial aerobic degradation of TBBPA, one strain with high efficiency of degrading TBBPA was isolated from activated sludge by selective enrichment method. The strain was identified as Pseudomonas.sp according to its morphological, physiological and biochemical characteristics and16S rDNA genesequences analysis.So as to studying the degradation efficiency of TBBPA by Pseudomonas.sp, different levels of phenol, methonal, ethonal, sodium formate, sodium acetate, glucose, yeast powder were employed as co-metabolism substrates. The results showed that ethonal, sodium acetate, glucose and yeast powder can all promote TBBPA degradation except phenol and methonal, and glucose has the most noticeable supporting effect on TBBPA degradation. Thus, glucose was chosen as the best carbon resource for TBBPA degradation.Based on glucose as co-metabolism substrates, single factor method was performed to determine the optimal condition for TBBPA degradation. The optimum aerobic conditions were as follows:8g/L glucose,0.5g/L beef extract,2g/L NH4NO3, pH7.0, temperature35℃, and oscillator speed150r/min. Under the optimal condition, TBBPA aerobic degradation reaction matches first-order kinetics model, and the degradation rate of10mg/L TBBPA was up to95.6%after six days. Meanwhile,2,4,6-tribromophenol and bisphenol A can be efficiently degraded in the same condition.The experiments of acute poisoning in zebrafish were also performed to investigate the toxicity of the parent compound and degradation products by extracting the supernatant in the aim system under the optimal condition. The results showed that degradation products were less toxic than the parent compound TBBPA. Degradation products were analyzed by LC-MS.3-(3- bromine-4-hydroxy-phenol)-3-hydroxy butyric acid,2-(3-bromine-4-hydroxy-phenol)-2-hydroxy propionic acid and2,6dibromo-4-(1-hydroxy-ethyl) phenol were identified as the main degradation productions, and the possible degradation pathway was proposed.