| Tetrabromobisphenol A(TBBPA),mainly used in electronics,textile,and plastics,is one of the most widely used brominated flame retardant(BFR)in the industry.TBBPA leachs from products during its production,usage and waste,and entered the environment during the waste recycling,dust particles migration and sewage treatment.TBBPA has a high lipid solubility,and easily accumulated in organisms.TBBPA was shown to be toxic to liver,immune system and neuro,and be able to disturb endocrine.As a result,the removal of TBBPA in the environment has attracted serious concern.Microbial degradation is very efficient in the biodegradation of TBBPA,and the isolation of TBBPA-degrading bacteria will be helpful in the research of TBBPA environmental fate.Humic acids and heavy metals are ubiquitous in the environment.To our knowledge,their effects on the degradation and biotransformation of TBBPA are still unknown.In this study,TBBPA-degrading bacteria were isolated,C-14 isotope tracer technique was used to study the aerobic degradation of TBBPA.To our knowledge,its was the first research to study the effects of humic acids and heavy metals(Cu2+and Cd2+)on TBBPA degradation.Two TBBPA-degrading bacteria were isolated from active sludge,and were named as Pseudomonas sp.JDT and Pseudomonas sp.CDT according to the results of 16S rDNA gene analysis.The growth of the bacteria was affected by extra carbon source and the concentration of TBBPA.Yeast extract promoted the growth of bacterial strain,while TBBPA with high concentration inhibited the growth.TBBPA debromination efficiencies of 12.9%and 40.9%,respectively,were achieved within 40 days incubation in the culture of strain JDT and CDT.In the culture of strain JDT and CDT,the relative amount of 14C-TBBPA mineralization was 0.11%and 1.47%,respectively,within 11 days incubation.Extra carbon source,especially yeast extract with low concentration promoted the mineralization of TBBPA.When the yeast extract was continually added to the bacterial culture for 18.5 days,the relative amount of TBBPA mineralization at the end of incubation in the culture of strain JDT and CDT increased to 2.67%and 3.61%,respectively.Two kinds of polar metabolites were detected.Compared with strain JDT,the ability of TBBPA biodegradation of strain CDT was much higher.Thus,strain CDT was chosen to study the effects of humic acid and heavy metals on TBBPA biodegradation.After 87 days incubation in the active culture of strain CDT,2.3%of initial 14C-TBBPA was mineralized to 14CO2,and the relative amount of 14C-BBPA in organic extraction was 47.3%.29.5%of initial 14C-TBBPA transformed to polar metabolites,and the rest rauioactivity rematined in the nonextractable water phase and bacterial cells.Humic acids(1000 mg L-1)and heavy metals(Cd2+and Cu2+,10 μM)showed no effects on the activity of strain CDT.But Cu2+ significantly affected the biodegradation and transformation of TBBPA and its hydrophobic and hydrophilic metabolites,and also obviously inhibited the mineralization of TBBPA.The effect of Cd2+on TBBPA biodegradation was slight,and only significantly affected the amount of hydrophilic metabolites in the transformation of TBBPA.The bound residues,formed through the association of TBBPA and its metabolites with humic acids,significantly inhibited the biotransformation and mineralization of TBBPA.The relative amounts of hydrophobic and hydrophilic metabolites in transformed fractions of TBBPA in the culture added with humic and Cu2+ were significantly lower than in the active culture,which indicated that the co-effect of humic acids and Cu2+ was greater than the single factors.our study provided a preliminary viewpoint on the effects of humic acids and heavy metals,which are ubiquitous in the environment,on TBBPA biodegradation and demonstrated that the important roles of humic acids and heavy metals in microbial degradation of TBBPA.This study promoted the basic study of TBBPA remediation in the environment. |
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