典型溴代酚类阻燃剂的环境行为及其微生物强化降解机制研究

This project aims to have a full insight of the biodegradation characteristics and performance of typical phenolic brominated flame retardants, tetrabromobisphenol A (TBBPA), 2,4,6-tribromophenol (TBP), and one of TBBPA degradation intermediate bisphenol A (BPA) by our previously isolated three bacteria, Ochrobactrum sp. T, Bacillus sp. GZT, and Bacillus sp. GZB. They were isolated from an electronic waste recycling site, and are able to simultaneously debrominate (except BPA) and mineralize TBBPA, TBP and BPA, respectively. In the present project, the functional enzymes able to degrade and/or debrominate the target organics will be isolated, purified and characterized. The genes encoding putative degradation and/or debromination reductive enzymes will also be cloned and identified. To understand the environmental behavior and fate of target compounds in water environment, the water and sediment will be sampled from heavily polluted sites to study the degradation of TBBPA, TBP and BPA under simulated condition by obtained functional enzymes. Particularly, the functional genes cloned will be acted as the potential molecular probes to aid in evaluating, monitoring, or predicting the performance of bioremediation systems treating target organics. To clarify their specific function of isolated enzymes and to establish the relationships between the C, H, and Br isotope fractionation with debromination and mineralization, the Multidimensional Compound specific Stable Isotope Analysis (MD-CSIA) technology will be employed. In addition, the potential aqueous ecotoxicity and estrogenic activity of the biodegradative intermediates/products will be monitored in order to evaluate the detoxification feasibility as well as the ability of these isolated functional enzymes. The success of the project will provide a fundamental knowledge for the transport, transformation, environmental fate of typical phenolic brominated flame retardants in field sites.

为了准确了解典型溴代酚类阻燃剂的生物降解特性，本项目拟利用我们已从电子垃圾拆解地驯化出的能分别高效降解四溴双酚A，三溴苯酚和双酚A的降解菌，分离、纯化出降解/脱溴酶；克隆出相应的功能基因；采集污染高风险区的水样及沉积物，在功能酶作用下模拟研究环境介质中目标污染物的迁移转化和微生物强化降解机制，建立功能酶/基因与目标污染物降解效率之间的关系，并以克隆出的功能基因为分子探针预测实际环境中目标污染物的行为与归趋。利用单体同位素技术分析目标污染物的C、H、Br元素同位素，了解他们在功能酶作用过程中同位素分馏特征，阐明不同功能酶/基因对其降解/脱溴效率和作用机制，建立目标污染物降解、矿化与同位素分馏之间的关系；同时对其降解过程中的联合毒性变化进行系统研究。本项目的成功实施将为实际环境介质中典型溴代阻燃剂的迁移、转化和归趋及其生物强化降解机制提供翔实的理论和实验依据。

溴代阻燃剂(BFRs)是一类具有持久性，亲脂性和生物累积性的含溴类化合物。本项目主要成果如下：①(a)开展了典型电子垃圾拆解地水体和沉积物中BFRs的分布及毒性，发现一个长期从事电子垃圾拆解回收的区域临近的主要河流水体和表面沉积物普遍受到多溴联苯醚、酚类溴代阻燃剂和双酚A的污染，且大部分采样点都存在可预测潜在的生态毒性。(b) 发现附近的电子垃圾拆解回收区域对北江流域的影响很小或者基本不受影响，且并不会给环境造成生态风险。②建立了环境样品中酚类溴代阻燃剂和双酚A的碳同位素组成的测定方法，并研究了酚类溴代阻燃剂和双酚A生物降解过程中碳同位素的分馏富集情况，结果发现酚类溴代阻燃剂和双酚A在生物降解过程中未发生明显单体碳同位素的分馏富集。③借助能够降解四溴双酚A(TBBPA)的苍白杆菌(Ochrobactrumsp.) T开展了对TBBPA生物强化(生物放大和生物刺激)的降解研究，同时也开展了能够降解2,4,6-三溴苯酚(TBP)的芽孢杆菌(Bacillussp.) GZT对TBP生物强化降解和能够降解双酚A(BPA)的芽孢杆菌(Bacillussp.) GZB对BPA的生物强化降解研究。另外，研究了生物强化降解过程中微生物菌群变化情况，认识生物强化降解过程中起主要作用的微生物菌群结构的变化。④能降解TBBPA和TBP的菌种苍白杆菌T和芽孢杆菌GZT为研究对象，通过全基因组测序获得两株菌株的全基因组序列，并通过克隆和表达分别对能够降解TBBPA和TBP的脱卤酶及其编码基因进行了考察。此外，利用超滤、盐析、离子交换和凝胶层析等纯化策略，也对野生菌株的脱卤酶进行了纯化研究和酶学性质的考察，最后对脱卤酶分别降解TBBPA和TBP过程中生成的中间产物进行了分析，提出和阐明了TBBPA和TBP生物降解的分子途径和机理。目前相关研究内容发表SCI论文22篇。本项目的成功实施可以为实际环境介质中典型溴代阻燃剂的迁移、转化和归趋及其生物强化降解机制提供翔实的理论和实验依据。