藻菌复合体系对珠江口典型环境激素壬基酚的降解效应与机制

Degradation Effect and Mechanism of alga-bacteria system on Representative Environmental Hormone Nonylphenol in the Coastal Water of Pearl River Estuary // Nonylphenol (NP) is a major material in the synthesis of nonionic surfactant nonylphenol polyethoxylates. It has been widely used in various industries, such as papermaking, textile, rubber, pesticide and detergent, which may easily releases into the environment. NP has been reported to possess strong estrogenic activity and to be high bioaccumulation. It is one of the representative endocrine disrupting chemicals and persistent toxic pollutants threatening to human health and ecosystems. It is urgently required to conduct researches on the degradation effect and mechanism of microalgae and alga-bacteria system on NP in the coastal water of Pearl River, and this is of significance in maintaining and protecting the ecological safety of Pearl River Estuary, and in promoting the economical sustainability of Guangdong, Hong Kong, Macau and Pan-Pearl River Delta. The main purposes of this proposal are to: (1) survey the characteristics of communities of microalgae and microbes in NP polluted aquatic water of Pearl River Estuary; (2) conduct researches on the isolation of microalgae and microbes and their degradation capability; (3) study the functions and effects of microalgae and alga-bacteria system on NP degradation; and (4) explore the mechanisms of NP biodegradation by microalgae and alga-bacteria system. Our findings will set up an experimental foundation for seeking and optimizing NP ecological degradation mode, and provide scientific basis for ecological restoration of NP or other toxic analogs in the coastal water of Pearl River Estuary.

壬基酚是合成非离子表面活性剂壬基酚聚氧乙烯醚的主要原料，在造纸、纺织、塑料、农药和清洗剂等行业被广泛大量使用并环境释放，具有明显的雌激素效应和极强的生物积累性，是对人类健康和生态安全构成严重威胁的环境激素类物质。开展微藻及藻菌复合体系对珠江口典型环境激素壬基酚的降解效应与机制研究，不仅反映了当前国际环境科学和修复生态学领域的最新趋势，而且对于维护和保障珠江口沿岸的生态安全、促进粤港澳及泛珠三角区域社会经济的可持续发展具有重大现实意义。项目旨在1）调查珠江口近岸壬基酚污染水域微藻及微生物群落结构特征；2）开展壬基酚降解微藻和微生物的分离筛选及其降解效能研究；3）研究微藻及藻菌复合体系对壬基酚的降解功能和效应；4）揭示微藻及藻菌复合体系降解壬基酚的生物学机制。预期研究结果可望为开辟环境激素污染物的生物降解新途径奠定理论基础，并为珠江口近岸水环境治理及环境激素污染水域的生态修复提供科学依据。

本项目选择了典型环境激素为研究对象，对环境激素污染河口区域进行了微藻和微生物群落的调查，并筛选出能够高效降解环境激素的微藻和微生物株系；结合实验室模拟实验，研究了环境激素对微藻生长速率、光合作用、生理生化等的影响，以及对微藻、微生物培养液、胞内、胞外对环境激素的吸附和吸收能力，深入了解了微藻和微生物对环境激素的去除能力。重点研究了微藻和微生物复合体系与环境激素之间的相关关系，揭示了微藻-微生物复合体对环境激素的降解过程。在此基础上，进一步探索了微藻对双酚A的降解产物分析，并深入探究了微藻在降解环境激素过程中基因在转录水平的变化。通过研究得出以下主要结论：（1）通过对珠江口环境激素污染严重区域采样，筛选并鉴定了11种壬基酚降解藻以及7种壬基酚降解微生物。（2）运用高通量测序技术对三种壬基酚降解藻进行了伴生菌群落组成研究。三种微藻的伴生菌分别以拟杆菌门，变形菌门，以及疣微菌门为优势，分属于11个属。（3）微藻对壬基酚、双酚A，雌二醇和乙烯雌酚均有显著的去除效能。微藻对壬基酚96小时的生物降解能力最大的是小球藻，降解率为68.80%。绿藻Desmodesmus sp.对13.5和33 mg/L BPA的60天降解率分别为98%和82.3%。羊角月牙藻对乙烯雌酚的96小时降解率为90.4%，对雌二醇的96小时降解率为81.3%。（4）筛选出的6种细菌，外源菌降解壬基酚的降解率，最高的是鞘氨醇单胞菌，半衰期为1.9509天；伴生菌降解壬基酚的降解率最高的是ZL-2 假单胞菌属，半衰期为4.57天。（5）四尾栅藻及其伴生菌和四尾栅藻与外源菌EB-4复合体系降解效率显著高于（P<0.05）单独四尾栅藻和降解菌处理组，其中C-XQ藻菌复合体系对壬基酚降解速率最高。（6）4种环境变化对藻菌复合体的降解能力均有影响， 4个因素对降解率的影响大小为光照>温度>氮磷比>PH。（7）微藻对双酚A的转录组分析得出绿藻可通过显著富集DNA复制来抵抗BPA胁迫造成的基因组不稳定和DNA损伤，并且上调氧化还原酶活性和糖基转移酶活性来增加对双酚A的解毒作用。