生物氧化锰诱导多环芳烃腐殖质化的机制研究

Humification is an important immobilization and detoxifcation way of PAHs and other organic matter in natural soil environment, involving two stages. In the first stage, PAHs are decomposed by microorganism; in the second stage, raw material monomers of humus are synthesized and then formed cyclic compounds. The main mechanism of humification is oxidative coupling reaction, which could be induced by the action of enzymes and metallic oxides, including manganese oxides and iron oxides. .Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenicity and carcinogenicity. Because of their hydrophobic nature, most PAHs bind to particulates in soil and sediments, rendering them less available for biological uptake. Microbial degradation represents the major mechanism responsible for the ecological recovery of PAH-contaminated sites. .Manganese (Mn) oxides are one of the most powerful catalyst and oxidant found in soils, and Mn-oxidizing microorganisms are recognized as the major drivers of the global Mn cycle. Microorganisms can accelerate the rate of Mn oxidization processes by up to 105 times compared to abiotic Mn oxidation. Manganese oxides could induce oxidative coupling reaction of phenanthrene in the presence of phenol, but its reaction mechanism remains to be clarified. .This research focuses on humification, the important detoxification way of PAHs in the presence of biogenic Mn oxides and manganese-oxidizing microorganisms. The results will provide new clues to the migration and transformation of PAHs in natural environment; and help us to understand the important role of the biogeochemial cycle of manganese on the fate of organic matters. Humification with biogenic Mn oxides could also be a promising method for the PAHs bioremediation.

腐殖质化是土壤环境中多环芳烃类有机污染物固定化和无害化的重要途径，其主要机制是氧化偶联反应。氧化锰是环境中重要的吸附剂、催化剂和氧化剂，在自然环境中主要由微生物合成。锰的生物地球化学循环对有机物的归趋中起到重要作用，可能诱导有机物发生氧化偶联反应，但其反应过程和机理不明确。本研究从腐殖质化角度研究多环芳烃的迁移转化规律和无害化治理，关注生物氧化锰在多环芳烃腐殖质化过程中作用、反应途径、反应产物的生物毒性并研究究反应机制。研究结果将为多环芳烃在环境中的迁移转化规律提供新的线索，为多环芳烃的腐殖质化无害化治理提供科学依据，并进一步阐明锰的生物地球化学循环在自然界多环芳烃归趋中的重要地位。

氧化锰通过吸附、氧化和催化作用对环境中有机物污染物的迁移转化产生重要影响，尤其是微生物形成的生物氧化锰。腐殖质化是土壤环境中多环芳烃等有机污染物固定化和无害化的重要途径，其主要机制是氧化偶联反应。生物氧化锰可能参与多环芳烃的氧化偶联反应。本课题研究锰的生物氧化机理和生物氧化锰的性质特点；考察生物氧化锰对芘的吸附作用，并对氧化锰介导的氧化偶联反应进行初探，主要取得了以下进展：（1）通过形态分析、生理生化和分子生物学方法，从锰矿区土壤中筛选鉴定得到8株锰氧化菌：包括6株芽孢杆菌，1株根瘤菌和1株寡养单胞菌。其中根瘤菌CP217是新发现与生物锰氧化相关的菌属，对研究锰生物氧化与氮循环之间的联系有重要启示；（2）通过扫描电镜-元素分析、透射电镜和X射线衍射表征，不同生物来源的生物氧化锰为无定型态或短程有序的纳米颗粒；（3）锰氧化细菌Bacillus sp. WH4的锰氧化蛋白CotA在Escherichia coli strain TranB（DE3）中成功表达并纯化，菌株形成的生物氧化锰沉积在细胞表面；（4）对锰氧化菌、生物氧化锰对芘吸附氧化的研究中发现，氧化锰可以吸附芘，但未能诱导芘的氧化偶联反应。以上研究结果表明锰氧化细菌和生物氧化锰在自然环境中的多样性；生物氧化锰通过吸附作用影响高环多环芳烃在环境中的归趋，也提示了氧化锰直接降解高环多环芳烃及发生氧化偶联反应的的复杂性。