土壤微生物胞外聚合物在多环芳烃降解过程中的作用与机理

PAHs microbial degradation is the main pathway for transformation and completely degradation of PAHs in soil, many researches concerning the mechanism of PAHs degradation by microorganism were carried out for the whole microbial cell, and the function of EPS in PAHs biodegradation seldom discussed. Many PAHs degradation strains were screened and the effect of added EPS on pyrene degradation were researched in the preliminary work of applicant. In the present project, EPS isolated from two effective PAHs degradation strains are selected as the research objectives, pyrene and benzpyrene are used as target contaminants, two strains and its EPS are introduced into soils contaminated by PAHs. The function of EPS in the process of degradation enzyme release, cometabolic degradation of PAHs by microbe growing on EPS substrate, competitive adsorption of EPS and soil to PAHs will be researched through degradation, desorption and simulation experiment. The relationship among degradation enzyme distribution characteristics, EPS components, microbial activity and PAHs degradation will be analyzed, function of EPS from microorganisms in the process of PAHs biodegradation will be revealed, and the contribution of EPS to PAHs biodegradation will be defined. Project implementation will provide theoretical support for illuminating the migrating behavior of PAHs from soil surface to cell surface through EPS secreted by microorganism in the biodegradation of PAHs in soil, and improve the principle of PAHs contaminated soil bioremediation.

多环芳烃（PAHs）微生物降解是土壤PAHs迁移转化至最终降解的主要途径，有关微生物对PAHs降解机制的报道主要针对整个微生物体而言，对胞外聚合物（EPS）的作用缺乏相关研究。申请人前期工作已筛选出PAHs高效降解菌并研究了EPS对芘降解效果的影响。本项目以两种高效降解菌EPS为研究对象，芘和苯并[a]芘为目标污染物，投加降解菌及EPS到PAHs污染土壤中，通过降解、吸附与模拟实验，研究EPS在PAHs降解酶释放过程中的作用、EPS作为微生物降解PAHs共代谢底物作用、EPS与土壤对PAHs竞争吸附，分析菌体及EPS中降解酶分布特征、EPS组分、微生物活性与PAHs降解效果之间的关系，揭示EPS在PAHs降解过程中的作用，明确EPS对PAHs降解效果的贡献。本项目实施将为阐释PAHs经菌体分泌EPS从土壤表面到菌体表面进行降解的迁移转化行为提供理论支持，完善PAHs污染土壤微生物修复原理。

多环芳烃（PAHs）微生物降解是土壤PAHs迁移转化至最终降解的主要途径，有关微生物对PAHs降解机制的报道主要针对整个微生物体而言，对胞外聚合物（EPS）的作用缺乏相关研究。本项目以高效降解菌EPS为研究对象，芘和苯并[a]芘为目标污染物，通过降解、吸附与模拟实验，研究EPS在PAHs降解酶释放过程中的作用、EPS作为微生物降解PAHs共代谢底物作用、EPS与土壤对PAHs竞争吸附。取得以下研究进展：.（1）确定了加热法是最高效的PAHs高效降解菌EPS提取方法，PAHs诱导影响了PAHs高效降解菌EPS的主要成分含量，特别是蛋白质，同时PAHs诱导也改变了EPS的微观结构。.（2）PAHs高效降解菌体及EPS中均含有多种PAHs关键降解酶，如双加氧酶，水解酶，和脱氢酶等。芘诱导和添加EPS均增加菌体中加氧酶基因拷贝数量，加入PAHs后，加氧酶基因拷贝量增加了2.5；加入PAHs和EPS后，加氧酶基因拷贝量增加了4.3。差异蛋白分析表明，菌体和EPS中均含有分子量在50kDa附近蛋白（具有双加氧酶活性），且EPS中蛋白含量随芘浓度增加（10-120mg/L）而降低。.（3） 证实了EPS能共基质促进菌体的生长和PAHs的降解。BM-EPS-PAHs、MM-EPS-PAHs培养体系中，分枝杆菌ETSA值分别为0.1μO2/g/min和0.9μO2/g/min，明显高于其它培养条件。分枝杆菌9.6×107CFU/kg，外加EPS 6661.51mg/kg时，土壤中芘和苯并[α]芘去除率各提高30%。.（4）发现EPS促进土壤中PAHs增溶，且与土壤表面PAHs形成竞争吸附。EPS存在情况下（264.3 mg/L）芘的溶解量8 h内由0.293 mg/L增加到0.368 mg/L；EPS（107.1 mg/L）在土壤颗粒表面的吸附量于10min达到最大值37.06 mg/L；EPS作用下，污染土壤中芘的解吸效果明显高于纯水相体系，解吸平衡时间为30h。