碳纳米材料杂化促进层层自组装微囊菌剂对农田污染土壤中多环芳烃的降解

There is a large area of polycyclic aromatic hydrocarbons (PAHs) contaminated farmland in China now, which is potential threat to ecological security and human health. The effect of immobilized microbial inoculum on its remediation is remarkable. Considering the traditional microbial immobilization methods all have defects in some degrees (e.g. limit protection effect or bad mass transfer) which are adverse for microbial degradation of pollutants, this project aims to carbon hybridize layer by layer assembly (LBL) microcapsules using carbon nanomaterials to achieve immobilized PAH-degrading bacteria (Mycobacterium gilvum CP13) microcapsules, which can in-situ “simultaneous adsorption and biodegradation” of PAHs in contaminated farmland. The effects of different carbon nanomaterials on the enhancing bioremediation ability of LBL microcapsules were discussed. The effects of carbon nanomaterials on the biochemical and biochemical properties of the microorganism, as well as its intrinsic relationship with the degradation effectiveness, were investigated. The distribution/migration rules of PAHs on soil particle/water/LBL carbon hybrid microcapsule system were studied by “migration between different phase simulator”, and its relationship with the biodegradability was also clarified. So that the mechanism of “simultaneous adsorption and biodegradation” could be ascertained. The ecological influence of hybrid microcapsule immobilization system on the soil restoration was evaluated by means such as monitoring soil microbial community structure change. So that the mechanism of hybrid microcapsule promoting the degradation effect of PAHs contaminated soil was explored.

我国存在大面积多环芳烃（PAHs）污染农田土壤，潜在威胁生态安全与人类健康。固定化菌剂对其修复效果显著，但传统菌剂往往具有保护性能有限、传质性能较差等局限性。基于此，采用高吸附性能的碳纳米材料杂化改性层层自组装（LBL）微囊材料，并将其运用于PAHs高效降解菌（微黄分支杆菌CP13）的固定化，强化固定化体系对PAHs的捕获性能，使其能实现农田土壤PAHs的原位“吸附富集-强化降解”。探讨不同碳纳米材料强化LBL微囊的修复效果的有效性；探明碳纳米材料对固定降解菌生理生化性质的影响，分析其与降解有效性的内在联系；通过分相迁移模拟装置，解析PAHs在水/土壤颗粒/LBL碳材料杂化微囊体系中的迁移分配规律，明确其与降解效能的相互关系，探明吸附-降解同步作用机理；从土壤微生物群落组成等角度评估杂化微囊应用于农田土壤修复的生态影响，最终揭示出杂化微囊菌剂促进PAHs污染土壤修复效果的机制。

为提高多环芳烃(PAHs)污染土壤的微生物修复效率，常需对微生物进行固定化处理。但固定化处理后污染物的生物可利用性降低，在一定程度上限制了修复效果。利用载体对目标污染物的吸附作用，可以增大目标污染物与微生物的接触机会，提高目标污染物的降解效率。本研究采用具备高比表面积和强吸附特性的纳米碳、碳纳米管、石墨烯等碳纳米材料杂化改性来强化层层自组装（LBL）固定化体系对PAHs的捕获性能，提高其修复效果。结果表明，碳纳米材料的掺杂可成功显著提升LBL微囊菌剂对菲污染土壤的修复性能，其机制很可能为：一方面，碳纳米材料刺激菲污染土壤中具有有机物降解功能的微生物繁殖，改善了土壤中生物多样性；同时刺激了与促进细胞生长和生殖、催化活性、代谢、运输、改善细胞膜渗透性等功能相关的基因表达；刺激降解菌的与细胞生长、代谢、免疫、翻译后修饰、过氧化氢酶、蛋白质周转、维持细胞稳定、产生机体能量等相关的蛋白表达，从而使其表现出对菲更佳的降解性能和修复效果。另一方面，碳纳米材料在菲-水-土壤体系中的使用可使得原本在土壤中的菲源源不断的向碳相迁移，从而利于被碳上的微生物所捕获并利用。此外，本研究还探明LBL微囊固定化处理影响微生物的性能的机制有：一方面，微囊可有效减缓细菌的细胞膜通透性的增大速度及膜电位的降低速度及幅度，从而使得细胞的死亡速度及数量均得到一定程度的降低，对降解菌有着一定的保护作用；另一方面，EPS通过其中的蛋白质组分与微囊材料中CHI相互作用，结合生成稳定的复合物，而且复合物比原始EPS大幅增大了平均分子量，也扩张了原始EPS的Z-轴均方旋转半径和水力学半径，降低了EPS的内部密度，使得EPS结构舒展，构型变得疏松，从而提升传质和污染物的俘获效率，最终使得细菌降解性能提高。