基于旋转电极生物膜反应器还原高氯酸盐的电子传递机制及微生物群落响应研究

Perchlorate pollution has affected drinking water safety and human health. The bio-electrochemical reactor (BER) which generated hydrogen on site by electrolysis of water for bio-reduction of perchlorate is an important method to remediate perchlorate-contaminated water. However, the electron transfer pathway and related mechanisms are still unclear. In this study, the river sediment of perchlorate pollution area was used as the microbial inoculums, and the Rotating Biofilm-Electrode Reactor (RBER) was developed to investigate the perchlorate bio-reduction process. The gas chromatography, ion chromatography, three-dimensional fluorescence spectroscopy, transmission electron microscope and atomic force microscopy technique were used to analysis hydrogen consumption, microbial hyphae conductivity and the role of electronic shuttle. We aim to reveal the pathway of electron transfer from cathode to terminal electron acceptor in perchlorate reduction process. Meanwhile, the high-throughput sequencing and metagenomics library-based technique was employed to analysis the main perchlorate-reducing bacteria and the key functional genes for reduction of perchlorate, which can lay the foundation for screening high-performance of perchlorate-reducing cultures in the future. This study will provide technical support to using nature microorganism for bioremediation of perchlorate-contaminated water.

高氯酸盐污染已影响到饮用水安全和人体健康。采用生物电化学反应器电解水原位产氢生物还原高氯酸盐是修复高氯酸盐污染水体的重要方法，但生物还原高氯酸盐的电子传递途径和机制尚不清楚。本项目拟采用高氯酸盐污染区域的河道底泥作为接种物，利用自主设计的双室旋转电极生物膜反应器为载体研究高氯酸盐生物还原为氯离子的过程。结合气相色谱、离子色谱、三维荧光光谱、透射电镜以及装载有导电探针的原子力显微镜分析高氯酸盐还原过程中氢气产生量及消耗量、电子穿梭体的作用、微生物菌丝间的电导率，揭示电子从阴极传递到末端电子受体高氯酸盐的途径；最后，基于高通量测序进行宏基因组学分析降解高氯酸盐的优势菌群和关键功能基因，为今后筛选培育高氯酸盐高效降解菌奠定基础。本项目有望为利用自然界中现存微生物修复高氯酸盐污染水体提供技术支撑。

本项目采集了世界著名的“花炮之乡”浏阳市内浏阳河的底泥，并利用自主设计的双室生物膜电极反应器（BER）对接种底泥进行培养，研究发现在BER阴极上富集的高氯酸盐还原菌生物膜，可以利用阴极产生的氢气作为电子供体，在高氯酸盐进水浓度10 mg/L条件下，对高氯酸盐降解效率达98.16%。通过高通量测序分析发现，BER中进水高氯酸盐浓度对微生物群落有重大影响，当高氯酸盐浓度低于10 mg/L时，降解高氯酸盐的主要功能微生物是拟杆菌和厚壁菌群。随着进水浓度增加到20 mg/L，变形菌迅速增长并在微生物群落结构中占据优势，其中，亚硝基单胞菌占比30%、单胞菌占比15%、热单胞菌占比9%、丛毛单胞菌占比8%。高氯酸盐在BER系统中主要降解途径是（1）H+在阴极电极表面接收电子产生氢气；（2）产生的氢气扩散到阴极室液体中，然后在磁力搅拌下通过液体的流动传输到附着在活性炭毡表面生长的高氯酸盐菌群（PRB）中；（3）高氯酸盐在PRB中被高氯酸盐还原酶（PCR）还原为氯酸盐，然后氯酸盐在氯酸盐歧化酶（CD）催化下转化为氯化物（Cl-）和分子氧（O2）。本研究结果可为利用浏阳河现存微生物修复高氯酸盐污染提供技术支撑。