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题名: 可见光强化微生物胞外电子传递的性能与机制研究
作者: 张博
学位类别: 博士后
答辩日期: 2016-08
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 王爱杰
关键词: 可见光,Geobacter, Shewanella, 细胞色素C,胞外电子传递,染料敏化,激发态 ; Geobacter, Shewanella, c-type cytochromes, extracellular electron transfer, dye-sensitization, excited state
其他题名: Visible light enhanced bacterial extracellular electron transfer: performance and mechanism
学位专业: 环境科学与工程
中文摘要:       微生物胞外电子传递在元素的生物地球化学循环、污染物的迁移转化和污染物的生物降解及资源化等环境过程中有着举足轻重的地位。近年来,伴随着生物电化学系统的发展,胞外电子传递的相关研究在广度上和深度上都取得了长足的进步。胞外电子传递过程依赖胞外电子传递微生物外膜上所镶嵌的氧化还原活性蛋白细胞色素C。因此,当微生物以电极为电子受体进行胞外电子传递时,电极的电势与电流都受细胞色素C控制,这就造成了生物电化学系统阳极电势偏高及电流密度偏低这两大缺欠。针对这两个方面的问题,本研究尝试借鉴光催化研究中染料敏化过程的研究思路和手段,利用激发态载色子通常具有较低的电势进而促进界面间电子传递这个特点,检验利用可见光激发外膜细胞色素C提升微生物与半导体界面间胞外电子传递的效能;在此基础上,尝试利用染料作为电子传递的中介体,在可见光照射的条件下利用染料在其激发态,还原态和氧化态之间的转换提升胞外电子传递的速率。
      以胞外电子传递模式微生物Geobacter Sulfurreducens PCA为研究对象发现,镶嵌在微生物外膜的细胞色素C能够在活体细胞中响应可见光的激发,并以激发态促进胞外电子传递过程,表现在Geobacter Sulfurreducens PCA覆盖的TiO2电极的电流密度在可见光照射下提升了7倍,电极的开路电势下降了150 mV并且产生阳极电流的起始电位负移了超过270 mV。电极电流的变化与电势的变化均表明在激发态下,G. Sulfurreducens PCA与电极间的电子传递得到了较为明显的提升。值得一提的是,在活体细胞中可见光诱导的激发态细胞色素C并没有影响微生物的生理活性或是破坏细胞色素C的结构,推测可能是微生物在新陈代谢的过程中修复了激发态细胞色素C可能带来的损坏。
      基于此,进一步利用染料Z907敏化TiO2电极,并在电极上培养另一种胞外电子传递模式微生物Shewanella Oneidensis MR-1的生物膜,在可见光照射下,在低电极电势条件下测试了染料敏化促进胞外电子传递的效能。结果表明在可见光照射下,S. Oneidensis MR-1能够在-0.4V的偏压下利用敏化的TiO2电极高效进行胞外电子传递,而S. Oneidensis MR-1在导体电极上无论有无光照均不能在此偏压下产电。S. Oneidensis MR-1在敏化电极上的胞外电子传递经过了一个明显的延迟期后才逐渐上升至最大值,推测可能是因为这个过程中S. Oneidensis MR-1合成了界面电子传递所必须的电子传递中介体。
      针对生物电化学系统中生物阳极电势偏高与电流密度偏低两大缺欠,本研究通过引入染料敏化的光催化过程,利用可见光照射强化了微生物的胞外电子传递速率,降低了电极的电势,从而为进一步提升生物电化学系统的阳极性能提出了一种新思路。
英文摘要:     The bacterial extracellular electron transfer (EET) is of vital importance in a number of environmental processes, such as the biogeochemical cycling of metal elements, the fate and transport of recalcitrant pollutants and the resource recovery using biotechnologies. In recent years, the research in EET has been brought to a new level along with the development of bioelectrochemical systems. EET relies on the c-type cytochromes that intercalated on the outer membrane of exoelectrogenic bacteria, therefore, when the exoelectrogens use electrode as the electron acceptors, the electrode potential and current density are controlled by the outer membrane c-type cytochromes, which leads to relatively high working potential and limited current density. To solve these two problems, this study made an effort to apply the knowledge and techniques in the study of dye-sensitized photoelectrochemical cells to the bioelectrochemical systems. More specifically, the current study tried to: (1) use visible light to bring the ground state outer membrane c-type cytochromes to the excited state to enhance the interfacial electron transfer between bacteria and electrode, and (2) use commercially available dye as an electron shuttle, which can transfer the electrons from the bacteria and then inject the electrons to a higher energy band of the electrode under the excitation of visible light.
    This study used a model microorganism, Geobacter Sulfurreducens PCA to study the enhanced EET through excited state outer membrane c-type cytochromes. The existence of excited state outer membrane c-type cytochromes was first confirmed by the photoluminescence spectroscopy. It has been shown that upon excitation the EET rate can be enhanced by 7 fold, with the anodic onset potential being negatively shifted by more than 270 mV. These facts indicated that the EET between bacteria and the electrode was more thermodynamically favorable to proceed, through the excited state outer membrane c-type cytochromes. In addition, the Geobacter Sulfurreducens PCA remained viable during the excitation and the outer membrane c-type cytochromes maintained their structure, possibly through the metabolic activity of the bacteria.
    Based on the above mentioned results, a dye-sensitized bioanode has been developed to further improve the rate of EET. On the dye-sensitized bioanode, the dye (Z907) that adsorbed on the TiO2 particles shifts its state among excited state, reduced state and oxidized state to facilitate the electron transfer from bacteria to the TiO2. It has been demonstrated that the dye-sensitized electrode with the biofilm of Shewanella Oneidensis MR-1 on it could efficiently perform EET at an extremely low working potential, which is -0.4V. It has been observed that there was a lag phase after S. Oneidensis MR-1 inoculation before the dye-sensitized electrode could generate anodic currents, which could be explained by the fact that the system lacks the electron mediator right after the inoculation.
    In order to lower the working potential and increase the current density of the bioanode, it has been demonstrated that dye-sensitization type of electron transfer could increase the EET rate and lower the working potential of the anode. This study offered a new opportunity to further improve the EET and develop more efficient bioelectrochemical systems.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/37044
Appears in Collections:中科院环境生物技术重点实验室_学位论文

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Recommended Citation:
张博. 可见光强化微生物胞外电子传递的性能与机制研究[D]. 北京. 中国科学院研究生院. 2016.
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