铁锰氧化物对梭菌电子输出率的影响及机制
刘进超
学位类型硕士
2019-05-16
学位授予单位中国科学院研究生院
学位授予地点烟台
学位名称工程硕士
关键词电子输出率梭菌铁锰氧化物黄河三角洲种间直接电子传递
摘要黄河三角洲湿地是由黄河携带的泥沙冲淤而成，铁氧化物是湿地中的重要金属氧化物。近年来，有研究发现以Fe₃O₄为代表的铁氧化物可加强微生物互营关系，如产电细菌与产甲烷古菌之间的种间直接电子传递。然而，相比于确定的纯培养体系，自然环境中的微生物群落和代谢途径丰富多样，其中的电子传递机制更加复杂多变，从电子输出率的角度量化Fe₃O₄对自然环境中微生物种间电子传递的影响，相关报道还较少。因而，第一部分探究了铁氧化物（Fe₃O₄）对湿地微生物电子输出率的影响。据已有的研究报道，梭菌属微生物与产甲烷菌之间存在潜在的种间直接电子传递关系。黄河三角洲含有丰富的梭菌属微生物，且越来越多的梭菌被证实是具有胞外电子传递能力的发酵型异化金属还原菌。因而，黄河三角洲中,梭菌的电子输出可能与变价金属氧化物之间存在紧密的联系。为进一步了解变价金属氧化物对微生物电子输出的影响及机制，第二部分以梭菌作为研究对象，探究铁锰氧化物对其电子输出的影响，该研究增加了我们对于发酵型异化金属还原菌与变价金属氧化物之间相互作用的认识，有利于初步评估变价金属氧化物对黄河三角洲中微生物电子输出的影响。研究结果如下：
（1）探究了铁氧化物（Fe₃O₄）对湿地微生物电子输出率的影响。为了真实模拟自然环境，与以往研究中添加的单一碳源不同，本部分研究中以黄河三角洲地区的主要植物（芦苇）为碳源。结果显示，Fe₃O₄在“小时”级别里提高湿地土壤甲烷的产生速率。对乙酸、CO₂、CH₄等的化学计量关系分析以及电流密度测定表明，电子作为还原力驱动二氧化碳还原是甲烷产生的重要途径，导电性的Fe₃O₄加速了这一电子传递过程。进一步通过电子驱动二氧化碳还原的关系式，最终计算得Fe₃O₄将黄河三角洲湿地微生物电子输出率提升了202.67%。
（2）探究了铁锰氧化物（Fe₂O₃和MnO₂）对巴斯德梭菌DSM 525（Clostridium pasteurianum DSM 525）电子输出率的影响及机制。添加不同浓度Fe₂O₃和MnO₂到以葡萄糖为代谢底物且接种DSM 525的发酵体系内，通过监测DSM 525代谢产物积累量，以此计算DSM 525发酵过程中的电子输出率。结果显示，接种DSM 525的微生物燃料电池内可监测到电流产生，且最大电流密度达0.93 mA/m²；随着发酵的进行，发酵体系内Fe²⁺和Mn²⁺物质的量逐渐增多；添加Fe₂O₃和MnO₂分别使体系的葡萄糖消耗量最大提高了9.4%和7.7%，同时，产乙酸量提高了37.5%和25%，产丁酸量提高了22.7%和6.8%，产氢气量提高了21.6%和9.8%，而总电子输出率提高了24.3%和10.8%；铁锰氧化物实验组的pH值相比对照组无明显差异。Fe²⁺/Mn²⁺对梭菌电子输出率的影响结果显示，1.35/2.55 mmol/L Fe²⁺的加入使梭菌电子输出率提高了14.6%/9.3%，Mn²⁺未表现出促进作用。随着Fe²⁺/Mn²⁺浓度的增加，梭菌的电子输出率逐渐降低。以上结果表明，DSM 525具有电化学活性，可厌氧还原Fe₂O₃和MnO₂；铁锰氧化物通过增加葡萄糖消耗、缓冲pH值和微量元素释放提高微生物氢酶活性等方式提高DSM 525电子输出率。
综上所述，本论文探索了铁锰氧化物对微生物电子传递的影响。Fe₃O₄促进湿地中微生物种间直接电子传递，该研究将种间直接电子传递的研究范围从确定的微生物培养物扩展到湿地土壤中，并进一步从电子输出率的角度量化了Fe₃O₄对自然环境中微生物电子输出的影响，拓展了我们对于铁氧化物（Fe₃O₄）在自然界中影响微生物电子输出的认知。另一部分研究中，铁锰氧化物（Fe₂O₃和MnO₂）提高梭菌电子输出率，该研究增加了我们对于微生物与变价金属氧化物之间相互作用的认识。
其他摘要The wetland in the Yellow River Delta is formed by siltation of the sediment carried by the Yellow River, iron oxides are important metal oxides in the wetland. In recent years, iron oxides, represented by Fe₃O₄, have been reported to strengthen the microbial interaction, such as the direct interspecies electron transfer between electricity-producing bacteria and methanogens. However, compared with defined pure culture systems, the microbial communities and metabolic pathways in natural environment are diverse, and the electron transfer mechanisms are more complex and changeable. Little is known about quantifying the effect of Fe₃O₄ on interspecies electron transfer in natural environment from the perspective of electron output efficiency. Therefore, the effect of iron oxide (Fe₃O₄) on electron output efficiency of microorganisms in the wetland was explored in the first part. It has been reported that Clostridium spp. could potentially directly transfer electrons to methanogens. Clostridium is rich in the Yellow River Delta, and more and more Clostridia have been confirmed to belong to fermentative dissimilatory metal-reducing microorganisms with the ability of extracellular electron transfer. Therefore, there may be a close relationship between the electron output of Clostridium in the Yellow River Delta and multivalent metal oxides. In order to understand the effects and mechanisms of multivalent metal oxides on microbial electron output comprehensively and preliminarily evaluate the effects of multivalent metal oxides on microbial electron output in the Yellow River Delta, Clostridium sp. was taken as the research object to explore the effects of multivalent metal oxides on its electron output. The results are as follows.
(1) The effect of iron oxide (Fe₃O₄) on the electron output efficiency of microorganisms in the wetland was explored. In order to realistically simulate the natural environment, unlike the single carbon sources used in previous studies, the main plant (reed) in the Yellow River Delta was used as the carbon source in this study. The result showed that the rate of methane production was increased in the presence of Fe₃O₄ on an hour-long timescale. The stoichiometric relationship between acetate, CH₄ and CO₂ and the current density measurements indicated that electron as the reducing agent to drive the CO₂ reduction was the key pathway for methane production, and conductive Fe₃O₄ played a key role in stimulating electron transfer for methane production. Further, according to the stoichiometric relationship in electromethanogenesis, it was finally calculated that Fe₃O₄ increased the electron output efficiency of microorganisms in the Yellow River Delta wetland by 202.67%.
?(2) The impacts of iron and manganese oxides (Fe₂O₃ and MnO₂) on DSM 525’s electron output efficiency were explored in the second part. We added different concentrations of Fe₂O₃ and MnO₂ to DSM 525’s fermented system containing glucose. By detecting the accumulative metabolites of DSM 525, we calculated DSM 525’s electron output efficiency. The result showed that, the current could be detected by the microbial fuel cells inoculated with DSM 525, and the maximum current density was 0.93 mA/m². The amount of substance of Fe²⁺/Mn²⁺ gradually increased. The consumption of glucose in the fermented system was increased by 9.4% and 7.7%, meanwhile, acetate-producing was increased by 37.5% and 25.0%, and butyrate-producing was increased by 22.7% and 6.8%. Besides, hydrogen-producing was increased by 21.6% and 9.8%, and the calculated total electron output efficiency was increased by 24.3% and 10.8%. The pH values between control and experimental group were no significant difference. The effect of Fe²⁺ on the electron output of Clostridium showed that the total electron output efficiency was increased by 24.3%/10.8% when 1.35/2.55 mmol/L Fe²⁺ was added, however, Mn²⁺ had no promoting effect. As the concentration of Fe²⁺/Mn²⁺ increased, the electron output efficiency of Clostridium decreased gradually. In conclusion, DSM 525 has the capacity for generating electricity and reducing Fe₂O₃ and MnO₂. Addition of iron and manganese oxides could enhance DSM 525’s electron output efficiency by increasing glucose consumption, buffering pH values and release of the trace elements enhancing microbial hydrogenase activity.
In summary, in this thesis, the effects of iron and manganese oxides on microbial electron transfer were explored. Fe₃O₄ accelerated direct interspecies electron transfer in wetland soil. This study extends the research scope of direct interspecies electron transfer from defined microbial cultures to wetland soil, and quantifies the effect of Fe₃O₄ on microbial electron output in natural environment from the perspective of electron output efficiency, and expands our understanding of the effect of iron oxide (Fe₃O₄) on microbial electron output in nature. In other part of the thesis, iron and manganese oxides (Fe₂O₃ and MnO₂) enhanced the electron output efficiency of Clostridium. This study has increased our understanding of the interaction between microorganisms and multivalent metal oxides.
语种中文
文献类型学位论文
条目标识符http://ir.yic.ac.cnhttp://ir.yic.ac.cn/handle/133337/25304
专题海岸带生物学与生物资源利用重点实验室_海岸带生物学与生物资源保护实验室

推荐引用方式
GB/T 7714刘进超. 铁锰氧化物对梭菌电子输出率的影响及机制[D]. 烟台. 中国科学院研究生院,2019.


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