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Syntrophic interactions between anode-respiring bacteria and non-anode-respiring bacteria in microbial electrochemical cells

机译：微生物电化学电池中阳极呼吸细菌与非阳极呼吸细菌之间的营养相互作用

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摘要

Microbial electrochemical cells (MECs), a promising technology for recovering value-added products from waste biomass and wastewater, require syntrophic interactions between anode-respiring bacteria (ARB) and non-ARB for high performance and versatile functionality. However, understanding of the syntrophic interactions is limited. Controlling the growth of unfavorable non-ARB, such as methanogens, is challenging, and the proliferation of these microorganisms seriously decreases energy recovery from MECs. Small-sized microbial fuel cells (MFCs), one kind of the MECs, have recently gained attention as renewable and portable power suppliers to small electronics. In spite of this potential, the serious deterioration of ARB’s catabolism in the absence of exogenous substrate limits the real-world application of small-sized MFCs. Additionally, MECs can be useful biosensors for various targets (e.g., volatile fatty acids, protons, and heavy metals), but the potential of sensing dissolved methane by anode biofilm has never been reported although methanogenesis and dissolved methane have been frequently observed in MECs. Therefore, the objective of this study was to explore the potentials of three new syntrophic interactions that can catalyze the applications of MECs to be (1) a sustainable anaerobic wastewater treatment technique, (2) portable power sources, and (3) biosensors for methane or methanogenesis detection. High current density of 10.0–14.6 A/m2 and high chemical oxygen demand (COD) removal up to 96% were obtained in an MEC fed with digestate at hydraulic retention time (HRT) of 4 day and 8 day. Volatile fatty acids (VFAs) became undetectable in the MEC effluent (HRT 8 day), except for low levels of acetate (4.16 ± 1.86 mg COD/l). Accumulated methane only accounted for 3.42% of removed COD. Pyrosequencing analyses showed abundant fermenters (Kosmotoga species) and homoacetogens (Treponema species) in anolytes. In the anode biofilm, propionate fermenters (Kosmotoga species and Syntrophobacter species), homoacetogens (Treponema species), and ARB (Geobacter species and Dysgonomonas species) were dominant. These results implied that syntrophic interactions among fermenters, homoacetogens, and ARB would enable MECs to maintain high current density and coulombic efficiency despite the presence of methanogens.Steady current density around 1.5 A/m2 in a dual-chamber MEC was sustained for over four days without exogenous electron donors. High efficiency, close to 100%, of electron recovery can be achieved once acetate was provided. The air-cathode MFC inoculated by this MEC showed stable anode-respiring activity over a seven-day starvation period. Nile red staining revealed that lipid-accumulating bacteria were abundant in the anode biofilm. Taken together, these results suggested that lipid-accumulating bacteria in syntrophy with ARB generated current without exogenous electron donors. This study implied that small-sized MFCs can be used as portable power sources in a discontinuous feeding manner. A long term of enrichment and growth of anode biofilm in MECs with dissolved methane, ~800 days, resulted in a syntrophy between Methanobacterium species and Geobacter species, which is the first anode-respiration-dependent anaerobic oxidation of methane (AOM) discovered so far. In this proposed syntrophy, Methanobacterium species anaerobically oxidize methane molecules and transfer electrons or certain reducing powers derived from methane to Geobacter species for anode respiration. No common electron mediators found in MECs were detected; instead, ethanol- or dimethyl ether-like compounds were detected. Electric current (2-12 mA/m2) was consistently produced from an MEC using methane as the sole carbon and electron source for over 440 days, whereas nitrogen gas sparging of the anolyte decreased the current to near zero. Deoxyribonucleic acid (DNA)-stable isotope probing (SIP) experiments employing 13CH4 combined with denaturing gradient gel electrophoresis (DGGE) demonstrated that the labeled carbon was found in DNA of dominant bacteria (Geobacter) and archaea (Methanobacterium). Fluorescence in situ hybridization (FISH) targeting the two genera clearly showed that Methanobacterium and Geobacter formed biofilm together on the surface of anode fibers. These results and the available information from literature support the explanation that AOM archaea and ARB built syntrophy for generating current from dissolved methane under anaerobic conditions.
机译：微生物电化学电池（MEC）是一种用于从废物生物质和废水中回收增值产品的有前途的技术，它需要阳极呼吸细菌（ARB）与非ARB之间的营养相互作用，以实现高性能和多功能性。但是，对同养相互作用的理解是有限的。控制不利的非ARB（如产甲烷菌）的生长具有挑战性，并且这些微生物的繁殖严重降低了MEC的能量回收率。小型微生物燃料电池（MFC）是一种MEC，最近作为小型电子设备的可再生和便携式电源供应商而受到关注。尽管有这种潜力，但在没有外源底物的情况下，ARB分解代谢的严重恶化限制了小型MFC的实际应用。另外，MEC对于各种靶标（例如，挥发性脂肪酸，质子和重金属）可以是有用的生物传感器，但是尽管在MEC中经常观察到甲烷生成和甲烷溶解，但从未报道过通过阳极生物膜感测甲烷溶解的潜力。因此，本研究的目的是探索三种新的同养相互作用的潜力，这些相互作用可以催化MEC的应用，它们是（1）可持续的厌氧废水处理技术，（2）便携式电源和（3）甲烷生物传感器或产甲烷检测。在4天和8天的水力停留时间（HRT）的消化物中加入MEC，可获得10.0-14.6 A / m2的高电流密度和高达96％的高化学需氧量（COD）去除。除乙酸盐含量低（4.16±1.86 mg COD / l）外，MEC废水（HRT 8天）中未检测到挥发性脂肪酸（VFA）。累积的甲烷仅占去除的COD的3.42％。焦磷酸测序分析表明，在阳极液中有丰富的发酵罐（Kosmotoga菌种）和纯乙酸原（Treponema菌种）。在阳极生物膜中，占主导地位的是丙酸盐发酵罐（科斯莫托加菌种和风化细菌菌种），高纯乙酸菌（生螺旋体菌属菌种）和ARB（土杆菌属菌种和假单胞菌属菌种）。这些结果表明，尽管存在产甲烷菌素，但发酵罐，高产乙酸菌和ARB之间的营养相互作用将使MEC保持高电流密度和库仑效率。双室MEC的稳定电流密度约为1.5 A / m2持续了四天。没有外源电子供体。提供乙酸盐后，可以实现接近100％的高电子回收率。用该MEC接种的空气阴极MFC在7天的饥饿期内表现出稳定的阳极呼吸活性。尼罗河红染色表明在阳极生物膜中脂质积累细菌丰富。综上所述，这些结果表明与ARB处于同养状态的脂质积累细菌在没有外源电子供体的情况下产生电流。这项研究表明，小型MFC可以不连续供电的方式用作便携式电源。大约800天后，溶解有甲烷的MEC中阳极生物膜的长期富集和生长导致甲烷杆菌属和Geobacter菌种之间的同质化，这是迄今为止发现的第一个依赖于阳极呼吸的甲烷厌氧氧化（AOM） 。在此拟议的同养中，甲烷杆菌属细菌厌氧氧化甲烷分子，并将电子或甲烷产生的某些还原能力转移至地球细菌菌种以进行阳极呼吸。在MEC中未发现常见的电子介体；而是检测到类似乙醇或二甲醚的化合物。使用甲烷作为唯一碳源和电子源的MEC持续产生了超过440天的电流（2-12 mA / m2），而阳极电解液的氮气喷射使电流降至接近零。使用13CH4结合变性梯度凝胶电泳（DGGE）进行的脱氧核糖核酸（DNA）稳定同位素探测（SIP）实验表明，在优势细菌（Geobacter）和古细菌（Methanobacterium）的DNA中发现了标记的碳。针对这两个属的荧光原位杂交（FISH）清楚地表明，甲烷杆菌和地球细菌在阳极纤维的表面上共同形成了生物膜。这些结果和文献中的可用信息支持了AOM古细菌和ARB建立了在厌氧条件下由溶解的甲烷产生电流的同养菌的解释。

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    Gao Yaohuan;

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  • 年度 2016
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  • 原文格式 PDF
  • 正文语种 en
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  • 入库时间 2022-08-20 20:13:38

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