Microorganism, microbial fuel cell composition, microbial fuel cell, microbial electrolysis cell composition and microbial electrolysis cells

Abstract

To provide a novel microorganism having higher current generating ability, a microbial fuel cell composition and microbial electrolysis cell composition comprising the microorganism, as well as a microbial electrolysis cell and microbial electrolysis cell using the microorganism.SOLUTION: Provided are: a microorganism, a Geobacter sp. strain 60473; a microbial fuel cell composition comprising the Geobacter sp. strain 60473 and an organic substance; a microbial fuel cell in which the Geobacter sp. strain 60473 is used to decompose the organic substance as a fuel; a microbial electrolysis cell composition comprising the Geobacter sp. strain 60473 and the organic substance; and a microbial electrolysis cell in which the Geobacter sp. strain 60473 is used to decompose the organic substance as the fuel.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a microorganism for use in a microbial fuel cell, and a microbial fuel cell using said microorganism. [Background technology]

[0002] As an aid in solving problems such as global warming and the depletion of natural resources, microbial electrochemical systems (BES), which are systems that produce energy and useful substances by electrochemically controlling the metabolism of microorganisms, are being actively developed. Electrochemically active bacteria (EAB), which can transfer electrons between electrodes, are one example of the microorganisms used in microbial electrochemical systems.

[0003] Microbial electrochemical systems include microbial fuel cells (MFCs), microbial electrolysis cells (MECs), and microbial electrosynthesis systems (MESs). Microbial fuel cells are devices that use the metabolic ability of microorganisms to convert organic fuels (substances that retain chemical energy) into electrical energy. Microbial fuel cells have attracted attention as devices that generate electricity while treating biomass waste and as energy-saving wastewater treatment devices (Non-Patent Document 1). Microbial electrolysis cells are devices that generate hydrogen and methane by reducing protons in water using an electric current generated by electrochemically active bacteria from organic fuels (Non-Patent Document 2). Microbial electrosynthesis systems are devices that supply electrons from a low-potential electrode to electrochemically active bacteria to synthesize useful substances from carbon dioxide, nitrogen, and the like, and are expected to become a process that will support humanity in the future when fossil fuels are depleted (Non-Patent Document 3). As described above, microbial electrochemical systems include various devices, and in order to implement them in society, it is desirable to improve their performance.

[0004] In each device of a microbial electrochemical system, it is said that the performance of the device is determined by the efficiency of electron transfer between the electrochemically active bacteria and the electrode, which is evaluated by the current value (current density) per electrode area. In fact, it has been reported that the transfer of electrons between the electrochemically active bacteria and the electrode is the rate-limiting step in a microbial electrochemical system (Non-Patent Document 4).

[0005] As a method for enhancing the activity (power generation capacity) of electrochemically active bacteria, a method (bioaugmentation) is known in which artificially cultured foreign microorganisms (e.g., electrochemically active bacteria) are introduced as a microbial preparation into the microbial ecosystem in the device to improve the performance of the device. For example, a case has been reported in which the rise of current generation was accelerated by introducing a microbial consortium containing electrochemically active bacteria into a microbial fuel cell for wastewater treatment (Non-Patent Document 5). However, in this example, the current value after the current rise was equivalent to that of a microbial fuel cell that was not bioaugmented, and further performance improvement is desired. In addition, it is known that bioaugmentation, in which Geobacter sulfurreducens strain YM18 is added to the anode electrode of a microbial fuel cell, promotes current generation and hydrogen generation (Non-Patent Document 6).

[0006] As a method for increasing the amount of electricity generated (output energy) by a microbial fuel cell, for example, there is a method using a compound (electron mediator) that transfers electrons, such as HNQ (2-hydroxy-1,4-naphthoquinone), and as an improvement of this method, a method has been reported in which electrochemically active bacteria that are active even in an environment without light are used and porphyrin is used as the electron mediator (Patent Document 1). In addition, in order to enhance the activity of electrochemically active bacteria, a method has been reported in which the activity of the electrochemically active bacteria is adjusted by a bacteriophage that uses the electrochemically active bacteria as a host (Patent Document 2). However, the use of a mediator requires continuous artificial addition because it disappears due to decomposition by microorganisms, and this increases the cost in practical use. In addition, the use of bacteriophages has the problem that it is costly to authenticate the phage to confirm that it does not have genes involved in pathogenicity and drug resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-218690 A [Patent Document 2] JP 2020-14418 A [Non-patent literature]

[0008] [Non-Patent Document 1] Shohei Yamada and Kazuya Watanabe, "Fundamentals and Applications of Microbial Fuel Cells," Fuel Cells, Fuel Cell Development Information Center (publisher), 2020, Vol. 20, pp. 33-38. [Non-Patent Document 2] Ichita Ochiai et al., "Hydrogen production using microbial electrolysis tanks," Power generation and hydrogen production using microorganisms, CMC Publishing, 2021, pp. 201-206. [Non-Patent Document 3] Yamada et al., Frontiers in Chemistry, 2022, vol.9, Article 805597. [Non-Patent Document 4] Lu and Ren, Bioresource Technology, 2016, vol.215, p.254-264. [Non-Patent Document 5] Yanuka-Golub et al., mBio, 2021, vol.12, e03629-20. [Non-Patent Document 6] Ochiai et al., Bioresource Technology, 2023, vol.386, 129508. [Non-Patent Document 7] Yoshitsu et al., Microorganisms, 2023, vol.11, 598. Summary of the Invention [Problem to be solved by the invention]

[0009] In order to improve the performance of each device in a microbial electrochemical system, electrochemically active bacteria capable of achieving a high current density are desired. For example, in the example of bioaugmentation reported in Non-Patent Document 4, it has not yet been possible to sufficiently increase the activity of the electrochemically active bacteria in the microbial electrochemical system, and this is thought to be due to the fact that electrochemically active bacteria with sufficiently high electrochemical activity have not been introduced. In addition, the YM16 strain used in the microbial fuel cell reported in Non-Patent Document 6 reduces the amount of generated current as the power generation time increases. For this reason, electrochemically active bacteria capable of stable power generation for a longer period of time are also desired.

[0010] The present invention aims to provide a novel microorganism having a higher current generation capability, a composition for a microbial fuel cell and a composition for a microbial electrolysis cell containing the microorganism, and a microbial fuel cell and a microbial electrolysis cell using the microorganism. [Means for solving the problem]

[0011] As a result of extensive research to solve the above problems, the inventors discovered that a novel microorganism isolated and identified from mud along the shores of Lake Suwa is a novel electrochemically active bacterium with high current generation capability and is suitable for use in microbial fuel cells and microbial electrolysis cells, thereby completing the present invention.

[0012] The microorganism, composition for a microbial fuel cell, microbial fuel cell, composition for a microbial electrolysis cell, and microbial electrolysis cell according to the present invention are as follows. [1] A microorganism, Geobacter sp. 60473 (NITE BP-03900). [2] The microorganism according to [1] above, for use in a microbial fuel cell. [3] A composition for a microbial fuel cell, comprising Geobacter sp. 60473 (NITE BP-03900) and organic matter. [4] The composition for a microbial fuel cell according to [3], further comprising electrochemically active bacteria other than Geobacter sp. strain 60473. [5] The composition for a microbial fuel cell according to [3] or [4], wherein at least a portion of the organic matter is sludge. [6] A microbial fuel cell in which Geobacter sp. 60473 (NITE BP-03900) is used to decompose organic matter for fuel. [7] A liquid containing organic matter and a water-based liquid. A container for containing the liquid; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed with at least one surface in contact with the liquid; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900), which is contained in the liquid and breaks down the organic matter and emits electrons; A microbial fuel cell comprising: [8] The container is partitioned by a membrane selectively permeable to protons into a chamber in which the anode electrode is disposed and a chamber in which the cathode electrode is disposed; The microbial fuel cell of [7], wherein the organic matter and the Geobacter sp. 60473 strain are contained in a liquid contained in a tank in which the anode electrode is placed. [9] The microbial fuel cell of [7], wherein one surface of the cathode electrode is in contact with the liquid in the container and the other surface is in contact with the atmosphere.

[10] A container containing organic mud and a liquid mainly composed of water; a conductive anode electrode disposed in the organic mud; a conductive cathode electrode disposed in or on the liquid surface; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) contained in the organic mud, A microbial fuel cell comprising:

[11] A conductive anode electrode disposed in the organic mud; A conductive cathode electrode disposed in the water or on the water surface; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) attached to the anode electrode; Microbial fuel cells are equipped with a microbial fuel cell that is installed to purify organic sludge at the bottom of rivers or lakes.

[12] The microbial fuel cell of

[10] or

[11] , further comprising a supply pipe for supplying a substrate and / or the Geobacter sp. 60473 strain from the outside to the inside of the organic mud.

[13] The microbial fuel cell of

[12] , wherein the supply pipe is branched so as to supply a plurality of dispersed components in the planar direction of the anode electrode in the liquid or the water.

[14] The microbial fuel cell of any of [7],

[10] , and

[11] , wherein the anode electrode is a conductive metal material having a lower internal electrical resistance than the cathode electrode.

[15] The microbial fuel cell of any of [7],

[10] , and

[11] , wherein the surface area of ​​the cathode electrode is at least 1.1 times larger than the surface area of ​​the cathode electrode.

[16] The microbial fuel cell of

[10] or

[11] , wherein the cathode electrode and the anode electrode are arranged in parallel, one end of the cathode electrode and one end of the anode electrode arranged on the same side as the one end are connected to a support extending in the depth direction of the liquid or water, the cathode electrode and the anode electrode are fixed and supported in an adjustable manner while maintaining a gap according to the depth, and the bottom side of the anode electrode is provided with an installation fixing portion protruding in the depth direction.

[17] A composition for a microbial electrolysis cell, comprising Geobacter sp. 60473 (NITE BP-03900) and organic matter.

[18] The composition for a microbial electrolysis cell according to

[17] , further comprising electrochemically active bacteria other than Geobacter sp. strain 60473.

[19] The composition for a microbial electrolysis cell according to

[17] or

[18] , wherein at least a portion of the organic matter is sludge.

[20] A microbial electrolysis cell in which Geobacter sp. 60473 (NITE BP-03900) is used to decompose organic matter for fuel.

[21] A liquid containing organic matter and a water-based liquid. A container for containing the liquid; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed in contact with the liquid; a potential control device having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; and Geobacter sp. 60473 (NITE BP-03900), which is contained in the liquid and breaks down the organic matter to emit electrons.

[22] The container is partitioned by a membrane selectively permeable to protons into a chamber in which the anode electrode is disposed and a chamber in which the cathode electrode is disposed; The microbial electrolysis cell of

[21] , wherein the organic matter and the Geobacter sp. 60473 strain are contained in a liquid contained in a tank in which the anode electrode is placed.

[23] A container containing organic mud and a liquid mainly composed of water; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed in the liquid; a potential control device having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) contained in the organic mud, A microbial electrolysis cell comprising:

[24] The microbial electrolysis cell of

[23] , further comprising a supply pipe for supplying a substrate and / or the Geobacter sp. 60473 strain from the outside to the inside of the liquid.

[25] The microbial electrolysis cell of

[24] , wherein the supply pipe is branched so that the liquid can be supplied to the anode electrode or the cathode electrode in a plurality of dispersed forms.

[26] The microbial electrolysis cell of any of

[21] ,

[23] , and

[24] , wherein the anode electrode is made of a conductive material having an internal electrical resistance lower than that of the cathode electrode.

[27] The microbial electrolysis cell of any of

[21] ,

[23] , and

[24] , wherein the surface area of ​​the cathode electrode is at least 1.1 times larger than the surface area of ​​the cathode electrode. Effect of the Invention

[0013] According to the present invention, it is possible to provide a microorganism having extremely high electric current generating capacity and hydrogen generating capacity. Furthermore, by using the microorganism, it is possible to provide a microbial fuel cell having high power generation efficiency and a microbial electrolysis cell having high electrolysis efficiency. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a microbial fuel cell equipped with a microbial supply device. [Diagram 2] FIG. 2 is a schematic diagram of one embodiment of a microbial fuel cell with a support device to facilitate movement. [Diagram 3] FIG. 3 is a schematic diagram of one embodiment of a three-pole, single-chamber type microbial electrolysis cell. [Figure 4] FIG. 2 is a schematic diagram showing the structure of a mud cell used in isolating strain 60473 in Example 1. [Diagram 5] FIG. 1 shows the results of measuring the current generated over time when strain 60473 and strain PCA were inoculated in an electrochemical cell using a graphite felt electrode as the working electrode in Example 1. [Figure 6] FIG. 1 shows the results of measuring the current generated over time when strain 60473 and strain PCA were planted in an electrochemical cell using a glassy carbon electrode as the working electrode in Example 1. [Figure 7] FIG. 2 shows the results of measuring the fluorescence intensity of a glassy carbon electrode by DAPI staining after completion of a current generation experiment in Example 1. [Figure 8] FIG. 1 shows the phylogenetic relationship between strain 60473 and closely related strains as shown by molecular phylogenetic analysis using the 16S rRNA gene in Example 1. [Figure 9]FIG. 1 shows the phylogenetic relationship between the 60473 strain and closely related strains as shown by molecular phylogenetic analysis using the gyrB gene in Example 1. [Figure 10] FIG. 13 shows the results of polarization analysis of a mud battery into which strain 60473 was added in Example 2. [Figure 11] FIG. 13 shows the results of polarization analysis of a mud battery in which the 60473 strain was not introduced in Example 2. [Figure 12] FIG. 12 is a diagram showing the maximum power density (Pmax mW / m2) calculated from the polarization analysis results shown in FIGS. 10 and 11 in Example 2. [Figure 13] FIG. 13 shows the results of measuring the current generated over time when strain 60473, strain PCA, strain KN400, or strain YM18 was planted in an electrochemical cell using a graphite felt electrode as a working electrode in Example 3. [Figure 14] FIG. 13 shows the results of measuring the maximum current density of the current generated when the 60473 strain, the PCA strain, the KN400 strain, or the YM18 strain was planted in an electrochemical cell using a graphite felt electrode as a working electrode in Example 3. [Figure 15] FIG. 13 shows the results of measuring the current generated over time when strains 60473, PCA, KN400, or YM18 were planted in an electrochemical cell using a glassy carbon electrode as the working electrode in Example 3. [Figure 16] FIG. 13 shows the results of measuring the maximum current density of the current generated when strains 60473, PCA, KN400, or YM18 were planted in an electrochemical cell using a glassy carbon electrode as the working electrode in Example 3. [Figure 17] FIG. 13 shows the results of measuring the affinity for graphite (GAI) of the 60473 strain, the PCA strain, the KN400 strain, and the YM18 strain in Example 3. [Figure 18] FIG. 13 shows the results of measuring the cellular hydrophobicity (HPI) of the 60473, PCA, KN400, and YM18 strains in Example 3. [Figure 19]FIG. 13 shows the results of measuring the cytochrome content (CCI) of the 60473 strain, the PCA strain, the KN400 strain, and the YM18 strain in Example 3. [Figure 20] FIG. 1 shows the results of measuring the current generated over time in electrolytic cells inoculated with strain 60473 (MEC3 and MEC4) and in electrolytic cells not inoculated with strain 60473 (MEC1 and MEC2) in Example 4. [Figure 21] FIG. 13 is an enlarged view showing the results of measuring the current generated over time in electrolysis cells (MEC1 and MEC2) not inoculated with strain 60473 in Example 4. [Figure 22] FIG. 1 shows the bacterial composition of the biofilm formed on the surface of the working electrode (anode electrode) after operation of the electrolytic cells (MEC3 and MEC4) inoculated with the 60473 strain and the electrolytic cells (MEC1 and MEC2) not inoculated with the 60473 strain in Example 4. [Figure 23] FIG. 13 shows the results of measuring the current generated over time in electrolytic cells inoculated with strain 60473 (60473_1 and 60473_2) and in electrolytic cells not inoculated with strain 60473 (NB_1 and NB_2) in Example 5. [Figure 24] 1 shows current-voltage curves obtained by cyclic voltammetry (CV) of electrolytic cells inoculated with strain 60473 (60473_1 and 60473_2) and electrolytic cells not inoculated with strain 60473 (NB_1 and NB_2) in Example 5. [Diagram 25] FIG. 13 shows the results of measuring the voltage (V) of each reactor over time in Example 6. [Figure 26] FIG. 13 shows the results of polarization analysis of MFC reactors (60473_1 and 60473_2) into which strain 60473 was introduced in Example 6. [Figure 27] FIG. 13 shows the results of polarization analysis of MFC reactors (NB_1 and NB_2) in which strain 60473 was not added in Example 6. [Figure 28] FIG. 28 shows the maximum power density (Pmax mW / m2) calculated from the polarization analysis results shown in FIGS. 26 and 27 in Example 6. [Figure 29] In Example 6, current-voltage curves obtained by CV of MFC reactors (60473_1 and 60473_2) inoculated with strain 60473 and MFC reactors (NB_1 and NB_2) not inoculated with strain 60473 are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In the present invention and the present specification, "X 1 ~X 2 (X 1 and X 2 X 1 <X 2 "X 1 More than X 2 "Less than or equal to" means a numerical range.

[0016] [Microorganisms for microbial fuel cells] A microorganism according to one embodiment of the present invention is Geobacter sp. 60473 (hereinafter, sometimes referred to as "60473 strain"). The 60473 strain is a novel electrochemically active bacterium isolated and identified from mud on the shore of Lake Suwa, which decomposes organic matter and emits electrons. As shown in Example 1 below, the results of genome analysis showed that the known closest relative of the 60473 strain was Geobacter sulfurreducens PCA strain (hereinafter, sometimes referred to as "PCA strain"), which is a type strain of Geobacter sulfurreducens, which is widely used as an electrochemically active bacterium. The inventors of the present invention have deposited the 60473 strain at the Patent Microorganism Deposit Center of the National Institute of Technology and Evaluation (Room 122, 2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture). The accession number of Geobacter sp. strain 60473 is NITE BP-03900 (accession date: June 8, 2023).

[0017] The 60473 strain is a flagellated gram-negative anaerobic bacillus, a type of iron-reducing bacteria that obtains energy by reducing iron (III) ions to oxidize acetate to carbon dioxide. The 60473 strain can be cultured in the same manner as other Geobacter bacteria. For example, the 60473 strain can be cultured in a medium containing necessary minerals and vitamins in an anaerobic environment at 10 to 40°C. The anaerobic environment in which the 60473 strain is cultured is not particularly limited as long as the oxygen gas concentration is 0.01% (v / v) or less. The 60473 strain can be cultured in an environment controlled to a nitrogen gas concentration of 99.99% (v / v) or more, preferably 99.999%. Cultivation in such an anaerobic environment can be performed by using an anaerobic bacteria culture system such as Anaeropack Pouch (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0018] The medium used for culturing the 60473 strain may contain necessary minerals and vitamins, and may be any medium or modified medium commonly used for culturing Geobacter sulphurducens and other Geobacter species, such as DSM826 medium (manufactured by DSMZ). The 60473 strain may be cultured in a liquid medium or an agar medium. Since Geobacter sulphurducens is a soil bacterium, the 60473 strain may also be cultured in soil or sludge. The 60473 strain can also be cultured in an anaerobic environment where organic matter is abundant.

[0019] The 60473 strain has a very high power generation capacity, and its current generation capacity in an electrochemical cell is higher than that of the PCA strain. Therefore, by using the 60473 strain as an electrochemically active bacterium, a microbial fuel cell with a high power generation capacity can be produced. Furthermore, the 60473 strain, like other electrochemically active bacteria, is also useful as an electrochemically active bacterium for use in other microbial electrochemical systems other than microbial fuel cells, such as microbial electrolysis cells and microbial electrosynthesis systems.

[0020] The 60473 strain has a very high affinity for graphite (GAI). Therefore, the 60473 strain is suitable for forming a biofilm on the surface of graphite, and is particularly suitable as an electrochemically active bacterium used in a microbial fuel cell or a microbial electrolysis cell that uses a conductive carbon-based anode electrode mainly composed of carbon or graphite. The GAI of the 60473 strain is 60 to 80%, preferably 65 to 80%. The GAI of microorganisms including the 60473 strain can be measured by the method shown in the Examples below.

[0021] The 60473 strain has a high cell hydrophobicity (HPI). Therefore, it has good adhesion to hydrophobic electrodes such as carbon-based electrodes and easily forms a biofilm on the surface of the hydrophobic electrode. The HPI of the 60473 strain is 50 to 90%, preferably 60 to 90%, and more preferably 65 to 90%. The HPI of microorganisms including the 60473 strain can be measured by the method shown in the Examples below.

[0022] The 60473 strain has a high cytochrome content (CCI) per protein (mass). Cytochrome is a general term for proteins that have hemes (containing iron atoms in the form of heme groups) bound to oxidizable iron, and is broadly classified into cytochromes a, b, c, d, etc., depending on the type and binding mode of hemes. Since cytochromes are molecules related to the extracellular electron transfer ability, this high CCI is presumably one of the reasons why the 60473 strain has excellent power generation ability. The 60473 strain has a CCI of 0.75 to 1.00 / mg. The CCI of microorganisms including the 60473 strain can be measured by the method shown in the Examples below.

[0023] When the 60473 strain is used as an electrochemically active bacterium in a microbial fuel cell, it may be used alone, or may be used in combination with other electrochemically active bacteria, and is also preferably used in combination with other microorganisms other than electrochemically active bacteria. For example, by using anaerobic bacteria capable of producing acetic acid in combination, the acetic acid that is reduced by the proliferation of the 60473 strain is supplied, so that the culture period during which the 60473 strain exerts its power generation ability can be extended.

[0024] The 60473 strain is also suitable as an active ingredient of a microbial preparation added to a microbial fuel cell by bioaugmentation. The microbial preparation for bioaugmentation can be a culture of the 60473 strain, a bacterial cell precipitated by centrifuging the culture, or a composition obtained by mixing these with other additives (e.g., excipients, etc.) as necessary, and the composition can be further prepared into a granular material. The 60473 strain bacterial cell can also be suspended in water or a culture medium, and other components can be further added as necessary to form a suspension composition. The microbial preparation for bioaugmentation may contain one or more microorganisms other than the 60473 strain. Examples of such microorganisms include anaerobic acetogenic bacteria.

[0025] [Composition for microbial fuel cells] The composition for microbial fuel cells in this embodiment contains the 60473 strain and an organic matter, and is used as an organic matter that serves as fuel for a microbial fuel cell, or is added to the fuel. The composition for microbial fuel cells can also be used as a microbial preparation for bioaugmentation. The form of the composition for microbial fuel cells in this embodiment is not particularly limited, and may be a solid such as granules or lumps, a paste, a gel, or a suspension.

[0026] The organic matter contained in the composition for microbial fuel cells in this embodiment is not particularly limited as long as it can be used as fuel for the microbial fuel cell, and biomass is preferably used, but it may be a chemically synthesized organic matter, or a fossil fuel or a processed product thereof. The organic matter contained in the composition for microbial fuel cells in this embodiment is preferably an organic matter derived from waste biomass such as food waste, agricultural residues, livestock manure, sewage sludge, bottom mud (organic mud at the bottom) of rivers and lakes, wood waste, paper waste, and wastewater. The organic matter contained in the composition for microbial fuel cells may be a mixture of organic matter derived from multiple biomasses.

[0027] The composition for microbial fuel cells in this embodiment may contain one or more microorganisms other than the 60473 strain. The microorganism may be an electrochemically active bacterium or may be other than an electrochemically active bacterium. In addition, any microorganism that can grow in an environment in which the 60473 strain can grow may be used, and is preferably an anaerobic bacterium, but may also be a microaerobic bacterium. Examples of the microorganism other than the 60473 strain contained in the composition for microbial fuel cells include electrochemically active bacteria and anaerobic acetic acid-producing bacteria.

[0028] [Microbial fuel cell] The microbial fuel cell in this embodiment is characterized in that the 60473 strain is used to decompose the organic matter that is the fuel. In the microbial fuel cell in this embodiment, the microorganisms used to decompose the organic matter may be only the 60473 strain, or the 60473 strain may be used in combination with other microorganisms. By using the 60473 strain in combination with anaerobic acetic acid-producing bacteria, acetic acid essential for power generation by the 60473 strain is stably supplied, and power generation by the 60473 strain can be stably performed for a longer period of time. In addition, by using a wide variety of microorganisms that decompose organic matter in combination, the organic matter of the fuel can be efficiently decomposed to a state that is easy for the 60473 strain to use. In addition, it is also preferable to use electrochemically active bacteria other than the 60473 strain in combination, since the power generation efficiency for the fuel organic matter can be increased.

[0029] In the microbial fuel cell of this embodiment, the amount of the 60473 strain used is not particularly limited, and is appropriately adjusted in consideration of the type and concentration of the organic matter used as fuel, the type of the anode electrode, whether or not it is attached to the anode electrode, etc. When the 60473 strain is dispersed in a liquid containing an organic matter, the amount of the 60473 strain per 1 g of the liquid can be, for example, 10,000 to 100,000,000 cells / g, and preferably 100,000 to 10,000,000 cells / g. When the 60473 strain is attached to the anode electrode, the amount of the 60473 strain per 1 cm of the surface area of ​​the anode electrode can be, for example, 10,000 to 10,000,000 cells / g. 2The amount of 60473 strain per gram can be, for example, 10,000 to 100,000,000 cells / g, and is preferably 100,000 to 10,000,000 cells / g.

[0030] In the microbial fuel cell of this embodiment, when the 60473 strain is used in combination with other electrochemically active bacteria, the ratio of the amount of the 60473 strain to the total amount of the electrochemically active bacteria in the microbial fuel cell is not particularly limited, and is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more. Since the 60473 strain has a high power generation capacity, even if a small amount is added to a microbial fuel cell using conventional electrochemically active bacteria, the effect of increasing the power generation can be expected.

[0031] The power generation capacity of the 60473 strain decreases as the time of use in the cell increases. Therefore, in the microbial fuel cell of this embodiment, it is preferable to newly supply the 60473 strain at the timing when the power generation capacity of the 60473 strain decreases after the start of operation of the cell. Anaerobic acetic acid-producing bacteria and other microorganisms can also be supplied together with the 60473 strain.

[0032] The timing of newly supplying the 60473 strain can be determined, for example, by monitoring the transition of the generated voltage of the microbial fuel cell. In the microbial fuel cell, the generated voltage stabilizes after a while from the start of operation. Using the generated voltage value in a stable state (stable generated voltage value) as a reference, when the generated voltage value falls below a preset threshold value (for example, 70% of the stable generated voltage value), newly supplying the 60473 strain allows stable power generation for a long period of time. The 60473 strain may be newly supplied at predetermined time intervals from the start of operation of the cell.

[0033] As the microbial fuel cell in this embodiment, the 60473 strain is used, and it is sufficient to have an anode electrode and a cathode electrode, which are essential components of a cell, a resistor through which electrons flow connected to both electrodes, and an organic substance as a fuel, and there is no particular limitation on other structures. Specifically, the microbial fuel cell in this embodiment includes a liquid containing organic matter as a main component, a container for containing the liquid, a conductive anode electrode disposed in the liquid, a conductive cathode electrode disposed with at least one surface in contact with the liquid, and a resistor through which electrons flow, one end of which is connected to the anode electrode and the other end of which is connected to the cathode electrode. Microorganisms including the 60473 strain are contained in the liquid in which the anode electrode is disposed. The organic matter used as the fuel may be the same as the organic matter contained in the composition for microbial fuel cells. In the microbial fuel cell in this embodiment, it is preferable that the organic matter contains phosphorus, nitrogen, and sulfide.

[0034] On the anode electrode side, the organic matter of the fuel is decomposed by the microorganisms to produce carbon dioxide, and during the reaction, the electrochemically active bacteria such as the 60473 strain release electrons. The anode electrode is not particularly limited as long as it is an electrode made of a conductive material that can receive electrons produced by the electrochemically active bacteria and transfer them to the cathode electrode through a resistor. In the microbial fuel cell of this embodiment, a conductive carbon-based anode electrode mainly composed of carbon or graphite is preferred because of its good adhesion to microorganisms, and an anode electrode made of carbon cloth (a cloth woven from carbonized fibers obtained by burning petroleum or acrylic fibers) is more preferred because of its large surface area.

[0035] The 60473 strain tends to adhere easily to smooth surfaces, and can also be attached to metal surfaces. In addition, metal electrodes have a lower internal electrical resistance than graphite electrodes, and can suppress a decrease in power generation efficiency. Therefore, in the microbial fuel cell of this embodiment, it is also preferable that the anode electrode is a conductive metal material having a lower internal electrical resistance than the cathode electrode. By using an anode electrode made of a metal such as stainless steel, iron, or magnesium and having the 60473 strain attached to its surface, a microbial fuel cell with higher power generation efficiency can be obtained.

[0036] In the cathode electrode, a reduction reaction occurs between the electrons received from the anode electrode via a resistor, a compound that acts as an oxidant (electron acceptor), and protons that have diffused from the anode electrode. The cathode electrode can be an electrode in which a catalyst for the reduction reaction, such as platinum, is applied to a conductive material. As the conductive material that constitutes the cathode electrode, a carbon-based material mainly composed of carbon or graphite is preferably used in terms of corrosion resistance, etc.

[0037] The size of the anode electrode and the cathode electrode is not particularly limited. The size of both electrodes may be the same or different. In a microbial fuel cell, the performance of the cathode electrode decreases as the operation continues. For this reason, it is preferable that the area of ​​the cathode electrode is larger than the area of ​​the anode electrode, and a structure in which the area of ​​the cathode electrode is 1.1 times or more larger than the area of ​​the anode electrode is more preferable. By increasing the area of ​​the cathode electrode, the operating time of the microbial fuel cell can be increased. In particular, in the case where the microbial fuel cell in this embodiment is a sediment microbial fuel cell installed to purify the bottom mud of a river or lake, the longer the operating time, the more the proliferation of the 60473 strain can be promoted, which is advantageous for purifying the bottom mud.

[0038] The resistor, one end of which is connected to the anode electrode and the other end of which is connected to the cathode electrode, is not particularly limited as long as it is a member that allows electrons to flow from the anode electrode to the cathode electrode due to the potential difference between the chemical reaction caused by microorganisms in which carbon dioxide is generated from organic matter on the anode electrode side and electrons are released, and the reduction reaction occurring on the cathode electrode side, and can be appropriately selected from resistors commonly used in batteries. The resistor may have resistance throughout from the connection part with the anode electrode to the connection part with the cathode electrode, but it is preferable that the connection part with the anode electrode to the connection part with the cathode electrode is made of a conductive material such as a titanium wire with a small internal resistance, and an external resistor that shows sufficient resistance is provided in the middle. The external resistor is preferably a variable resistor because it can be adjusted according to the state of the fuel and the state of the microorganisms. The resistor and the external resistor are held and fixed on the cathode electrode, and are arranged in a state where they can be easily seen on the liquid (liquid surface).

[0039] The microbial fuel cell in this embodiment may be a two-tank microbial fuel cell or a single-tank microbial fuel cell. The structure and members of the two-tank microbial fuel cell and the single-tank microbial fuel cell may be the same as those used in known two-tank microbial fuel cells and single-tank microbial fuel cells.

[0040] In the case of a two-tank microbial fuel cell, a container that contains a liquid mainly composed of water containing organic matter is divided into a tank (anode tank) in which the anode electrode is disposed and a tank (cathode tank) in which the cathode electrode is disposed, by a membrane that is selectively permeable to protons. The membrane that is selectively permeable to protons is mainly H + A proton exchange membrane (PEM) that is selectively permeable to the 60473 strain can be used. The organic matter and the 60473 strain are contained in a liquid contained in the anode tank.

[0041] In the case of a two-tank microbial fuel cell, the amount of oxygen contained in the liquid contained in the anode tank is preferably maintained at about 2 to 10% (v / v) of the amount of oxygen contained in the liquid contained in the cathode tank. In order to maintain this oxygen concentration gradient, it is preferable that the liquid in the cathode tank also contains an oxidizing agent that reacts with protons as an oxygen supply source. Potassium ferricyanide, manganese oxide, etc. are used as the oxidizing agent.

[0042] In the case of a one-tank microbial fuel cell, the cathode electrode is disposed with one surface in contact with the liquid in the container and the other surface in contact with the atmosphere. Oxygen from the atmosphere is taken in from the surface of the cathode electrode in contact with the atmosphere, and a reduction reaction takes place. For example, the cathode electrode can be placed so that it floats on the surface of the liquid in the container. It is preferable that a water-repellent layer is provided on the side of the cathode electrode in contact with the atmosphere. Examples of the water-repellent layer include a coating of a fluorine-based resin such as PTFE (polytetrafluoroethylene). In addition, it is preferable that a catalyst for the reduction reaction is attached to the surface of the cathode electrode in contact with the liquid. For example, the surface of the cathode electrode in contact with the liquid can be covered with platinum.

[0043] The microbial fuel cell in this embodiment may be a microbial fuel cell that uses organic mud instead of a liquid containing organic matter. Specifically, the container contains organic mud and a liquid mainly composed of water. In the container, the anode electrode is placed in the organic mud, and the cathode electrode is placed in the liquid or on the liquid surface. When the cathode electrode is floated on the liquid surface, the same cathode electrode as that used in the one-tank microbial fuel cell can be used. On the other hand, when the cathode electrode is placed in the liquid, it is preferable to contain an oxidizing agent that reacts with protons as an oxygen source, as in the liquid in the cathode tank in the two-tank microbial fuel cell. In the case of a microbial fuel cell that uses organic mud, the microorganisms originally contained in the organic mud are also used in the microbial fuel cell. The 60473 strain may be contained in the organic mud, or the 60473 strain may be attached to the anode electrode in advance.

[0044] The microbial fuel cell in this embodiment is also preferably a sediment microbial fuel cell used for purifying water environments. The sediment microbial fuel cell is a microbial fuel cell that generates electricity by installing an anode electrode on the sediment (bottom mud) at the bottom of a river or lake and installing a cathode electrode in the water above the sediment. When the sediment microbial fuel cell is operated, the amount of dissolved oxygen and organic matter in the bottom mud is reduced, and the mud quality of the bottom mud is expected to improve. For this reason, the sediment microbial fuel cell is installed to purify the bottom mud of a river or lake. In the case of a sediment microbial fuel cell, it is preferable that the cathode electrode is floated on the liquid surface, and the 60473 strain may be directly injected into the bottom mud near the anode electrode, but is preferably attached to the anode electrode in advance. When the 60473 strain is attached to the anode electrode, the 60473 strain may be directly attached to the anode electrode, or the 60473 strain may be prevented from moving to a position away from the anode electrode.

[0045] In the microbial fuel cell of this embodiment, it is preferable to install a voltage measuring device on the resistor to measure the generated voltage. When an external resistor is used, the voltage measuring device can be installed so as to sandwich the external resistor. By measuring the generated voltage over time, it is possible to monitor the power generation state, and the timing for newly supplying the 60473 strain or other microorganisms can be determined.

[0046] The microbial fuel cell in this embodiment is also preferably equipped with a supply device for newly supplying the 60473 strain and other microorganisms. In the case where the microbial fuel cell in this embodiment is a sediment microbial fuel cell, it is more important that it operates stably for a long period of time, and therefore it is particularly preferable that a microbial supply device effective for extending the operating time is provided. The supply device can be composed of, for example, a supply microorganism storage container that stores a microbial solution in which the 60473 strain and other microorganisms are suspended in water, a culture medium, or the like, and a microorganism supply pipe that supplies the microbial solution from the container to the anode electrode.

[0047] FIG. 1 shows a schematic diagram of one embodiment of a microbial fuel cell equipped with a microbial supply device. 1 shows a microbial fuel cell 1 connected to bottom mud 2 and water 3 of a river or lake. The microbial fuel cell 1 includes an anode electrode 4, a cathode electrode 5, a resistor 6, a voltage measuring device 7, and a microorganism supply device 8.

[0048] In this embodiment, the anode electrode 4 is made of graphite felt inoculated with the 60473 strain. The anode electrode 4 is placed in contact with the bottom mud 2. In this embodiment, the cathode electrode 5 is made of graphite felt supporting a catalyst such as platinum. The cathode electrode 5 is placed in contact with the water 3. The electrode conductor may be a porous conductor such as titanium foam or stainless steel foam, in addition to graphite felt.

[0049] A resistor 6 is electrically connected between the anode electrode 4 and the cathode electrode 5. The resistor 6 has conductors 6a and 6b and an external variable resistor 6c. The external variable resistor 6c is connected to the anode electrode 4 via the conductor 6a. The external variable resistor 6c is connected to the cathode electrode 5 via the conductor 6b. A voltage measuring device 7 for measuring the generated voltage is installed across the external variable resistor 6c.

[0050] The microorganism supply device 8 includes a supply microorganism storage container 8a and a microorganism supply pipe 8b. The supply microorganism storage container 8a is disposed outside the water 3. The microorganism supply pipe 8b extends from the supply microorganism storage container 8a toward the water. The tip of the microorganism supply pipe 8b reaches the inside of the bottom mud 2. The microorganism supply pipe 8b is a single pipe at the portion extending from the supply microorganism storage container 8a, but the portion on the bottom mud 2 side is branched into multiple (five in the figure) branch pipes 8c. The multiple branch pipes 8c are disposed in a multiple distributed manner in the planar direction of the anode electrode 4. The open ends of the multiple branch pipes 8c are disposed around the anode electrode 4 and inside the anode electrode 4. By charging the 60473 strain or a substrate (e.g., acetic acid, etc.) into the supply microorganism storage container 8a, the 60473 strain or the substrate can be supplied to the anode electrode 4 at any time through the microorganism supply pipe 8b. By providing a plurality of branch pipes 8c, the 60473 strain or the substrate can be supplied in a dispersed manner in the planar direction of the anode electrode 4.

[0051] The microbial fuel cell 1 shown in FIG. 1 is provided with a microbial supply device 8, which allows the 60473 strain or substrate to be supplied to the anode electrode 4 at any time. This allows for long-term continuous operation. In a specific operation, for example, the voltage measurement device 7 of the microbial fuel cell 1 monitors the progress of the generated voltage, and when the generated voltage falls below the threshold voltage, the substrate or the 60473 strain is supplied to the anode electrode 4 through the microbial supply pipe 8b of the microbial supply device 8. The threshold voltage that specifies the supply timing is set to, for example, 70% of the generated voltage two weeks after the start of operation of the microbial fuel cell 1 as the reference voltage. Since it takes about two weeks for the microbial fuel cell 1 to operate stably, when the voltage drops by 30% from the generated voltage after the transition to stable operation, it is determined that a shortage of the substrate or the 60473 strain has occurred, and replenishment is performed.

[0052] In the case where the microbial fuel cell in this embodiment is a sediment microbial fuel cell, it is preferable that it can easily move through bottom mud (sediment). By operating the sediment microbial fuel cell, the mud quality is improved in the bottom mud part where the anode electrode is embedded due to a decrease in organic matter and an increase in the amount of dissolved oxygen, but this creates an unfavorable environment for the growth of the 60473 strain. If the sediment microbial fuel cell can be quickly moved to a place where the mud quality has not improved, operation can be continued, which is preferable.

[0053] A schematic diagram of one embodiment of a microbial fuel cell equipped with a support device for facilitating movement is shown in Figure 2. In Figure 2, components common to those in Figure 1 are given the same reference numerals and detailed descriptions are omitted. The sediment microbial fuel cell 11 shown in FIG. 2 has an anode electrode 4, a cathode electrode 5, a resistor 6, and a support device 17.

[0054] The support device 17 has two supports 17a, 17b, and an installation fixing part 17c fixed to the lower ends of the supports 17a, 17b. The supports 17a, 17b are rod- or plate-shaped bodies extending vertically. The installation fixing part 17c is, for example, a cone-shaped structure arranged with its tip facing downward in the depth direction (the lower side in the figure). It is preferable that the angle of the cone tip of the installation fixing part 17c is an acute angle. The installation fixing part 17c may have a shape having a portion that protrudes downward in the depth direction so that the support device 17 can be easily embedded in the bottom mud 2. Yo The installation and fixing part 17c may be, for example, pyramidal. By inserting the installation and fixing part 17c into the bottom mud 2, the sediment microbial fuel cell 11 can be easily inserted and fixed in the bottom mud 2.

[0055] The anode electrode 4 and the cathode electrode 5 are connected to the two supports 17a, 17b. In the example shown in Fig. 2, the anode electrode 4 and the cathode electrode 5 are disposed between the supports 17a, 17b that are disposed at a distance in the horizontal direction. The supports 17a, 17b are connected to both ends of the anode electrode 4 in the horizontal direction and both ends of the cathode electrode 5 in the horizontal direction, respectively. In other words, the anode electrode 4 and the cathode electrode 5 are connected in parallel and fixed between the two supports 17a, 17b, with the anode electrode 4 at the top and the cathode electrode 5 at the bottom. The support device 17 may be configured to include only the support 17a. In this case, one end of the anode electrode 4 and one end of the cathode electrode 5 are each connected to the support 17a.

[0056] The support device 17 is provided with a position adjustment mechanism that can adjust and fix the positions and intervals of the anode electrode 4 and the cathode electrode 5 supported in parallel by the supports 17a and 17b. This allows the relative positions of the anode electrode 4, the cathode electrode 5, and the installation fixing part 17c to be adjusted according to the water depth, the installation position in the bottom mud 2, etc.

[0057] According to the sediment microbial fuel cell 11 shown in FIG. 2, both the anode electrode 4 and the cathode electrode 5 are supported by one support device 17, so that transportation and installation can be performed efficiently. In addition, when the sediment microbial fuel cell 11 is operated, the amount of dissolved oxygen and organic matter in the bottom mud 2 is reduced, and the mud quality of the bottom mud 2 can be expected to improve. However, when the condition of the bottom mud 2 is improved, the amount of oxygen and organic matter in the bottom mud 2 is reduced, which creates an unfavorable environment for the growth of the facultative anaerobic 60473 strain. Therefore, if the cell can be quickly moved to a place where the mud quality has not improved (a place where the amount of dissolved oxygen and the amount of organic matter are large), the operation can be continued efficiently. In the sediment microbial fuel cell 11 of this embodiment, the anode electrode 4 and the cathode electrode 5 can be moved together, and since it is equipped with a support device 17 with a sharp tip, it can be easily moved to an environment where the 60473 strain is likely to grow.

[0058] [Composition for microbial electrolysis cells] The composition for microbial electrolysis cells in this embodiment contains the 60473 strain and an organic matter, and is used as an organic matter that serves as fuel for a microbial electrolysis cell, or is added to the fuel. The composition for microbial electrolysis cells can also be used as a microbial preparation for bioaugmentation. The form of the composition for microbial electrolysis cells in this embodiment is not particularly limited, and may be a solid such as granules or lumps, a paste, a gel, or a suspension.

[0059] The organic matter contained in the composition for microbial electrolysis cells in this embodiment is not particularly limited as long as it serves as fuel for the microbial electrolysis cell, and the same organic matter as those listed as organic matter contained in the composition for microbial fuel cells can be used.

[0060] The composition for microbial electrolysis cells in this embodiment may contain one or more microorganisms other than the 60473 strain. The microorganism may be an electrochemically active bacterium or may be other than an electrochemically active bacterium. In addition, any microorganism that can grow in an environment in which the 60473 strain can grow may be used, and is preferably an anaerobic bacterium, but may also be a microaerobic bacterium. Examples of the microorganism other than the 60473 strain contained in the composition for microbial electrolysis cells include electrochemically active bacteria and anaerobic acetic acid-producing bacteria.

[0061] [Microbial electrolysis cell] The microbial electrolysis cell in this embodiment is characterized in that the 60473 strain is used to decompose the organic matter that is the fuel. In the microbial electrolysis cell in this embodiment, the microorganisms used to decompose the organic matter may be only the 60473 strain, or the 60473 strain may be used in combination with other microorganisms. By using the 60473 strain in combination with anaerobic acetic acid-producing bacteria, acetic acid essential for power generation and hydrogen production by the 60473 strain is stably supplied, and power generation and hydrogen production by the 60473 strain can be stably performed for a longer period of time. In addition, by using a wide variety of microorganisms that decompose organic matter in combination, the organic matter of the fuel can be efficiently decomposed to a state that is easy for the 60473 strain to use. In addition, it is also preferable to use electrochemically active bacteria other than the 60473 strain in combination because the hydrogen production efficiency for the fuel organic matter can be increased.

[0062] In the microbial electrolysis cell of this embodiment, the amount of the 60473 strain used is not particularly limited, and is appropriately adjusted in consideration of the type and concentration of the organic matter used as fuel, the type of the anode electrode, whether or not it is attached to the anode electrode, etc. When the 60473 strain is dispersed in a liquid containing an organic matter, the amount of the 60473 strain per 1 g of the liquid can be, for example, 10,000 to 100,000,000 cells / g, and preferably 100,000 to 10,000,000 cells / g. When the 60473 strain is attached to the anode electrode, the amount of the 60473 strain per 1 cm of the surface area of ​​the anode electrode can be, for example, 10,000 to 10,000,000 cells / g. 2 The amount of 60473 strain per gram can be, for example, 10,000 to 100,000,000 cells / g, and is preferably 100,000 to 10,000,000 cells / g.

[0063] In the microbial electrolysis cell of this embodiment, when the 60473 strain is used in combination with other electrochemically active bacteria, the ratio of the amount of the 60473 strain to the total amount of the electrochemically active bacteria in the microbial electrolysis cell is not particularly limited, and is preferably 1 mass% or more, more preferably 10 mass% or more, and even more preferably 30 mass% or more. Since the 60473 strain has a high electrolysis ability, even if a small amount is added to a microbial fuel cell using conventional electrochemically active bacteria, the effect of increasing the amount of hydrogen production can be expected.

[0064] The electrolytic ability of the 60473 strain decreases as the time of use in the battery increases. Therefore, in the microbial electrolytic cell of this embodiment, it is preferable to newly supply the 60473 strain at a timing when the electrolytic ability of the 60473 strain decreases after the start of operation of the cell. Anaerobic acetic acid producing bacteria and other microorganisms can also be supplied together with the 60473 strain.

[0065] The timing of newly supplying the 60473 strain can be determined, for example, by monitoring the transition of the generated voltage of the microbial electrolysis cell. In the microbial electrolysis cell, the generated voltage stabilizes after a while from the start of operation. Using the generated voltage value in a stable state (stable generated voltage value) as a reference, when the generated voltage value falls below a preset threshold value (for example, 70% of the stable generated voltage value), newly supplying the 60473 strain allows stable power generation and hydrogen production for a long period of time. The 60473 strain may be newly supplied at predetermined time intervals from the start of operation of the cell.

[0066] As the microbial electrolysis cell in this embodiment, the 60473 strain is used, and the cell is required to have an anode electrode, a cathode electrode, and a potential control device connected to both electrodes through which electrons flow, and an organic matter as fuel, and other structures are not particularly limited. Specifically, the microbial electrolysis cell in this embodiment includes a liquid containing organic matter as a main component, a container for containing the liquid, a conductive anode electrode disposed in the liquid, a conductive cathode electrode disposed with at least one surface in contact with the liquid, and a potential control device connected to the anode electrode at one end and the cathode electrode at the other end, through which electrons flow. Microorganisms including the 60473 strain are contained in the liquid in which the anode electrode is disposed. The organic matter to be used as fuel may be the same as the organic matter contained in the composition for the microbial electrolysis cell. In the microbial electrolysis cell in this embodiment, it is preferable that the organic matter contains phosphorus, nitrogen, and sulfide.

[0067] On the anode electrode side, organic matter in the fuel is decomposed by microorganisms to generate carbon dioxide, and electrochemically active bacteria such as the 60473 strain release electrons during the reaction. The anode electrode is not particularly limited as long as it is an electrode made of a conductive material that can receive electrons produced by the electrochemically active bacteria and transfer them to the cathode electrode through a potential control device. In the microbial electrolysis cell of this embodiment, a conductive carbon-based anode electrode mainly composed of carbon or graphite is preferred because of its good adhesion to microorganisms, and an anode electrode made of carbon cloth (a cloth woven from carbonized fibers obtained by burning petroleum or acrylic fibers) is more preferred because of its large surface area. In addition, in the microbial electrolysis cell of this embodiment, it is also preferable that the anode electrode is made of a conductive metal material with a smaller internal electrical resistance than the cathode electrode. Specifically, in the microbial electrolysis cell of this embodiment, an anode electrode made of a metal such as stainless steel, iron, or magnesium and having the 60473 strain attached to its surface is also preferred.

[0068] In the cathode electrode, a reduction reaction occurs between the electrons received from the anode electrode via the potential control device and the protons diffused from the anode electrode, producing hydrogen. The cathode electrode can be an electrode in which a catalyst for the reduction reaction, such as platinum, is applied to a conductive material. As the conductive material constituting the cathode electrode, a carbon-based material mainly composed of carbon or graphite is preferably used in terms of corrosion resistance, etc.

[0069] The size of the anode electrode and the cathode electrode is not particularly limited. The size of both electrodes may be the same or different. In a microbial electrolysis cell, the performance of the cathode electrode decreases as the operation continues. For this reason, it is preferable that the area of ​​the cathode electrode is larger than the area of ​​the anode electrode, and a structure in which the area of ​​the cathode electrode is 1.1 times or more larger than the area of ​​the anode electrode is more preferable. By increasing the area of ​​the cathode electrode, the operation time of the microbial electrolysis cell can be increased.

[0070] The potential control device, one end of which is connected to the anode electrode and the other end of which is connected to the cathode electrode, is not particularly limited as long as it is a member that allows electrons to flow from the anode electrode to the cathode electrode due to the potential difference between the chemical reaction caused by the microorganisms in which carbon dioxide is generated from the organic matter on the anode electrode side and electrons are released, and the reduction reaction occurring on the cathode electrode side, and can be appropriately selected from potential control devices that are commonly used in microbial electrolysis cells. Examples of the potential control device include a potentiostud that uses a working electrode (anode electrode), a counter electrode (cathode electrode), and a reference electrode. In addition, the potential control device may have resistance throughout from the connection part with the anode electrode to the connection part with the cathode electrode, but it is preferable that the connection part with the anode electrode is made of a conductive material such as a titanium wire with a small internal resistance and an external resistor that shows sufficient resistance is provided in the middle. It is preferable that the external resistor is a variable resistor because it can be adjusted according to the state of the fuel and the state of the microorganisms. The potential control device and the external resistor are held and fixed on the cathode electrode, and are arranged in a state where they can be easily seen above the liquid (liquid surface).

[0071] The microbial electrolysis cell in this embodiment may be a two-tank microbial electrolysis cell or a single-tank microbial electrolysis cell. The structures and members of the two-tank microbial electrolysis cell and the single-tank microbial electrolysis cell can be the same as those used in known two-tank microbial electrolysis cells and single-tank microbial electrolysis cells.

[0072] In the case of a two-tank microbial electrolysis cell, the container that contains a liquid mainly composed of water containing organic matter is divided into a tank in which the anode electrode is disposed (anode tank) and a tank in which the cathode electrode is disposed (cathode tank) by a membrane that is selectively permeable to protons. The membrane that is selectively permeable to protons is mainly H + A proton exchange membrane (PEM) that is selectively permeable to the 60473 strain can be used. The organic matter and the 60473 strain are contained in a liquid contained in the anode tank.

[0073] In the case of a two-tank microbial electrolysis cell, the amount of oxygen contained in the liquid contained in the anode tank is preferably maintained at about 2 to 10% (v / v) of the amount of oxygen contained in the liquid contained in the cathode tank. In order to maintain this oxygen concentration gradient, it is preferable that the liquid in the cathode tank also contains an oxidizing agent that reacts with protons as an oxygen source. Potassium ferricyanide, manganese oxide, etc. are used as the oxidizing agent.

[0074] The microbial electrolysis cell in this embodiment may be a microbial electrolysis cell that uses organic mud instead of a liquid containing organic matter. Specifically, the container contains organic mud and a liquid mainly composed of water. In the container, the anode electrode is placed in the organic mud, and the cathode electrode is placed in the liquid. As with the liquid in the cathode tank in the two-tank microbial electrolysis cell, it is preferable that the cathode electrode contains an oxidizing agent that reacts with protons as a source of oxygen. In the case of a microbial electrolysis cell that uses organic mud, the microbial group originally contained in the organic mud is also used in the microbial electrolysis cell. The 60473 strain may be contained in the organic mud, or the 60473 strain may be attached to the anode electrode in advance.

[0075] The microbial electrolysis cell in this embodiment is also preferably a sediment microbial electrolysis cell used for purifying water environments. The sediment microbial electrolysis cell is a microbial electrolysis cell that generates electricity and hydrogen by installing an anode electrode in the sediment (bottom mud) at the bottom of a river or lake and installing a cathode electrode in the water above the sediment. When the sediment microbial electrolysis cell is operated, the amount of dissolved oxygen and organic matter in the bottom mud is reduced, and the mud quality of the bottom mud is expected to improve. For this reason, the sediment microbial electrolysis cell can be installed in a river or lake in the same manner as the above-mentioned sediment microbial fuel cell in order to purify the bottom mud.

[0076] In the microbial electrolysis cell of this embodiment, it is preferable to install a voltage measuring device in the potential control device in order to measure the generated voltage. When an external resistor is used, the voltage measuring device can be installed so as to sandwich the external resistor. By measuring the generated voltage over time, it is possible to monitor the power generation state and determine the timing to newly supply the 60473 strain or other microorganisms.

[0077] The microbial electrolysis cell in this embodiment is also preferably equipped with a supply device for newly supplying the 60473 strain and other microorganisms. In the case where the microbial electrolysis cell in this embodiment is a sediment microbial electrolysis cell, it is more important that the cell operates stably for a long period of time, and therefore it is particularly preferable that the cell is equipped with a microbial supply device that is effective in extending the operation time. The supply device can be composed of, for example, a supply microbial storage container that stores a microbial solution in which the 60473 strain and other microorganisms are suspended in water, a culture medium, or the like, and a microbial supply pipe that supplies the microbial solution from the container to the anode electrode.

[0078] 3 shows a schematic diagram of one embodiment of a three-electrode, single-tank type microbial electrolysis cell. The microbial electrolysis cell 20 includes an anode electrode 24, a cathode electrode 25, and a potentiostud 26 in a container 21. The potentiostud 26 has a reference electrode 26c. In the anode electrode 24, organic matter is decomposed by microorganisms such as the 60473 strain, and the generated electrons move through the potentiostud 26 to the cathode electrode 25. In the cathode electrode 25, the electrons react with protons to generate hydrogen. EXAMPLES

[0079] The present invention will now be described in more detail with reference to examples and reference examples, but the present invention is not limited to the following examples.

[0080] [Example 1] Electrochemically active bacteria with the power generation capacity usable in microbial fuel cells were isolated and identified from mud on the shore of Lake Suwa (Okaya City, Nagano Prefecture).

[0081] (1) Isolation of strain 60473 Specifically, first, a mud battery shown in FIG. 4 was created [101: data logger for measuring voltage, 102: external resistor, 103: titanium wire, 104: water, 105: cathode (platinum-coated graphite felt), 106: anode (graphite felt), 107: mud]. This mud battery was operated in an incubator at 30° C. while measuring the voltage across the external resistor (10 kΩ), and the electricity-generating bacteria was grown on the anode. After the voltage rose to 0.5 V or more, a part of the anode was cut off and placed in a liquid medium of DSM826 medium (manufactured by DSMZ) and stirred to suspend the deposits. A diluted solution of the obtained suspension was applied to an agar plate of DSM826 medium, placed in an Anaeropack pouch (manufactured by Mitsubishi Gas Chemical Co., Ltd.), and colonies were formed at 30° C. The red colonies formed on the plate were inoculated and cultured in DSM826 liquid medium in an anaerobic vial in which the gas phase had been replaced with nitrogen gas (99.999% (v / v)). The culture was again cultured on a DSM826 medium agar plate to allow colonies to form, and the formed colonies were again cultured in DSM826 liquid medium. This procedure was repeated until only colonies with the same shape were formed on the plate. The anaerobic bacteria from the colonies formed on this plate was named strain 60473.

[0082] (2) Evaluation of current generation ability of strain 60473 The 60473 strain was cultured in DSM826 liquid medium to obtain a culture. This was then placed in a three-electrode, one-chamber electrochemical cell to measure the current generated. In the electrochemical cell, the working electrode was graphite felt (2.00 cm 2The electrode was a Ag / AgCl electrode (RE-T8A, EC Frontier), the reference electrode was a Ag / AgCl electrode (RE-T8A, EC Frontier), the counter electrode was a platinum wire (12 cm long, 0.3 mm thick, Nilaco), and the electrolyte was DSM826 liquid medium (65 mL) without fumaric acid. The culture was added to this electrolyte so that the turbidity at 600 nm was 0.02, and the cell was connected to a potentiostat (VMP3, Biologic), the working electrode potential was set to -0.2 V vs. Ag / AgCl electrode, and current measurement was started. For comparison, the current from the PCA strain, known as a highly capable electricity-generating bacterium, was measured (n=2).

[0083] The results of measuring the current of the electrochemical cell inoculated with strain 60473 and strain PCA are shown in Figure 5. As shown in Figure 5, the maximum value of the current generated by strain 60473 was about two times higher than that of strain PCA.

[0084] The working electrode of the electrochemical cell was made of glassy carbon (1 cm 2 The current was measured in the same manner as above (n=2) using a 100-μL ion exchanger (BAS, manufacturer). The results are shown in Figure 6. As a result, the current value for the PCA strain was 0.02 mA / cm 2 In strain 60473, the current increased to 0.28 mA / cm 2 The amount of bacteria adhering to the glassy carbon electrode increased to about 100%. This result indicates that the 60473 strain can efficiently interact electrochemically with the smooth glassy carbon electrode. When the bacteria attached to the electrode surface were stained with a fluorescent dye (4,6-diamidino-2-phenylindole, DAPI; 0.1 μg / mL) and observed under a confocal microscope (FV1200 / BX61WI system, Olympus), it was confirmed that many cells of the 60473 strain were attached to the smooth electrode. The amount of bacteria adhering to the glassy carbon electrode was compared based on the intensity of DAPI staining. The results are shown in Figure 7. The amount of the 60473 strain adhering to the glassy carbon electrode was nearly three times that of the PCA strain.

[0085] (3) Genome analysis of strain 60473 The genome sequence was determined to identify the species of strain 60473 from the genome sequence and to further clarify its genomic characteristics. Strain 60473 was cultured in DSM826 medium, and genomic DNA was extracted from 100 mL of culture according to the method of Fujikawa et al. (Fujikawa et al., FEMS Microbiology Letters, 2021, vol.368(17), fnab119.). It was confirmed that high molecular weight genomic DNA was extracted by agarose gel electrophoresis, and the whole genome sequence was determined using the Sequel lle system (PacBio). The results of the genome sequence analysis and comparison with the PCA strain are shown in Table 1.

[0086] [Table 1]

[0087] To clarify the molecular phylogenetic characteristics of strain 60473, we performed BLAST analysis in the NCBI database using the 16S rRNA gene in the genome. As a result, the closest relative of strain 60473 was strain PCA, with a homology (sequence identity) of 99.48%. Therefore, to clarify the phylogenetic relationship with known Geobacter sulfurducens, we created a phylogenetic tree using the 16S rRNA gene and gyrB gene (Figures 8 and 9). As a result, although strain 60473 belongs to the genus Geobacter, further investigation is considered necessary to determine whether it belongs to Geobacter sulfurducens.

[0088] [Example 2] A mud battery is an experimental device that mimics a sediment microbial fuel cell (sMFC), which is a power generation device in the environment. An sMFC is a device that generates electricity using organic matter in sediments (mud and bottom sediments) as fuel, and can reduce the amount of organic matter in the sediments by generating electricity. Therefore, in order to investigate whether the 60473 strain can be used to improve the performance of an sMFC, a mud battery was created using bottom sediments from Lake Suwa, and the 60473 strain was introduced.

[0089] The mud battery used had a structure similar to that shown in Fig. 4. The mud battery used consisted of mud (approximately 400 mL), an anode (graphite felt, area 36 cm 2 ), cathode (platinum-coated graphite felt, area 24 cm 2 ) and was operated with an external resistance of 10 kΩ connected. One day after the start of operation, 250 mL of culture solution of the 60473 strain cultivated in DSM826 liquid medium was centrifuged to concentrate the bacterial solution, which was then injected around the anode, and operation was continued. The results of the polarization analysis carried out on the fifth day after the start of operation are shown in Figures 10 and 11. Figure 10 shows the polarization analysis results (n=2) of the mud battery with the 60473 strain added, and Figure 11 shows the polarization analysis results (n=2) of the mud battery without the 60473 strain added. In addition, from the polarization analysis results shown in Figures 10 and 11, it was found that the maximum power density (P max mW / m 2 ) were calculated and compared as shown in Figure 12. In the figure, the error bars indicate standard deviations. The introduction of strain 60473 dramatically improved the maximum power density of the mud battery. These results demonstrate that the performance of existing microbial fuel cells, particularly sMFCs, can be improved by bioaugmentation using strain 60473.

[0090] [Example 3] The power generation capacity of the 60473 strain was compared with that of known Geobacter bacteria. The PCA strain used in Example 1, Geobacter sulfurreducens KN400 (KEGG GENOME: Geobacter sulfurreducens KN400), and Geobacter sulfurreducens YM18 strain described in Non-Patent Document 6 were used for comparison.

[0091] (1) Evaluation of current generation ability Specifically, in the same manner as in Example 1, “(2) Evaluation of the electric current generation ability of strain 60473,” the Geobacter bacteria to be evaluated were planted in a three-pole, single-chamber electrochemical cell, and the electric current generated was measured (n=2).

[0092] The results of measuring the current density over time when graphite felt was used as the working electrode (anode electrode) are shown in FIG. 13, and the maximum current density is shown in FIG. 14. The results of measuring the current density over time when glassy carbon was used as the working electrode (anode electrode) are shown in FIG. 15, and the maximum current density is shown in FIG. 16. As shown in FIGS. 13 and 14, when a graphite felt electrode was used, the 60473 strain, the KN400 strain, and the YM18 strain all showed relatively high current densities compared to the PCA strain, and among them, the YM18 strain showed the highest current density. In addition, in the electrochemical cell inoculated with the 60473 strain and the KN400 strain, it was shown that the current density increased relatively rapidly compared to the YM18 strain. On the other hand, as shown in FIGS. 15 and 16, when a glassy carbon electrode was used, the 60473 strain generated the highest current among these strains, and the maximum current density (J max ) was more than three times that of the KN400 and YM18 strains.

[0093] In the same manner as in Example 1, the graphite felt electrode and the glassy carbon electrode after the current generation experiment were stained with DAPI and observed under a confocal microscope. As a result, the KN400 strain and the YM18 strain formed a thick biofilm on the graphite fibers of the graphite felt electrode. In addition, the biofilm of the 60473 strain on the graphite felt fibers was thinner than that of the KN400 strain and the YM18 strain, but the cell density of the biofilm of the 60473 strain was the highest. Furthermore, the 60473 strain also formed a high-density biofilm on the glassy carbon electrode, and its density was much higher than that of the biofilms of the other strains. On the other hand, the KN400 strain formed a biofilm with a low cell density that was evenly distributed on the glassy carbon electrode, and the biofilm of the YM18 strain only partially covered the surface of the glassy carbon electrode. From these observations, it was concluded that the high current density of the 60473 strain is related to its ability to form a high-density biofilm on the graphite surface.

[0094] (2) Physiological characteristics of Geobacter sp. For strains 60473, KN400, YM18, and PCA, among the physiological traits considered to be related to biofilm formation and current generation, the affinity for graphite (GAI), cell hydrophobicity (HPI), and cytochrome content per protein (CCI) were examined, respectively.

[0095] <Measurement of GAI (%)> The GAI (%) of each Geobacter bacterium was measured by the following method. First, the test microorganism was anaerobically cultured and grown in DSM826 medium, and then washed with DSM826 buffer (DSM826 medium without acetate, fumarate, and mineral solution). Next, the test microorganism was suspended in 3.5 mL of DSM826 buffer to an optical density (Optical density 600nm: OD 600 ) of 0.3 at a wavelength of 600 nm to prepare a cell suspension. OD 600 was measured with a digital colorimeter (miniphoto 518R, manufactured by Taitec Corporation). Graphite felt (0.5 cm 2 × 5 mm) was added to the prepared cell suspension, and the mixture was stirred at 30 °C and 200 rpm. Sixty minutes after the start of stirring, OD 600 was measured with the digital colorimeter. Based on the obtained measurement value and the following formula, GAI (%) was calculated. In the formula, A 1 is the OD 600 of the cell suspension after stirring, and A 0 is the OD 600 (0.3) of the cell suspension before stirring.

[0096] [GAI (%)] = (1 - A 1 / A 0 ) × 100

[0097] <Measurement of HPI (%)> The HPI (%) of each Geobacter bacterium was measured by the following method. The test microorganism was suspended in 4.8 mL of an aqueous sodium chloride solution (0.15 M) to an optical density (Optical density 600nm: OD 600) was suspended so that OD became 0.3 to prepare a cell suspension. OD 600 was measured with a digital colorimeter (miniphoto 518R, manufactured by Taitec Corporation). To the prepared cell suspension, 0.8 mL of hexadecane was added and stirred with a vortex mixer for 60 seconds. Then, the cell suspension was left standing overnight. After the two phases were completely separated, the upper layer was removed by decantation, and then the OD of the lower layer 600 was measured. Based on the following formula, HPI (%) was calculated from the ratio of the cells transferred to the hexadecane phase. In the formula, A 2 is the OD of the cell suspension in the aqueous phase after mixing the cell suspension with hexadecane 600 , and A 0 is the OD of the cell suspension before stirring 600 (0.3).

[0098] [HPI (%)]=(1 - A 2 / A 0 )×100

[0099] [Measurement of CCI ( / mg)] The CCI ( / mg) of each Geobacter bacterium was measured by the following method. First, the test microorganism was anaerobically cultured and grown in DSM826 medium, and then centrifuged (10,000×g, 15 minutes) to recover the microbial pellet. The obtained microbial pellet was washed with TE buffer and then suspended in TE buffer containing 1 mg / mL lysozyme. The obtained cell suspension was homogenized using a homogenizer, incubated at 37°C for 1.5 hours, and further incubated at room temperature for 10 minutes after adding Triton X-100 (1% w / v). The absorption spectrum of the supernatant of the cell suspension after incubation was measured in the range of 700 to 350 nm using a spectrophotometer (UH5300, manufactured by Hitachi, Ltd.). Next, in order to measure the absorption spectrum of reduced cytochrome, sodium bisulfite was added to the cell suspension so that the final concentration became 68 mM, and the absorbance at the peak of the Soret band (about 420 nm) of reduced cytochrome was measured. Furthermore, the protein content (μg) of the bacterial cell suspension was measured using a commercially available BCA assay kit (Micro BCA protein assay kit, Thermo Fisher Scientific). The CCI ( / mg) was calculated based on the measured values ​​and the following formula: 1 is the OD of the bacterial suspension after stirring. 600 And A 0 is the OD of the bacterial suspension before stirring 600 (0.3). In the formula, A Soret is the absorbance of the peak of the Soret band of reduced cytochrome in the cell suspension, and PC is the protein content (μg) of the cell suspension.

[0100] [CCI( / mg)]=A Soret / PC

[0101] The measurement results of GAI, HPI and CCI of each Geobacter spp. are shown in Figures 17 to 19. The CCI of YM18 and 60473 strains was higher than that of PCA and KN400 strains. That is, while the 60473 strain was able to generate a relatively high current density on both the graphite felt electrode and the glassy carbon electrode, the YM18 strain generated a high current density only on the graphite felt electrode. The reason why the YM18 strain was able to form an electrochemically active biofilm (EABF) on the graphite felt electrode was that the cells were physically trapped between the graphite felt fibers, and this strain was thought to have difficulty attaching to flat surfaces. On the other hand, it was interesting that the 60473 strain formed a dense biofilm on the flat and slippery surface of the glassy carbon electrode, and it was thought that the high GAI and high HPI properties of the 60473 strain promoted this behavior.

[0102] [Example 4] To evaluate the utility of strain 60473 in bioaugmentation of a microbial electrolysis cell, we operated it with starch as the main anode substrate and investigated the electricity and hydrogen production.

[0103] Specifically, four single-layer electrolysis cells were inoculated with soil and operated with starch as the main anode substrate (MEC1 to MEC4). One day after the start of operation, two electrolysis cells (MEC3 and MEC4) were inoculated with 60473 strain, respectively, and operation was continued. The remaining two electrolysis cells (MEC1 and MEC2) were not inoculated with 60473 strain, and these continued to operate as controls without bioaugmentation. During operation, the electrolyte was exchanged intermittently to add substrate (starch) to the electrolysis cells. The period from the time of electrolyte exchange to the next electrolyte exchange was defined as "one cycle," and operation was continued until the sixth cycle (after five electrolyte exchanges).

[0104] The results of measuring the power generation amount (current density) of each cell over time are shown in Figures 20 and 21. Figure 21 is a diagram in which the vertical axis of the measurement data in Figure 20 is enlarged. In Figures 20 and 21, the time points indicated by the arrowheads indicate the time points when the electrolyte was replaced.

[0105] After the operation was completed, the biofilm formed on the working electrode (anode electrode) surface of each cell was collected, and the constituent bacteria were classified by genus to examine the composition. The amount of each bacteria was measured by quantitative PCR, as in Non-Patent Document 6. The results are shown in Figure 22. In MEC3 and MEC4, which were subjected to bioaugmentation with the 60473 strain, more than 40% of the biofilm on the anode electrode surface was Geobacter genus bacteria, and it was confirmed that the inoculated 60473 strain preferentially attached to the anode electrode surface.

[0106] As shown in Figures 20 and 21, MEC3 and MEC4 bioaugmented with strain 60473 generated significantly larger currents than the non-bioaugmented controls (MEC1 and MEC2). Even after repeated electrolyte exchanges, the maximum current density (peak current density) achieved by MEC3 and MEC4 (J max ) is always around 1.5mA / cm 2 , whereas MEC1 and MEC2 reached 0.04 mA / cm 2The maximum current density of MEC3 and MEC4 bioaugmented with strain 60473 was unexpectedly high and comparable to that achieved in pure culture electrolysis cells using acetate as a substrate. These results suggest that bioaugmentation with strain 60473 may be able to improve the performance of electrolysis cells using high molecular weight fermentable organic matter (HFO) such as starch as a substrate to the same level as that using acetate as a substrate.

[0107] In addition, in the electrolytic cell bioaugmented with the YM18 strain, the maximum current density begins to decrease in the fourth and fifth cycles (Non-Patent Document 6). In contrast, as shown in Figure 21, the maximum current density of MEC3 and MEC4 does not change significantly and does not decrease substantially even during six cycles of operation, confirming that high current generation capacity can be maintained for a long time. It was speculated that the constant current generation in the electrolytic cell bioaugmented with the 60473 strain is due to the high affinity of the 60473 strain for the graphite electrode.

[0108] For the electrolysis performed in each electrolysis cell, the maximum current density [J max (mA / cm 2 )], hydrogen production rate per day (HPR: [volume of hydrogen produced (L)] / [volume of electrolyte solution in cell (L)] / [Day]), and COD (chemical oxygen demand) removal rate [COD R The COD at the end of operation was calculated as follows: (1-[COD at the start of operation] / [COD at the end of operation]) x 100 (%)) in the same manner as in Non-Patent Document 6. The results are shown in Table 2.

[0109] [Table 2]

[0110] Hydrogen was produced only in MEC3 and MEC4 at a rate of about 0.5 L / L / Day. Rwas significantly increased compared to MEC1 and MEC2. These results suggest that in the electrolysis cells bioaugmented with strain 60473, most of the starch was decomposed concomitantly with current generation. In addition, the results in Table 2 indicate that current generation (e.g., coupled with acetate oxidation) is the rate-limiting step of starch degradation in the electrolysis cells, and we confirmed that enhancing this step by introducing strong electrochemically active bacteria is a promising strategy to enhance the performance of electrolysis cells treating polymeric fermentable organic matter.

[0111] [Example 5] To evaluate the usefulness of strain 60473 in the bioaugmentation of microbial electrolysis cells, a three-electrode, single-chamber electrochemical cell was operated using food waste as the anode substrate, and the generated current was measured to investigate the amount of electricity and hydrogen produced (n=2).

[0112] The food waste used was vegetable scraps from an actual restaurant. Water was added to the crushed food waste, and the mixture was left for several days before being centrifuged to collect the supernatant. The supernatant was adjusted to pH 8.0 (COD value: approximately 55,000 ppm) and used as the anode substrate.

[0113] For a three-electrode, single-chamber electrochemical cell, the working electrode is graphite felt (6.00 cm 2 The electrode was a Ag / AgCl electrode (RE-T8A, EC Frontier), the counter electrode was a platinum mesh (0.12 mm thick, Nilaco), and the electrolyte was 50 mL. The electrolyte was 0.1 M PBS (pH 8.0) containing 12.3 g / L Na 2 HPO 4 , 1.9g / L KH 2 PO 4 , 0.26g / L NH 4The solutions used contained 10 mL / L of Cl, 10 mL / L Modified Wolin's mineral solution (Deutsche Sammlung von Mikroorganismen und Zellkulturen), and 10 mL / L Wolin's vitamin solution (Deutsche Sammlung von Mikroorganismen und Zellkulturen).

[0114] Specifically, 5.5 mL of anode substrate and 5 mL of anaerobic digestion sludge as inoculum source were added to the electrolyte of the electrochemical cell, and the cell was connected to a potentiostat (VMP3, Biologic) and the working electrode potential was set to -0.2 V vs. Ag / AgCl electrode, and current measurement was started. During operation, the electrolytic cell was intermittently replaced with a new electrolyte containing the anode substrate in order to add the anode substrate. The period from the electrolyte replacement to the next electrolyte replacement was defined as "one cycle," and the cell was operated until the sixth cycle (after five electrolyte replacements).

[0115] Of the four electrolysis cells, two (60473_1 and 60473_2) showed that the OD of the 60473 strain in the cell was 4 hours after the current value of the first cycle became positive. 600 The 60473 strain was added so that the β-amino acid concentration was 0.04 (bioaugmentation). The remaining two cells (NB_1, NB_2) were not administered with the 60473 strain, and these were continued to be operated as controls without bioaugmentation.

[0116] Figure 23 shows the results of measuring the amount of power generated (current density) over time for each cell. In Figure 23, the numbers at the top indicate "cycles." In the cells to which strain 60473 was added (60473_1, 60473_2), the current density increased significantly. These results confirmed that the effects of bioaugmentation using strain 60473 were sufficient even when food waste was used as the anode substrate.

[0117] In addition, the removal rate of COD (chemical oxygen demand) [COD R The coulombic efficiency (%) was calculated as follows: (1-[COD at the end of operation] / [COD at the start of operation]) x 100 (%). Coulombic efficiency is the ratio of the discharge capacity during discharge to the charge capacity, expressed as a percentage. The higher the coulombic efficiency of a battery, the longer the lifespan will be, since the capacity charged can be used for discharge without loss. COD R was determined in the same manner as in Example 4. The coulombic efficiency was determined by the following formula.

[0118] [Coulomb efficiency (%)] = [Coulomb equivalent of integrated amount of generated current] / [Coulomb equivalent of amount of COD removed] x 100 (%)

[0119] COD of each electrolysis cell R The results of measuring the Coulombic efficiency at the 1st cycle and the 6th cycle are shown in Table 3. The cells to which strain 60473 was added (60473_1, 60473_2) had a higher COD removal rate and higher Coulombic efficiency than the control cells (NB_1, NB_2). These results demonstrated that even when food waste was used as the anode substrate, bioaugmentation with strain 60473 made it easier to reduce COD and extend the life of the electrolysis cell.

[0120] [Table 3]

[0121] In addition, for the electrolysis performed in each electrolysis cell, the hydrogen production rate per day (HPR: [volume of hydrogen produced (L)] / [volume of electrolyte solution in cell (L)] / [Day]), the methane production rate per day (MPR: [volume of methane produced (L)] / [volume of electrolyte solution in cell (L)] / [Day]), and the amount of methane produced (L / L / day) were measured by gas chromatography. The results are shown in Table 4.

[0122] [Table 4]

[0123] As shown in Table 4, hydrogen generation was observed initially in the cell to which strain 60473 was added, but from the fourth cycle onwards, hydrogen was hardly detected. This was presumed to be because the generated hydrogen was consumed by methanogens and the like. On the other hand, no significant difference was found in the amount of methane generated between the cell to which strain 60473 was added and the control cell.

[0124] After the sixth cycle, cyclic voltammetry (CV) was performed on each electrolysis cell. CV is an electrochemical measurement method in which an electrode is immersed in a stationary sample solution, the potential is repeatedly scanned, and the flowing current is measured, and is expressed as a current-voltage curve. The CV results for each cell are shown in Figure 24.

[0125] As shown in Figure 24, the cells to which the 60473 strain was added (60473_1, 60473_2) had a larger CV peak than the control cells (NB_1, NB_2). This was presumably because the cells to which the 60473 strain was added had a larger amount of electrochemically active bacteria attached to the electrode.

[0126] [Example 6] To evaluate the usefulness of strain 60473 in bioaugmentation of microbial fuel cells (MFCs), a single-tank air cathode MFC reactor was operated using food waste as the anode substrate, and the generated current was measured to examine the amount of electricity generated (n=2). Food waste prepared in the same manner as in Example 5 was used.

[0127] The single-chamber air cathode MFC reactor had a reactor volume of 85 mL and an anode electrode made of graphite felt (12.56 cm 2 , 3 mm thick, manufactured by Nippon Carbon Co., Ltd.), and the cathode electrode was coated with a platinum catalyst (TEC10V20E, manufactured by Tanaka Kikinzoku Co., Ltd.) (0.64 mg / cm 2 ) air cathode (25cm 2 , Non-Patent Document 7), and the amount of the electrolyte was 60 mL. The electrolyte used had the same composition as in Example 5.

[0128] Specifically, 5.5 mL of anode substrate and 6.5 mL of anaerobic digestion sludge as inoculum source were added to the electrolyte of the MFC reactor, and operation was started. The initial resistance was set to 10 kΩ, and was gradually lowered when the pressure increased sufficiently. During operation, the reactor was intermittently exchanged for new electrolyte containing anode substrate in order to add anode substrate. The period from electrolyte exchange to the next electrolyte exchange was defined as "1 cycle," and the reactor was operated until the 10th cycle (after 9 electrolyte exchanges).

[0129] In two of the four MFC reactors (60473_1 and 60473_2), the OD of the 60473 strain in the reactor was measured 4 hours after the current value of the first cycle became positive. 600 Strain 60473 was added so that the β-amino acid concentration was 0.04 (bioaugmentation). The remaining two reactors (NB_1, NB_2) were not administered with strain 60473 and continued to operate as controls without bioaugmentation.

[0130] The voltage (V) of each reactor was measured over time and the results are shown in Figure 25. In Figure 25, the numbers at the top indicate "cycles." Table 5 shows the resistance value of each reactor measured over time for each cycle.

[0131] [Table 5]

[0132] As shown in Figure 25 and Table 5, in the reactors (60473_1, 60473_2) to which strain 60473 was added, sufficient voltage (about 0.4 V or more) was output even when the resistance was lowered. Lowering the resistance means that more current flows, which places a heavy burden on the electrochemically active bacteria. Nevertheless, a high voltage was maintained, confirming that the effects of bioaugmentation using strain 60473 can be fully obtained even in MFCs that use food waste as the anode substrate.

[0133] The results of the polarization analysis for each reactor in the 9th cycle are shown in Figures 26 and 27. Figure 26 shows the polarization analysis results (n=2) for the reactors (60473_1, 60473_2) in which the 60473 strain was added, and Figure 27 shows the polarization analysis results (n=2) for the reactors (NB_1, NB_2) in which the 60473 strain was not added. In addition, from the results of the polarization analysis shown in Figures 26 and 27, the maximum power density (P max mW / m 2 ) were calculated and compared, as shown in Figure 28. In the figure, the error bars indicate standard deviation. As shown in Figure 28, when comparing the maximum power densities obtained in the polarization analysis of the 9th cycle, the output of the MFC to which strain 60473 was added increased significantly by adding strain 60473. A similar trend was observed in other cycles. These results demonstrated that even when food waste is used as the anode substrate, the performance of the cell can be improved by bioaugmenting existing microbial fuel cells with strain 60473.

[0134] In addition, the removal rate of COD (chemical oxygen demand) was calculated for the electrolysis performed in each reactor (COD R The electrical conductivity (%) and coulombic efficiency (%) were determined in the same manner as in Example 5. The measurement results are shown in Table 6.

[0135] [Table 6]

[0136] As shown in Table 6, the reactors to which strain 60473 was added (60473_1, 60473_2) had a higher COD removal rate and higher Coulombic efficiency than the control reactors (NB_1, NB_2). These results demonstrated that even when food waste was used as the anode substrate, bioaugmentation using strain 60473 made it easier to reduce COD and extend the life of the MFC reactor.

[0137] CV was performed on each MFC reactor after the 10th cycle. The CV results for each reactor are shown in Figure 29. As shown in Figure 29, the reactors to which strain 60473 was added (60473_1, 60473_2) had a larger CV peak than the control reactors (NB_1, NB_2). This was presumably because the cells to which strain 60473 was added had a larger amount of electrochemically active bacteria attached to the electrodes. [Explanation of symbols]

[0138] 1... Sediment microbial fuel cell, 2... Bottom mud, 3... Water, 4... Anode electrode, 5... Cathode electrode, 6... Resistor, 6a, 6b... Conductor, 6c... External variable resistor, 7... Voltage measuring device, 8... Microorganism supply device, 8a... Supply microorganism storage container, 8b... Microorganism supply pipe, 11... Sediment microbial fuel cell, 12... Bottom mud, 13... Water, 14... Anode electrode, 15... Cathode electrode, 16... Resistor, 16a, 16b... Conductor, 16c... External variable resistor, 17... Support device, 17a...anode electrode support part, 17b...cathode electrode support part, 17c...connection part, microbial electrolysis cell...20, container...21, anode electrode...24, cathode electrode...25, potentiostud...26, reference electrode 26c, 101...data logger for voltage measurement, 102...external resistor, 103...titanium wire, 104...water, 105...cathode (platinum-coated graphite felt), 106...anode (graphite felt), 107...mud. [Accession number]

[0139] NITE BP-03900

Claims

1. A microorganism, which is Geobacter sp. 60473 (NITE BP-03900).

2. The microorganism according to claim 1 for use in a microbial fuel cell.

3. A composition for a microbial fuel cell, comprising Geobacter sp. 60473 (NITE BP-03900) and an organic matter.

4. The composition for a microbial fuel cell according to claim 3, further comprising electrochemically active bacteria other than Geobacter sp. strain 60473.

5. The composition for a microbial fuel cell according to claim 3 , wherein at least a portion of the organic matter is sludge.

6. A microbial fuel cell in which Geobacter sp. 60473 (NITE BP-03900) is used to decompose organic matter for fuel.

7. A liquid mainly composed of water containing organic matter; A container for containing the liquid; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed with at least one surface in contact with the liquid; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900), which is contained in the liquid and decomposes the organic matter and emits electrons; A microbial fuel cell comprising:

8. the container is partitioned by a membrane selectively permeable to protons into a chamber in which the anode electrode is disposed and a chamber in which the cathode electrode is disposed, The microbial fuel cell according to claim 7 , wherein the organic matter and the Geobacter sp. 60473 strain are contained in a liquid contained in a tank in which the anode electrode is placed.

9. The microbial fuel cell according to claim 7 , wherein one surface of the cathode electrode is in contact with the liquid in the container and the other surface is in contact with the atmosphere.

10. A container containing organic mud and a liquid mainly composed of water; a conductive anode electrode disposed in the organic mud; a conductive cathode electrode disposed in or on the liquid surface; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) contained in the organic mud; A microbial fuel cell comprising:

11. a conductive anode electrode disposed in the organic mud; A conductive cathode electrode disposed in the water or on the water surface; a resistor having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) attached to the anode electrode; Microbial fuel cells are equipped with a microbial fuel cell that is installed to purify the organic mud at the bottom of rivers or lakes.

12. The microbial fuel cell according to claim 10 or 11, comprising a supply pipe for supplying a substrate and / or the Geobacter sp. 60473 strain from the outside to the inside of the organic mud.

13. The microbial fuel cell according to claim 12 , wherein the supply pipe is branched so as to be capable of supplying a plurality of dispersed components in the planar direction of the anode electrode in the liquid or the water.

14. The microbial fuel cell according to any one of claims 7, 10 and 11, wherein the anode electrode is made of a conductive metal material having a lower internal electrical resistance than the cathode electrode.

15. A microbial fuel cell according to any one of claims 7, 10 and 11, wherein the surface area of ​​the cathode electrode is at least 1.1 times greater than the surface area of ​​the cathode electrode.

16. A microbial fuel cell as described in claim 10 or claim 11, wherein the cathode electrode and the anode electrode are arranged in parallel, one end of the cathode electrode and one end of the anode electrode arranged on the same side as the one end are connected to a support extending in the depth direction of the liquid or the water, the cathode electrode and the anode electrode are fixed and supported in an adjustable manner while maintaining a gap according to the depth, and the bottom side of the anode electrode is provided with an installation fixing portion that protrudes in the depth direction.

17. A composition for a microbial electrolysis cell, comprising Geobacter sp. 60473 (NITE BP-03900) and an organic matter.

18. The composition for a microbial electrolysis cell according to claim 17, further comprising electrochemically active bacteria other than Geobacter sp. strain 60473.

19. 18. The composition for a microbial electrolysis cell according to claim 17, wherein at least a portion of the organic matter is sludge.

20. A microbial electrolysis cell in which Geobacter sp. 60473 (NITE BP-03900) is used to decompose organic matter for fuel.

21. A liquid mainly composed of water containing organic matter; A container for containing the liquid; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed in contact with the liquid; a potential control device having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; A microbial electrolysis cell comprising: Geobacter sp. 60473 (NITE BP-03900) contained in the liquid, which decomposes the organic matter and emits electrons.

22. the container is partitioned by a membrane selectively permeable to protons into a chamber in which the anode electrode is disposed and a chamber in which the cathode electrode is disposed, 22. The microbial electrolysis cell of claim 21, wherein the organic matter and the Geobacter sp. 60473 strain are contained in a liquid contained in a tank in which the anode electrode is disposed.

23. A container containing organic mud and a liquid mainly composed of water; a conductive anode electrode disposed in the liquid; a conductive cathode electrode disposed in the liquid; a potential control device having one end connected to the anode electrode and the other end connected to the cathode electrode, through which electrons flow; Geobacter sp. 60473 (NITE BP-03900) contained in the organic mud; A microbial electrolysis cell comprising:

24. 24. The microbial electrolysis cell of claim 23, comprising a supply pipe for supplying a substrate and / or said Geobacter sp. 60473 strain from the outside to the inside of said liquid.

25. The microbial electrolysis cell according to claim 24 , wherein the supply pipe is branched so as to supply the liquid to the anode electrode or the cathode electrode in a plurality of branches.

26. 25. The microbial electrolysis cell of claim 21, claim 23, or claim 24, wherein the anode electrode is a conductive material having a lower internal electrical resistance than the cathode electrode.

27. 25. The microbial electrolysis cell of claim 21, claim 23, or claim 24, wherein the surface area of ​​the cathode electrode is at least 1.1 times greater than the surface area of ​​the cathode electrode.

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