KR101892982B1 - Cathode for production of biofuel, and microbial electrosynthesis system for production of biofuel comprising the same - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a cathode for producing biofuels and a microbial electricity synthesis system for producing biofuels containing the same.
According to the present invention, the surface of a conventional carbon electrode is modified with an amine compound having a positive charge to improve the adsorption amount of electroactive microorganisms on the surface of the electrode and, at the same time, the electron transfer efficiency is improved through introduction of metal nanoparticles, It can maximize the production of various biofuels including hexanol and biomethanol.

Description

TECHNICAL FIELD The present invention relates to a cathode for producing a biofuel, and a microbial electricity synthesizing system for producing the biofuel,

TECHNICAL FIELD The present invention relates to a cathode for producing biofuels and a microbial electricity synthesis system for producing biofuels containing the same.

The microbial electrochemical system refers to a system that generates electricity by using electrons generated by oxidation / reduction of organic substances through various electrochemical reactions using microorganisms or produces chemical substances required for scientific / industrial purposes. Research on this system has expanded the application fields of microbial fuel cell, microbial electrolysis cell, microbial electrosynthesis and microbial seawater desalination cell. Microbial electrochemical systems are collectively referred to as these various application systems and have received much attention due to their potential to obtain sustainable energy and high value chemicals.

In a microbial electrosynthesis system that produces organic materials and biofuels by applying electricity to the microorganisms using electrodes, the cathodes (reducing electrodes) supply electrons to the microorganisms, The electrons are converted into NADH (Nicotinamide adenine dinucleotide) in metabolic circuits and used to produce biofuels, or they are first converted to other compounds and then the compounds are fed into microorganisms to synthesize the necessary metabolites ( Science , 2012, 335, 1596).

Electrodes used to apply electrons to microorganisms are preferably those that have few side reactions and do not show toxicity to microorganisms. Commercialized electrodes that are compatible with them include graphite felt, carbon felt, and carbon cloth (paper). However, when these electrodes are used, the electron transfer rate between the electrode and the microorganism is slow and the amount of electrons transferred from the electrode to the microorganism is small ( Energy Environ. Sci . , 2015, 8, 3418) There is a limit to the amount of conversion to organic materials and biofuels. In order to overcome these limitations, in most cases microorganisms are increasing their production by controlling the metabolism of microorganisms through genetic manipulation to be used for producing specific organic substances or biofuels, which is the energy source of NADH, There is a problem in that there is a limit in utilizing electrons supplied with microorganisms even if electrons are supplied from the electrodes.

Direct electron transfer and indirect electron transfer are methods for supplying electrons from the electrode to microorganisms. In the case of the indirect electron transfer method, the oxidation / reduction rate of the electron transport receptor is a major factor because it uses an electron mediator to transfer electrons from the electrode to the microorganism ( Nature , 2010, 8, 706) On the other hand, the direct electron transfer method is a direct transfer of electrons from the electrode to the microorganism, so that the interaction between the electrode and the microorganism plays a major role. The performance and surface properties of the electrode are influenced by the biofuel and metabolite production It has a great influence.

The main factors influencing the production of metabolites such as bioalcohols and acetates produced from microorganisms include the culture conditions of the microorganisms, the voltage conditions for applying electricity to the microorganisms on the electrodes, and the types and properties of the electrodes . Particularly, depending on the nature of the electrode surface, the amount of microbes adsorbed on the biofilm, that is, the surface of the electrode is changed, and the production efficiency of the metabolite through the supply of electricity varies depending on the amount of contact of the microbes on the electrode surface ( Energy Environ. Sci . , 2011, 4, 4813; Energy Environ. Sci ., 2015, 8, 3418).

Recently, a literature has been reported on a technique for controlling the surface charge of an electrode in order to increase production of metabolites of microorganisms through electron direct transfer to microorganisms. In particular, in the case of an electrode having a positive charge, it induces the adsorption of microorganisms on the electrode surface through electrostatic attraction with the surface of the microorganism that exhibits a negative charge. If the microorganism is adsorbed to the electrode surface, the electrode-direct the fact that electron transfer efficiency can be improved when using the electrode surface with a recent positive microorganism is carbon dioxide (CO ₂₎ from a microorganism interface with microorganisms with acetate (acetate) ( Energy Environ. Sci . , 2013, 6, 217; J. Mater. Chem . A , 2016, 4, 8395). However, in the energy industry, there is no report on the possibility that the electro-active microorganisms capable of producing biofuels can exhibit the same performance as the microorganisms capable of converting CO ₂ into acetate through the surface charge changes described in the literature, There has been no report on increasing the direct delivery probability of electrons and ultimately promoting the production of metabolites of microorganisms by increasing the adsorption amount on the electrode surface of microorganisms and more efficiently delivering the electrons supplied from the electrodes. That is, in order to ultimately improve the production of metabolites of microorganisms, it is necessary to increase the adsorption amount of microorganisms capable of producing the metabolites by receiving electrons supplied from the electrodes, and to efficiently transfer the electrons supplied from the electrodes to microorganisms. No studies have been reported on electrodes that meet both requirements.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and an object of the present invention is to provide a cathode for biofuel production capable of increasing the amount of adsorbed microorganisms on the electrode surface and efficiently transferring electrons to microorganisms, And to provide a microbial electricity synthesis system for production.

In order to solve the above problems,

A carbon electrode coated with a metal film; And an amine compound introduced into the surface of the metal film.

The metal film may be selected from gold, silver, platinum, palladium and copper.

The thickness of the metal film may be 10-50 nm.

The cathode may further include metal nanoparticles bound to the amine compound by electrostatic attraction.

The metal nanoparticles may be selected from gold, silver, platinum, palladium, and copper.

The metal nanoparticles may be selected from the group consisting of spherical, rod-shaped, wire-shaped, pyramid-shaped, cube-shaped and prism-shaped.

The size of the metal nanoparticles may be 5-100 nm.

The carbon electrode may be a graphite felt (GF), a carbon cloth, a reticulated vetrous carbon, a graphite fiber fabric (GFF), a graphite particle and a carbon fiber brush a carbon fiber brush, and the like.

The amine compound may be selected from the group consisting of aminoalkane thiol (the alkane is 1 to 6 carbon atoms), poly (allylamine hydrochloride), and polyethyleneimine (poly (ethyleneimine)) .

The microorganisms adsorbed on the surface of the cathode are selected from the group consisting of Shewanella oneidensis MR-1, Alpha-proteobacteria, Beta-proteobacteria, Delta- Delta-proteobacteria, Clostridia, Shewanella oneidensis DSP-10, Shewanella putrefaciens SR-21, Geobacter sulfurreducens, Geobacter sulfurreducens KN400, Orcopyridylsulperidone KN400, Orthoquaternospora spp., And the like. Ochrobactrum anthropi YZ-1, Brevibacillus spp. PTH1 (Brevibacillus sp. PTH1), E. coli K12 HB101, Aeromonas hydrophila, Corynebacterium sp. MFC03 (Corynebacterium sp. MFC03), Leptothrix discophora SP-6, Bacillus licheniformis, Bacillus thermoglucosidasius, Spirulina plicensis Platensis, Bacillus subtilis, Enterococcus gallinarum, Acetobacter aceti, Gluconobacter roseus, clostridium sp., and Bacillus subtilis. Clostridium sp., And Clostridium sp. Strain.

The voltage applied to the cathode may be -100 mV to -1000 mV (versus Ag / AgCl).

The present invention also provides a microorganism biosynthesis system for producing biofuels, comprising a cathode for producing biofuel, an anode, and a cation exchange membrane for separating the region of the cathode and the anode.

According to the present invention, the surface of a conventional carbon electrode is modified with an amine compound having a positive charge to improve the adsorption amount of electroactive microorganisms on the surface of the electrode and, at the same time, the electron transfer efficiency is improved through introduction of metal nanoparticles, It can maximize the production of various biofuels including hexanol and biomethanol.

1 is a schematic view showing a cathode for producing biofuel and a principle of producing biobutanol from the cathode according to the present invention.
2 is a schematic diagram of a system for synthesizing a microbial cell for producing biofuel and candidate materials for a cathode for producing biofuel according to the present invention.
3 (A) to 3 (D) are graphs showing the adsorption amounts of Shewanella oneidensis MR-1 PJL23 according to the voltage applied when the graphite felt cathode was used as an electrode according to the comparative example of the present invention (C) -600 mV, and (D) -900 mV when the electricity is not applied (indicated by NE, no electricity), (B) (Versus Ag / AgCl). (E) is the cell density according to the applied voltage of Schwannella annesiensis MR-1 adsorbed on the surface of the graphite felt cathode, and (F) is the cell density of Shwenella annesiensis MR-1 Isobutanol production. All data was obtained through working for 50 hours.
4A is a SEM image of a graphite felt cathode electrode (Au-GF) whose surface is coated with a gold film (thickness of 50 nm), and Figs. 4B to 4D are SEM images of a surface modified with various organic molecules SEM image showing the adsorption pattern of Shwonnera onensis MR-1 after 50 hours of operation of the reactor for electrical synthesis (-600 mV) of isobutanol on the surface of a graphite felt cathode coated with gold film coated with gold film to be. The (B) is a graphite felt cathode coated with a gold film electrode (Au-GF), (C ) is PEG gold film of graphite felt cathode (PEG-Au-GF) coating, (D) is NH ₂ treatment gold film is coated graphite felt cathode (NH ₂ -Au-GF). (E) represents the cell density at the surface of Shwonella annenidis MR-1 by electrode type, and (F) represents the isobutanol production per electrode type. All data were obtained after working for 50 hours at -600 mV (versus Ag / AgCl).
FIG. 5A is a SEM image showing the surface of a cysteamine-gold film coated graphite felt electrode (Au NPs-NH ₂ -Au-GF) in which gold nanoparticles (diameter: 15 nm) to be. (B) was performed for 50 hours for electrical synthesis of isobutanol (-600 mV) on the surface of gold nanoparticle coated and amine treated gold film coated graphite felt electrodes (Au NPs-NH ₂ -Au-GF) Is an SEM image showing the adsorption pattern of Schwannella onesensis MR-1 after the operation. (C) is a graphite felt electrode (bare GF), an amine-treated gold film coated graphite felt electrode (NH ₂ -Au-GF), gold nanoparticles coated with the amine treatment, and a gold film coated graphite felt electrode (Au NPs- _{2 is} a graph comparing the isobutanol production of Schwannella annuidensis MR-1 in the case of applying a voltage of -600 mV (versus Ag / AgCl) to the NH ₂ -Au-GF, Is a graph comparing the effects of electricity on the production of isobutanol in three electrodes. All data were obtained after working for 50 hours at -600 mV.

Hereinafter, the present invention will be described in more detail.

The production of bio-alcohol, Shewanella oneidensis MR-1 pJL23, is genetically altered in its pathway to produce isobutanol. Shewanella oneidensis MR-1 pJL23 requires part of NADH to produce isobutanol. Some of the electrons for NADH synthesis can be obtained during the glucosamine degradation process, but require additional electrons to produce isobutanol. Because the bacteria have cytochrome C on their membrane surface, they have the conductivity to transfer electrons supplied from outside for their metabolism. Thus, the bacteria can improve the production of isobutanol under conditions of electricity supply. At the anode, water is oxidized to produce protons and the generated protons are transferred to the cathode or bacteria and converted to NADH. Thus, the function of the cathode plays a very important role for the production of isobutanol. When the electrons are directly transferred to the cell, the interaction between the bacteria and the electrode must be considered during design of the electrode.

In addition, as can be seen from the foregoing studies, the electrode surface must be modified to a positive charge in order to increase the affinity with the electroactive microorganism to increase their adsorption amount. Adsorption of the microorganism and thus the influence on the effect of biochemical substances produced by the surface charge of the biochemical substance and has a correlation, foil TB ah absorption that is produced is Sporomusa the conversion of CO ₂ to acetate It has been reported by Ovata bar (Energy Environ Sci, 2013, 6 , 217;.... J. Mater Chem A, 2016, 4, 8395).

In addition, it has been reported that the addition of metal layers (Au, Pt, Ni) at the carbon electrode is effective in increasing the yield of acetate, and the use of nanostructures such as carbon nanotubes and Ni nanowires is effective in increasing the yield of acetate .

Under such technical background, the present invention provides a cathode for producing biofuel, which can maximize the production of biofuel by increasing the adsorption amount of microorganisms on the electrode surface and efficiently transferring electrons supplied from the electrode to microorganisms.

Accordingly, the present invention provides a carbon electrode coated with a metal film; And an amine compound introduced into the surface of the metal film (Fig. 1).

At this time, the metal film may be any metal film having high electrical conductivity, and may be selected from gold, silver, platinum, palladium and copper, for example, and the thickness of the metal film may preferably be 10-50 nm .

In addition, since the surface of the cathode has a positive electrode in the aqueous solution due to the introduction of the amine compound, the adsorption of microorganisms on the electrode can be induced. At this time, the amine compound may be selected from the group consisting of aminoalkane thiol (the alkane is 1 to 6 carbon atoms), poly (allylamine hydrochloride), and polyethyleneimine (poly (ethyleneimine) . When the amine compound is an aminoalkanethiol, the alkane preferably has 1 to 6 carbon atoms, and when the number of carbon atoms in the alkane is 7 or more, there is a high possibility of forming a crystalline organic phase by self-assembly among alkyl chains There is a problem that the electron-transporting ability drops sharply. At this time, the aminoalkanethiol preferably has 1 to 6 carbon atoms, and examples thereof include aminomethane thiol, aminoethane thiol, cysteamine, aminopropane thiol, aminobutane thiol, aminopentane thiol, and aminohexane thiol.

In addition, even if the adsorption of microorganisms on the electrode can be induced by the introduction of the amine compound described above, how much the positively charged surface itself affects the increase of the production of biochemicals such as bio-alcohol, It has not been sufficiently confirmed whether the surface with a positive charge itself supplies electrons to the microorganism to produce biochemicals. In order to increase the production amount of the biofuel, it is necessary not only to increase the amount of adsorbed microorganisms but also to efficiently transfer the electrons supplied from the electrodes to the microorganisms. The cathode according to the present invention is characterized in that the metal nanoparticles bound to the amine compound by electrostatic attraction .

At this time, the metal nanoparticles may be any metal particles that are negatively charged ligand-substituted to enable electrostatic attraction or coordination with a compound on the surface of the positive electrode. For example, gold, silver, platinum, palladium And copper.

The metal nanoparticles are not limited in shape and size as long as they are capable of binding electrons to microorganisms by electrostatic attraction or coordination bonding to the amine compound. However, the metal nanoparticles may be spherical, rod-shaped, wire- , Pyramidal, cube, and prism types, and may be 5-100 nm in size.

As described above, since the cathode for producing biofuel according to the present invention can continuously improve the affinity between the electrode and the microorganism and the electron transferring ability by continuously modifying the surface thereof with a metal film, an amine compound and metal nanoparticles, As can be seen, the production of biofuels can be maximized.

The carbon electrode may be formed of graphite felt (GF), carbon cloth, reticulated vatrous carbon, graphite fiber fabric (GFF), graphite particles and carbon A carbon fiber brush, and the like.

The microorganisms adsorbed on the surface of the cathode are selected from the group consisting of Shewanella oneidensis MR-1, Alpha-proteobacteria, Beta-proteobacteria, Delta- Delta-proteobacteria, Clostridia, Shewanella oneidensis DSP-10, Shewanella putrefaciens SR-21, Geobacter sulfurreducens, Geobacter sulfurreducens KN400, Orcopyridylsulperidone KN400, Orthoquaternospora spp., And the like. Ochrobactrum anthropi YZ-1, Brevibacillus spp. PTH1 (Brevibacillus sp. PTH1), E. coli K12 HB101, Aeromonas hydrophila, Corynebacterium sp. MFC03 (Corynebacterium sp. MFC03), Leptothrix discophora SP-6, Bacillus licheniformis, Bacillus thermoglucosidasius, Spirulina plicensis Platensis, Bacillus subtilis, Enterococcus gallinarum, Acetobacter aceti, Gluconobacter roseus, clostridium sp., and Bacillus subtilis. Clostridium sp., And Clostridium sp. Strain.

The voltage applied to the cathode is preferably -100 mV to -1000 mV, as can be seen from the results of the following examples.

In addition, the biofuel may be different depending on the type of the microorganism that produces the biofuel, and may be, for example, high-grade bio-alcohol having 4 or more carbon atoms such as biobutanol and biohexanol.

According to another aspect of the present invention, there is provided a microorganism biosynthesis system for producing biofuels comprising a cathode for producing biofuel, an anode, and a cation exchange membrane for separating the region of the cathode and the anode (Fig. 2) .

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments and the like. It will be apparent to those skilled in the art, however, that these examples are provided for further illustrating the present invention and that the scope of the present invention is not limited thereto.

Amine  Treated gold film coated graphite felt (NH ₂ -Au- GF ) Cathode  Produce

The NH ₂ -Au-GF cathodes were prepared in the following sequence. First, commercialized graphite felt was cut into 3 cm × 6 cm rectangle and coated with gold on both sides of graphite felt using E-beam evaporator. The coating thickness was 10 nm and the thickness was calculated from the thickness deposited on the planar silicon substrate. The gold film coated on the graphite felt has a 50 nm-sized nano island shape as shown at 5A. Nano-islands of gold were coated on the surface of the graphite felt, and the electrode was immersed in 2 mM cysteamine ethanol solution at low temperature to induce the reaction for 3 days to prepare the NH ₂ -Au-GF cathode. After the reaction, After the third march, the residual solvent was evaporated at room temperature and dried and stored at room temperature until use.

Gold nanoparticle coating and Amine  Treated gold film coated graphite felt (Au NPs -NH ₂ -Au-GF) < / RTI > Cathode:

The NH ₂ -Au-GF electrode surface-modified with cysteamine as described above was treated for 1 day with surface-stabilized gold nanoparticle (15 nm diameter) aqueous dispersion with citric acid, and cysteamine-treated electrode and gold nanoparticle Au NPs-NH ₂ -Au-GF cathodes were prepared by inducing gold nanoparticles to adsorb onto the electrode surface through electrostatic attraction between the electrodes. The prepared cathode was taken out from the aqueous solution of nanoparticles, dried at room temperature, and stored at room temperature until use.

PEG-treated gold film coated graphite felt (PEG-Au- GF ) Cathode  Produce

The graphite felt was coated with a gold film using an E-beam evaporator in the same manner as described above. The gold coated graphite felt electrode was immersed in a 1 mM methoxy-terminated poly (ethylene glycol) -SH (number average molecular weight 5000 g / mol ) Aqueous solution to induce the reaction at a low temperature for 3 days to prepare a PEG-Au-GF cathode. After the reaction, the cells were rinsed with deionized water 2-3 times, dried at room temperature, and stored at room temperature until use.

Microbial cultivation and electrochemical experiments and isobutanol  analysis

(1) Microbial reactor (Microorganism Electrical synthesis  System)

The microbial reactor equipped with electrodes was made of Pyrex glass and made into H-type and separated into anode and cathode parts (FIG. 2). The reactor may include a 300 mL culture, a commercially available carbon cloth having an anode portion coated with platinum, and a cathode having a size of 3 cm x 6 cm manufactured by the method described above, that is, a graphite felt (bare GF), Au -GF, NH 2 -Au-GF, PEG-Au-GF, Au NPs-NH 2 -Au-GF was used.

(2) Culture of microorganisms

As described above, in the present invention, any microorganism that is adsorbed on the surface of the cathode electrode and is capable of producing biofuel such as bioalcohol by receiving electrons from the electrode can be used. In this embodiment, Shwonella oenadicis MR-1 / pJL23 was used. The strain was cultured in M9 minimal media containing 2 wt% n-acetylglucosamine, 1.5 wt% sodium pyruvate, 2 wt% sodium lactate and 0.1 wt% yeast extract at a culture temperature of 30 ° C.

In the reactor, a certain amount of Shewanella oneidensis MR-1 / pJL23 cultured in a thermostat was preliminarily inoculated to M9 minimal media containing the above components, and the reactor was maintained at 30 ° C and constant speed (200 rpm) for 50 hours to 96 hours Lt; / RTI > During the operation of the reactor, a voltage of -0.1 V to -0.9 V was applied, and the device used for voltage application was potentiostat / galvanostat (WonAe Tek, Korea). The voltage was applied and the change of the current was observed during the reaction.

Isobutanol ( Isobutanol ) Concentration analysis

The concentration of isobutanol, a biofuel produced through the reaction, was measured by gas chromatography (Agilent, CA, USA). After completion of the reaction in the microbial reactor, 1 mL of the culture containing isobutanol was sampled and mixed in 1 mL of chloroform for 10 seconds. The chloroform phase was separated from the culture supernatant, and then Na ₂ SO ₄ Transferred to a clean borosilicate organic tube containing. The sample transferred to the autosampler was injected under a flow of helium gas through a fused silica capillary column (Supelco SPB-5, 30 m 9, 0.32 mm, id 0.25 lm film) equipped with gas chromatography. At this time, the injection port was maintained at 250 ° C. During the analysis, the oven was kept at 40 ° C for 5 minutes, heated to 220 ° C at 20 ° C per minute, and maintained at 220 ° C for 5 minutes. Peaks corresponding to isobutanol were detected using a flame ionization detector.

result

3 (A) to 3 (D) are graphs showing the adsorption of Shewanella oneidensis MR-1 PJL23 according to the voltage applied when the graphite felt cathode is used as an electrode according to the comparative example of the present invention (A) was applied with a voltage of -100 mV, (C) -600 mV, and (D) -900 mV when no electricity was applied (indicated by NE) versus Ag / AgCl). (E) is the cell density according to the applied voltage of Schwannella annesiensis MR-1 adsorbed on the surface of the graphite felt cathode, and (F) is the cell density of Shwenella annesiensis MR-1 Isobutanol production. All data was obtained through working for 50 hours.

As shown in FIG. 3, when the voltage was applied to most of the electrodes, it was confirmed that the amount of microorganisms adsorbed on the electrode was increased compared with the case where the reactor was operated without applying voltage. However, when the voltage was excessively applied, . It can be seen that the production of isobutanol varies depending on the applied voltage. Interestingly, it can be seen that the production of isobutanol is correlated with the amount of adsorbed microorganisms on the electrode. As described above, since a protein capable of accepting electrons (containing Fe) is present on the surface of the microorganism used in the present invention, as the amount of adsorbed microorganisms on the electrode increases, It is possible to obtain a large amount of electrons necessary for the production of isobutanol. In addition, as shown in FIG. 3, when the voltage applied to the electrode is -600 mV (versus Ag / AgCl), the amount of adsorbed microorganisms is maximized, and thus the production of isobutanol is also maximized.

4A is an SEM image of a graphite felt cathode electrode (Au islands-GF) whose surface is coated with a gold film (coated to a thickness of 10 nm), and Figs. 4B to 4D show various organic molecules After the reactor was operated for 50 hours at -600 mV (versus Ag / AgCl) for electrical synthesis of isobutanol on the surface of a graphite felt cathode coated with a gold film with a modified surface, the Shwonella oenidensis MR- 1 < / RTI > The (B) is a graphite felt cathode coated with a gold film electrode (Au-GF), (C ) is PEG gold film of graphite felt cathode (PEG-Au-GF) coating, (D) is NH ₂ treatment gold film is coated graphite felt cathode (NH ₂ -Au-GF). (E) represents the cell density at the surface of Shwonella annenidis MR-1 by electrode type, and (F) represents the isobutanol production per electrode type. All data were obtained after working for 50 hours at -600 mV (versus Ag / AgCl).

As shown in FIG. 4, it can be seen that the amount of adsorbed microorganisms and the adsorbed morphology vary greatly depending on the surface conditions of the electrode. When pure gold film alone was coated, there was no significant difference in adsorption behavior or adsorption amount when compared with bare GF, but the amount of isobutanol production was significantly increased from 5.8 mg / L to 9.0 mg / L. Also, the difference between the average currents of the two electrodes during the reaction (= relative to the amount of charge over time, ie, the current density of how much electrons can be supplied per unit time) ± 3.55 μA for Au-GF and -44.18 ± 6.25 μA for Au-GF. This implies that not only the adsorption amount of microorganisms but also the amount of current flowing through the electrodes (or chemical species on the surface of the electrode) under the condition of constant voltage application affects the amount of isobutanol production of microorganisms.

In addition, it was confirmed that when the surface of the graphite felt coated with gold film was treated with various organic compounds, the surface property of the electrode was changed and the amount of microorganisms adsorbed on the electrode was changed. In the case of PEG-Au-GF modified with mPEG-SH surface, the amount of adsorbed microorganisms was not observed. NH ₂ -Au-GF treated with cysteamine on the surface increased the amount of adsorbed microorganisms. It was confirmed that a film was formed on the surface of the electrode which was not observed in the electrodes. The amount of current in the two electrodes was reduced compared to Au-GF. PEG-Au-GF was -42.01 ± 5.97 μA and NH ₂ -Au-GF was -37.25 ± 5.36 μA. . Interestingly, the yield of isobutanol production was 6.95 mg / L for PEG-Au-GF and 13.94 mg / L for NH ₂ -Au-GF. It is confirmed that the adsorption behavior of microorganisms is more influenced than the current amount. As shown in FIG. 3, the same was true for bare graphite.

FIG. 5A is a SEM image showing the surface of a cysteamine-gold film coated graphite felt electrode (Au NPs-NH ₂ -Au-GF) in which gold nanoparticles (diameter: 15 nm) to be. (B) was performed for 50 hours for electrical synthesis of isobutanol (-600 mV) on the surface of gold nanoparticle coated and amine treated gold film coated graphite felt electrodes (Au NPs-NH ₂ -Au-GF) Is an SEM image showing the adsorption pattern of Schwannella onesensis MR-1 after the operation. (C) is a graphite felt electrode (bare GF), an amine-treated gold film coated graphite felt electrode (NH ₂ -Au-GF), gold nanoparticles coated with the amine treatment, and a gold film coated graphite felt electrode (Au NPs- NH ₂ -Au-GF) with or without a voltage of -600 mV, and (D) is a graph comparing the isobutanol production of Schwannella onesensis MR-1 This is a comparative analysis of the effects of electricity on isobutanol production. All data were obtained after 50 hours of operation at -0.6 V.

FIG. 4 shows that although the isobutanol production is increased due to the increase in the amount of adsorbed microorganisms, it is suspected that there is a possibility that the average current amount decreases due to the coating of the organic film on the surface of the electrode, thereby lowering the production of isobutanol of the microorganism. To verify this hypothesis, Au NPs-NH ₂ -Au-GF electrodes were prepared by adsorbing gold nanoparticles (15 nm in diameter) on the surface of NH ₂ -Au-GF through electrostatic attraction. As shown in FIG. 5A It was confirmed that the gold nanoparticles were partially adsorbed on the gold film. The reason why the gold nanoparticles are partially adsorbed is that the NH _{2 that} has been modified on the surface of the gold film is continuously exposed to the surface to induce the microorganisms to be adsorbed on the surface of the electrode. After the gold nanoparticles are adsorbed, So that the electron can be rapidly transferred to the microorganism by the presence thereof. In fact, after the surface modification with gold nanoparticles, the average current value was found to be -45.96 ± 3.97 μA, which was almost similar to the average current value of Au-GF before Au-GF reforming to organisms in gold nano-island -44.18 ± 6.25 μA. In addition, it was confirmed that coating of the gold nanoparticles partially does not affect the adsorption behavior of microorganisms (FIG. 5B). In order to observe the difference in the ability of microorganisms to produce isobutanol by applying a voltage to electrodes having various surfaces, the amount of isobutanol produced when no voltage was applied was measured and compared with that of bare graphite (before voltage application: 3.1 → voltage is then: 5.9 mg / L) and NH ₂ -Au-GF (voltage application before: 10.9 → voltage is then: on the other hand exhibit similar growth rate for 13.5 mg / L) Au NPs- NH 2 -Au-GF , It was confirmed that the increase was remarkably increased to 27.3 mg / L after voltage application at 12.3 mg / L before voltage application. The fact that the change of the surface of the metal surface exposed to the surface of the electrode itself can have a significant effect on the production of isobutanol without applying electricity is also known as the first fact. Second, the gold nanoparticles are modified on the electrode surface It was confirmed that the effect of increasing microbial production of isobutanol on voltage application was greatly increased.

As a result, as shown in FIG. 5, iso-butanol is produced at about 3 mg / L (2.9-5.8 mg / L) using bare GF and iso-butanol at 10-13 mg / L using NH ₂ -Au- Butanol production was significantly increased and the yield was increased to 13-27.5 mg / L when using the Au NPs-NH ₂ -Au-GF electrode. This was confirmed that the isobutanol production more than doubled as compared to at least 4 times higher than the Au NPs-NH ₂ -Au-GF electrode, in use _{bare GF, NH 2 -Au-GF} . Also, it was confirmed that the production amount during long-term operation for 96 hours was further increased to 79.6 mg / L.

As a result, the reason why the current value of the electrode surface is increased due to the partial coating of the gold nanoparticles on the surface is due to the ability of the gold nanoparticles to effectively transfer the electrons supplied from the electrodes. However, it has not been known whether the ability of effectively supplying electrons to the outside in the electrochemical reaction of gold nanoparticles or transferring electrons produced from the outside to the electrodes can effectively transfer electrons into the microorganisms. It was found that gold nanoparticles effectively transfer electrons into microorganisms and thus have a great influence on the increase of isobutanol production of microorganisms. Thus, it was found that the optimized electrode required for a system for producing microbial metabolites by supplying electricity It is of great significance to be able to provide.

Claims (12)

A carbon electrode coated with a metal film;
An amine compound introduced into the surface of the metal film and positively charged; And
Negatively charged ligand-substituted metal nanoparticles bound to the amine compound by electrostatic attraction;
/ RTI >
Wherein the metal nanoparticles are partially adsorbed on the metal film. The method according to claim 1,
Wherein the metal film is selected from gold, silver, platinum, palladium and copper. The method according to claim 1,
Wherein the metal film has a thickness of 10-50 nm. The method according to claim 1,
Wherein the biofuel is isobutanol. 5. The method of claim 4,
Wherein the metal of the metal nanoparticles is selected from gold, silver, platinum, palladium and copper. The method according to claim 1,
Wherein the metal nanoparticles are selected from the group consisting of spherical, rod-shaped, wire-shaped, pyramid-shaped, cube-shaped and prism-shaped. The method according to claim 1,
Wherein the metal nanoparticles have a size of 5-100 nm. The method according to claim 1,
The carbon electrode may be a graphite felt (GF), a carbon cloth, a reticulated vetrous carbon, a graphite fiber fabric (GFF), a graphite particle and a carbon fiber brush and a carbon fiber brush. The method according to claim 1,
The amine compound may be selected from the group consisting of aminoalkane thiol (the alkane is 1 to 6 carbon atoms), poly (allylamine hydrochloride), and polyethyleneimine (poly (ethyleneimine) Production cathode. The method according to claim 1,
The microorganisms adsorbed on the surface of the cathode are selected from the group consisting of Shewanella oneidensis MR-1, Alpha-proteobacteria, Beta-proteobacteria, Delta- Delta-proteobacteria, Clostridia, Shewanella oneidensis DSP-10, Shewanella putrefaciens SR-21, Geobacter sulfurreducens, Geobacter sulfurreducens KN400, Orcopyridylsulperidone KN400, Orthoquaternospora spp., And the like. Ochrobactrum anthropi YZ-1, Brevibacillus spp. PTH1 (Brevibacillus sp. PTH1), E. coli K12 HB101, Aeromonas hydrophila, Corynebacterium sp. MFC03 (Corynebacterium sp. MFC03), Leptothrix discophora SP-6, Bacillus licheniformis, Bacillus thermoglucosidasius, Spirulina plicensis Platensis, Bacillus subtilis, Enterococcus gallinarum, Acetobacter aceti, Gluconobacter roseus, clostridium sp., and Bacillus subtilis. A Clostridium sp. Strain; and a cathode for producing biofuel. The method according to claim 1,
Wherein the voltage applied to the cathode is -100 mV to -1000 mV (versus Ag / AgCl). A microorganism electrochemical synthesis system for producing biofuels according to claim 1, comprising a cathode for producing biofuel, an anode, and a cation exchange membrane for separating the region of the cathode and the anode.

Images