Method for decomposing fructose, device for decomposing fructose, method for producing mannitol, and device for producing mannitol

Abstract

The present disclosure provides technology that is advantageous from the point of view of decomposing fructose by an enzymatic reaction. A method for decomposing fructose according to the present disclosure includes bringing a working electrode into contact with a liquid containing a mannitol dehydrogenase, fructose, and a coenzyme, thereby electrochemically reducing the coenzyme, and decomposing the fructose by means of the mannitol dehydrogenase.

Description

Fructose decomposition method, fructose decomposition device, mannitol production method, and mannitol production device

[0001] The present disclosure relates to a method for decomposing fructose, an apparatus for decomposing fructose, a method for producing mannitol, and an apparatus for producing mannitol.

[0002] It has been known in the past to convert sugars such as fructose and glucose using enzymes and coenzymes.

[0003] For example, Patent Document 1 describes an enzyme electrode in which D-mannitol dehydrogenase (DMDH) is immobilized on a current collector. This enzyme electrode is used in a method for analyzing the concentration of fructose contained in food. For example, in a measurement system equipped with this enzyme electrode, reduced nicotinamide adenine dinucleotide (NADH) is dissolved in a buffer solution as a coenzyme, and the potential of the enzyme electrode is set to −1.2 V relative to a reference electrode. In this case, when fructose is added to the buffer solution, the cathodic current increases. This increase in cathodic current is due to the reaction in which fructose is reduced by the action of DMDH, and the oxidized NADH is reduced back to its original reduced form in conjunction with this reaction. The concentration of fructose can be measured by electrochemically measuring the NADH, whose concentration decreases in conjunction with the enzymatic reaction.

[0004] Patent Document 2 describes an electrochemical reaction device. This electrochemical reaction device includes a first tank, a second tank, a membrane, and a voltage application device. The first tank contains glucose dehydrogenase and nicotinamide adenine dinucleotide (NAD). + In this electrochemical reaction device, glucose dehydrogenase functions as a catalyst and NAD + As a coenzyme, glucose is broken down to produce gluconolactone. + When a voltage is applied between the working electrode and the counter electrode by the voltage application device, the NADH produced in the above reaction is oxidized by the working electrode, and NAD +In the electrochemical reactor, NADH is continuously oxidized to NAD + is produced, allowing glucose to continue to be broken down even without large amounts of nicotinamide adenine dinucleotide.

[0005] Japanese Patent Publication No. 63-14301 International Publication No. 2023 / 074453

[0006] The techniques described in the above patent documents need to be reconsidered from the viewpoint of decomposing fructose by an enzymatic reaction. Therefore, the present disclosure provides an advantageous technique from the viewpoint of decomposing fructose by an enzymatic reaction.

[0007] The present disclosure provides a method for decomposing fructose, comprising contacting a liquid containing mannitol dehydrogenase, fructose, and a coenzyme with a working electrode to electrochemically reduce the coenzyme, and decomposing the fructose with the mannitol dehydrogenase.

[0008] The method for decomposing fructose of the present disclosure is advantageous in that fructose is decomposed by an enzymatic reaction.

[0009] FIG. 1 is a diagram schematically illustrating an example of a fructose decomposition device according to an embodiment. FIG. 2 is a functional block diagram illustrating an example of a fructose decomposition device according to an embodiment. FIG. 3 is a diagram schematically illustrating the mechanism of fructose decomposition. FIG. 4 is a graph showing the relationship between the current value of the working electrode and the voltage application time in the decomposition of fructose. FIG. 5 is a flowchart showing an example of a fructose decomposition method according to an embodiment. FIG. 6 is a graph showing the change in the amount of fructose in Example 1. FIG. 7 is a graph showing the change in the amount of fructose in Comparative Example 1.

[0010] (Findings that Form the Basis of the Present Disclosure) In recent years, excessive fructose intake has been associated with obesity and some cancers. Therefore, it is expected that there will be an increasing need for a technology that can efficiently convert fructose into sugar alcohols and the like. Mannitol dehydrogenase (MDH) functions as a catalyst in the reaction of the following formula (1), which involves reduced nicotinamide adenine dinucleotide (NADH) as a coenzyme:

[0011] D-fructose + NADH + H + → D-mannitol + NAD + Formula (1) As described in Patent Document 1, when measuring the fructose concentration in a given sample using the above reaction, for example, the change in the concentration of NADH conjugated to this reaction can be measured. In this case, it is thought that the amount of NADH consumed for measuring the fructose concentration is not very large. On the other hand, in order to convert fructose in a fructose-containing liquid to mannitol using the above reaction, it may be difficult to add a coenzyme such as NADH at a concentration corresponding to the amount of fructose contained in the liquid. This is because there is an upper limit to the concentration of NADH that can dissolve in the liquid. For this reason, it is not easy to decompose fructose by an enzymatic reaction.

[0012] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have newly discovered that by electrochemically and continuously reducing the oxidized coenzyme produced in conjunction with the catalytic action of MDH, the coenzyme can be regenerated to a state suitable for fructose degradation. As a result, fructose can be decomposed by adding a small amount of coenzyme. Based on this new finding, the present inventors have completed the disclosed fructose degradation method, fructose degradation apparatus, mannitol production method, and mannitol production apparatus. In this disclosure, "continuously" means "repeatedly."

[0013] (Embodiments of the Present Disclosure) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, each drawing is not necessarily an exact illustration. In each drawing, substantially identical configurations are assigned the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, below, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangular," and numerical ranges do not only indicate the strict meaning, but also include substantially equivalent ranges, for example, differences of a few percent. These embodiments shown as comprehensive or specific examples may be realized using a system, an apparatus, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized using any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0014] (Embodiment) Hereinafter, an embodiment will be specifically described with reference to FIGS. 1 to 5. FIG.

[0015] FIG. 1 is a schematic diagram illustrating an example of a fructose decomposition apparatus according to an embodiment. As shown in FIG. 1, the fructose decomposition apparatus 100 includes a working electrode 1, a counter electrode 3, and a voltage application device 20. The voltage application device 20 is a device for applying a voltage between the working electrode 1 and the counter electrode 3. The decomposition apparatus 100 electrochemically and continuously reduces a coenzyme by applying a voltage between the working electrode 1 and the counter electrode 3, and decomposes fructose using mannitol dehydrogenase. It is believed that fructose is converted to mannitol by the decomposition. Therefore, the decomposition apparatus 100 can also be referred to as a mannitol manufacturing apparatus. Fructose is, for example, D-fructose, and mannitol is, for example, D-mannitol.

[0016] The decomposition device 100 can electrochemically and continuously reduce the coenzyme by contacting the working electrode 1 with a liquid 9a containing mannitol dehydrogenase, fructose, and a coenzyme. Additionally, fructose can be decomposed by the mannitol dehydrogenase. As described above, fructose is considered to be converted to mannitol through its decomposition. Therefore, this method can also be understood as a method for producing mannitol from fructose by an enzymatic reaction.

[0017] The coenzyme is oxidized as mannitol is produced from fructose by mannitol dehydrogenase, for example, and is reduced by receiving electrons from the working electrode 1. FIG. 3 is a diagram schematically showing the mechanism of fructose decomposition. As shown in FIG. 3, as mannitol is produced from fructose by mannitol dehydrogenase, the reduced coenzyme is converted into an oxidized coenzyme. In addition, the oxidized coenzyme receives electrons from the working electrode 1 and is converted into a reduced coenzyme. These changes are repeated, resulting in the decomposition of fructose. Therefore, for example, it is possible to reduce the concentration of fructose contained in the liquid 9a to a predetermined value or less.

[0018] In the decomposition device 100, for example, a voltage is applied between the working electrode 1 and the counter electrode 3 for a predetermined period of time. For example, the period during which the voltage is applied between the working electrode 1 and the counter electrode 3 is adjusted depending on the amount of the liquid 9a and the initial concentration of fructose in the liquid 9a. The period during which the voltage is applied between the working electrode 1 and the counter electrode 3 becomes longer as the amount of the liquid 9a increases or the initial concentration of fructose in the liquid 9a increases.

[0019] In the decomposition device 100, for example, a voltage may be applied to the working electrode 1 until the current value at the working electrode 1 becomes equal to or less than a predetermined value Ie. FIG. 4 is a graph showing the relationship between the current value at the working electrode 1 and the voltage application time during the decomposition of fructose. As shown in FIG. 4, the current value at the working electrode 1 decreases as the voltage application time increases. When fructose is converted to mannitol and the concentration of fructose contained in the liquid 9a decreases, the enzyme reaction becomes less likely to occur, and the conversion from reduced coenzyme to oxidized coenzyme also becomes less likely. Therefore, the amount of oxidized coenzyme that accepts electrons from the working electrode 1 decreases, and the current value at the working electrode 1 decreases. In other words, a small current value at the working electrode 1 suggests that the fructose concentration has decreased.

[0020] As long as fructose can be converted into mannitol by mannitol dehydrogenase in the decomposition device 100, the coenzyme is not limited to a specific one. The coenzyme is, for example, nicotinamide adenine dinucleotide (NADH). In this case, as mannitol is produced from fructose by mannitol dehydrogenase, reduced NADH is oxidized to produce oxidized nicotinamide adenine dinucleotide (NADH). + ) is generated. Also, by receiving electrons from the working electrode 1, oxidized NAD + is reduced to produce reduced NADH. The coenzyme may be nicotinamide adenine dinucleotide phosphate (NADPH).

[0021] 1 , the decomposition apparatus 100 further includes, for example, a reference electrode 2, a cell 4, a lid 5, terminals 6a, 6b, and 6c, leads 7a, 7b, and 7c, a stirrer 8, a control device 30, and a stirrer 40. The working electrode 1, the reference electrode 2, the counter electrode 3, the cell 4, the lid 5, the terminals 6a, 6b, and 6c, and the leads 7a, 7b, and 7c form an electrochemical reactor 10, which is a three-electrode cell. The electrochemical reactor 10 may also be configured as a two-electrode cell that includes the working electrode 1 and the counter electrode 3 and omits the reference electrode 2.

[0022] The cell 4 has, for example, a first space 4a and a second space 4b therein. A working electrode 1 and a reference electrode 2 are disposed in the first space 4a, and a counter electrode 3 is disposed in the second space 4b. The cell 4 has, for example, a connection portion 4c. The connection portion 4c connects the first space 4a and the second space 4b, and a separator 4s is disposed in the connection portion 4c. The separator 4s separates the space on the first space 4a side of the connection portion 4c from the space on the second space 4b side.

[0023] The first space 4a may contain a liquid 9a containing mannitol dehydrogenase, fructose, and a coenzyme. This allows the liquid 9a to come into contact with the working electrode 1. The second space 4b may contain, for example, a liquid 9b. This allows the liquid 9b to come into contact with the counter electrode 3. The liquid 9b may be, for example, an electrolyte solution such as a phosphate buffer solution.

[0024] The separator 4s has, for example, ion conductivity and blocks the permeation of some of the components contained in the liquid 9a and the liquid 9b. For example, the separator 4s blocks the permeation of mannitol dehydrogenase, fructose, and coenzymes contained in the liquid 9a. The separator 4s has, for example, proton conductivity. The separator 4s includes, for example, a polymer having a perfluoro side chain containing a sulfonic acid group.

[0025] The surfaces of the working electrode 1 and the counter electrode 3 include, for example, a conductive material. Examples of the conductive material include a carbon material, a conductive polymer, a semiconductor material, or a metal material. The conductive material is, for example, a material that does not decompose when the conductive material is oxidized. Examples of the conductive material include a carbon material, a conductive polymer, a semiconductor material, and a metal material. Examples of the carbon material include carbon nanotubes, Ketjen Black (registered trademark), glassy carbon, graphene, fullerene, carbon fiber, carbon fabric, and carbon aerogel. Examples of the conductive polymer include polyaniline, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene), poly(p-phenylene vinylene), polythiophene, and poly(p-phenylene sulfide). Examples of the semiconductor material include silicon, germanium, indium tin oxide (ITO), titanium oxide, copper oxide, and silver oxide. Examples of the metal material include gold, platinum, silver, titanium, aluminum, tungsten, copper, iron, and palladium. The working electrode 1 may be a glassy carbon electrode, and the counter electrode 3 may be a platinum electrode.

[0026] In the decomposition device 100, for example, the working electrode 1 functions as a cathode electrode, and the counter electrode 3 functions as an anode electrode. When a voltage is applied between the working electrode 1 and the counter electrode 3, the potential of the working electrode 1 is adjusted to, for example, a potential that can reduce the oxidized coenzyme. The surface area of ​​the counter electrode 3 is, for example, larger than the surface area of ​​the working electrode 1. With this configuration, the reaction rate of the reaction in which the coenzyme is electrochemically reduced tends to increase. Therefore, a large amount of mannitol is likely to be produced in a short period of time from the fructose contained in the liquid 9a.

[0027] The reference electrode 2 does not react with the components contained in the liquid 9a and is maintained at a specific potential. The reference electrode 2 is, for example, a silver / silver chloride electrode.

[0028] In the electrochemical reactor 10, the cell 4 is closed by, for example, a lid 5. Terminals 6a, 6b, and 6c are attached to the lid 5. A lead 7a extends from the terminal 6a and electrically connects the terminal 6a to the working electrode 1. A lead 7b extends from the terminal 6b and electrically connects the terminal 6b to the reference electrode 2. A lead 7c extends from the terminal 6c and electrically connects the terminal 6c to the counter electrode 3. The terminals 6a, 6b, and 6c are electrically connected to a voltage application device 20.

[0029] The voltage application device 20 applies a voltage between the working electrode 1 and the counter electrode 3 in accordance with, for example, a control signal output from the control device 30, and adjusts the potential difference between the working electrode 1 and the reference electrode 2 to a predetermined value.

[0030] The control device 30 performs information processing to control the application of voltage by the voltage application device 20 and the movement of the motor (not shown) of the agitation device 40. The control device 30 includes, for example, a memory that stores a program for controlling the application of voltage by the voltage application device 20 and the movement of the motor of the agitation device 40, and an arithmetic device such as a processor that reads out the program and performs predetermined calculations.

[0031] In the stirring device 40, the operation of the motor is controlled in accordance with the control signal output from the control device 30. This adjusts the rotation speed and rotation time of the stirring bars 8 arranged in the first space 4 a and the second space 4 b, respectively.

[0032] Fig. 2 is a functional block diagram showing the decomposition device 100. As shown in Fig. 2, the voltage application device 20 includes, for example, an acquisition unit 21, an information processing unit 22, and a voltage control unit 23.

[0033] The acquiring unit 21 acquires the control signal output from the control unit 30. The acquiring unit 21 may also acquire measurement data such as the potential of each electrode in the electrochemical reactor 10a and the value of the current flowing through the liquid 9b.

[0034] The information processing unit 22 processes the information acquired by the acquisition unit 21. For example, when the information processing unit 22 acquires a control signal from the acquisition unit 21, it outputs the acquired control signal to the voltage control unit 23. When the voltage control unit 23 starts applying a voltage to each electrode of the electrochemical reactor 10, the information processing unit 22 acquires measurement data, such as the potential of each electrode of the electrochemical reactor 10 and the value of the current flowing through the liquid 9b, acquired from the acquisition unit 21. Based on the acquired data, the information processing unit 22 calculates a voltage to be applied to the working electrode 1 so as to maintain the potential difference between the working electrode 1 and the reference electrode 2 at a predetermined value. Then, it outputs a control signal to the voltage control unit 23 to adjust the voltage of the working electrode 1 to the calculated voltage.

[0035] The voltage control unit 23 applies a voltage to each electrode of the electrochemical reactor 10 based on the control signal output from the information processing unit 22 .

[0036] As shown in FIG. 1, the voltage application device 20 and the control device 30 may be separate entities, or the voltage application device 20 and the control device 30 may be integrally configured.

[0037] The control device 30 includes, for example, an acquisition unit 31, an information processing unit 32, a storage unit 33, and an output unit 34.

[0038] The acquisition unit 31 acquires, for example, instruction information, which is information relating to an instruction input by a user, and outputs the acquired instruction information to the information processing unit 32 .

[0039] The information processing unit 32 determines the conditions for applying a voltage to each electrode of the electrochemical reactor 10, for example, based on the instruction information acquired by the acquisition unit 31. The instruction information includes, for example, the type of enzyme, the amount of the liquid 9a, the completion time of the reaction to produce mannitol, the completion time of the reaction, etc. The instruction information may include the ratio of the target fructose concentration to the initial fructose concentration in the liquid 9a, or information corresponding to that ratio.

[0040] The information processing unit 32 may output to the output unit 34 a control signal that controls voltage application under conditions determined based on the instruction information, or may output to the output unit 34 a control signal that controls voltage application under voltage application conditions preset by the user.

[0041] The output unit 34 outputs the control signal obtained from the information processing unit 32 to the voltage application device 20 .

[0042] The storage unit 33 stores data such as instruction information acquired by the acquisition unit 31, computer programs executed by the control unit 30 (for example, application programs for controlling the voltage application device 20), and the like.

[0043] 5 is a flowchart showing an example of a method for decomposing fructose. For example, liquids 9a and 9b are contained in cell 4. Next, in step S101, instruction information is input to decomposition apparatus 100. The instruction information includes, for example, the amount of liquid 9a, the completion time of the reaction for producing mannitol, the completion time of the reaction, the ratio of the target fructose concentration to the initial fructose concentration in liquid 9a, or information corresponding to that ratio.

[0044] Next, in step S102, a condition for terminating the production of mannitol is set based on the instruction information. This condition is, for example, that a predetermined time has elapsed since the start of voltage application or that the current at the working electrode 1 has become equal to or less than a predetermined value Ie. In step S102, conditions related to a target value for the potential of the working electrode 1, a target value for the voltage between the working electrode 1 and the counter electrode 3, and the rotation speed of the stirrer 40 can be set.

[0045] Next, in step S103, voltage application is started. For example, the control device 30 generates a control signal in accordance with a target value of the potential of the working electrode 1 and a target value of the voltage between the working electrode 1 and the counter electrode 3. The voltage application device 20 applies a voltage between the working electrode 1 and the counter electrode 3 in accordance with the control signal acquired from the control device 30.

[0046] Next, in step S104, the oxidized coenzyme is converted into a reduced coenzyme, and fructose is converted into mannitol by an enzymatic reaction involving mannitol dehydrogenase.

[0047] Next, the process proceeds to step S105, where it is determined whether the condition for terminating the production of mannitol, set in step S102, is met. If the result of the determination in step S105 is negative, the process proceeds to step S107, where the application of voltage between the working electrode 1 and the counter electrode 3 is continued, and steps S104 and S105 are repeated.

[0048] If the determination in step S105 is positive, the process proceeds to step S106, where the voltage application by the voltage application device 20 is terminated. Thereafter, the liquid 9a is collected, and the series of processes is completed.

[0049] (Other Embodiments) The fructose decomposition method, fructose decomposition apparatus, mannitol production method, and mannitol production apparatus have been described based on the embodiments. However, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications that a person skilled in the art can make to the embodiments and other embodiments formed by combining some of the components of the embodiments are included in the scope of the present disclosure.

[0050] (Additional Note) From the above description, the following techniques are disclosed.

[0051] (Technology 1) A method for decomposing fructose, comprising contacting a liquid containing mannitol dehydrogenase, fructose, and a coenzyme with a working electrode to electrochemically reduce the coenzyme, and decomposing the fructose with the mannitol dehydrogenase.

[0052] (Technology 2) The method for decomposing fructose according to Technology 1, wherein the coenzyme is oxidized as mannitol is produced from the fructose by the mannitol dehydrogenase, and is reduced by receiving electrons from the working electrode.

[0053] (Technology 3) The method for decomposing fructose according to Technology 1 or 2, wherein the coenzyme is nicotinamide adenine dinucleotide.

[0054] (Technology 4) The method for decomposing fructose according to any one of Techniques 1 to 3, wherein a voltage is applied to the working electrode for a predetermined period of time.

[0055] (Technology 5) The method for decomposing fructose according to any one of Techniques 1 to 4, wherein a voltage is applied to the working electrode until a current value at the working electrode becomes equal to or less than a predetermined value.

[0056] (Technology 6) A fructose decomposition device comprising: a working electrode; a counter electrode; and a voltage application device for applying a voltage between the working electrode and the counter electrode, wherein the decomposition device electrochemically reduces a coenzyme by the application of the voltage, and decomposes fructose by mannitol dehydrogenase.

[0057] (Technology 7) The fructose decomposition device according to Technology 6, wherein the working electrode donates electrons to the coenzyme when the voltage is applied.

[0058] (Technology 8) The fructose decomposition apparatus according to Technology 6 or 7, wherein the coenzyme is nicotinamide adenine dinucleotide.

[0059] (Technology 9) The fructose decomposition device according to any one of Technologies 6 to 8, wherein the voltage application device continues to apply the voltage for a predetermined period of time.

[0060] (Technology 10) The fructose decomposition device according to any one of Technologies 6 to 9, wherein the voltage application device continues to apply the voltage until a current value at the working electrode becomes equal to or less than a predetermined value.

[0061] (Technology 11) A method for producing mannitol, comprising contacting a liquid containing mannitol dehydrogenase, fructose, and a coenzyme with a working electrode to electrochemically reduce the coenzyme, and converting the fructose into mannitol by the mannitol dehydrogenase.

[0062] (Technology 12) A mannitol production apparatus comprising: a working electrode; a counter electrode; and a voltage application device for applying a voltage between the working electrode and the counter electrode, wherein the production apparatus electrochemically reduces a coenzyme by applying the voltage, and converts fructose into mannitol by mannitol dehydrogenase.

[0063] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0064] Example 1 An apparatus equivalent to the decomposition apparatus 100 shown in FIG. 2 A platinum plate with an area of ​​1000 μm was used as the working electrode. A silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode. A platinum wire coil with a wire diameter of 0.5 mm and a length of 23 cm was used as the counter electrode. The surface area of ​​the counter electrode was larger than that of the working electrode. A potentiostat OctoStat30 provided by Ivium Technologies BV was used as the voltage application device. A three-electrode cell was constructed by electrically connecting the working electrode, reference electrode, and counter electrode to the working electrode terminal, reference electrode terminal, and counter electrode terminal of the potentiostat, respectively. An ion-exchange membrane, Nafion 117 provided by MTI Corporation, was used as the membrane separating the space inside the three-electrode cell where the working electrode and reference electrode were located from the space inside the three-electrode cell where the counter electrode was located. Nafion is a registered trademark.

[0065] A phosphate buffer solution (PBS) with a pH of 7.4 provided by Nippon Gene Co., Ltd. was placed in the space inside the three-electrode cell where the counter electrode was placed. In this space, a portion of the counter electrode was in contact with the PBS. The amount of PBS placed in the space where the counter electrode was placed was 20 mL.

[0066] Fructose, reduced NADH, and mannitol dehydrogenase were added to the PBS prepared separately to prepare the stock solution of Example 1. D(+)-fructose provided by Fujifilm Wako Pure Chemical Industries, Ltd. was used as the fructose. β-nicotinamide adenine dinucleotide, reduced disodium salt provided by Sigma-Aldrich was used as the reduced NADH. Mannitol dehydrogenase (MDH) provided by Megazyme was used as the mannitol dehydrogenase. The fructose concentration in the stock solution of Example 1 was 350 mM. The reduced NADH concentration in the stock solution of Example 1 was 5.6 mM. The MDH concentration in the stock solution of Example 1 was 2 Units / mL. 20 mL of the stock solution of Example 1 was placed in the space inside the three-electrode cell where the working electrode and reference electrode were located. The stock solution of Example 1 contacted a portion of the working electrode and a portion of the reference electrode.

[0067] While the PBS and the raw material solution of Example 1 contained in the space where the counter electrode was placed were stirred with a magnetic stirrer, a predetermined voltage was applied between the working electrode and the electrode at a temperature ranging from 20°C to 25°C for 16 hours. In this manner, the treatment solution of Example 1 was obtained from the raw material solution of Example 1. The fructose concentration in the treatment solution of Example 1 was measured using a Fructose Colorimetric / Fluorometric Assay Kit provided by Sigma-Aldrich. The results are shown in Figure 6.

[0068] Fig. 6 is a graph showing the change in the amount of fructose in Example 1. In Fig. 6, the vertical axis represents the concentration of fructose. As shown in Fig. 6, the concentration of fructose in the treated solution in Example 1 was 184 mM. It is believed that 48% of the fructose in the raw material solution in Example 1 was converted by the enzymatic reaction.

[0069] Comparative Example 1 A treatment solution according to Comparative Example 1 was obtained in the same manner as in Example 1, except for the following points. PBS contained in the space in which the counter electrode was placed and the raw material solution according to Example 1 were stirred with a magnetic stirrer for 16 hours at temperatures ranging from 15°C to 25°C without applying a voltage between the working electrode and the electrode. The fructose concentration in the treatment solution according to Comparative Example 1 was measured using a Fructose Colorimetric / Fluorometric Assay Kit provided by Sigma-Aldrich. The results are shown in Figure 7.

[0070] Fig. 7 is a graph showing the change in the amount of fructose in Comparative Example 1. In Fig. 7, the vertical axis represents the concentration of fructose. As shown in Fig. 7, the concentration of fructose in the treatment solution in Comparative Example 1 was 320 mM. It is believed that approximately 8% of the fructose in the raw material solution was converted by the enzymatic reaction.

[0071] NADH in the raw material solution acts as a coenzyme for MDH, and in the enzymatic reaction involving MDH, NAD + In addition, this enzymatic reaction is thought to reduce fructose to mannitol.

[0072] According to Example 1, when a voltage is applied between the working electrode and the counter electrode, NAD produced by the enzyme reaction is + is reduced to NADH and regenerated by the transfer of electrons from the working electrode. The regenerated NADH acts again as a coenzyme for MDH, + In this way, it is believed that in Example 1, the fructose contained in the raw material solution at a high concentration was converted to mannitol.

[0073] On the other hand, according to Comparative Example 1, when no voltage is applied between the working electrode and the counter electrode, NAD produced in association with the enzyme reaction + is not thought to be reduced to NADH.

[0074] Therefore, it is believed that the technology of the present disclosure can efficiently convert fructose.

[0075] According to the present disclosure, for example, fructose contained in food can be efficiently converted into mannitol.

[0076] 1 Working electrode 3 Counter electrode 9a Liquid 20 Voltage application device 100 Decomposition device

Claims

1. A method for decomposing fructose, comprising contacting a liquid containing mannitol dehydrogenase, fructose, and a coenzyme with a working electrode to electrochemically reduce the coenzyme and decomposing the fructose by the mannitol dehydrogenase.

2. The method for decomposing fructose according to claim 1, wherein the coenzyme is oxidized as mannitol is produced from the fructose by the mannitol dehydrogenase and is reduced by receiving electrons from the working electrode.

3. The method for decomposing fructose according to claim 1, wherein the coenzyme is nicotinamide adenine dinucleotide.

4. The method for decomposing fructose according to claim 1, wherein a voltage is applied to the working electrode for a predetermined period.

5. The method for decomposing fructose according to claim 1, wherein the voltage is applied to the working electrode until the current value at the working electrode becomes equal to or less than a predetermined value.

6. A fructose decomposition apparatus comprising: a working electrode; a counter electrode; and a voltage application device for applying a voltage between the working electrode and the counter electrode, wherein the decomposition apparatus electrochemically reduces a coenzyme by applying the voltage and decomposes fructose by mannitol dehydrogenase.

7. The fructose decomposition apparatus according to claim 6, wherein the working electrode donates electrons to the coenzyme by applying the voltage.

8. The fructose decomposition apparatus according to claim 6, wherein the coenzyme is nicotinamide adenine dinucleotide.

9. The fructose decomposition apparatus according to claim 6, wherein the voltage application device continues to apply the voltage for a predetermined period.

10. The fructose decomposition apparatus according to claim 6, wherein the voltage application device continues to apply the voltage until the current value at the working electrode becomes equal to or less than a predetermined value.

11. A method for producing mannitol, comprising contacting a liquid containing mannitol dehydrogenase, fructose, and a coenzyme with a working electrode to electrochemically reduce the coenzyme and converting the fructose to mannitol by the mannitol dehydrogenase.

12. A mannitol production apparatus, comprising: a working electrode; a counter electrode; and a voltage application device for applying a voltage between the working electrode and the counter electrode, wherein the production apparatus electrochemically reduces a coenzyme by applying the voltage and converts fructose to mannitol by mannitol dehydrogenase.

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