Method for producing saccharified product of cassava leftovers, and method for producing fermented product derived from cassava leftovers

Abstract

The present invention provides a method for producing a saccharified product of cassava leftovers, the method capable of reducing the energy required for pulverizing the cassava leftovers for the purpose of improving the fluidity of the cassava leftovers, or reducing an increase in the energy required for heating in a gelatinization step including addition of water or for cooling after the gelatinization, or reducing the energy required for use as a plant after the saccharification step including addition of water, or reducing any two or more of these energies. Also provided is a method for producing a fermented product derived from cassava leftovers using a saccharified product of cassava leftovers obtained by the aforesaid method for producing a saccharified product of cassava leftovers. The method for producing a saccharified product of cassava leftovers includes: a gelatinization step for heating and gelatinizing the cassava leftovers by directly blowing steam thereto in a solid transport device of a kneader or conveyor type; and a saccharification step for saccharifying a gelatinized product of the cassava leftovers with a saccharifying enzyme. The method for producing a fermented product derived from cassava leftovers includes a fermentation step for fermenting a saccharified product of cassava leftovers with a microorganism, the saccharified product being obtained by the aforesaid method for producing a saccharified product of cassava leftovers.

Description

Method for producing saccharified cassava residue and method for producing fermented cassava residue-derived product

[0001] The present invention relates to a method for producing a saccharified product of cassava residue and a method for producing a fermented product derived from cassava residue. This application claims priority based on Japanese Patent Application No. 2023-089926 filed on May 31, 2023, the contents of which are incorporated herein by reference.

[0002] As a sustainable, decarbonized raw material, the production of sugars, fuel, plastics, etc. from non-edible biomass such as wood and factory residues has attracted attention. Among non-edible biomass, factory residues have great merits in utilization because they do not need to be cultivated or collected, and there are no costs associated with cultivation or collection, or the carbon dioxide generated by cultivation or collection.

[0003] Among the factory residues, cassava residue generated during the process of producing tapioca starch from cassava or ethanol from cassava is inedible and difficult to use as boiler fuel or animal feed due to its high moisture content and resulting susceptibility to spoilage. Cassava residue generated during the tapioca starch production process is called cassava pulp. Currently, it is sold as dried cassava pulp after being sun-dried to reduce its moisture content, or partially used as animal feed or as biogas fuel after undergoing methane fermentation. However, it is discarded during the rainy season when drying is difficult, or in areas where there are no recipients nearby, and further utilization is desired.

[0004] Cassava ethanol production involves saccharification of the starch components followed by ethanol fermentation. As mentioned above, cassava is an edible raw material that can be used to produce edible starch. Compared to inedible cassava residue, however, it is not only more expensive but also has a greater environmental impact. Therefore, ethanol production from cassava residue, particularly cassava pulp, has been studied in recent years as a highly sustainable inedible raw material that is in need of further utilization. Cassava pulp is rich in starch that remains unrecovered during the starch production process, as well as cellulose, another component that can be converted into sugar. Therefore, it is expected to be a potentially valuable raw material for producing valuable products such as sugar or ethanol by fermenting sugar. However, several technical challenges have prevented commercialization.

[0005] Ethanol production from cassava follows the method used for ethanol production from corn, which is also a starch-based raw material and was developed primarily in the United States. Specifically, the dry mill method is commonly used for ethanol production from corn, and consists of four main steps: 1) grinding and adding water to form a slurry, 2) gelatinization (hydration), 3) saccharification, and 4) fermentation (ethanol fermentation, etc.). The specific process flow is as follows: 1) the cassava is ground into fine particles using a grinder, and then mixed with water and an enzyme (α-amylase) to form a slurry. 2) The slurry is then pressurized and heated to 90-120°C by directly mixing it with steam while being transported through a pump. The temperature is then maintained in a liquefaction tank to ensure the reaction time is sufficient. Although the cassava is already in a slurry state before gelatinization, the viscosity of the cassava decreases significantly in this tank, hence the name liquefaction tank. The gelatinized material is then cooled to 50-60°C using an external heat exchanger such as a plate-type heat exchanger (3), which is suitable for saccharification, and enzymes such as glucoamylase are added to completely break down the starch into sugars. Then, the material is similarly cooled to a temperature suitable for yeast fermentation (4), and yeast is added to carry out ethanol fermentation. Here, in the gelatinization step (2), which is characteristic of starch-based raw materials, a device that uses steam to raise the temperature and pressure inside the piping as the raw material slurry is transported by a pump is called a jet cooker.

[0006] 1) Regarding milling, milling reduces particle size and fiber length, which reduces viscosity and increases fluidity when mixed with water to form a slurry. This has several advantages. First, high fluidity of the slurry facilitates mixing with starch-based raw materials, including α-amylase, the enzyme used for gelatinization. Second, it facilitates pumping, allowing for temperature control using a highly efficient liquid-liquid external heat exchanger, assuming pumping, or the use of a jet cooker that directly mixes with steam in the piping. Third, it increases fluidity not only in gelatinization but also in the saccharification process, making it easier to mix. 3) Agitation in saccharification is an important operation for maintaining sufficient contact between the enzyme and substrate to promote the enzymatic reaction and for maintaining uniform temperature and pH in the tank.

[0007] Corn-based ethanol production uses dried corn kernels as the raw material, which are easily pulverized and can be turned into powder with low energy consumption. When mixed with water, they form a low-viscosity slurry even before gelatinization, and the viscosity decreases even further after gelatinization. Cassava can also be pulverized with relatively low energy consumption, but its fiber content is higher than that of corn, and its viscosity is somewhat higher due to its pectin content. Pectin is a type of polysaccharide that has the property of increasing viscosity, and is used as a food thickener. It is found in all plants, but potatoes in particular contain a high pectin content. Therefore, after mixing cassava pulverized material with water, although the resulting slurry is somewhat viscous, it is pumpable and fully stirrable. Therefore, for cooling from the gelatinization temperature (approximately 90-120°C) to the enzymatic saccharification temperature (approximately 50-60°C), a highly efficient external liquid-liquid heat exchanger, such as a plate heat exchanger, can be used, which requires pumping. Generally, the material is cooled to the optimum temperature for enzymatic saccharification (90°C → 50°C) during pumping from the gelatinization tank to the saccharification tank, and then fed into the saccharification tank.

[0008] So far, in the study of ethanol production from cassava pulp, studies have been carried out following the flows 1) to 4), assuming that the same dry mill method and jet cooker used in the corn and cassava processing process will be applied (see, for example, Patent Document 1, etc.).

[0009] Patent No. 5824074

[0010] However, because cassava residue is the residue left after utilizing the starch component of easily fluidizable cassava root, the fiber and pectin contents, which determine the fluidity of the raw material, are more than four times higher than those of cassava root. Therefore, to ensure sufficient fluidity for pumping and uniform mixing with α-amylase, it is necessary to reduce the viscosity by thoroughly grinding the large amount of fiber contained, adding a large amount of water, or both. Conventional technologies have encountered problems, such as the high energy required for grinding cassava residue, the increased energy required for heating and cooling after gelatinization due to the addition of water, or the reduced energy efficiency of the plant after the saccharification process due to the addition of water, or any combination of these.

[0011] The present invention has been made in consideration of the above circumstances, and provides a method for producing a saccharified product of cassava residue, which aims to improve the fluidity of cassava residue and can reduce the energy required for pulverization, the increase in energy required for heating in the gelatinization step by adding water and for cooling after gelatinization, and / or the deterioration of the plant's energy efficiency after the saccharification step by adding water, or any two or more of these. The present invention also provides a method for producing a cassava residue-derived fermented product using the saccharified product of cassava residue obtained by the method for producing a saccharified product of cassava residue.

[0012] That is, the present invention includes the following aspects: (1) A method for producing a saccharified product of cassava residue, comprising: a gelatinization step of heating and gelatinizing cassava residue by directly injecting steam into a kneader-type or conveyor-type solid transport device; and a saccharification step of saccharifying the gelatinized cassava residue with a saccharifying enzyme. (2) The method for producing a saccharified product of cassava residue according to (1), wherein the cassava residue is uncrushed or comprises cassava pulp having an average particle size of 300 μm or more. (3) The method for producing a saccharified product of cassava residue according to (2), wherein the cassava residue is uncrushed or comprises cassava pulp having an average particle size of 350 μm or more. (4) The method for producing a saccharified product of cassava residue according to any one of (1) to (3), wherein the cassava residue comprises wet cassava pulp. (5) The method for producing a saccharified product of cassava residue according to any one of (1) to (4), wherein the gelatinization step includes an addition step of adding α-amylase to the cassava residue before feeding the cassava residue into the solid conveying device. (6) The method for producing a saccharified product of cassava residue according to any one of (1) to (5), wherein the saccharifying enzymes include pectinase, cellulase, and glucoamylase. (7) The method for producing a saccharified product of cassava residue according to any one of (1) to (6), wherein the saccharification step includes a mixing step of preparing a mixture containing a portion of the gelatinized product of the cassava residue, water, and the saccharifying enzymes, and initiating saccharification, and a temperature adjustment step of sequentially adding the remaining gelatinized product of the cassava residue after the mixing step, removing heat from the saccharified solution by heat exchange between the saccharified solution and cooling water, and saccharifying the saccharified solution while adjusting the temperature of the saccharified solution to a temperature suitable for saccharification by the saccharifying enzymes.(8) The method for producing a saccharified product of cassava residue according to any one of (1) to (7), wherein the saccharification step includes: a mixing step of preparing a mixture containing the gelatinized product of cassava residue, water, and the saccharifying enzyme, and initiating saccharification; a temperature adjustment step of sequentially adding the gelatinized product of cassava residue after the mixing step, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme; and a continuous saccharification step of, after the saccharified product reaches a predetermined volume by the temperature adjustment step, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water while removing heat from the saccharified product and adding the gelatinized product of cassava residue and the saccharifying enzyme, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme, so as to maintain the predetermined volume of the saccharified product. (9) A method for producing a saccharified product of cassava residue, comprising: a mixing step of preparing a mixture containing gelatinized cassava residue, water, and the saccharifying enzyme, and initiating saccharification; a temperature adjustment step of sequentially adding the gelatinized cassava residue after the mixing step, removing heat from the saccharified liquid by heat exchange between the saccharified liquid and cooling water, and saccharifying the saccharified liquid while adjusting its temperature to a temperature suitable for saccharification by the saccharifying enzyme; and a continuous saccharification step of, after the saccharified liquid reaches a predetermined volume by the temperature adjustment step, removing a portion of the saccharified liquid, adding the gelatinized cassava residue and the saccharifying enzyme, and removing heat from the saccharified liquid by heat exchange between the saccharified liquid and cooling water, while adjusting the temperature of the saccharified liquid to a temperature suitable for saccharification by the saccharifying enzyme, so as to maintain the predetermined volume of the saccharified liquid. (10) The method for producing a saccharified product of cassava residue according to (7), wherein the amount of water added to the mixture in the mixing step is an amount that causes a mixture containing a portion of the gelatinized product of cassava residue, the water, and the saccharifying enzyme to have a viscosity of 500 mPa·s or less. (11) The method for producing a saccharified product of cassava residue according to (8) or (9), wherein the amount of water added to the mixture in the mixing step is an amount that causes a mixture containing the gelatinized product of cassava residue, the water, and the saccharifying enzyme to have a viscosity of 500 mPa·s or less.(12) The method for producing a saccharified product of cassava residue according to any one of (7) to (9), wherein the viscosity of the saccharification system is controlled to 500 mPa·s or less by adjusting one or more of the group consisting of the addition rate of the gelatinized product of cassava residue, the concentration of the saccharifying enzyme, and the amount of water added in the temperature adjustment step. (13) The method for producing a saccharified product of cassava residue according to (8) or (9), wherein the viscosity of the saccharification system is controlled to 500 mPa·s or less by adjusting one or more of the group consisting of the addition rate of the gelatinized product of cassava residue, the concentration of the saccharifying enzyme, and the amount of water added in the continuous saccharification step. (14) The method for producing a saccharified product of cassava residue according to any one of (7) to (13), wherein the heat exchange is performed by circulating the saccharified solution with a pump and using an external heat exchanger. (15) The method for producing a saccharified product of cassava residue according to any one of (8), (9), and (11) to (13), wherein the continuous saccharification step involves saccharification in a continuous saccharification tank comprising a plurality of saccharification tanks connected in series. (16) The method for producing a saccharified product of cassava residue according to (15), wherein the continuous saccharification tank comprises two saccharification tanks connected in series, and the capacity of the second saccharification tank is 10% to 50% of the capacity of the first saccharification tank. (17) The method for producing a saccharified product of cassava residue according to any one of (1) to (8), wherein the gelatinization step includes an insulation step of keeping the heated cassava residue warm in an insulation tank after heating in the solid conveying device. (18) A method for producing a fermented product derived from cassava residue, comprising a fermentation step of fermenting the saccharified product of cassava residue obtained by the method for producing a saccharified product of cassava residue according to any one of (1) to (17) with a microorganism. (19) The method for producing a cassava residue-derived fermented product according to (18), further comprising a distillation step of distilling the cassava residue-derived fermented product obtained in the fermentation step.

[0013] The above-described method for producing saccharified cassava residue eliminates the need for improving the fluidity of the raw material by grinding or adding water, or both, for the purpose of uniformly mixing α-amylase and pumping. This reduces the energy required for grinding the raw material, the energy required for heating for gelatinization, the energy required for cooling from the gelatinization temperature to the saccharification temperature, and / or the energy required for the plant after the saccharification process by adding water. Furthermore, gelatinization can be performed without using an α-amylase mixing device or a grinding device that may cause problems. Alternatively, the above-described method for producing saccharified cassava residue reduces the energy required for the plant after the saccharification process by adding water. The above-described method for producing a fermented product derived from cassava residue uses the saccharified cassava residue obtained by the above-described method for producing saccharified cassava residue. The easily spoiled saccharified solution can be fermented immediately after saccharification, preventing spoilage and allowing it to be utilized.

[0014] FIG. 1 is a schematic diagram showing a saccharification apparatus used in a method for producing a saccharified product of cassava residue according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a saccharification apparatus used in a method for producing a saccharified product of cassava residue according to a second embodiment of the present invention. FIG. 3 is a schematic diagram showing a production system used in a method for producing a fermented product derived from cassava residue according to a third embodiment of the present invention. FIG. 4 is a schematic diagram showing a production system used in a method for producing a fermented product derived from cassava residue according to a fourth embodiment of the present invention. FIG. 5 is a schematic diagram showing a saccharification apparatus used in a method for producing a saccharified product of cassava residue according to a fifth embodiment of the present invention. FIG. 6 is a graph showing the changes over time in viscosity and total residue concentration (TS) of the enzymatic saccharification reaction solution in Example 2. FIG. 7 is a graph showing the changes over time in viscosity and total residue concentration (TS) of the enzymatic saccharification reaction solution in Example 4. FIG. 8 is a graph showing the residence time distribution in Example 5. FIG. 9 is a graph showing the progress of cumulative discharge amount in Example 5.

[0015] Hereinafter, a method for producing a saccharified product of cassava residue according to an embodiment of the present invention (hereinafter, simply referred to as "a method for producing a saccharified product of the present embodiment") will be described in detail with reference to the drawings. Note that in each drawing, parts not relevant to the description may be omitted.

[0016] <<Method for Producing Saccharified Cassava Residue>> <First Embodiment> A method for producing a saccharified cassava residue according to a first embodiment of the present invention includes: a gelatinization step of heating and gelatinizing the cassava residue by directly injecting steam into a kneader-type or conveyor-type solid transport device; and a saccharification step of saccharifying the gelatinized cassava residue with a saccharifying enzyme.

[0017] In a conventional method for producing cassava residue saccharified material, the cassava residue is crushed, mixed with α-amylase and water to form a slurry, which is then pumped and heated in a heating device such as a jet cooker that mixes the slurry with steam in a pipe. The mixture is then kept warm for a certain period of time to gelatinize the cassava residue, producing a gelatinized cassava residue. To ensure fluidity for pumping and uniform mixing with α-amylase, the cassava residue must be crushed and water must be added to the crushed material to achieve a dry mass of cassava residue to water ratio of at least 1:2.5. In addition to the large energy required for crushing, adding an excess amount of water before heating, which is unnecessary for the gelatinization reaction, increases the energy required for heating and cooling from the gelatinization temperature to the saccharification temperature.

[0018] In contrast, the method for producing a saccharified product of this embodiment uses a solid transport device with a specific structure that combines transport, mixing, and heating functions, allowing the cassava residue to be transported and heated without being slurried. Furthermore, simply adding α-amylase diluted with water (1 / 10 or less of the amount required in conventional methods) allows the unpulverized cassava residue and α-amylase to be thoroughly mixed. Therefore, the energy required for the above-mentioned pulverization, or the energy required for heating and cooling, or both, can be significantly reduced compared to conventional methods.

[0019] According to the method for producing a saccharified product of this embodiment, it is possible to reduce the energy required for grinding the raw materials, the energy required for heating for gelatinization and cooling from the gelatinization temperature to the saccharification temperature, and the energy required for the plant after the saccharification process, thereby efficiently producing a saccharified product of cassava residue while keeping production costs down.The method for producing a saccharified product of this embodiment can also be called a method for saccharifying cassava residue.

[0020] Next, each step of the method for producing a saccharified product of this embodiment will be described in detail below.

[0021] [Gelatinization Step] In the gelatinization step, the cassava residue is heated and gelatinized by directly blowing steam into a kneader-type or conveyor-type solid transport device.

[0022] As described above, the gelatinization process in the method for producing a saccharified product of this embodiment differs from the gelatinization process in conventional methods for producing saccharified products of cassava residue in that, by using a solid conveying device having a specific structure and function, it is possible to reduce the energy required for pumping and pulverization to improve fluidity for the purpose of uniformly mixing the α-amylase, or the amount of dilution water used, and the energy required for heating for gelatinization and cooling after gelatinization, or both.

[0023] That is, in one embodiment, the present invention provides a method for gelatinizing cassava residue, comprising heating and gelatinizing the cassava residue by directly blowing steam into a kneader-type or conveyor-type solid transport device in the gelatinization step.

[0024] (Cassava Residue) Cassava residue may be any residue discharged after utilizing starch contained in cassava (scientific name: Manihot esculenta). Examples of cassava residue include the residue obtained by extracting starch from cassava (also called "cassava pulp") and the residue obtained after saccharifying starch contained in cassava and producing ethanol using the resulting glucose as a substrate. Among these, cassava pulp is preferred because it has a higher amount of starch bound to the fiber.

[0025] Cassava pulp is typically discharged as a residue from the production of tapioca starch (cassava starch). Specifically, harvested raw cassava is first washed and peeled. The peeled cassava is then coarsely crushed, and the coarsely crushed material is then finely ground to extract the starch granules. The crushed material is then added with water and bleached, and the starch granules are filtered out through a sieve. The non-starch residue remaining on the sieve is then separated as cassava pulp. The cassava pulp is discharged wet from the sieve.

[0026] Cassava pulp generally contains moisture of approximately 70% to 85% by mass of the total mass of wet cassava residue, starch of approximately 20% to 55% by mass of the dry mass of the cassava residue, and cellulose of approximately 10% to 30% by mass of the dry mass of the cassava residue, as well as other polysaccharides such as pectin, lignin, ash, etc.

[0027] Wet cassava pulp with a moisture content of more than 30% by mass is called wet cassava pulp. The moisture content of wet cassava pulp is more than 30% by mass, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 70% by mass to 90% by mass or less, and particularly preferably 70% by mass to 85% by mass or less. On the other hand, cassava pulp that has been dried by sun drying or the like to reduce its moisture content to 30% by mass or less is called dry cassava pulp. The moisture content of dry cassava pulp is 30% by mass or less, preferably 7% by mass to 30% by mass or less.

[0028] The composition of cassava residue discharged from ethanol production plants generally includes moisture of approximately 70% to 85% by mass of the total mass of the wet cassava residue, starch of approximately 8% to 10% by mass of the dry mass of the cassava residue, and cellulose of approximately 25% to 30% by mass of the dry mass of the cassava residue, as well as polysaccharides such as pectin, lignin, and ash.

[0029] The moisture content herein refers to the ratio of the mass of moisture to the mass of the residue containing moisture, expressed as a percentage. The moisture content can be measured, for example, using an infrared moisture meter FD-720 manufactured by Kett Electric Laboratory (KETT).

[0030] The amount of starch can be measured, for example, by dispersing cassava residue in water, saccharifying it with α-amylase and glucoamylase, and quantifying the resulting glucose.

[0031] The amount of cellulose can be calculated, for example, by measuring the amount of glucose produced by hydrolysis with acid after saccharification with α-amylase and glucoamylase for the sample used to calculate the amount of starch. Alternatively, the amount of cellulose can be calculated by hydrolyzing cassava residue with acid, measuring the amount of glucose produced, and subtracting the amount of glucose derived from starch from the amount of glucose.

[0032] The cassava residue used in the method for producing a saccharified product of this embodiment has a high moisture content of 70% by mass or more, as described above, and may be used as is in a wet state without being dried, or may be dried in the sun or the like to improve shelf life.

[0033] Wet cassava residue is inexpensive but prone to spoilage due to its high moisture content. Cassava residue contains dietary fiber and pectin at concentrations four times or more higher than cassava, depending on the composition of the cassava root and the starch recovery rate from the cassava root. The dietary fiber content (NDF: Natural Detergent Fiber) based on feed analysis standards is approximately 2% to 5% by weight (per dry weight) for cassava root and approximately 15% to 40% by weight (per dry weight) for cassava pulp. Therefore, wet cassava residue maintains a solid form, rather than a liquid (slurry), even at a moisture content of 70% or more by weight. Therefore, in conventional methods for producing saccharified products, if wet cassava residue is used as a raw material for gelatinization without being slurried by crushing or adding water, the fluidity is poor, and it is difficult to pump the liquid or to uniformly mix the cassava residue with α-amylase.

[0034] When attempting to grind wet cassava residue to a particle size sufficient for easy handling, the high moisture content of wet cassava residue limits the grinding methods available, and wet grinding typically requires significant energy. To achieve sufficient grinding for easy handling, grinders require approximately 50-100 kW / t of dry cassava residue, making them the most power-hungry machine in the cassava residue saccharification process. Dry cassava residue requires slightly less power than wet cassava residue, but drying in the sun can result in high contamination rates of foreign matter such as stones and metal fragments, which can cause breakage of grinder blades or holes in the mesh, which is often installed at the outlet of the grinder to ensure uniform grind size.

[0035] It is generally known that the starch gelatinization reaction proceeds stably when the mass of water relative to the dry mass of the raw material is 1:1.5 or more. In conventional technology, when processing dry cassava residue, water must be added so that the mass of water relative to the dry mass of the cassava residue is at least 1:2.5 or more in order to create a slurry for pumping and uniform mixing of α-amylase. However, this is more water than is required for the gelatinization reaction to proceed, increasing the energy required for heating and cooling. On the other hand, in the case of wet cassava residue, the raw material often already contains water at a ratio of 1:2.5 or more, and it is desirable to process it without adding water as much as possible. However, the amount of α-amylase added is very small, at approximately 0.01 to 0.1% by mass relative to the dry mass of the raw material, and adding it as a raw solution makes it difficult to mix uniformly. Therefore, the α-amylase must be diluted at least several thousand times before being added, which increases the energy required for heating and cooling.

[0036] In contrast, in the method for producing a saccharified product of this embodiment, crushing of the cassava residue is not an essential step, and preferably, no crushing step is performed, and no slurrying is performed. In the method for producing a saccharified product of this embodiment, by using a solid transport device with a specific structure and function, even cassava residue that has not been crushed or hydrated to form a slurry or low viscosity can be smoothly transported.

[0037] Furthermore, wet cassava residue can be uniformly mixed with α-amylase using about 1 / 10 the amount of dilution water used in the past. By using wet cassava residue, particularly preferably wet cassava pulp, the moisture contained in the residue can be used as is, further reducing the amount of dilution water used for the enzyme, and eliminating the need for labor and equipment for drying the cassava residue (large areas for sun-drying or a large heat source for drying). Furthermore, there is no risk of foreign matter being mixed in when the cassava residue is sun-dried. Therefore, in the method for producing a saccharified product of this embodiment, it is preferable to use wet cassava residue, and it is more preferable to use wet cassava pulp.

[0038] In addition, when using wet cassava residue, particularly preferably wet cassava pulp, it is desirable to use the residue immediately after it is generated because it is prone to spoilage. Therefore, it is preferable to install facilities for performing the saccharified product manufacturing method of this embodiment adjacent to the starch production plant and ethanol production plant. In addition, wet cassava residue generated in the starch production plant and ethanol production plant may be transported in a refrigerated state to the facility for performing the saccharified product manufacturing method of this embodiment, and then used while still refrigerated or after returning to room temperature. Alternatively, it may be frozen and transported to the facility for performing the saccharified product manufacturing method of this embodiment, and then thawed for use.

[0039] The cassava residue used in the saccharified product manufacturing method of this embodiment may be unpulverized or pre-pulverized. In particular, the saccharified product manufacturing method of this embodiment preferably uses unpulverized cassava residue because the cassava residue can be transported, sufficiently gelatinized, and then efficiently saccharified without pulverization. Furthermore, pulverized cassava residue with a relatively large average particle size can also be used. Specifically, pulverized cassava residue preferably has an average particle size of 300 μm or more, more preferably 350 μm or more. There is no particular upper limit to the average particle size, but it can be, for example, about 800 μm.

[0040] In this specification, the term "average particle size" refers to the cumulative 50% particle size (also referred to as the volume average particle size or median size) in the volume frequency particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. The measurement can be carried out, for example, using a laser diffraction / scattering particle size distribution analyzer LA-960 manufactured by Horiba, Ltd., selecting water as the dispersion solvent, under the conditions of a refractive index real term of 1.490, an imaginary term of 0.000, and a dispersion solvent refractive index real term of 1.333.

[0041] Crushers and grinders can be used to crush cassava residue. The use of crushers and grinders improves the crushing efficiency of cassava residue. Crushing methods include impact, grinding, cutting, mortar, and colloid mill.

[0042] (Solid conveying device) The solid conveying device may be any device having a function of conveying and mixing solids, and may be a kneader-type or conveyor-type device. Among these, a kneader-type device is preferred because it has a higher mixing function and a better filling rate of solids.

[0043] The solid transport device may be of a batch type or a continuous type, but from the viewpoint of plant operation, a continuous type is preferred because the supply amount and withdrawal amount are constant and easy to control.

[0044] The continuous solid transport device may be of a screw type or a rotor type, but the rotor type is preferred as it has a stronger dispersing function.

[0045] The continuous solid material conveying device may be a single-screw, a twin-screw, or a multi-screw, and any type of solid material conveying device is applicable. Among them, a type in which all parts except the inlet and outlet for the raw material are sealed is preferred from the viewpoint of preventing heat loss due to steam leakage.

[0046] The solid conveying device has a means for heating the cassava residue. The heating means may be, for example, one or more steam inlets provided in the body of the solid conveying device. By providing the steam inlets in the solid conveying device, steam can be brought into direct contact with the cassava residue, thereby heating the cassava residue.

[0047] For example, since the gelatinization temperature of cassava starch is about 60°C, the temperature of the cassava residue during heating can be 60°C or higher, preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher. In order to minimize the deactivation of α-amylase, the upper limit of the temperature of the cassava residue during heating can be, for example, 120°C or lower, preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 100°C or lower.

[0048] Specific examples of usable solid material conveying devices include, but are not limited to, KD1 manufactured by Aikawa Iron Works, which is a kneader-type single-axis rotor type solid material conveying device.

[0049] (α-Amylase) In the gelatinization process, it is preferable to add α-amylase to the cassava residue. By adding α-amylase, a starch hydrolysis reaction occurs, resulting in a sufficiently gelatinized cassava residue.

[0050] α-Amylase, also called 1,4-α-D-glucan glucanohydrolase or glycogenase, is an enzyme that randomly cleaves 1,4-α-bonds in starch or glycogen to produce polysaccharides and oligosaccharides.

[0051] As the α-amylase, it is preferable to use, for example, a thermostable α-amylase with an optimum temperature of 90°C or higher. When a thermostable α-amylase is used, for example, it can be allowed to act at a temperature higher than the gelatinization temperature (60°C) of the starch contained in the cassava residue, thereby improving the efficiency of liquefaction. In addition, it becomes possible to advance liquefaction in the gelatinization process.

[0052] As the α-amylase, for example, the trade name "Liquozyme SC DS" manufactured by Novozymes can be used.

[0053] The timing of adding α-amylase is not particularly limited, and may be before or after adding the cassava residue to the solid conveying device, before adding and heating, or after adding and heating. May be.

[0054] In particular, in the gelatinization step, it is preferable that α-amylase is pre-mixed with water and added to the cassava residue before being charged into the solid conveying device. That is, the gelatinization step preferably includes an addition step of adding α-amylase to the cassava residue before being charged into the solid conveying device.

[0055] For example, in the case of the trade name "Liquozyme SC DS" manufactured by Novozymes, the amount of α-amylase added is preferably about 0.010% by mass or more and 0.100% by mass or less with respect to the dry mass of cassava residue.

[0056] The dilution ratio of α-amylase with water is preferably about 50 to 300 times in the case of, for example, Liquozyme SC DS, a product name manufactured by Novozymes.

[0057] The gelatinization reaction time can be, for example, 5 minutes or more and 4 hours or less.

[0058] [Saccharification Step] In the saccharification step, the gelatinized cassava residue is saccharified using a saccharifying enzyme.

[0059] (Saccharification Enzymes) The saccharification enzymes used in the saccharified product production method of this embodiment may be any enzyme capable of saccharifying the substrate components contained in cassava residue, particularly an enzyme capable of saccharifying starch, the main component of the substrate, i.e., at least glucoamylase. Among these, saccharification enzymes preferably include pectinase, cellulase, and glucoamylase, because saccharifying pectin and cellulose in addition to starch contained in cassava residue can improve the sugar recovery rate and reduce the viscosity of the saccharified solution.

[0060] Pectinase is a general term for a group of enzymes that decompose polygalacturonic acid (pectin). Examples of pectinases include at least one selected from the group consisting of polygalacturonase (endo-polygalacturonase, exopolygalacturonase), pectin lyase, pectin esterase, and pectin methylesterase. Examples of pectinases include all of polygalacturonase (endo-polygalacturonase, exopolygalacturonase), pectin lyase, pectin esterase, and pectin methylesterase.

[0061] The addition of pectinase decomposes pectin derived from cassava residue, liberating more sugars and improving saccharification efficiency. It also reduces the viscosity of the saccharified solution and the amount of insoluble impurities in the saccharified solution.

[0062] Cellulase is an enzyme that hydrolyzes glycosidic bonds in β-1,4-glucan (e.g., cellulose). The cellulase may include at least one selected from the group consisting of endoglucanase (endo-type cellulase), exoglucanase (exo-type cellulase), hemicellulase (endo-type and exo-type), other β-glucanases, and β-glucosidases. The cellulase preferably includes all of endoglucanases, exoglucanases, hemicellulases (endo-type and exo-type), other β-glucanases, and β-glucosidases.

[0063] Commercially available preparations of pectinase and cellulase can be used, and a mixed preparation of these two enzymes may also be used.

[0064] Glucoamylase, also known as glucan 1,4-α-glucosidase, degrades the 1,4-α bond at the non-reducing end of the sugar chain to produce glucose. Commercially available glucoamylase preparations can be used as glucoamylase. For example, the product name "Spirizyme Fuel HS" manufactured by Nonozyme can be used.

[0065] The starch or starch hydrolysates in the gelatinized product are saccharified by the action of glucoamylase and broken down into sugars that can be metabolised by the microorganisms used in the fermentation process described below. Celluloses in the gelatinized product are hydrolyzed by the action of endo-cellulase, hemicellulase and exo-cellulase, and the hydrolysates are broken down into oligomers by exo-cellulase and hemicellulase, and then saccharified into monosaccharides by β-glucosidase, and further broken down into sugars that can be metabolised by the microorganisms used in the fermentation process described below.

[0066] For example, when using the product "Spirizyme Fuel HS" (1425 AGU / g) manufactured by Novozymes, the amount of glucoamylase added is preferably 0.1 AGU / g or more, more preferably 0.2 AGU / g or more, and even more preferably 0.3 AGU / g or more, relative to the dry mass of cassava residue. There is no particular upper limit on the amount of glucoamylase added, but from the viewpoint of reducing the amount of enzyme used and reducing production costs, it can be, for example, 2.0 AGU / g or less.

[0067] Examples of commercially available cellulases include those manufactured by Novozymes under the trade names "Celluclast 1.5L" and "Cellic CTec2," and those manufactured by Meiji Seika Pharma under the trade name "Meicelase." Examples of commercially available pectinases include those manufactured by Shin-Nihon Chemical Industry Co., Ltd. under the trade name "Sumiteam AP2" and those manufactured by Mitsubishi Chemical Corporation under the trade name "Sucrase N." Examples of mixtures of pectinases and cellulases include an enzyme solution obtained by culturing a strain of Trichoderma reesei, a cellulase-producing filamentous fungus described in JP 2023-46320 A, into which a polygalacturonase gene derived from Aspergillus niger and a pectin lyase gene derived from Aspergillus niger have been introduced. PgaB is preferred as the polygalacturonase gene, and PelD is preferred as the pectin lyase gene. In this case, the protein content is preferably 0.05 mg / g or more relative to the dry mass of cassava residue. By being equal to or greater than the above lower limit, the viscosity of the saccharified solution can be more sufficiently reduced. There is no particular upper limit to the amount of the mixture of pectinase and cellulase added. However, from the viewpoint of reducing the amount of the mixture of pectinase and cellulase used and reducing production costs, the upper limit can be set to, for example, 2.0 mg / g.

[0068] The saccharification process may be a batch process, a semi-continuous process, or a continuous process. The batch process refers to a process in which saccharification is initiated after all of the gelatinized cassava residue has been added. The semi-continuous process refers to a process in which a portion of the gelatinized cassava residue is added, saccharification is initiated, and then the remaining gelatinized cassava residue is sequentially added. Specifically, a process including a mixing process and a temperature adjustment process, as described below (when the saccharification process is semi-continuous), can be used. The continuous process refers to a process in which the gelatinized cassava residue is sequentially added and the saccharified solution is sequentially withdrawn. Specifically, a process including a mixing process, a temperature adjustment process, and a continuous saccharification process, as described below (when the saccharification process is continuous), can be used. The saccharification process is preferably a semi-continuous or continuous process from the viewpoint of excellent heat exchange efficiency, as described below. A continuous process is more preferable from the viewpoint of obtaining a saccharified solution with a high sugar concentration and achieving better energy efficiency as a plant after the saccharification process.

[0069] That is, even when cassava residue is thoroughly pulverized, as described above, the dietary fiber and pectin contents are concentrated at more than four times that of cassava root. Therefore, the viscosity after gelatinization is very high, ranging from tens of thousands to hundreds of thousands of mPa·s. This makes it difficult to use an external heat exchanger to cool the gelatinized product from the temperature after gelatinization (approximately 90°C) to the optimal temperature for enzymatic saccharification (approximately 50°C to 60°C). On the other hand, cooling using a jacket or the like results in poor cooling efficiency and requires a significant amount of time. Therefore, conventional technology does not provide a method for cooling gelatinized cassava pulp within a time range acceptable for actual production. Furthermore, if enzymatic saccharification is initiated using a gelatinized product with a very high viscosity (tens of thousands to hundreds of thousands of mPa·s), a special mixer is required, which requires a large amount of power for mixing. Furthermore, large-scale production of such a special mixer is difficult.

[0070] (Semi-continuous saccharification process) In contrast, in a semi-continuous process, a portion of the gelatinized material is first used without cooling to prepare a mixture containing the gelatinized material, an amount of water sufficient to achieve the desired viscosity, and a saccharifying enzyme. The temperature is then adjusted to a range suitable for saccharification, specifically, approximately 50°C to 60°C, to initiate the saccharification system. The remaining gelatinized material is then added sequentially. In this case, there is a concern that the temperature within the saccharification system may rise. However, by removing heat from the saccharified solution through liquid-liquid heat exchange between the saccharified solution and cooling water, the saccharification system can be cooled with excellent heat exchange efficiency. This cooling efficiently cools the saccharification system in a short time, allowing the temperature of the saccharified solution to be maintained at a temperature suitable for saccharification. Furthermore, if the moisture content of the cassava residue is low and, as a result, the gelatinized material concentration exceeds the range suitable for enzymatic saccharification during the sequential addition process, water may be added during the sequential addition of the gelatinized material. If water is added before gelatinization, the energy required for heating and cooling increases, but if it is added after gelatinization, during saccharification, the increase in energy can be avoided. Furthermore, because the temperature of water is lower than the gelatinization temperature (approximately 90°C), adding water is also expected to have a cooling effect.

[0071] That is, in the case of a semi-continuous system, the saccharification process preferably includes: a mixing process in which a mixture containing a portion of the gelatinized cassava residue, water, and the saccharifying enzyme is prepared and saccharification is initiated; and a temperature adjustment process in which, after the mixing process, the remaining gelatinized cassava residue is successively added, the saccharified liquid is removed from the heat by heat exchange between the saccharified liquid and cooling water, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharifying enzyme while saccharifying.

[0072] In another embodiment, the present invention provides a method for producing a saccharified product of cassava residue, the method comprising: a mixing step of preparing a mixture containing a portion of the gelatinized product of cassava residue, water, and the saccharifying enzyme, and initiating saccharification; and a temperature adjustment step of, after the mixing step, sequentially adding the remaining gelatinized product of cassava residue, removing heat from the saccharified solution by heat exchange with cooling water, and saccharifying the saccharified solution while adjusting its temperature to a temperature suitable for saccharification by the saccharifying enzyme.

[0073] Alternatively, in another embodiment, the present invention provides a method for producing a saccharified product of cassava residue, the method comprising: a mixing step of preparing a mixture containing a portion of the gelatinized product of cassava residue, water, and the saccharifying enzyme, and initiating saccharification; and a temperature adjustment step of, after the mixing step, sequentially adding the remaining gelatinized product of cassava residue, removing heat from the saccharified solution by heat exchange between the saccharified solution and cooling water, and saccharifying the saccharified solution while adjusting its temperature to a temperature suitable for saccharification by the saccharifying enzyme.

[0074] (Continuous Saccharification Process) In the continuous process, first, the gelatinized material is used as is without cooling, and a mixture containing the gelatinized material, an amount of water sufficient to achieve the desired viscosity, and a saccharifying enzyme is prepared. The temperature is then adjusted to a range suitable for saccharification, specifically, approximately 50°C to 60°C, to initiate the saccharification system. Next, the gelatinized material is sequentially added to the saccharified material while adjusting the temperature of the saccharified material by heat exchange between the saccharified material and cooling water. As with the semi-continuous process described above, this enables cooling of the saccharification system with excellent heat exchange efficiency, allowing the saccharified material to be efficiently cooled in a short time and maintain a temperature suitable for saccharification. Furthermore, if the moisture content of the cassava residue is low and, as a result, the gelatinized material concentration exceeds the range suitable for enzymatic saccharification during the sequential addition process, additional water may be added during the sequential addition of the gelatinized material, as with the semi-continuous process described above. Adding water after gelatinization during saccharification can avoid an increase in energy consumption, and the addition of water is also expected to have a cooling effect.

[0075] In the continuous system, when the volume of the saccharified solution in the saccharification system reaches a predetermined volume through the sequential addition of gelatinized cassava residue, a portion of the saccharified solution is withdrawn, and the gelatinized cassava residue and the saccharification enzyme are added to maintain the saccharified solution at the predetermined volume. The saccharified solution is then heat-exchanged with cooling water to remove heat, and the temperature of the saccharified solution is adjusted to a temperature suitable for saccharification by the saccharification enzyme. The "predetermined volume" refers to the normal operating volume specified in plant operation, typically approximately 70% to 90% of the effective volume of the tank. By continuing to withdraw the saccharified solution and add gelatinized cassava residue, the TS of the saccharified solution gradually approaches that of the gelatinized solution, resulting in a saccharified solution with a high sugar concentration. By obtaining a saccharified solution with a high sugar concentration, the process of concentrating the saccharified solution to a sugar concentration suitable for fermentation in the subsequent process is unnecessary, and when the fermented saccharified solution is distilled, the distillation efficiency is improved, thereby improving the energy efficiency of the plant. Furthermore, according to the method for producing a saccharified product of this embodiment, all processes from gelatinization of cassava residue to saccharification can be operated continuously, making the plant operation easier.

[0076] In the continuous saccharification process, the gelatinized cassava residue added to the saccharification system is preferably a mixture with a saccharifying enzyme. By supplying new saccharifying enzyme along with the gelatinized cassava residue, saccharification proceeds more efficiently. In the continuous saccharification process, the temperature of the saccharified solution is adjusted by heat exchange between the saccharified solution and cooling water, as in the temperature adjustment process. It is also preferable to measure the viscosity of the saccharified solution over time and appropriately adjust the amount of gelatinized cassava residue added and the timing of addition to prevent the viscosity of the saccharified solution from becoming excessively high.

[0077] That is, in the case of a continuous system, the saccharification process preferably includes: a mixing process in which a mixture containing the gelatinized cassava residue, water, and the saccharifying enzyme is prepared and saccharification is initiated; a temperature adjustment process in which, after the mixing process, the gelatinized cassava residue is successively added, the saccharified liquid is removed from the saccharified liquid by heat exchange with cooling water, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharifying enzyme, and saccharification is carried out; and a continuous saccharification process in which, after the saccharified liquid has reached a predetermined volume by the temperature adjustment process, a portion of the saccharified liquid is removed from the saccharified liquid, and the gelatinized cassava residue and the saccharifying enzyme are added, while the saccharified liquid is removed from the saccharified liquid by heat exchange with cooling water, and the temperature is adjusted to a temperature suitable for saccharification by the saccharifying enzyme, so as to maintain the saccharified liquid at the predetermined volume.

[0078] Alternatively, in another embodiment, the present invention provides a method for producing a saccharified product of cassava residue, the method comprising: a mixing step of preparing a mixture containing the gelatinized product of cassava residue, water, and the saccharifying enzyme, and initiating saccharification; a temperature adjustment step of, after the mixing step, sequentially adding the gelatinized product of cassava residue, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme; and a continuous saccharification step of, after the saccharified product has reached a predetermined volume by the temperature adjustment step, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water while removing heat from the saccharified product and adding the gelatinized product of cassava residue and the saccharifying enzyme, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme, so as to maintain the predetermined volume of the saccharified product.

[0079] Alternatively, in another embodiment, the present invention provides a method for producing a saccharified product of cassava residue, the method comprising: a mixing step of preparing a mixture containing the gelatinized product of cassava residue, water, and the saccharifying enzyme, and initiating saccharification; a temperature adjustment step of, after the mixing step, sequentially adding the gelatinized product of cassava residue, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme; and a continuous saccharification step of, after the saccharified product has reached a predetermined volume by the temperature adjustment step, removing heat from the saccharified product by heat exchange between the saccharified product and cooling water while removing heat from the saccharified product and adding the gelatinized product of cassava residue and the saccharifying enzyme, and saccharifying the product while adjusting the temperature of the saccharified product to a temperature suitable for saccharification by the saccharifying enzyme, so as to maintain the predetermined volume of the saccharified product.

[0080] In the mixing step, a mixture containing the gelatinized cassava residue or a portion thereof, water, and the saccharifying enzyme is prepared to initiate saccharification. When preparing the mixture, the order in which the gelatinized cassava residue or a portion thereof, water, and saccharifying enzyme are added does not matter. For example, when water and the saccharifying enzyme are added to the gelatinized cassava residue or a portion thereof and mixed to initiate saccharification, a portion of the gelatinized cassava residue may be previously placed in the saccharification tank, and water and the saccharifying enzyme may be added thereto and mixed. Alternatively, a liquid prepared by mixing water and the saccharifying enzyme may be previously placed in the saccharification tank, and the gelatinized product or a portion thereof may be added thereto and mixed to initiate saccharification. Alternatively, a mixture prepared by mixing water and the gelatinized product or a portion thereof may be previously placed in the saccharification tank, and the saccharifying enzyme may be added thereto and mixed to initiate saccharification. Alternatively, water may be charged into the saccharification tank in advance, and the gelatinized material and saccharifying enzyme may be added to the saccharification tank in sequence from the beginning and mixed to initiate saccharification. In this case, the process of mixing the gelatinized material and saccharifying enzyme that are first charged into the saccharification tank with water can be considered the mixing process. Alternatively, water may be charged into the saccharification tank in advance, and the gelatinized material or a portion thereof may be added and mixed, and then the saccharifying enzyme may be added and mixed to initiate saccharification. Alternatively, the gelatinized material or a portion thereof, water, and saccharifying enzyme may be added to the saccharification tank simultaneously and mixed to initiate saccharification.

[0081] The amount of water added in the mixing step is an amount that results in a viscosity of the mixture containing the gelatinized cassava residue or a portion thereof, the water, and the saccharifying enzyme of 500 mPa·s or less, preferably 300 mPa·s or less, and more preferably 100 mPa·s or less. Adding water in an amount that results in a viscosity of the above-mentioned upper limit or less can improve the fluidity of the saccharification system and enable efficient saccharification. Meanwhile, the lower limit of the viscosity of the mixture is not particularly limited, and the lower the viscosity, the better. For example, it can be set to 10 mPa·s.

[0082] In this specification, "viscosity" is a value measured using a Brookfield viscometer (BL II, manufactured by Toki Sangyo Co., Ltd.) by heating a measurement sample to 50°C. The rotor used for measurement may be a high viscosity rotor, a medium viscosity rotor, or a low viscosity rotor, as appropriate, depending on the sample, so that the viscosity falls within the measurement limit range.

[0083] The temperature of the cooling water used in the temperature adjustment step and the continuous saccharification step need only be a temperature that can reduce the temperature of the saccharification system (approximately 90°C) that has risen due to the gelatinized material to a temperature suitable for saccharification (approximately 50°C or higher and 60°C or lower), and can be, for example, 40°C or lower. There are no particular limitations on the lower limit of the cooling water temperature, but it is preferable to consume as little energy as possible to lower or maintain the temperature of the cooling water low, and recycling is important to reduce the amount of water used and the amount of wastewater. Therefore, industrial water, groundwater, or the like can be circulated by a pump and heat can be removed in an energy-efficient cooling tower. Specifically, the lower limit of the cooling water temperature can be, for example, 5°C.

[0084] The heat exchange method in the temperature adjustment step and the continuous saccharification step is not particularly limited, and examples include methods in which a jacket-type, coil-type, multi-tube-type, plate-type, fin-tube-type, spiral-type, or other heat exchanger is installed inside or outside the saccharification system. Among these, it is preferable to circulate the saccharified solution using a pump and use an external heat exchanger installed on the circulation line, as this allows for efficient heat exchange and heat removal. By adjusting the amount of circulated saccharified solution and the amount of cooling water, heat can be removed instantly and the temperature in the system can be adjusted.

[0085] As the external heat exchanger, for example, a spiral heat exchanger manufactured by Kurose under the trade name "KSHS-1H-12L" can be used.

[0086] The amount of saccharified solution circulated in the external heat exchanger can be, for example, 5% by mass or more and 30% by mass or less per hour relative to the total amount of saccharified solution at the time when the sequential addition of gelatinized material is completed.

[0087] The temperature in the system during the saccharification step can be adjusted appropriately depending on the type of saccharifying enzyme, but is preferably 50°C or higher and 60°C or lower.

[0088] The saccharification time in the batch and semi-continuous systems is not particularly limited as long as it is the period required to achieve the desired sugar recovery rate, but it can usually be 1 hour or more and 48 hours or less, 5 hours or more and 36 hours or less, or 10 hours or more and 24 hours or less.

[0089] In a continuous system, the saccharification time actually varies depending on the residence time distribution. An indicator of the saccharification time in a continuous system is the apparent residence time, calculated by dividing the volume of the saccharified solution in the saccharification tank by the withdrawal flow rate of the saccharified solution, i.e., the apparent saccharification time. The saccharification time may be the period required to achieve a desired sugar recovery rate, and is not particularly limited, but typically is 5 hours to 100 hours, 10 hours to 48 hours, or 15 hours to 36 hours. The duration of continuous saccharification may be the period required to clean the system, and is not particularly limited, but typically is 24 hours to 60 days, 2 days to 45 days, or 7 days to 30 days.

[0090] Furthermore, it is preferable to control the viscosity of the saccharification system to a constant value during the temperature adjustment process and the continuous saccharification process. That is, during the sequential addition of the gelatinized material, it is preferable to control the viscosity of the saccharification system to 500 mPa·s or less, preferably 300 mPa·s or less, by adjusting one or more of the following: the rate of addition of the cassava residue gelatinized material, the concentration of the saccharification enzyme, and the amount of water added. By controlling the viscosity of the saccharification system to the above upper limit or less, the saccharification system can be thoroughly mixed using a general-purpose mixer, eliminating the need for specialized mixers that are difficult to manufacture and consume a lot of power. This reduces energy consumption and enables a socially implementable equipment configuration. Furthermore, if the viscosity of the saccharification system is below the above upper limit, it can be used with heat exchangers such as plates, which have excellent heat exchange efficiency but have a small flow path area and are prone to clogging. This allows for instant cooling even in large commercial machines using heat exchangers of a practical size.

[0091] The rate of addition of gelatinized cassava residue can be, for example, 1% by mass to 5% by mass per hour relative to the total amount of saccharified solution at the time of completion of sequential addition of the gelatinized solution. Furthermore, in the case of semi-continuous saccharification, the amount of gelatinized solution added per hour relative to the total amount of saccharified solution at the time of completion of sequential addition can be 1% by mass to 10% by mass, preferably 2% by mass to 8% by mass, and more preferably 2.5% by mass to 6% by mass. In the case of continuous saccharification, the amount of gelatinized solution added per hour during sequential addition can be 1% by mass to 10% by mass, preferably 2% by mass to 8% by mass, and more preferably 2.5% by mass to 6% by mass.

[0092] Regardless of whether the saccharification process is batch, semi-continuous, or continuous, the method for transporting cassava residue is preferably a conveyor-type solid transport device such as a screw, belt, or flight type when transporting the cassava residue in a solid state, and preferably a piping transport device using a pump when transporting the cassava residue in a slurry state.

[0093] When the saccharification process is continuous, the heating method for the sequentially added cassava residue is not particularly limited as long as the cassava residue can be uniformly heated. In the continuous process, when the cassava residue is transported in a solid state, it may be heated by directly injecting steam into a kneader-type or conveyor-type solid transport device. When the cassava residue is transported in a slurry state, it may be heated using, for example, a jet cooker or a batch-type steam heating device. Among these, heating by directly injecting steam into a kneader-type or conveyor-type solid transport device is preferred.

[0094] In the mixing step, the saccharifying enzyme may be added in the total amount required to saccharify the gelatinized material added by the time the temperature adjustment step is completed, or a portion may be added and the remainder may be added sequentially during the temperature adjustment step. While the enzyme concentrations may be higher than those described above for the saccharifying enzymes at the beginning of the mixing and temperature adjustment steps, sequential addition of the cassava residue gelatinized material during the temperature adjustment step keeps the enzyme concentrations within the ranges described above for the saccharifying enzymes. In the continuous saccharification step, the enzyme addition rate, etc., can be appropriately adjusted to achieve the concentration ranges for each enzyme described above for the saccharifying enzymes.

[0095] The amount of water to be added is an amount that makes the viscosity of the saccharification system equal to or less than the above upper limit, and can be appropriately determined by those skilled in the art according to the viscosity.

[0096] In the continuous saccharification process, the start of sequential withdrawal of the saccharified solution, i.e., the transition from the temperature adjustment process to the continuous saccharification process, is not particularly limited as long as a saccharified solution with a predetermined sugar concentration can be obtained. However, from the viewpoint of excellent plant operating efficiency, it is preferable to continuously transition without stopping the addition of gelatinized material when the effective volume of the saccharified solution in the saccharification tank reaches 70% to 90%.

[0097] In the continuous saccharification process, the withdrawal of a portion of the saccharified solution and the addition of the gelatinized cassava residue and saccharification enzymes may be performed so as to maintain a predetermined volume of the saccharified solution. From the viewpoints of preventing a rise in the liquid level due to agitation in the saccharification tank containing the saccharified solution and reducing the adhesion of dirt to the top plate, it is preferable to set the target volume of the saccharification tank within a range of 70% to 90%, and more preferably within a range of 75% to 85%. Furthermore, from the viewpoint of excellent plant operating efficiency, it is preferable to perform the withdrawal and addition so that the actual volume of the saccharified solution falls within a range of -10% to 10% of the set target volume (volume of the saccharified solution at the end of the temperature adjustment process), more preferably within a range of -8% to 8%, and even more preferably within a range of -5% to 5%. In the continuous saccharification process, the withdrawal of the saccharified solution and the addition of the gelatinized cassava residue and the saccharifying enzyme may be carried out continuously at a constant flow rate, or a predetermined amount of the saccharified solution may be withdrawn and added simultaneously with the addition of the gelatinized cassava residue and the saccharifying enzyme in an amount equal to the amount of the extracted saccharified solution. For example, the withdrawal and addition are preferably carried out simultaneously once every 30 minutes, more preferably once every 15 minutes, and even more preferably continuously at a constant flow rate. Furthermore, the timing of the withdrawal of the saccharified solution and the timing of the addition of the gelatinized cassava residue and the saccharifying enzyme may be simultaneous or may be delayed. For example, the delay is preferably within 30 minutes, more preferably within 15 minutes, and even more preferably, the withdrawal and addition are carried out continuously without stopping.

[0098] In the continuous saccharification process, the sugar concentration of the saccharified solution successively extracted is not particularly limited as long as a saccharified solution with a predetermined sugar concentration can be obtained. However, from the viewpoint of excellent energy efficiency as a plant after the saccharification process, the sugar concentration is preferably 30 g / L or more, more preferably 45 g / L or more, and even more preferably 60 g / L or more.

[0099] FIG. 1 is a schematic diagram showing a saccharification apparatus used in a method for producing a saccharified product of cassava residue according to a first embodiment of the present invention.

[0100] The cassava residue saccharification apparatus 10 includes a solid material conveying device 1 and a saccharification tank 2. The saccharification tank 2 has an external heat exchanger 3 on a circulation line for the saccharified liquid.

[0101] As the solid material conveying device 1, the devices exemplified in the gelatinization step can be used.

[0102] There are no particular limitations on the saccharification tank 2, and any known saccharification tank can be used. Specific examples include stirring type, aeration stirring type, bubble column type, and fluidized bed type saccharification tanks.

[0103] As the external heat exchanger 3, those exemplified in the temperature adjustment step can be used.

[0104] A method for saccharifying cassava residue using the saccharification apparatus 10 is described below. First, cassava residue is fed into the solid feeder 1 through the raw material inlet. The solid feeder 1 has an α-amylase dilution adding means at the raw material inlet, and the α-amylase dilution is added to the cassava residue before or simultaneously with the feeding. The cassava residue is then mixed with the α-amylase and heated within the solid feeder 1, promoting gelatinization of the cassava residue. Next, the gelatinized cassava residue removed from the outlet of the solid feeder 1 is fed into the saccharification tank 2. Specifically, when saccharification is performed using a semi-continuous system, a portion of the gelatinized material, water, and saccharification enzymes (preferably including glucoamylase, cellulase, and pectinase) are mixed. At this time, it is preferable to adjust the viscosity to 500 mPa·s or less and the temperature to approximately 50°C to 60°C. In order to maintain the viscosity of the liquid in the saccharification tank at 500 mPa·s or less, the amount of gelatinized material initially added is desirably 0% by mass to 20% by mass or less of the total amount. Next, while the remaining gelatinized material is gradually added, the saccharified liquid is circulated through the circulation line, and heat is removed in the external heat exchanger 3 by liquid-liquid heat exchange between the saccharified liquid and cooling water. During this process, it is preferable to control the temperature of the saccharification system to between 50°C and 60°C, and the viscosity to 500 mPa·s or less. When saccharification is performed using a semi-continuous system, the saccharification time after the completion of the sequential additions is not particularly limited, as long as it is the period required to achieve the desired sugar recovery rate. However, the saccharification reaction is typically carried out for between 1 hour and 36 hours after the completion of the addition of the entire amount of gelatinized material to obtain a cassava residue saccharified product.

[0105] When saccharification is performed using a continuous method, a mixture containing gelatinized material, water, and saccharifying enzymes (preferably including glucoamylase, cellulase, and pectinase) is prepared. At this time, it is preferable to adjust the viscosity to 500 mPa·s or less and the temperature to approximately 50°C or higher and 60°C or lower. Next, while the gelatinized material is gradually added, the saccharified solution is circulated through the circulation line, and heat is removed by liquid-liquid heat exchange between the saccharified solution and cooling water in the external heat exchanger 3. At this time, it is preferable to control the temperature of the saccharification system within the range of 50°C or higher and 60°C or lower, and the viscosity to 500 mPa·s or lower.

[0106] Second Embodiment In a method for producing a saccharified product of cassava residue according to a second embodiment of the present invention, the gelatinization step preferably includes a heat-retaining step of keeping the heated cassava residue warm in a heat-retaining tank after the heating in the solid conveying device.

[0107] In the method for producing a saccharified product of the present embodiment, the gelatinization step includes an incubation step, whereby the cassava residue can be sufficiently gelatinized.

[0108] [Insulation Step] In the insulation step, after heating in the solid conveying device, the heated cassava residue is kept warm in an insulation tank.

[0109] The warming step may be a batch process, a semi-continuous process, or a continuous process. When either or both of the gelatinization process and the saccharification process are continuous, the warming step can also be continuous. The batch process in the warming step refers to a process in which all of the heated cassava residue is added to the warming tank before warming begins. The semi-continuous process in the warming step refers to a process in which a portion of the heated cassava residue is added to the warming tank, warming begins, and then the remaining heated cassava residue is added sequentially. The continuous process in the warming step refers to a process in which the heated cassava residue is sequentially added to the warming tank and the heated cassava residue is sequentially removed.

[0110] For example, since the gelatinization temperature of cassava starch is about 60° C., the temperature of the heat retention tank can be set to 60° C. or higher, preferably 70° C. or higher, more preferably 75° C. or higher, and even more preferably 80° C. or higher. The upper limit of the heating temperature can be set to, for example, 120° C. or lower, preferably 110° C. or lower, more preferably 105° C. or lower, and even more preferably 100° C. or lower.

[0111] The warming time can be, for example, from 5 minutes to 4 hours.

[0112] By holding the heated cassava residue in an insulation tank rather than a solid conveying device, equipment costs and operating costs can be reduced, resulting in a realistic equipment configuration.

[0113] FIG. 2 is a schematic diagram showing a saccharification apparatus used in a method for producing saccharified cassava residue according to a second embodiment of the present invention.

[0114] The saccharification apparatus 20 shown in Figure 2 differs from the saccharification apparatus 10 shown in Figure 1 in that it further includes an insulated tank 4. Note that in Figure 2 and subsequent figures, the same components as those shown in Figure 1 are designated by the same reference numerals and will not be described again.

[0115] The heat-retaining tank 4 may be any tank capable of keeping the heated cassava residue warm and temporarily holding it therein. Specifically, examples thereof include, but are not limited to, cylindrical or square tanks equipped with a mechanism for extracting the gelatinized material at the bottom.

[0116] The heat-retaining tank may also be provided with a temperature control device such as a hot water circulating jacket on the outside of the tank in order to maintain a constant temperature inside the tank.

[0117] A method for saccharifying cassava residue using the saccharification apparatus 20 is described below. First, cassava residue is mixed with α-amylase and heated in the solid conveying apparatus 1 in a manner similar to that of the saccharification apparatus 10 shown in FIG. 1. Next, the heated cassava residue removed from the outlet of the solid conveying apparatus 1 is placed in the incubator 4 and maintained at a temperature of 60°C to 120°C, preferably 80°C to 110°C, for 5 minutes to 4 hours to gelatinize the cassava residue. The resulting gelatinized cassava residue is placed in the saccharification tank 2, where it is saccharified using a saccharifying enzyme in a manner similar to that of the saccharification apparatus 10 shown in FIG. 1, yielding a saccharified cassava residue.

[0118] <Method for Producing a Fermented Product Derived from Cassava Residue> <Third Embodiment> A method for producing a fermented product derived from cassava residue according to a third embodiment of the present invention includes a fermentation step of fermenting, with a microorganism, the saccharified product of cassava residue obtained by the method for producing a saccharified product of cassava residue according to the above embodiment.

[0119] In the production method of this embodiment, the sugar solution, which is prone to spoilage, can be fermented immediately after saccharification, so that it can be utilized without spoilage.

[0120] [Fermentation Step] In the fermentation step, the saccharified product of the cassava residue is fermented by microorganisms.

[0121] (Microorganisms) There are no particular limitations on the microorganisms used for fermentation, as long as they can produce the target product. Specific examples include yeast and bacteria, and genetically modified microorganisms are also preferably used. Genetically modified microorganisms are microorganisms that do not have enzyme genes necessary for conversion to the target product, but have these genes introduced into them by genetic engineering techniques, making it possible to produce the target product. Examples of genetically modified microorganisms include genetically modified Escherichia coli, etc., which have the activity of fermenting the target product. Among these, yeast, bacteria, or genetically modified microorganisms which have the activity of fermenting alcohol are preferred as microorganisms.

[0122] Furthermore, the microorganism may be used as a culture solution containing the microorganism as it is, or may be used as appropriate in the form of a culture solution containing the microorganism concentrated by centrifugation, or in a dried state.

[0123] The amount of microorganisms to be used may be calculated based on the growth rate of the microorganisms, the size of the fermenter, the amount of saccharified solution to be used for fermentation, etc., so as to achieve the target yield of the target product.

[0124] (Fermented product derived from cassava residue) The fermented product derived from cassava residue refers to a compound produced by microorganisms ingesting sugars obtained by decomposing cassava residue. Specific examples of fermented products derived from cassava residue include alcohols such as ethanol, butanol, 1,3-propanediol, 1,4-butanediol, and glycerol; organic acids such as pyruvic acid, succinic acid, malic acid, itaconic acid, citric acid, and lactic acid; nucleosides such as inosinic acid and guanosine; nucleotides such as inosinic acid and guanylic acid; and diamine compounds such as cadaverine. When the compound produced by the microorganism is a monomer such as lactic acid, it may be converted into a polymer by polymerization. Among these, alcohol is preferred as the fermented product derived from cassava residue, and ethanol is particularly preferred.

[0125] The cassava residue saccharification product used may consist of only the saccharification liquid, or may contain both the saccharification liquid and the saccharification residue. In particular, the saccharification residue contains saccharification substrates such as cellulose, starch, and pectin, as well as saccharification enzymes adsorbed to the saccharification residue. Therefore, it is preferable to use a saccharification product containing both the saccharification liquid and the saccharification residue in the fermentation process, since the saccharification process can be performed simultaneously in the fermentation process to produce sugars that can be used as a substrate for microbial fermentation.

[0126] The fermentation temperature can be, for example, 25°C or higher and 40°C or lower, 28°C or higher and 38°C or lower, or 30°C or higher and 35°C or lower.

[0127] The fermentation time depends on the sugar concentration in the saccharified product used, but can be 12 hours or more and 96 hours or less, 24 hours or more and 72 hours or less, or 24 hours or more and 48 hours or less.

[0128] FIG. 3 is a schematic diagram showing a production system used in a method for producing a fermented product derived from cassava residue according to a third embodiment of the present invention.

[0129] The system 100 for producing a cassava residue-derived fermented product shown in FIG. 3 differs from the saccharification apparatus 20 shown in FIG. 2 in that it further includes a fermenter 5 .

[0130] Examples of the fermenter 5 include, but are not limited to, a stirring type, an aeration stirring type, and a bubble column type.

[0131] The fermenter 5 may be equipped with a temperature control device such as a cooling water circulating jacket or internal coil, or an external heat exchanger with cooling water, in order to maintain a constant temperature inside the tank.

[0132] A method for producing a cassava residue-derived fermented product using the production system 100 is described below. First, the process up to the production of a saccharified product is performed in the same manner as the method using the saccharification apparatus 20 shown in Figure 2. Next, the obtained saccharified product and microorganisms are added to the fermenter 5, and fermentation is carried out while stirring to obtain a cassava residue-derived fermented product.

[0133] <Fourth embodiment> The method for producing a cassava residue-derived fermented product according to a fourth embodiment of the present invention preferably further includes a distillation step of distilling the cassava residue-derived fermented product obtained in the fermentation step.

[0134] The production method of this embodiment further includes a distillation step, thereby obtaining a highly pure cassava residue-derived fermented product.

[0135] [Distillation Step] In the distillation step, the cassava residue-derived fermented product obtained in the fermentation step is distilled.

[0136] The conditions for separation and purification of the cassava residue-derived fermentation product by distillation can be appropriately set depending on the type of cassava residue-derived fermentation product.

[0137] FIG. 4 is a schematic diagram showing a production system used in a method for producing a fermented product derived from cassava residue according to a fourth embodiment of the present invention.

[0138] The production system 200 shown in FIG. 4 differs from the production system 100 shown in FIG. 3 in that it further includes a distillation apparatus 6 .

[0139] Examples of the distillation apparatus 6 include a plate column having a plurality of plates therein, and a packed column filled with packing for gas-liquid contact.

[0140] The distillation apparatus 6 may be equipped with a reboiler for boiling steam, a condenser for condensing steam, and the like.

[0141] A method for producing a cassava residue-derived fermented product using the production system 200 is described below. First, the saccharified cassava residue is fermented by microorganisms in the same manner as the method using the production system 100 shown in Figure 3. Next, the obtained cassava residue-derived fermented product is charged into the distillation apparatus 6, and distillation is performed by appropriately adjusting the reboiler heat amount, reflux ratio, etc., to separate and purify the cassava residue-derived fermented product.

[0142] Fifth Embodiment In a method for producing a saccharified product of cassava residue according to a fifth embodiment of the present invention, the saccharification step preferably involves saccharification in a continuous saccharification tank in which a plurality of saccharification tanks are connected in series.

[0143] When saccharification is performed using a continuous system, gelatinized material and saccharification enzymes are added while the saccharified material is withdrawn to maintain a predetermined volume. This means that the residence time of the added gelatinized material in the saccharification tank is not constant, resulting in a distribution of residence times. As a result, some gelatinized material is discharged after a short residence time without the saccharification reaction having progressed sufficiently. This results in a lower sugar recovery rate. Extending the saccharification time reduces the proportion of unreacted gelatinized material discharged after a short residence time, but it also requires a larger saccharification tank, which increases equipment costs.

[0144] From the viewpoint of improving the sugar recovery rate when saccharifying continuously, it is preferable to perform saccharification in a continuous saccharification tank in which multiple saccharification tanks are connected in series. Furthermore, when saccharification is performed in a continuous saccharification tank in which multiple saccharification tanks are connected in series, it is preferable to add the gelatinized material and saccharifying enzymes to the first saccharification tank and recover the saccharified solution from the final saccharification tank. By performing saccharification in such a continuous saccharification tank, the unsaccharified gelatinized material discharged in the first saccharification tank after a short residence time can be saccharified again in the subsequent saccharification tank.

[0145] The method for producing a saccharified product of this embodiment performs saccharification in a continuous saccharification tank in which multiple saccharification tanks are connected in series, thereby improving the sugar recovery rate when saccharifying using a continuous method.

[0146] FIG. 5 is a schematic diagram showing a saccharification apparatus used in a method for producing a saccharified product of cassava residue according to a fifth embodiment of the present invention.

[0147] The saccharification apparatus 30 shown in FIG. 5 differs from the saccharification apparatus 10 shown in FIG. 1 in that it further includes a saccharification tank (last stage) 7 .

[0148] As the saccharification tank (last stage) 7, the one exemplified in the saccharification tank 2 of the first embodiment can be used.

[0149] Although not shown in Fig. 5, an additional saccharification tank may be provided between the saccharification tank 2 and the saccharification tank (last stage) 7. Furthermore, the saccharification tank and the saccharification tank (last stage) 7 may or may not have an external heat exchanger 3.

[0150] 5, an insulated tank 4 may be provided between the solid conveying device 1 and the saccharification tank 2. As the insulated tank 4, the one exemplified in the method for producing saccharified material from cassava residue according to the second embodiment can be used.

[0151] The following describes a method for saccharifying cassava residue using the saccharification apparatus 30. First, cassava residue is mixed with α-amylase and heated in the solid conveying device 1 in the same manner as in the saccharification apparatus 10 shown in Figure 1. The resulting gelatinized cassava residue is then placed in the saccharification tank 2, where it is continuously saccharified in the same manner as in the saccharification apparatus 10 shown in Figure 1, to obtain a saccharified cassava residue.

[0152] The residence time distribution of the gelatinized material can be calculated by regarding the continuous saccharification tank in this embodiment as a complete mixing tank. Here, a complete mixing tank refers to a model in which the substances that flow in are instantaneously mixed to a uniform concentration within the tank, and the concentration within the tank is equal to the concentration of the fluid at the tank outlet. When simply expressed as residence time in a continuous saccharification tank, this refers to the apparent residence time obtained by dividing the liquid volume within the saccharification tank by the addition flow rate or withdrawal flow rate, and is generally different from the average residence time derived from the actual residence time distribution.

[0153] In this case, the required capacity of the continuous saccharification tank in this embodiment is constrained by the viscosity of the saccharified solution and an economical sugar recovery rate. For example, when saccharification is performed using only one tank, the required capacity of the saccharification tank, which is determined by an economical sugar recovery rate, is larger than the required capacity of the saccharification tank, which is determined by the viscosity of the saccharified solution. Therefore, when saccharification is performed using only one tank, the capacity of the saccharification tank is determined by the constraints to ensure an economical sugar recovery rate, and a saccharification tank larger than the capacity determined by the viscosity of the saccharified solution is required.

[0154] On the other hand, when saccharification is performed using a two-tank saccharification tank, the required capacity of the first saccharification tank can be limited to a minimum required capacity determined solely by the viscosity of the saccharified solution. The required capacity of the second saccharification tank can be calculated by subtracting the required capacity of the first saccharification tank, determined by the viscosity of the saccharified solution, from the required capacity of the two tanks in series required to achieve an economical sugar recovery rate. Therefore, the required capacity of the second saccharification tank is approximately 10 to 50% of the required capacity of the first saccharification tank. For the same target sugar recovery rate, the total required capacity of the two saccharification tanks in series is approximately 1 / 2 to 2 / 3 of that required when saccharification is performed using only one saccharification tank. This allows for a smaller plant and reduced equipment costs.

[0155] The viscosity of the saccharified solution is preferably 500 mPa s or less, more preferably 300 mPa s or less, and even more preferably 100 mPa s or less, from the viewpoint of enabling the use of a general-purpose stirrer and an external heat exchanger with a high heat exchange rate, and from the viewpoint of reducing the required capacity. An economical sugar recovery rate is preferably 80% to 99%, more preferably 85% to 98%, even more preferably 88% to 97%, and particularly preferably 90% to 96%.

[0156] In the continuous saccharification tank, as the number of saccharification tanks connected in series increases, the total required capacity of the saccharification tanks for the same sugar recovery rate decreases, while the cost of plant equipment, including associated pumps and piping, increases. Therefore, from an economical point of view, a system in which two saccharification tanks are connected in series is more preferable, and it is even more preferable that the required capacity of the second saccharification tank be 10% to 50% of the required capacity of the first saccharification tank. Note that, because the temperature of the saccharified solution is already adjusted to a temperature suitable for saccharification in the first saccharification tank, temperature adjustment may or may not be required in the second and subsequent saccharification tanks.

[0157] Furthermore, continuous saccharification requires a longer operating time than batch or semi-continuous saccharification, which can lead to the proliferation of unwanted bacteria over time, potentially resulting in a decrease in sugar recovery rate or a decrease in yield in downstream fermentation processes, etc. Therefore, as a countermeasure against bacterial contamination, the entire amount of raw material in the system may be periodically removed and the saccharification tank cleaned.

[0158] When only one continuous saccharification tank is provided, the receipt of raw materials and their processing, i.e., the production of saccharified liquid, is suspended until the entire content of the saccharification tank is removed, i.e., for the total time equivalent to the apparent residence time of the gelatinized material from the time when the addition of gelatinized material and enzymes is stopped and the time required for washing, resulting in a corresponding decrease in the amount of saccharified liquid produced.

[0159] On the other hand, when two continuous saccharification tanks are connected in series, once the first saccharification tank has been drained and cleaned, the first tank can resume receiving and processing the raw material without waiting for the second tank to be drained. By using two continuous saccharification tanks in series, if the total capacity of the continuous saccharification tanks is half the volume of just one saccharification tank, the capacity of the first saccharification tank will be less than half. In other words, the time required to drain the entire amount of content liquid will be less than half the time required to drain the entire amount of content liquid when only one saccharification tank is used. Therefore, the downtime required for cleaning can be reduced by the difference in time required to drain the entire amount of content liquid, preventing a decrease in the production volume of saccharified liquid.

[0160] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0161] Example 1 (Gelatinization test of cassava pulp using a kneader-type solid conveying device) It was investigated using a kneader-type solid conveying device whether a gelatinization reaction can be carried out using wet cassava pulp as a raw material without pulverization.

[0162] As a raw material, wet cassava pulp (produced in Thailand) was frozen and transported from a local starch factory, thawed at room temperature, and used as is without grinding. The moisture content of the thawed wet cassava pulp was 83.0% by mass, which is the ratio of the mass of water to the total mass of the thawed wet cassava pulp, expressed as a percentage. The moisture content was measured using a KETT infrared moisture meter FD-720.

[0163] The equipment used was a kneader-type solid conveying device (KD1 manufactured by Aikawa Iron Works). The kneader section is a single shaft formed by a rotor and a stator, and there is a screw section at the inlet so that the raw materials are absorbed into the kneader section. The rotor-type kneader section has a mechanism whereby the raw materials are continuously fed into the kneaded material, and the kneaded material is pushed out of the device by the raw materials, and the screw section at the inlet has the function of pushing it into the kneader section.

[0164] There are four steam inlets at the bottom of the device, and the raw materials are heated by direct contact with the steam. The entrance to the kneader section is open, and the exit has a lid whose opening can be adjusted with an air cylinder, but it is not a sealed mechanism, so the inside of the kneader does not become pressurized. On the other hand, the kneader section operates at a filling rate of nearly 100%, and because the cassava pulp is packed densely, even without a sealing mechanism at the entrance or exit, very little steam escapes through gaps to the outside of the device, resulting in high heating efficiency and a simple device configuration.

[0165] In addition, α-amylase (manufactured by Novozymes, trade name "Liquezyme SC DS") was diluted 200 times at an addition rate of 0.28 g per kg of dry mass of cassava pulp (α-amylase diluted solution: 56 g) and dripped from a hose installed in the raw material injection chute. The α-amylase diluted solution was dripped into the chute from the hose using a metering pump, and no special operation was performed to apply it evenly to the cassava pulp.

[0166] The test method involved feeding cassava pulp into the kneader section through a chute at a rate of approximately 70 kg / min, and then injecting steam directly into the kneader from the bottom of the kneader to heat it. The steam pressure was saturated steam (128°C) at 0.16 MPaG, and the input rate was approximately 8 kg-stm / min. Steam was continuously fed for approximately 20 minutes, and the temperature of the cassava pulp at the outlet was measured every 3 minutes. The cassava pulp discharged from the kneader section was kept at 80°C or higher in an insulated container for 2 hours after discharge to ensure the time required for the gelatinization reaction.

[0167] The test results showed that a kneader-type solid conveying device could mix unground cassava pulp without clogging. Furthermore, since there was no pushing device in front of the kneader and the raw material could be steadily absorbed into the device using only the screw section at the inlet, it was confirmed that there was little pressure loss and that there was no need for a separate pushing device.

[0168] Furthermore, when the temperature of the cassava pulp was measured at the outlet every three minutes, it was confirmed that it was consistently between 93 and 97°C, and that a stable temperature of 90°C or higher could be achieved.

[0169] [Example 2] (Enzymatic saccharification test using gelatinized cassava pulp using a kneader-type solid conveying device) In order to confirm that α-amylase was uniformly mixed by kneading using the kneader-type solid conveying device in Example 1, an enzymatic saccharification test was conducted on the gelatinized cassava pulp obtained in Example 1.

[0170] The raw material used was the gelatinized cassava pulp obtained in Example 1. The moisture content of the gelatinized product, which is the ratio of the mass of water to the total mass of the gelatinized product expressed as a percentage, was 83.4% by mass. The moisture content was measured using a KETT infrared moisture meter FD-720.

[0171] The saccharification equipment used was an 80 L stainless steel saccharification tank equipped with a 0.04 kW motor agitator (Elepon Kakoki, KVS-0408) with two-stage paddle blades.

[0172] As a test method, 2.1 kg-wet of 25.4 kg-wet gelatinized cassava pulp to be enzymatically saccharified was added to 35 kg of water, 0.97 mL of glucoamylase (manufactured by Nonozyme, trade name "Spirizyme Fuel HS"), and 110 mL of a mixed enzyme solution of cellulase and pectinase (cellulase activity 77 FPU / mL, polygalacturonase activity 1400 U / mL, pectin lyase activity 74 U / mL), and the mixture was mixed with a stirrer at 50 ° C. for 1 hour. The viscosity of the saccharified solution after 1 hour was approximately 5 mPa s. The saccharified solution was maintained at 50°C, and the viscosity was monitored over time while the remaining gelatinized cassava pulp was added in an amount of 1.06 kg every 30 minutes (the rate of addition of gelatinized cassava pulp was such that the amount added per hour was 2.8% by mass of the total amount of the saccharified solution at the time the sequential addition of gelatinized material was completed).

[0173] The mixed enzyme solution of cellulase and pectinase was prepared by culturing a strain into which the polygalacturonase gene PgaB derived from Aspergillus niger and the pectin lyase gene PelD derived from Aspergillus niger were introduced into Trichoderma reesei FV21 strain (Applied Glycoscience, 2019, Vol. 9, No. 4, pp. 249-253), and obtaining the culture supernatant, in a manner similar to that described in JP 2023-46320 A.

[0174] Cellulase activity was measured using a microplate-scale filter paper decomposition activity test ('MICROPLATE-BASED FILTER PAPER ASSAY TO MEASURE TOTAL CELLULASE ACTIVITY' BIOTECHNOLOGY AND BIOENGINEERING, 2004, vol. 88(7), pp. 832-837. DOI: 10.1002 / BIT.20286.). 20 μL of an appropriately diluted sample was added to 40 μL of citrate buffer (50 mM, pH 4.8) containing filter paper (WHATMAN NO. 1, GE HEALTHCARE) cut to a diameter of 7 mm, and the mixture was incubated at 50°C for 1 hour. A sample without filter paper was prepared in the same manner as a blank sample. The reaction was then stopped by adding 120 μL of 3,5-dinitrosalicylic acid reagent (0.5% 3,5-dinitrosalicylic acid, 1.6% sodium hydroxide, 30% (+)-potassium sodium tartrate). The mixture was heated at 95°C for 5 minutes and then cooled in ice water for 5 minutes. 36 μL of the cooled solution was mixed with 160 μL of ultrapure water, and the absorbance at 540 nm of the resulting mixture was measured. The increase in absorbance was calculated by subtracting the absorbance of the blank. Next, the amount of reducing sugar produced in the reaction solution was calculated in terms of the amount of glucose using a calibration curve prepared using serially diluted glucose solutions and the absorbance at 540 nm. The same procedure was performed on samples with different dilutions to determine the dilution rate required to produce reducing sugars equivalent to 0.08 mg glucose / 20 μL cellulase solution, and the filter paper decomposition activity (FPU / mL) of the undiluted sample was calculated. The activity unit was defined as "1 FPU": the enzyme activity required to produce reducing sugars equivalent to 1 μmol of glucose from filter paper in 1 minute.

[0175] Pectin lyase activity was measured using polygalacturonic acid as a substrate. Specifically, 25 μL of 1% (mass / volume) polygalacturonic acid (polygalacturonic acid sodium salt, Sigma-Aldrich), 10 μL of 0.5 M sodium acetate buffer (pH 4.0), and 45 μL of ultrapure water were mixed to prepare 80 μL of substrate solution. 20 μL of enzyme solution appropriately diluted with ultrapure water was added to the substrate solution, and the mixture was incubated at 50°C for 5 minutes. The enzyme reaction was then terminated by adding 100 μL of 50 mM aqueous hydrochloric acid. After stirring and mixing, the absorbance at 235 nm was measured. A blank was prepared by adding aqueous hydrochloric acid to a reaction solution without the enzyme solution, followed by the addition of the enzyme solution. The amount of unsaturated oligogalacturonide produced was measured using the molar extinction coefficient of unsaturated digalacturonide, 4600 M －１ cm －１ One unit (1 U) of enzyme was defined as the amount of enzyme that produces unsaturated oligogalacturonide equivalent to 1 μmol of unsaturated digalacturonide per minute under the above reaction conditions.

[0176] Polygalacturonase activity was measured using polygalacturonic acid as a substrate. Specifically, 25 μL of 1% (mass / volume) polygalacturonic acid (polygalacturonic acid sodium salt, Sigma-Aldrich), 10 μL of 0.5 M sodium acetate buffer (pH 4.0), and 45 μL of ultrapure water were mixed to prepare 80 μL of substrate solution. To this was added 20 μL of enzyme solution appropriately diluted with ultrapure water. The mixture was incubated at 50°C for 5 minutes, after which 100 μL of 3,5-dinitrosalicylic acid reagent was added, and the reducing sugars were allowed to develop for 10 minutes at 99°C. After rapid cooling in ice water, the absorbance at 540 nm was measured to determine the amount of reducing sugar produced. A blank was prepared by adding 3,5-dinitrosalicylic acid reagent to a reaction mixture without enzyme, followed by the addition of enzyme solution, followed by similar color development. One unit of enzyme (1 U) was defined as the amount of enzyme that liberates reducing sugars equivalent to 1 μmol of D-galacturonic acid per minute under the above reaction conditions. However, when both polygalacturonase and pectin lyase were present in the enzyme solution, the polygalacturonase activity was calculated by subtracting the number of pectin lyase units determined by the above-mentioned pectin lyase activity measurement from the number of units calculated from the amount of reducing sugars.

[0177] The viscosity was measured using a Brookfield viscometer (BL II, manufactured by Toki Sangyo Co., Ltd.) by immersing the sample liquid in a warm water bath at 50°C and maintaining the temperature. The measurement was performed at a rotation speed of 100 rpm for a measurement time of 1 minute, and the average of two measurements was taken for each. An R20 rotor was used, and if the viscosity in the first measurement was 50 mPa s or higher, the rotor was replaced with an R21 rotor, and two measurements were performed with the R21, and the average value was recorded.

[0178] Twelve hours after the start of enzymatic saccharification, addition of the entire gelatinized material was completed, and the TS (total evaporation residue concentration) reached 7% by mass. Because the liquid had a high water content, the TS was measured by weighing a 5 mL sample into an aluminum cup and measuring the mass before and after drying, as shown in the following formula. The sample was dried in a constant temperature bath at 100°C for at least 12 hours.

[0179] TS = (mass of sample after drying) × 100 / (mass of sample before drying)

[0180] The changes in viscosity and TS of the enzymatic saccharification reaction solution over time are shown in FIG.

[0181] As shown in Figure 6, the addition of the gelatinized cassava pulp was repeated until the entire gelatinized material was added after 12 hours. However, the viscosity remained below 100 mPa·s, the fluidity was high, and good stirrability was maintained. These results confirmed that the sequential addition of gelatinized cassava pulp to the saccharification tank maintained a sufficiently low viscosity, even for uncrushed gelatinized cassava pulp, which has inherently low fluidity.

[0182] Furthermore, after the entire gelatinized material was added and enzymatic saccharification was continued for one hour, i.e., 13 hours after the start of enzymatic saccharification, the saccharification rate was approximately 80%, indicating that a sufficiently high enzymatic saccharification rate could be achieved even just one hour after the addition was completed. Furthermore, since saccharification progressed sufficiently, it was confirmed that the α-amylase added dropwise at the inlet of the kneader in Example 1 was sufficiently and uniformly mixed with the cassava pulp to the extent necessary for starch gelatinization. These results demonstrate that the use of a kneader-type solid conveying device makes it possible to omit the previously required mixing step of α-amylase and cassava pulp.

[0183] Example 3 (Heat Removal Test of Enzymatic Saccharification Solution of Cassava Pulp Using External Heat Exchanger) Using the enzymatic saccharification solution of cassava pulp obtained in Example 2, a heat removal test was carried out using an external heat exchanger.

[0184] A spiral heat exchanger (KSHS-1H-12L, manufactured by Kurose) was used as the external heat exchanger.

[0185] As a test method, first, the enzymatic saccharification liquid (45 ° C) of cassava pulp obtained in Example 2 was pumped through a spiral heat exchanger. The saccharification liquid with a viscosity of 50 mPa s was circulated at 100 L / hour for 60 minutes, and the liquid permeability was confirmed and the pressure loss was measured. Next, a mixed liquid (43 ° C) was prepared by adding 5 kg of gelatinized cassava pulp (25 ° C) obtained in Example 1 to the enzymatic saccharification liquid (160 kg) of cassava pulp obtained in Example 2, and circulated at 400 L / hour for 30 minutes to confirm the liquid permeability and measure the pressure loss. Next, the mixed liquid of the enzymatic saccharification liquid and gelatinized product was heat exchanged with tap water (22 ° C) to confirm the cooling performance. After circulating for another 60 minutes, an open inspection was performed to check for the presence or absence of residue adhesion or accumulation inside that would interfere with continuous operation.

[0186] As a result of the test, when only the enzymatic saccharification liquid was passed through, no particular clogging occurred, and the pressure loss was stable at around 20 kPa.

[0187] When the mixture of enzymatic saccharification solution and gelatinized product was passed through the system, the flow rate was high, the gelatinized product concentration was high, and the pressure loss was large. However, the pressure loss was stable at around 45 kPa, which was within the economical range of the pump capacity requirements.

[0188] In the heat exchange between the mixed liquid and tap water, the mixed liquid was cooled from an inlet temperature of 43°C to an outlet temperature of 39°C, confirming that the saccharified liquid could be cooled using pump circulation and a spiral heat exchanger. Furthermore, an overhaul inspection revealed that although there was a small amount of adhesion, it could be easily washed away with water, and no signs of strong adhesion or buildup were found. Therefore, it is believed that continuous operation is possible with only periodic online cleaning in plant operation.

[0189] [Example 4] (Continuous enzymatic saccharification test using gelatinized cassava pulp using a kneader-type solid conveying device) In order to confirm the increase in TS and sugar concentration by adding gelatinized cassava pulp and extracting the saccharified solution in parallel, a continuous enzymatic saccharification test was conducted on the gelatinized cassava pulp obtained in Example 1.

[0190] The raw material used was the same as the gelatinized cassava pulp described in Example 2.

[0191] The same apparatus as that described in Example 2 was used.

[0192] The test method was the same as that described in Example 2. Water, glucoamylase, and a mixed enzyme solution of cellulase and pectinase were added to the gelatinized cassava pulp to be enzymatically saccharified, and the enzymatic saccharification reaction was carried out at 50 ° C for 1 hour. The viscosity of the saccharified solution after 1 hour was approximately 5 mPa s. The saccharified solution was maintained at 50 ° C, and the viscosity was monitored over time. The remaining gelatinized cassava pulp was added at a rate of 1.06 kg every 30 minutes. This was repeated for 12 hours from the start of enzymatic saccharification (the rate of addition of gelatinized cassava pulp was 3.0% by mass per hour relative to the total amount of the saccharified solution at the time of completion of the sequential addition of gelatinized cassava pulp). 12 hours after the start of enzymatic saccharification, the saccharified solution reached a full capacity of 70 kg in the saccharification tank. The full capacity of the saccharification tank refers to 85% of the effective volume of the saccharification tank. After 12 hours from the start of enzymatic saccharification, the enzymatic saccharification solution was extracted so that the total amount of cassava pulp gelatinized material and enzyme was equal to the total amount of the gelatinized material added every 30 minutes. The gelatinized material and enzyme were then added every 30 minutes to maintain a constant volume of the solution in the saccharification tank. The gelatinized material and enzyme added every 30 minutes consisted of 1.06 kg of gelatinized cassava pulp, 0.0403 mL of the same glucoamylase as added at the start of enzymatic saccharification, and 4.55 mL of a mixed enzyme solution of cellulase and pectinase. The above procedure was repeated for 24 hours from the start of enzymatic saccharification, and the TS and viscosity of the extracted solution were measured.

[0193] The mixed enzyme solution of cellulase and pectinase was prepared in the same manner as in Example 2.

[0194] The cellulase activity, pectin lyase activity, and polygalacturonase activity were measured in the same manner as in Example 2.

[0195] The viscosity and TS were measured in the same manner as in Example 2.

[0196] The glucose concentration of the saccharified solution was measured using HPLC (Shimadzu Corporation, detector: FLD, column oven: CTO-20A).

[0197] The changes in viscosity and TS of the enzymatic saccharification reaction solution over time are shown in FIG.

[0198] As shown in Figure 7, the addition of the cassava pulp gelatinized material was repeated until the saccharified solution reached a full volume of 70 kg 12 hours after the start of saccharification. The viscosity remained below 70 mPa·s, and the fluidity and stirability were maintained. The saccharified solution had a TS of 7% and a glucose concentration of 29.6 g / L after 12 hours of saccharification. After reaching full volume, the cassava pulp gelatinized material was added and the saccharified solution was withdrawn repeatedly for 12 hours. The viscosity remained below 70 mPa·s, and the fluidity and stirability were maintained. The TS of the saccharified solution increased to 9.5% and 42.3 g / L after 24 hours of saccharification. These results confirmed that continuous saccharification, which involves sequential addition of gelatinized cassava pulp and sequential withdrawal of saccharified solution, can maintain a stable low viscosity even for gelatinized cassava pulp, which is inherently low in fluidity due to its uncrushed nature.Furthermore, it was confirmed that continuous saccharification can produce a saccharified solution with high TS and sugar concentrations.

[0199] Example 5 (Simulation of a continuous saccharification tank with two saccharification tanks connected in series) The residence time distribution, saccharification rate, and viscosity in a continuous saccharification tank with two saccharification tanks connected in series were estimated, and the total volume of the saccharification tanks required to achieve a specified saccharification rate was determined.

[0200] The residence time distribution was estimated by regarding the saccharification tank as a complete mixing tank. Specifically, the residence time distribution (impulse response) when the tracer was added all at once was estimated using the following formula. In the formula, E is the residence time distribution function, t is the residence time, and t ａｖｅ means the average residence time.

[0201]

[0202] The residence time distribution when saccharification tanks are connected in series with N tanks was estimated using the following formula.

[0203]

[0204] The time integration of the above residence time distribution gives the ratio of the cumulative tracer discharge amount to the initial tracer input amount. Using this model, the residence time distributions for a single saccharification tank and a series connection of two saccharification tanks were compared. For the comparison, the volume of a single saccharification tank and the total volume of two saccharification tanks connected in series were set to be the same. In other words, the apparent residence time was set to 18 hours in both cases.

[0205] As a result, the residence time distribution shown in Figure 8 was obtained. By integrating the obtained residence time distribution, the change in cumulative discharge amount was obtained as shown in Figure 9. It became clear that when two saccharification tanks were connected in series, there was less outflow at a stage where elapsed time had been short compared to when there was only one saccharification tank.

[0206] Next, the saccharification rate and viscosity at each residence time were measured. The obtained measurement data were fitted to the Michaelis-Menten equation, which is a rate model equation for enzyme reactions, using the least squares method to create a prediction model for the saccharification rate and viscosity at each residence time. For example, the saccharification rate in a continuous saccharification tank is expressed as the integral value of the product of the saccharification rate at each residence time and the proportion of raw material discharged during that residence time.

[0207] Using the above prediction model for saccharification rate and viscosity, the apparent residence time required to achieve a saccharification rate of 95% when the enzyme addition amount and substrate concentration are the same, i.e., the volume of the saccharification tank or total volume, was estimated. When two saccharification tanks are connected in series, the required volume of the first tank was calculated to maintain a viscosity of 100 mPa s or less, which allows for maintaining agitation in the first tank and facilitating temperature control using an external heat exchanger. The required volume of the second tank was the remaining volume. The estimated results are shown in Table 1.

[0208]

[0209] As shown in Table 1, it was revealed that the total volume required to obtain the same saccharification rate of 95% in the case of two tanks connected in series was less than half the volume in the case of only one tank.

[0210] The method for producing a saccharified product of this embodiment can reduce the energy required for grinding raw materials, heating for gelatinization, and cooling from the gelatinization temperature to the saccharification temperature, and can perform gelatinization without using an α-amylase mixer or pumping, which may cause problems. Furthermore, the method for producing a saccharified product of this embodiment can obtain a saccharified solution with a high sugar concentration, thereby reducing the energy required for the plant after the saccharification process. The method for producing a cassava residue-derived fermented product of this embodiment uses the saccharified product of cassava residue obtained by the method for producing a saccharified product of cassava residue. The saccharified solution, which is prone to spoilage, can be fermented immediately after saccharification, allowing it to be utilized without spoiling.

[0211] 1...solid conveying device, 2...saccharification tank, 3...external heat exchanger, 4...heat retention tank, 5...fermentation tank, 6...distillation apparatus, 7...saccharification tank (final stage), 10, 20, 30...cassava residue saccharification device, 100, 200...cassava residue-derived fermentation product production system

Claims

1. A gelatinization process in which cassava residue is heated and gelatinized by directly blowing steam into a kneader-type or conveyor-type solid transport device; A saccharification step of saccharifying the gelatinized cassava residue using a saccharification enzyme; Including, The cassava residue includes uncrushed cassava pulp or cassava pulp having an average particle diameter of 350 μm or more.

2. The method for producing sugar products from cassava residue as described in claim 1, wherein the solid conveying device is a kneader type.

3. The method for producing sugar products from cassava residues as described in claim 1, wherein the solid conveying device is a continuous type and a rotor type.

4. The method for producing a saccharified product of cassava residue according to claim 1 , wherein the cassava residue comprises wet cassava pulp.

5. The method for producing a saccharified product of cassava residue according to claim 1, wherein the gelatinization step includes an addition step of adding α-amylase to the cassava residue before being fed into the solid conveying device.

6. The method for producing a saccharified product of cassava residue according to claim 1, wherein the saccharifying enzymes include pectinase, cellulase, and glucoamylase.

7. The saccharification step comprises: A mixing step of preparing a mixture containing a portion of the gelatinized cassava residue, water, and the saccharification enzyme to start saccharification; After the mixing step, the remaining gelatinized material of the cassava residue is successively added, the saccharified liquid is removed by heat exchange between the saccharified liquid and cooling water, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharification enzyme while saccharifying the temperature of the saccharified liquid. The method for producing the saccharified cassava residue according to claim 1, comprising:

8. The saccharification step comprises: A mixing step of preparing a mixture containing the gelatinized cassava residue, water, and the saccharification enzyme to start saccharification; After the mixing step, the gelatinized material of the cassava residue is successively added, the saccharified liquid is removed by heat exchange between the saccharified liquid and cooling water, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharification enzyme while saccharifying the temperature of the saccharified liquid. a continuous saccharification step in which, after the saccharified liquid reaches a predetermined volume by the temperature adjustment step, a portion of the saccharified liquid is removed, and the gelatinized material of the cassava residue and the saccharification enzyme are added to the saccharified liquid so as to maintain the saccharified liquid at the predetermined volume, while the saccharified liquid is heat-exchanged with cooling water to remove heat, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharification enzyme; The method for producing the saccharified cassava residue according to claim 1, comprising:

9. A mixing step of preparing a mixture containing gelatinized cassava residue, water, and a saccharification enzyme to start saccharification; After the mixing step, the gelatinized material of the cassava residue is successively added, the saccharified liquid is removed by heat exchange between the saccharified liquid and cooling water, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharification enzyme while saccharifying the temperature of the saccharified liquid. a continuous saccharification step in which, after the saccharified liquid reaches a predetermined volume by the temperature adjustment step, a portion of the saccharified liquid is removed, and the gelatinized material of the cassava residue and the saccharification enzyme are added to the saccharified liquid so as to maintain the saccharified liquid at the predetermined volume, while the saccharified liquid is heat-exchanged with cooling water to remove heat, and the temperature of the saccharified liquid is adjusted to a temperature suitable for saccharification by the saccharification enzyme; The method for producing a saccharified product of cassava residue comprises:

10. 8. The method for producing a saccharified product of cassava residue according to claim 7, wherein the amount of water contained in the mixture in the mixing step is an amount such that the viscosity of the mixture containing a portion of the gelatinized product of the cassava residue, the water, and the saccharification enzyme is 500 mPa s or less.

11. 10. The method for producing a saccharified product of cassava residue according to claim 8 or 9, wherein the amount of water contained in the mixture in the mixing step is an amount such that the viscosity of the mixture containing the gelatinized product of cassava residue, the water, and the saccharifying enzyme is 500 mPa s or less.

12. 10. The method for producing a saccharified product of cassava residue according to any one of claims 7 to 9, wherein in the temperature adjustment step, the viscosity of the saccharification system is controlled to 500 mPa · s or less by adjusting one or more of the group consisting of the addition rate of the gelatinized product of the cassava residue, the concentration of the saccharification enzyme, and the amount of water added.

13. 10. The method for producing a saccharified product of cassava residue according to claim 8 or 9, wherein in the continuous saccharification process, the viscosity of the saccharification system is controlled to 500 mPa s or less by adjusting one or more of the group consisting of the addition rate of the gelatinized product of the cassava residue, the concentration of the saccharification enzyme, and the amount of water added.

14. The method for producing a saccharified product of cassava residue according to any one of claims 7 to 9, wherein the heat exchange is performed by circulating the saccharified solution with a pump and using an external heat exchanger.

15. The method for producing a saccharified product of cassava residue according to claim 8 or 9, wherein in the continuous saccharification step, saccharification is performed in a continuous saccharification tank in which a plurality of saccharification tanks are connected in series.

16. The continuous saccharification tank is a tank in which two saccharification tanks are connected in series, and the capacity of the second saccharification tank is 10% to 50% of the capacity of the first saccharification tank. The method for producing saccharified product of cassava residue according to claim 15.

17. The method for producing a saccharified product of cassava residue according to claim 1, wherein the gelatinization step includes a heat-retaining step of keeping the heated cassava residue warm in a heat-retaining tank after heating in the solid conveying device.

18. A method for producing a cassava residue-derived fermented product, comprising a fermentation step of fermenting a cassava residue saccharified product obtained by the method for producing a cassava residue saccharified product according to any one of claims 1 to 9 using a microorganism.

19. The method for producing a cassava residue-derived fermented product according to claim 18, further comprising a distillation step of distilling the cassava residue-derived fermented product obtained in the fermentation step.