JP5951181B2 - Method for saccharification of lignocellulosic biomass - Google Patents

Description

  The present invention relates to a method for saccharification of lignocellulosic biomass, which is a non-edible biomass resource.

In recent years, the release of global warming substances such as carbon dioxide due to large consumption of oil has become a problem, and various biomass resources have attracted attention as energy or raw materials to replace petroleum from the viewpoint of carbon neutral.
In particular, in the production of bioethanol and other fuels, consideration is being given to the use of non-edible lignocellulosic biomass with abundant abundance instead of sugar-based biomass, such as corn and sugarcane, where there are concerns about competition with food. Has been.
Cellulose, which is a constituent of this lignocellulose, is a condensate of glucose, and saccharides such as glucose can be obtained by hydrolysis.
In addition to bioethanol, it is also possible to produce various chemical basic raw materials produced in the petrochemical industry by using the obtained saccharide as a starting material, so that rapid establishment of utilization technology is possible. It has been demanded.

Among lignocelluloses, herbaceous biomass such as rice straw and pasture has been widely used by harvesters, and can be cultivated as resource crops using abandoned cultivated land and fallow fields in the future. Therefore, it is positioned as an important biomass resource, and processing means for actively using it as an alternative raw material for petroleum both at home and abroad are being studied.
For example, as a saccharification method of herbaceous biomass, after treating with a dilute alkali or dilute acid having a concentration of 0.01 wt% or more and less than 10 wt%, an organic solvent, the herbaceous biomass after the dilute alkali treatment is treated with Clostridium bacteria or culture thereof. A method of treating with a liquid is disclosed (Patent Document 1). Moreover, the manufacturing method of the saccharified liquid including the process of grind | pulverizing herbaceous biomass and the process of hydrolyzing the obtained ground material using a hydrolase is disclosed (patent document 2).

By the way, herbaceous biomass such as rice straw and pasture has a characteristic that it tends to be bulky because it has a higher proportion of leaves than woody biomass such as wood, eucalyptus, and bamboo. Taking rice straw as an example, the bulk specific gravity is only around 0.2 even if a roll baler that winds and packs in a roll shape is used, and a shearing machine such as a general cutter mill or hammer mill is used for shearing. In the case of crushing, it can be said that the crushing efficiency is low because the volume of the processing unit is limited and the raw material supply amount needs to be suppressed.
In addition, even if it is finely crushed to 3 mm or less using a hammer mill, the crushed material will be in a state of containing fibrous air, and the bulk specific gravity and fluidity will be easy to handle as with the raw material before processing. is not.

In particular, saccharification treatment of herbaceous biomass is usually performed in a reaction solution to which an acid or an enzyme has been added. However, as described above, in the crushing treatment of the prior art, the fluidity is poor and, as described above, The charging operation becomes difficult, and further, there is a problem that the dispersibility of the raw material in the reaction solution or the permeability of the reaction solution is poor.
Although it is difficult to handle due to the property problem in this way, in the above prior art, there is no reference to the problem about the processing step (saccharification pretreatment) from the raw material to saccharification, and the mere grinding Is only performed as a means of pre-saccharification treatment.

JP 2010-110230 A JP 2010-104361 A

  Therefore, in view of the problems of the prior art, the present invention improves the handling problems due to the properties of the raw materials in the processing steps from raw materials to saccharification when saccharifying lignocellulosic biomass, and the saccharification rate is improved. An object of the present invention is to provide a pretreatment method for lignocellulosic biomass that can be improved.

  As a result of diligent studies to solve the above problems, by saccharifying lignocellulosic biomass, problems due to the properties of the raw materials are improved by providing a compression molding process in the process from raw materials to saccharification. In addition, the inventors have found a new finding that the reaction efficiency for saccharification is higher than that of the crushing treatment studied in the prior art, and have completed the present invention.

The gist of the present invention is as follows.
In the saccharification method of saccharifying herbaceous biomass, a compression molding step of compressing the herbaceous biomass and forming it into a pellet form, and a saccharification treatment step of saccharifying the compression molded product compressed in the compression molding step are performed. The compression molding step includes a compression molding apparatus having a main body having a frame, a die fixedly arranged in the frame, and a roller for crushing herbaceous biomass by sliding and rotating the upper surface of the die. The roller is rotated at a peripheral speed of 0.5 to 2 m / sec, and the herbaceous biomass is cut into a length of 50 to 200 mm before being compressed in the compression molding step. A method for saccharification of herbaceous biomass, wherein the biomass is rice straw .

According to the present invention, the compression molding step includes a main body having a frame, a die fixedly arranged in the frame, and a roller that crushes rice straw by sliding and rotating the upper surface of the die. By using a compression molding apparatus, the raw material charged is subjected to compression molding while being subjected to shearing and grinding action between the die and the roller, so that a long fiber raw material such as herbaceous biomass is used. However, the compression molding obtained is composed of finely pulverized particles. As a result, fine particles are generated due to water absorption and collapse when the compression-molded product is introduced into the reaction solution, so that the contact rate with acid or enzyme is increased, and the saccharification rate is improved.
Further, by setting the peripheral speed of rotation of the roller to 0.5 to 2 m / second, winding up of rice straw by wind generated by the rotation of the roller is suppressed, and the ability to generate a compression molded product is improved.

It is drawing which illustrates four compression molding apparatuses used for this invention. It is sectional drawing of the compression molding apparatus used for an Example. 3 is a graph showing a particle size distribution of a compression molded product in Example 1. It is a graph which shows the reaction time and saccharification rate of the compression molding in Example 2, and a comparison thing. It is a graph which shows the saccharification rate of the compression molding in Example 3, and a comparison material.

Embodiments of the present invention will be described below.
Examples of lignocellulosic biomass used in the present invention include woody biomass such as wood, eucalyptus and bamboo, and herbaceous biomass such as rice straw, pasture and wheat straw, or building waste, waste paper, palm palm empty fruit bunch, bagasse, etc. Of waste biomass.

FIG. 1 shows compression molding apparatuses (A) to (D) as an example of the compression molding apparatus used in the compression molding process according to the present invention.
As shown in FIG. 1, a compression molding apparatus (A) (see Japanese Patent Application Laid-Open No. 10-75759) for compressing and molding a raw material into a cylindrical shape with a single screw rotating in a hollow cylindrical molding part, a raw material of a pair of rotating rolls Compression molding device (B) (see Japanese Patent Application Laid-Open No. 2010-285691) for compression molding in an almond shape sandwiched between them, a plurality of holes provided in a rotating ring-shaped die, and a cylindrical shape that is pushed by a roller that rotates in the ring Any apparatus can be used as long as it can form the raw material to be charged only by a compression action without using an adhesive or the like, such as a compression molding apparatus (C) (see JP 2000-355006 A).
In particular, for raw materials with long fibers such as herbaceous biomass, it is composed of a die fixedly placed in the main body frame and a roller that slides and rotates on the upper surface of the die. A compression molding apparatus (D) (see Japanese Patent Application Laid-Open No. 2006-272044) that performs compression molding in a cylindrical shape while applying shearing and grinding action between rollers can be suitably used.

The Example using the above-mentioned compression molding apparatus (D) is shown below.
As shown in FIG. 2, the compression molding apparatus (D) used in the present embodiment includes a disk-shaped die 2 fixed to the main body frame 1, and a roller driving unit 3 disposed at the center of the die 2. The roller 4 attached to the outer periphery in the circumferential direction of the roller drive unit 3 is provided.
A large number of small holes 5 are formed in the die 2 so as to penetrate in the vertical direction. The small holes 5 have a diameter of 4 to 20 mm, preferably 6 to 13 mm.
The roller driving unit 3 can be driven to rotate about the vertical axis of the die 2 by a driving source (not shown), and the roller 4 attached to the roller driving unit 3 is rotated by a driving source (not shown). The upper surface of the die 2 is slidably rotatable.

The method for saccharification of lignocellulosic biomass of the present invention is shown below.
In the compression molding process, when the lignocellulosic biomass W is introduced into the compression molding apparatus described above, the lignocellulosic biomass W is formed by the roller 4 and the die 2 by the sliding rotation of the roller 4 accompanying the rotation of the roller driving unit 3. It is sandwiched between and compressed. At this time, the roller 4 slides and rotates on the upper surface of the die 2, so that the lignocellulosic biomass W is crushed between the roller 4 and the die 2, and is subjected to a shearing / grinding action so that the internal fibers are It is crushed and finely crushed.
This pulverized material is pushed into the small hole 5 provided in the die 2 by the sliding rotation of the roller 4 from one to the next, is pressurized, and is pushed out from the small hole 5 below the die 2 to form a cylindrical shape. Compression molding.

The pellet-shaped compression molded product P obtained by the compression molding step is saccharified by a saccharification processing step which is the next step. In the saccharification treatment step, the compression molded product P is introduced into the reaction solution, and the saccharification treatment is performed by the action of the reaction solution. Thereby, saccharides, such as glucose, can be obtained.
At this time, the lignocellulosic biomass W can be quickly formed in the reaction solution by being compression-molded, disintegrated while absorbing water and swelling, and can quickly disperse the biomass raw material in the reaction solution at a high concentration. it can. Thereby, the effect that the saccharification rate is remarkably improved is obtained.

The small holes 5 of the compression molding apparatus in the embodiment are formed to have a diameter of 4 to 20 mm. When the small holes 5 are 20 mm or more in diameter, the lignocellulosic biomass W is sheared and ground by the roller 4. Therefore, it is difficult to obtain the effect of the present invention because the density of the compression molded product P is reduced and the particles constituting the compression molded product P are also coarsened.
Moreover, when the herbaceous biomass is a raw material, the peripheral speed at the time of rotation of the roller 4 is preferably 0.5 to 2 m / sec. When the peripheral speed of the roller 4 is 2 m / second or more, the fibrous raw material is wound up by the wind generated by the rotation of the roller 4, and the generation ability of the compression molded product P is reduced.

The present invention is characterized in that before lignocellulosic biomass W is saccharified, it is crushed and compression-molded in a compression molding step.
The lignocellulosic biomass W is compressed so that it is not shredded shortly as in the conventional method, but is crushed and compression-molded while undergoing shearing and grinding, and the fibers themselves are crushed. At that time, the hollow portion in the fiber of the lignocellulosic biomass W is also crushed, the air space disappears, and the air is pushed out. Therefore, the air in the fine structure of the particles constituting the lignocellulosic biomass is removed, and the bulk density of the lignocellulosic biomass itself is increased, resulting in high density.

  Thus, when the compression molded product P compressed in the compression molding step is put into the reaction solution in the saccharification treatment step, the reaction solution is rapidly absorbed into the inside of the fine structure that has been crushed and the air removed. The By increasing the water absorption of the compression molded product P, the reaction solution penetrates deeply into the compression molded product P, and the saccharification reaction is promoted to every corner of the compression molded product P to simply crush the biomass raw material. As compared with the case where the saccharification is performed, the saccharification rate is significantly improved.

  In particular, in the compression molding step of the present invention, the compression molded product P of lignocellulosic biomass as a raw material is preferably compression molded so that its bulk density is 0.4 or more. By compressing the bulk specific gravity of the compression molded product P to 0.4 or more, the air in the microstructure of the particles constituting the compression molded product P is removed, and when it is put into the reaction solution, the reaction into the microstructure The penetration of the liquid becomes smooth and the effect of further improving the saccharification rate is obtained.

In addition, when the length of the lignocellulosic biomass W, which is a raw material used for the saccharification treatment of the present invention, is particularly long, by performing a crushing process for cutting the lignocellulosic biomass raw material shortly as a pretreatment of the compression molding step. In the compression molding process, the lignocellulosic biomass raw material can be compressed in a short time, and the compression molding process can be carried out more efficiently.
For example, the lignocellulosic biomass raw material is crushed in advance to a size suitable for a compression molding apparatus used in the subsequent compression molding process using a crushing processing apparatus such as a hammer mill or a cutter mill. When the compression molding apparatus used for the compression molding process is a compression molding apparatus (A), a compression molding apparatus (B), or a compression molding apparatus (C), the optimum length of the lignocellulosic biomass raw material W is a woody system. Either 1 mm to 5 mm is preferable for both biomass and herbaceous biomass.
When the compression molding apparatus is the compression molding apparatus (D), the optimum length of lignocellulosic biomass W is about 1 mm to 10 mm for woody biomass and about 1 mm to 200 mm for herbaceous biomass. Even if the length of the herbaceous biomass is about 200 mm, the particles constituting the compression molded product P are obtained by crushing the raw material using the roller 4 and the die 2 as described above, and subjecting to shearing and grinding. The diameter can be approximately 3 mm or less, and the saccharification treatment is facilitated.

  In another embodiment of the present invention, the saccharification reaction is more efficiently performed by performing a pulverization step of pulverizing the compression-molded product P between the compression molding step and the saccharification treatment step. It becomes possible to promote. In the pulverization step, the compression molded product P obtained in the compression molding step is pulverized and pulverized using a crusher such as a hammer mill or a cutter mill. This fine powder is put into the reaction solution in the reaction tank in the saccharification treatment step. Once the compression-molded raw material is pulverized and pulverized, a powder product with a high bulk density can be obtained with a small amount of power, and the effect of increasing the contact rate with the reaction solution in the saccharification treatment step can be obtained.

  The catalyst used in the saccharification treatment step of the present invention is not particularly limited, but biochemical ones include cellulase, hemicellulase, xylanase, β-glucosidase, etc., and these enzymes are appropriately combined as necessary. Can be used. Moreover, dilute sulfuric acid is mentioned as a chemical thing. It can also be used as a pretreatment step for pyrolytic saccharification treatment with high-temperature, high-pressure water or the like.

  In addition, a compression molded product P of lignocellulosic biomass, or a powder product obtained by finely pulverizing the compression molded product in the pulverization step, is treated with an alkaline substance such as sodium hydroxide, calcium hydroxide, ammonia, delignified or cellulose. The saccharification rate can be further increased by carrying out a saccharification treatment step with a catalyst after changing the crystal state of the solution and neutralizing or washing.

  Hereinafter, the present invention will be described in more detail by comparing examples and effects of the conventional example. However, the present invention is not limited to the examples described later.

A die in which rice straw (produced by Shobara City, Hiroshima Prefecture) cut into a length of 50 mm to 200 mm with a combiner is fixedly placed in the main body frame, and a roller that slides and rotates on the upper surface of the die. A compression molding apparatus (trade name: Pellemake (registered trademark), manufactured by Kitagawa Iron Works Co., Ltd.) configured in the form of a cylinder with a diameter of 7 mm and a length of about 20 mm, and the bulk specific gravity when filled into a container is Three types of compression molded products having 0.58, 0.56, and 0.46 were produced.
About the produced compression molding products having different bulk specific gravity, about 200 g was wetted with water and dried at 105 ° C., and the particle size distribution of the particles constituting the compression molding products was examined. As shown in FIG. 3, most of the particles were ground to 3 mm or less.

  Furthermore, in order to confirm the disintegration and dispersibility due to water absorption of the three compression molded products having different bulk specific gravities, each compression molded product was prepared by adding 20 g of water to a glass container having a straight line of 50 mm and a depth of 60 mm. 1 g each was added, the container was set in a shaking water bath whose water temperature was adjusted to 30 ° C., and then vibrated at a rotation speed of 150 rpm and an amplitude of 20 mm. The time from the start of shaking until each compression molded product absorbed water, disintegrated and dispersed was measured. The compression molded product absorbed water from the state where it was submerged in water, and the disintegration and dispersion proceeded.

(Comparative Example 1)
Rice straw (produced by Shobara City, Hiroshima Prefecture) having a moisture content of 14%, which was cut into a length of 50 mm to 200 mm with a combine, was crushed to 3 mm or less by a cutting process to produce a crushed rice straw. In order to confirm the dispersibility due to water absorption, 1 g of the obtained rice straw crushed material was put into a glass container having a straight line of 50 mm and a depth of 60 mm, and 20 g of water was added. The time until the crushed rice straw was absorbed and dispersed was measured. The crushed rice straw was absorbed from the state of floating on the water, and the dispersion into water proceeded.
Table 1 shows the time required for dispersion in Example 1 and Comparative Example 1. The result is the average of the values obtained from each of the three replicates. As shown in Table 1, it can be seen that the compression molded product of the present invention has better dispersibility in water than the crushed rice straw.

Fine powder produced by crushing the compression molded product produced in Example 1 and the compression molded product having a bulk specific gravity of 0.56 with a rice husk crusher (trade name: MILLKURU (registered trademark), manufactured by Kitagawa Iron Works Co., Ltd.). A saccharification test was conducted on the crushed rice straw prepared in Comparative Example 1.
For each sample, 75 mg was weighed into a sample bottle, and 22.5 mL of acetate buffer (pH 5.0) was added. Next, 3 mL of an enzyme solution in which 75.4 mg of Mecelase (registered trademark, manufactured by Meiji Seika Co., Ltd.) was dissolved in 75 mL of an acetate buffer solution was added, and saccharification was performed in a shaking water bath (45 ° C., 230 rpm).

After 0 hours, 3 hours, 18 hours, 24 hours, and 48 hours after saccharification treatment, 500 μL was sampled, and the produced glucose concentration was measured. The glucose concentration was measured using glucose CII-Test Wako (manufactured by Wako Pure Chemical Industries, Ltd.) after inactivating the enzyme by heat treatment (95 ° C., 15 min).
In addition, the saccharification rate calculated | required theoretical glucose amount from the cellulose amount of the rice straw used for the test, and calculated | required by following Formula.
Saccharification rate (%) = glucose production amount after saccharification (mg) / theoretical glucose amount in the sample (mg) × 100
The resulting graph is shown in FIG. As shown in FIG. 4, the rice straw compression-molded product of the present invention tends to have a higher saccharification rate than the crushed rice straw product, and in particular, the saccharification rate of the finely pulverized product prepared by pulverizing the compression-molded product. Became the highest.

The compression molded product produced in Example 1 and the rice straw crushed product produced in Comparative Example 1 were subjected to alkali treatment and then saccharification treatment.
After adding 135 mL of pure water and 3 g of calcium hydroxide to 15 g (dry weight) of each sample in a 200 mL container and thoroughly blending the chemical solution, the sample was heated and pressurized in an autoclave at 120 ° C. for 1 hour. . After the treatment, the solution was neutralized with hydrochloric acid until the pH of the solution became near neutral, and solid-liquid separation was performed by centrifugation (8000 × g, 20 minutes, 4 ° C.). The precipitate (alkali-treated rice straw) was washed several times with pure water and dried at 65 ° C. for 3 days, and weighed into a 50 mL container, then 10 mL of 50 mM acetate buffer (pH 5.0), and 20 mL Commercially available enzyme preparation (trade name: Cellcrust 1.5L (registered trademark), Novozyme 188 (registered trademark), Ultraflo L (registered trademark), manufactured by Novozyme) was added at 50 ° C for 24 hours (6 Enzyme saccharification was performed under the conditions of rotation / min). 0.02% sodium azide was added as a preservative during the enzymatic saccharification reaction. After the reaction, the enzyme is inactivated by heat treatment (100 ° C., 20 minutes), and the supernatant is recovered by centrifugation (6000 × g, 10 minutes, 4 ° C.). The amount of glucose and xylose in the recovered solution Were measured using a glucose test (manufactured by Wako Pure Chemical Industries, Ltd.) and a xylose quantification kit (manufactured by Megazyme), respectively.

The saccharification rate was determined by weighing 100 mg of the raw rice straw crushed to 250 μm or less, adding 1 mL of 72% sulfuric acid, treating it at 30 ° C. for 1 hour, and then measuring up to a sulfuric acid concentration of 9%. For 2 hours at 100 ° C. A part of this was sampled and neutralized with a 10% NaOH aqueous solution, and the total amount of glucose and the total amount of xylose in the raw material were determined using glucose C-II test Wako (manufactured by Wako Pure Chemical Industries, Ltd.) and xylose quantification kit ( And the glucan saccharification rate and the xylan saccharification rate were calculated according to the following equations.
Glucan saccharification rate (%) = glucose production amount after saccharification (mg) / total glucose amount in sample (mg) × 100
Xylan saccharification rate (%) = xylose production after saccharification (mg) / total amount of xylose in sample (mg) × 100
Measurement was performed in triplicate. The results are shown in FIG. As shown in FIG. 5, the compression-molded products of the Examples both had higher values for the glucan saccharification rate and the xylan saccharification rate after the alkali treatment than the rice straw crushed product of the comparative example.

1 Body frame 2 Dies 3 Roller drive 4 Roller 5 Small hole

Claims (1)

In the saccharification method of saccharifying herbaceous biomass, a compression molding step of compressing the herbaceous biomass and forming it into a pellet form, and a saccharification treatment step of saccharifying the compression molded product compressed in the compression molding step are performed. The compression molding step includes a compression molding apparatus having a main body having a frame, a die fixedly arranged in the frame, and a roller for crushing herbaceous biomass by sliding and rotating the upper surface of the die. The roller is rotated at a peripheral speed of 0.5 to 2 m / sec, and the herbaceous biomass is cut into a length of 50 to 200 mm before being compressed in the compression molding step. A method for saccharification of herbaceous biomass, wherein the biomass is rice straw .

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