JP5880827B2 - Method for producing cellulose nanofiber - Google Patents

Description

  The present invention relates to a method for producing cellulose nanofibers, and more particularly to a method for producing cellulose nanofibers that are excellent in enzyme reaction efficiency and can easily adjust the aspect ratio and crystallinity.

In general, cellulose nanofibers extracted from woody biomass resources are cellulose elementary fibrils that are aggregates of a minimum unit of dozens of cellulose molecules, cellulose microfibrils having a diameter of 15 to 30 nm, and aggregates thereof. It can be roughly classified into three types of highly crystalline cellulose nanocrystals obtained by sulfuric acid hydrolysis of cellulose.
In recent years, these cellulose nanofibers have attracted attention in various fields such as reinforcing materials for high-performance polymer composite materials, transparent materials, and membrane filters.

  As a method for producing cellulose nanofibers, by combining an enzyme action promoting treatment and a physical destruction treatment, an endoglucanase is allowed to act on an aggregate of cellulose microfibrils or an amorphous part of cellulose microfibril itself, thereby producing cellulose nanofibers. Is known (see, for example, Patent Document 1).

  By the way, in recent years, cellulose nanofibers having various aspect ratios and crystallinity levels have been demanded as the application fields of cellulose nanofibers have expanded. In the present specification, the aspect ratio means “diameter of cross section of cellulose nanofiber / length of cellulose nanofiber”.

For example, in the production of fiber reinforced plastic (FRP), in a method of making a mat (nonwoven fabric) of fibers and precipitating a thermosetting resin, followed by heat pressure curing, cellulose nanofibers having a large aspect ratio are used. Thus, the physical interaction (for example, hydrogen bonding) can be strengthened and the physical properties can be improved.
However, in the method of compounding cellulose nanofibers with a thermoplastic polymer, especially when kneading using an extruder or kneader, cellulose nanofibers with a large aspect ratio are entangled and aggregated during kneading, resulting in dispersibility. Therefore, there is a need for cellulose nanofibers with controlled aspect ratios.

By the way, cellulose nanocrystals made of woody biomass have the advantage of exhibiting high crystallinity and strong strength characteristics. Generally, the diameter is 4 to 6 nm and the length is 100 to 300 nm, so the aspect ratio is very high. Get smaller.
However, when cellulose nanocrystals are produced, there is a drawback that a strong acid catalyst is required and that the recovery and removal of the used strong acid is very costly. In addition, it can be said that the method using an enzyme without using an acid catalyst is an environment-friendly method.

JP 2008-150719 A

However, in the conventional method for producing cellulose nanofibers including the method for producing cellulose nanofibers described in Patent Document 1, it is difficult to adjust the aspect ratio and the crystallinity.
Adjustment of the aspect ratio and crystallinity of cellulose nanofibers is a very important research subject, and the development of cellulose nanofibers with controlled aspect ratio and crystallinity is required.

  Cellulosic biomass decomposition reaction is generally an enzyme using a normal temperature cellulase group (optimum reaction temperature of about 50 ° C) derived from filamentous fungi, but in the case of an industrially used reactor However, there are problems such as contamination of bacteria during a long-time decomposition reaction and mass consumption of enzymes, and a high-efficiency decomposition reaction has not been realized.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the cellulose nanofiber which can adjust an aspect ratio and a crystallinity easily while being excellent in enzyme reaction efficiency. .

  The present inventors have intensively studied to solve the above-mentioned problems. As a result, the enzyme reaction that is normally performed is 40 to 50 ° C., but it has been considered to perform the enzyme reaction at a temperature higher than 50 ° C. Then, by selecting a thermostable cellulase, using the thermostable cellulase, cellulose microfibrils are thermally decomposed at high temperature, and further, the heating temperature, heating time and enzyme concentration at that time are adjusted to solve the above-mentioned problems. The present inventors have found that the present invention can be accomplished and have completed the present invention.

In the present invention, (1) in advance, an oxidant is added to biomass in the presence of an alkali catalyst or an acid catalyst, and the biomass is weakened by heating and stirring. mechanically pulverized by the mill, the weakening process of the cellulose microfibrils, the cellulose microfibrils, comprising a heating decomposing thermal decomposition process of a heat-resistant cellulase cellobiohydrolase are mixed, and grinding media , Water and a mixture of a low molecular weight compound, a high molecular compound or fatty acids, after heat-resistant cellulase is heat-treated at 80 ° C. or higher, and after heat treatment at 80 ° C. or higher with purified heat-resistant endoglucanase , which consist of a purified thermostable β- glucosidase, heat resistance endoglucanase, cellulose micro-off Is intended to selectively degrade the amorphous portion of the Brill, the enzyme concentration of the heat-resistant endoglucanase, with respect to the substrate 1M, is 0.01 to 10 mM, and heat resistance endoglucanase, and heat resistance β- glucosidase Of the cellulose nanofiber is 20: 0.1 to 1, the heating temperature in the thermal decomposition step is 80 ° C. to 105 ° C., and the heating time in the thermal decomposition step is 0.1 to 72 hours. Lies in the way.

The present invention resides in (2) the method for producing cellulose nanofibers according to (1) above , wherein the aspect ratio of the cellulose nanofibers is 4 to 1000 and the crystallinity is 5 to 90% .

  According to the method for producing cellulose nanofibers of the present invention, biomass can be made into cellulose nanofibers having a predetermined aspect ratio and crystallinity. That is, in the method for producing cellulose nanofibers, the enzymatic reaction efficiency can be improved by performing a thermal decomposition step of thermally decomposing cellulose microfibrils with a heat-resistant cellulase at a temperature higher than 50 ° C.

  In the thermolysis step, the aspect ratio and the crystallinity can be adjusted with high accuracy by adjusting the heating temperature, heating time and enzyme concentration. Incidentally, in mechanical pulverization, it is the limit to adjust the length of the cellulose nanofibers at the micron level, but in the present invention, the length of the cellulose nanofibers can be adjusted at the nano level. In particular, the heating temperature is preferably 80 ° C. or higher.

In the method for producing cellulose nanofibers, the thermostable cellulase comprises a heat-resistant endoglucanase purified after heat treatment at 80 ° C. or higher, and a heat-resistant β- glucosidase purified after heat treatment at 80 ° C. or higher. , The thermostable endoglucanase selectively degrades the amorphous part of cellulose microfibrils, and the thermostable β- glucosidase degrades cellobiose, a by-product that inhibits the activity of thermostable endoglucanase. Efficiency is greatly improved.

In the manufacturing method of the said cellulose nanofiber, when the mixture ratio of heat resistant endoglucanase and heat resistant beta- glucosidase is 20: 0.1-1, decomposition | disassembly by heat resistant beta- glucosidase, and heat resistant end Degradation by glucanase is performed in a well-balanced manner.

  In the method for producing cellulose nanofibers, when the weakening step is a step of mechanically pulverizing biomass with a mill to form cellulose microfibrils, or the biomass is weakened by an oxidizing agent and hydrothermal treatment, In the case of the process of mechanically pulverizing to make cellulose microfibril, cellulose nanofibers can be produced from natural biomass by a relatively simple process.

FIG. 1 is a flowchart showing each step in the method for producing cellulose nanofibers according to this embodiment. 2 is a photograph of an atomic force microscope image of cellulose microfibril A obtained in Example 1. FIG. FIG. 3 is a photograph of an atomic force microscope image of cellulose microfibril B obtained in Example 2. 4 is a photograph of an atomic force microscope image of cellulose nanofiber C obtained in Example 3. FIG. FIG. 5 shows an atomic force microscope image of a sample after 0 hours as a blank and samples (cellulose nanofibers) after 1.0, 2.7, and 17.5 hours obtained in Evaluation 1 of the examples. It is a photograph.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary.
FIG. 1 is a flowchart showing each step in the method for producing cellulose nanofibers according to this embodiment.
As shown in FIG. 1, the method for producing cellulose nanofibers according to the present embodiment includes a weakening step S1 for pulverizing biomass to make cellulose microfibrils, and thermal decomposition for thermally decomposing the cellulose microfibrils with a heat-resistant cellulase. Step S2.

According to the method for producing cellulose nanofibers according to the present embodiment, cellulose nanofibers having a predetermined aspect ratio and crystallinity can be efficiently produced from biomass.
Hereinafter, each step will be described in more detail.

(Vulnerability process)
The weakening step S1 is a step of mechanically pulverizing the biomass. By the weakening step S1, the biomass becomes cellulose microfibril.

The biomass is a natural product containing cellulose, hemicellulose, and lignin, and has a three-dimensional network hierarchical structure in which cellulose is firmly bound to lignin and hemicellulose.
Such biomass generally includes woody biomass obtained from plants such as wood, vegetation, agricultural products, and cotton, and bacterial cellulose produced by living organisms.

  The size of the biomass is preferably 5 cm square or less. In this case, it becomes easy to grind in weakening process S1. In addition, when biomass exceeds 5 cm, it is preferable to perform the preliminary weakening process which carries out a mechanical grinding | pulverization preliminary.

The pulverization method in the weakening step S1 is not particularly limited, and a method in which a medium (hereinafter referred to as “a pulverization medium” for convenience) can coexist and a shear force can be applied to the biomass is preferable.
For example, ball mill (vibrating ball mill, rotating ball mill, planetary ball mill), rod mill, bead mill, disc mill, cutter mill, hammer mill, impeller mill, extruder, mixer (high-speed rotary blade mixer, homomixer), homogenizer (high pressure homogenizer) , Mechanical homogenizer, ultrasonic homogenizer) and the like.

  Among these, the pulverization is preferably performed by a mill such as a ball mill, a rod mill, a bead mill, a disk mill, or a cutter mill, and more preferably performed by a ball mill or a disk mill. In particular, when a ball mill is used, the crystallinity can be lowered, so that the obtained cellulose nanofibers have a low crystallinity (higher amorphousness), and as a result, there is an advantage that the enzymatic decomposition efficiency is improved. .

Although it does not specifically limit as a grinding medium used in embrittlement process S1, Water, a low molecular compound, a high molecular compound, fatty acids, etc. are used suitably. These may be used alone or in combination of two or more.
Among these, the pulverizing medium is preferably used by mixing water with a low molecular compound, a high molecular compound, or a fatty acid.

  Examples of the low molecular weight compound include alcohols, ethers, ketones, sulfoxides, amides, amines, aromatics, morpholines, ionic liquids, and the like. , Ether polymers, amide polymers, amine polymers, aromatic polymers, and the like, and examples of fatty acids include saturated fatty acids and unsaturated fatty acids. At this time, the low molecular weight compound, the high molecular weight compound and the fatty acids are preferably water-soluble.

  In the method for producing cellulose nanofibers according to the present embodiment, cellulose whose aspect ratio and crystallinity are adjusted in a relatively simple process from natural biomass in the thermal decomposition process S2 described later by passing through the weakening process S1. Nanofibers can be produced.

(Thermal decomposition process)
The thermal decomposition step S2 is a step in which the cellulose microfibril obtained in the weakening step S1 is thermally decomposed with a heat-resistant cellulase.

Here, the thermostable cellulase is a cellulase having heat resistance and exhibiting reaction activity under reaction conditions higher than 50 ° C., and has a property different from general cellulase.
Specifically, thermostable cellulase consists of thermostable endoglucanase and thermostable β- glucosidase. Since these enzymes are heat resistant, they can be reacted at temperatures higher than 50 ° C. Thereby, enzyme reaction efficiency improves.

The thermostable endoglucanase (EGPh) is obtained by expressing endoglucanase, heat-treating at 80 ° C. or higher, and purifying by ammonium sulfate fractionation, centrifugation, column chromatography, or the like.
The heat-resistant β- glucosidase (BGL) is obtained by expressing β- glucosidase, heat-treating at 80 ° C. or higher, and purifying with ammonium sulfate fractionation, centrifugation, column chromatography, or the like.

A thermostable endoglucanase is characterized by being active in the amorphous region of cellulose and inactive in the crystalline region. That is, the thermostable endoglucanase can selectively decompose the amorphous part of cellulose microfibrils. Thereby, it becomes possible to obtain a cellulose nanofiber with high crystallinity.
In addition, thermostable endoglucanase is derived from thermostable archaea Pyrococcus horikoshii, which decomposes cellulose into cellobiose. Cellobiose, which is a by-product of endoglucanase, has an action of inhibiting the enzyme reaction by heat-resistant endoglucanase.

Thermostable β- glucosidase is characterized in that it uses 2-7 sugar cellooligosaccharide as a substrate to release glucose, but crystalline cellulose does not react. Thereby, it becomes possible to obtain a cellulose nanofiber with high crystallinity.
In addition, thermostable β- glucosidase is derived from thermostable archaea Pyrococcus furiosus and degrades the cellobiose.
Therefore, in the method for producing cellulose nanofibers, the thermostable endoglucanase selectively decomposes the amorphous part of cellulose microfibrils, and the thermostable β- glucosidase inhibits the activity of the thermostable endoglucanase by cellobiose. As a result, the enzyme reaction efficiency is greatly improved.

The blending ratio of the thermostable endoglucanase and the thermostable β- glucosidase is preferably 20: 0.1-1. When the thermostable β- glucosidase is less than 0.1 parts by mass with respect to 20 parts by mass of thermostable endoglucanase, cellobiose cannot be sufficiently decomposed compared to the case where the blending ratio is within the above range, and the heat resistance The enzyme reaction efficiency of endoglucanase may deteriorate, and when 20 parts by mass of thermostable endoglucanase exceeds 1 part by mass of thermostable β- glucosidase, the enzyme reaction efficiency of thermostable endoglucanase becomes substantially constant and improved. No longer.

The heating temperature in the thermal decomposition step S2 is higher than 50 ° C, preferably 80 ° C or higher, and more preferably 80 to 105 ° C. By setting the heating temperature to 80 ° C. or higher, cellulose nanofibers with better heat resistance can be obtained.
Moreover, when heating temperature is 80-105 degreeC, it is preferable that heating time is 0.1 to 72 hours.
Furthermore, the enzyme concentration of the thermostable endoglucanase in these cases is preferably 0.01 to 10 mM with respect to 1 M of the substrate.

In the method for producing cellulose nanofibers, the aspect ratio and crystallinity can be adjusted by adjusting the heating temperature, heating time and enzyme concentration.
For example, the heating temperature in the thermal decomposition step S2 can be increased by decreasing the heating temperature in the above-described heating temperature range, thereby increasing the length of the cellulose nanofibers. The length of the fiber can be reduced.
The heating time in the thermal decomposition step S2 can increase the length of the cellulose nanofiber by shortening the heating time in the above-described range of the heating time, and can increase the length of the cellulose nanofiber by increasing the heating time. The length can be reduced.
The enzyme concentration of the thermostable endoglucanase in the thermal decomposition step S2 can be increased by decreasing the enzyme concentration within the above enzyme concentration range, thereby increasing the length of the cellulose nanofibers, and increasing the enzyme concentration. The length of the cellulose nanofiber can be reduced.

In the method for producing cellulose nanofibers according to the present embodiment, the enzyme reaction efficiency can be improved through the thermal decomposition step S2.
In addition, the length of the cellulose nanofiber can be changed at the nano level by adjusting the heating temperature, the heating time, and the enzyme concentration, so that the aspect ratio can be adjusted with high accuracy.

The obtained cellulose nanofiber is a natural product and can be used for a reinforcing material composed of a polymer, a transparent material, a membrane filter, a coating agent, and the like.
Moreover, when using for these uses, it is preferable that the aspect-ratio of a cellulose nanofiber is 4-1000, and it is preferable that a crystallinity degree is 5-90%.

  The obtained cellulose nanofibers are tasteless, odorless and nontoxic, and are fine fibers and do not feel a foreign body feeling on the tongue, so they can also be added to foods. In this case, water retention, oil retention, texture, form stability, or diet can be imparted.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the method for producing cellulose nanofibers according to the present embodiment, the weakening step S1 is a step of mechanically pulverizing the biomass, but the biomass is previously subjected to acid treatment, alkali treatment, hydrothermal treatment or oxidation. The weakening treatment may be performed by agent treatment or the like. That is, in the weakening step, the biomass may be weakened by these treatments and then mechanically pulverized by a mill to form cellulose microfibrils.

In this case, holocellulose which is weakened by adding an oxidizing agent to the biomass in the presence of an alkali catalyst or an acid catalyst and then stirred under heating to remove lignin from the biomass is obtained. By pulverizing the holocellulose mechanically, holocellulose microfibrils are obtained.
As the alkali catalyst, caustic soda, sodium carbonate and the like are preferably used.
As the acid catalyst, sulfuric acid, various organic acids and the like are preferably used.
As the oxidizing agent, sodium chlorite, TEMPO oxidizing agent, ozone and the like are preferably used.

In the method for producing cellulose nanofibers according to this embodiment, heat-resistant endoglucanase and heat-resistant β- glucosidase are used in the thermal decomposition step S2, but if necessary, cellobiohydrolase is mixed and used. Also good. Incidentally, cellobiohydrolase shows particularly high activity in crystalline cellulose.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Production of thermostable endoglucanase)
For expression of endoglucanase, expression plasmid vector pET11 and E. coli BL21 (DE3) for expression were used. The expressed endoglucanase was heat-treated at 85 ° C. and purified using a Hitrap Phenyl column to obtain a thermostable endoglucanase (enzyme number: EC 3.2.1.4, belonging to family 5).

(Production of thermostable β- glucosidase)
Expression plasmid vector pET11 and E. coli BL21 (DE3) for expression were used for expression of β- glucosidase. The expressed β- glucosidase was heat-treated at 85 ° C. and purified using Hitrap Phenyl column to obtain heat-resistant β- glucosidase (enzyme number: EC 3.2.1.21).

Example 1
(Production of cellulose microfibril A)
As woody biomass, 5 cm square eucalyptus kraft pulp was used. As a result of component analysis of eucalyptus kraft pulp, which is a hardwood, the cellulose component was 0.2%, hemicellulose was 22.3%, and lignin was 10.3%.
Eucalyptus kraft pulp was mechanically pulverized using a disk mill (weakening process). Specifically, water is added to eucalyptus kraft pulp to form a water suspension so that the solid content concentration becomes 1%, and this is mechanically pulverized 10 times using a disk mill to obtain cellulose microfibril A. It was.

An atomic force microscope image of cellulose microfibril A is shown in FIG. In the atomic force microscope observation, water was added to the obtained cellulose microfibril A to a solid content concentration of 0.05%, and this was added to polyethyleneimine (0.01) which is a cationic polymer.
A thin film was formed and observed by spin coating (3000 rpm, 1 minute) on the surface of the gold plate coated with (% aqueous solution).
Cellulose microfibril A had a diameter of 5 to 30 nm and a length of 1 μm or more, and thus was found to have a very high aspect ratio.

(Production of cellulose nanofiber A)
Cellulose microfibril A was thermally decomposed with heat-resistant cellulase. Specifically, water was added to cellulose microfibril A so that the solid content concentration was 0.2%, and 2 mL of 0.1 M acetate buffer (pH 5.5) was added thereto. Then, 0.2 mL each of 10 μM heat-resistant endoglucanase and 0.2 μM β- glucosidase were added and stirred at a heating temperature of 85 ° C. (thermal decomposition step), so that cellulose microfibril A was thermally decomposed. Nanofiber A was obtained. In addition, it sampled after 0.5, 1.0, 2.7, and 17.5 hours, respectively.

(Example 2)
(Production of cellulose microfibril B)
As woody biomass, cypress wood powder (0.2 mm), which is a conifer, was used.
First, cypress wood flour was delignified (weakened) with atrium chlorite. Specifically, 750 ml of distilled water, 7.5 g of sodium chlorite (oxidizer) and 1.5 ml of acetic acid (acid catalyst) are added to 25 g of hinoki wood flour, and stirred in a hot water bath at 80 to 90 ° C. The mixture was warmed for 1 hour. Thereafter, 7.5 g of sodium chlorite and 1.5 ml of acetic acid were added to carry out the reaction, and this operation was repeated 5 times, followed by washing with 3 L of distilled water to obtain holocellulose.
And the obtained holocellulose was pulverized mechanically using a disk mill (weakening step). Specifically, water is added to cypress wood flour to form an aqueous suspension so that the solid content concentration becomes 1%, and this is mechanically pulverized twice using a disk mill to obtain cellulose microfibril B and did.

An atomic force microscope image of cellulose microfibril B is shown in FIG. In the atomic force microscope observation, water was added to the obtained cellulose microfibril B so as to have a solid content concentration of 0.05%, and this was added to polyethyleneimine (0.01) which is a cationic polymer.
A thin film was formed and observed by spin coating (3000 rpm, 1 minute) on the surface of the gold plate coated with (% aqueous solution).
Cellulose microfibril B was found to have a very large aspect ratio, like cellulose microfibril A.

(Production of cellulose nanofiber B)
Cellulose microfibril B was pyrolyzed with heat-resistant cellulase. Specifically, water was added to cellulose microfibril B so as to have a solid content concentration of 0.2%, and 2 mL of 0.1 M acetate buffer (pH 5.5) was added thereto. Then, 0.2 mL each of 10 μM thermostable endoglucanase and 0.2 μM β- glucosidase were added and stirred at a heating temperature of 85 ° C. (thermal decomposition step), whereby cellulose microfibril B was thermally decomposed. Nanofiber B was obtained. In addition, it sampled after 0.5, 1.0, 2.7, and 17.5 hours, respectively.

(Example 3)
(Production of cellulose microfibril C)
As woody biomass, 1 g of sugarcane residue (bagasse) was used.
First, the sugarcane residue was mechanically pulverized using a planetary ball mill (weakening step). Specifically, water was added to the sugarcane residue and treated at 400 rpm for 2 hours to obtain cellulose microfibril C.

(Production of cellulose nanofiber C)
Cellulose microfibril C was thermally decomposed with heat-resistant cellulase. Specifically, water was added to 350 mg of cellulose microfibril C, and 50 mM citrate buffer (pH 5.0) was added thereto to make the substrate concentration 1%. And thermostable endoglucanase (345
UI / g of bagase) was added, and the heating temperature was 85 ° C. and the mixture was stirred for 72 hours (thermal decomposition step) to obtain cellulose nanofiber C obtained by thermally decomposing cellulose microfibril C. In addition, the amount of glucose produced at this time was 33.42%.
An atomic force microscope image of the cellulose nanofiber C is shown in FIG.
As shown in FIG. 4, it was found that the cellulose nanofiber C is a highly crystalline cellulose nanocrystal.

(Evaluation 1)
In the production of cellulose nanofibers, a sample after 0 hours as a blank and a sample (cellulose nanofibers) after 1.0, 2.7, and 17.5 hours obtained by thermally decomposing cellulose microfibril A Observed with an atomic force microscope. A photograph of the obtained atomic force microscope image is shown in FIG. In the atomic force microscope observation, water was added to the sample so that the solid content concentration was 0.05%, and this was added to polyethyleneimine (0.01) which is a cationic polymer.
A thin film was formed and observed by spin coating (3000 rpm, 1 minute) on the surface of the gold plate coated with (% aqueous solution). The upper and lower atomic force micrographs in FIG. 5 are obtained by observing different portions of the same sample.

  As can be seen from the photograph after 1.0 hour in FIG. 5, long fibers of cellulose microfibril A are cut. Moreover, it turned out that the length of most fibers has become 1 micrometer or less after progress for 2.7 hours. Further, it was found that after 17.5 hours, most of the fibers were decomposed to cellulose nanocrystals having a diameter of 4 to 10 nm and a length of around 200 nm obtained by sulfuric acid hydrolysis. From these results, it was found that cellulose nanofibers having various aspect ratios can be prepared by adjusting the heating temperature, the heating time, or the enzyme concentration. In addition, although the thermostable endoglucanase mainly decomposes | disassembles an amorphous area | region from the photograph of FIG. 5, it has shown that the preparation of the highly crystalline nanocrystal from a cellulose nanofiber is also possible.

(Evaluation 2)
In the production of cellulose nanofibers, glucose after 0.5, 1.0, 2.7, and 17.5 hours obtained by thermally decomposing cellulose microfibrils A and B was measured. The results are shown in Table 1.

(Table 1)

  From the results in Table 1, it was found that the enzymatic reaction was promoted because the amount of glucose produced increased with the elapse of the heating time.

  From the above, according to the method for producing cellulose nanofibers of the present invention, it was confirmed that the enzyme reaction efficiency was excellent and the aspect ratio and crystallinity could be easily adjusted.

Cellulose nanofibers obtained by the method for producing cellulose nanofibers of the present invention can be used in various fields such as a polymer reinforcing material, a transparent material, and a membrane filter.
Moreover, according to the manufacturing method of the cellulose nanofiber of this invention, the cellulose nanofiber which has the aspect-ratio and the crystallinity degree according to the needs of the field | area used can be provided.

S1 ... Fragility process S2 ... Thermal decomposition process

Claims (2)

In advance, an oxidant is added to the biomass in the presence of an alkali catalyst or an acid catalyst, and the biomass is weakened by heating and stirring. Then, the biomass is made to coexist with the biomass and mechanically pulverized by a ball mill or a disk mill. , Embrittlement process to make cellulose microfibrils,
A thermal decomposition step of thermally decomposing the cellulose microfibrils with a thermostable cellulase mixed with cellobiohydrolase ;
With
The grinding medium is a mixture of water and a low molecular compound, a high molecular compound or fatty acids,
The thermostable cellulase comprises a heat-resistant endoglucanase purified after heat treatment at 80 ° C. or higher, and a heat-resistant β- glucosidase purified after heat treatment at 80 ° C. or higher,
The thermostable endoglucanase selectively decomposes the amorphous part of the cellulose microfibril,
The enzyme concentration of the thermostable endoglucanase is 0.01 to 10 mM with respect to the substrate 1M,
The blending ratio of the thermostable endoglucanase and the thermostable β- glucosidase is 20: 0.1-1;
The heating temperature in the thermal decomposition step is 80 ° C to 105 ° C,
The manufacturing method of the cellulose nanofiber whose heating time in the said thermal decomposition process is 0.1 to 72 hours.   The method for producing cellulose nanofiber according to claim 1, wherein the cellulose nanofiber has an aspect ratio of 4 to 1000 and a crystallinity of 5 to 90%.

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