JP6993248B2 - How to grow cellulose-degrading bacteria - Google Patents

Description

The present invention relates to a method for growing cellulose-degrading bacteria.

Cellulase is an enzyme that hydrolyzes cellulose. Fungi having cellulase use this enzyme to decompose cellulose into glucose and oligosaccharides having a structure in which multiple molecules of glucose are bound, and these decomposition products are used as a nutrient source. Such fungi are referred to herein as "cellulose-degrading fungi".

On the other hand, a problem in decomposing cellulose into a final product such as glucose using cellulase is that the decomposition rate is slow. That is, the decomposition of cellulose using cellulase is currently very inefficient. This also applies to cellulose-degrading bacteria.

For example, a mushroom is mentioned as one of the cellulose-degrading bacteria. Conventionally, as a mushroom cultivation medium, a medium containing sawdust, bran or the like as a cellulose source has been used. However, when mushrooms are cultivated using such a medium, there is a limit to shortening the cultivation period of mushrooms due to the slow decomposition rate of cellulose by cellulase, and there is a problem that mushrooms cannot be harvested in a short period of time. was there.

Therefore, it is desired to develop a method for improving the decomposition rate when decomposing cellulose into a final product using cellulase. As such a method, cellulose type I, which is a natural type cellulose, is treated with ammonia to obtain low-density crystalline cellulose having a lower crystal density than cellulose type I, and then this low-density crystal is obtained by using cellulase. A method for decomposing sex cellulose into glucose is disclosed (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-161125

However, the method disclosed in Patent Document 1 has a problem that a special operation of ammonia treatment is required. It is also unclear whether cellulolytic bacteria can efficiently degrade low-density crystalline cellulose.
Therefore, it has been desired to develop a highly versatile means capable of improving the decomposition rate of cellulose into a final product in a cellulose-degrading bacterium. If such a means is realized, the cellulose-degrading bacteria can be grown in a short time, which is very useful.

Therefore, it is an object of the present invention to provide a method capable of growing cellulose-degrading bacteria in a short time.

The present invention is a method for growing a cellulose-degrading bacterium, which comprises adding water containing cellulose nanofibers to a sterilized medium having the cellulose-degrading bacterium and then growing the cellulose-degrading bacterium in the medium. offer.
In the method for growing a cellulolytic bacterium of the present invention, it is preferable that the cellulolytic bacterium is a mushroom.

INDUSTRIAL APPLICABILITY According to the present invention, a method capable of growing cellulose-degrading bacteria in a short time is provided.

It is the imaging data which shows the state of the growth of Oyster Mushroom in Example 1. It is the imaging data which shows the state of the growth of Oyster Mushroom in Comparative Example 1.

<< Growth method of cellulose-degrading bacteria >>
The method for growing a cellulolytic bacterium of the present invention is to use a cellulolytic bacterium and a sterilized medium (referred to as an "initial medium" in the present specification) and a cellulose nanofiber (in the present specification). Is added water containing (sometimes referred to as "CNF") (sometimes referred to as "CNF-containing water" in the present specification), and then the medium (in the present specification, "CNF"). It is used to grow the cellulolytic bacteria in (sometimes referred to as "containing medium").

In the above-mentioned growth method, a sterilized medium finally containing CNF (the CNF-containing medium) is used to grow cellulose-degrading bacteria. Then, the cellulose-degrading bacterium hydrolyzes this CNF as cellulose, and produces glucose or an oligosaccharide having a structure in which a plurality of glucose molecules are bound as a final product. The decomposition rate of CNF at this time is significantly faster than the decomposition rate when decomposition of cellulose not corresponding to CNF (in this specification, it may be referred to as “non-CNF cellulose”) under the same conditions. That is, by growing the cellulose-degrading bacteria by the above-mentioned growth method, a large amount of the cellulose-degrading bacteria can be grown in a short time. Further, in this case, it is specified that CNF-containing water is added to a medium having and sterilized with cellulose-degrading bacteria (the initial medium), and then the cellulose-degrading bacteria are grown in the medium (the CNF-containing medium). It is possible to grow the cellulose-degrading bacteria by the same method as the conventional method except that the above operation is adopted, and no special operation is required. Therefore, the growth method is highly versatile.

The high growth rate of the cellulolytic bacteria means that the rate of decomposition of cellulose in the cellulolytic bacteria is high. Although the reason why the growth rate of the cellulose-degrading bacterium is increased by the above-mentioned growth method (the cellulolytic rate of the cellulose-degrading bacterium is improved) is not clear, the crystallinity of CNF is low, and the cellulase of CNF is in contact with the cellulase. It is presumed that this is because the possible surface area is large and the decomposition reaction of cellulose (CNF) is easily promoted.

Further, in the growth method, the growth rate of the cellulose-degrading bacteria is stabilized by adopting a specific operation of adding CNF-containing water to the initial medium and then growing the cellulose-degrading bacteria in the medium. It is possible to improve it. For example, when the cellulose-degrading fungus is a specific range of fungi, the medium is sterilized, and then the cellulose-degrading bacteria are inoculated into this medium and grown in this medium. For the sterilization process, an autoclave that processes the medium under high pressure and high temperature may be adopted. At this time, if the medium containing CNF is autoclaved, the CNF in the medium may be denatured by heating. Then, even if the cellulose-degrading bacteria are grown in such a medium, the growth rate does not improve. It is presumed that this is because the contact area between the denatured CNF and the cellulase derived from the cellulolytic bacteria is reduced.
On the other hand, in the above-mentioned growth method, since CNF-containing water is added to the pre-sterilized initial medium, CNF that has not been autoclaved can be contained in the medium, and the growth rate of cellulose-degrading bacteria is stable. It is possible to improve it.

As the growth rate of the cellulose-degrading bacteria, the growth amount of the cellulose-degrading bacteria can be used as a guide. For example, when comparing the growth rates of cellulolytic bacteria, the superiority or inferiority of the growth rate can be determined by comparing the growth amounts of the cellulose-degrading bacteria at the same growth time.

<Initial medium>
The initial medium (medium having cellulolytic bacteria and sterilized) before adding the CNF-containing water contains essential components necessary for the growth of cellulolytic bacteria, and the cellulolytic bacteria have already been inoculated. There is no particular limitation as long as it is a sterilized medium.

For example, the initial medium may be either a liquid medium or a solid medium.
The initial medium may contain other components in addition to the essential components and cellulose-degrading bacteria.

[Cellulolytic bacteria]
The cellulolytic bacterium to which the present invention is applied is a fungus having cellulase, which is a cellulose hydrolase, and by using cellulase, cellulose is decomposed into glucose or oligosaccharide, which is the final product. Cellulolytic bacteria usually utilize this end product as a nutrient source.
Cellulose-degrading bacteria have a common property in that they hydrolyze cellulose (CNF) with cellulase to produce monosaccharides or oligosaccharides.

Examples of the cellulose-degrading bacterium include fungi classified into bacteria, fungi and the like. Bacteria are microorganisms, but fungi include mushrooms that form fruiting bodies in addition to microorganisms. That is, the above-mentioned growth method can be used not only for culturing (growing) microorganisms but also for cultivating (growing) mushrooms.

Among the cellulose-degrading bacteria, preferred bacteria include, for example, microorganisms belonging to the genus Bacillus.
Among the cellulose-degrading bacteria, those preferred as fungi are, for example, microorganisms belonging to the genus Trichoderma such as Trichoderma reesei; and Clostridium belonging to the genus Clostridium such as Clostridium thermocellum. ; Mushrooms such as Maitake, Hiratake, Enoki, and Shiitake can be mentioned.
It is important that mushrooms have high utility value in their own right and can be harvested in a short period of time by shortening the cultivation period. That is, among the cellulose-degrading bacteria, mushrooms are mentioned as an example of particularly preferable ones.

The cellulolytic bacteria contained in the initial medium may be only one kind, may be two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily adjusted.

The content of the cellulolytic bacteria in the initial medium can be appropriately adjusted according to the type of the initial medium, the type of the cellulolytic bacteria, and the like, and is not particularly limited.

[Essential ingredients]
The essential component is determined by the type of cellulose-degrading bacteria.

[Other ingredients]
The other components in the initial medium can be arbitrarily selected depending on the intended purpose, and are not particularly limited.
The other component may be, for example, either an organic component or an inorganic component.
For example, the initial medium may or may not contain CNF. Here, examples of the CNF include the same CNF contained in the CNF-containing water described later.

The essential component and other components contained in the initial medium may be only one kind, may be two or more kinds, and when there are two or more kinds, the combination and ratio thereof shall be. It can be adjusted arbitrarily.

The contents of the essential component and other components of the initial medium can be appropriately adjusted according to the type of the initial medium, the type of cellulose-degrading bacteria, and the like, and are not particularly limited.

The initial medium can be prepared, for example, by sterilizing a medium capable of growing cellulose-degrading bacteria and inoculating the obtained sterilized medium with cellulose-degrading bacteria.
The medium before sterilization contains the essential components. Examples of the medium before sterilization include Triptic Soy Broth, Potato Dextrose Agar, and the like, and further, these known media are separately known as constituents of the medium. Can also be mentioned with the addition of.

Sterilization of the medium can be performed in an autoclave that treats the medium under high pressure and high temperature.
The pressure, temperature and time during autoclaving can be set to normal conditions in consideration of the type of medium and the like. For example, the temperature may be 80 to 140 ° C., the pressure may be 0.01 to 0.2 MPa, and the time may be 10 to 90 minutes.

When inoculating the cellulose-degrading bacterium into the sterilized medium, the cellulose-degrading bacterium may be placed on the sterilized medium and can be inoculated by a known method.

The amount of cellulolytic bacteria inoculated into the sterilized medium is not particularly limited, and can be appropriately adjusted according to the type of initial medium, the type of cellulolytic bacteria, and the like.
For example, when the cellulose-degrading bacterium is a microorganism, the inoculation amount may be 0.01 to 10 g per medium.
When the cellulose-degrading bacterium is a mushroom, the inoculation amount may be 0.1 to 50 g per medium.

The cellulolytic bacteria after inoculation may be grown (cultured) in the sterile medium before adding the CNF-containing water to the sterile medium. Conditions such as temperature, humidity, and time at this time can be appropriately adjusted according to the type of initial medium, the type of cellulose-degrading bacteria, and the like, and are not particularly limited.

The initial medium may be, for example, a sterilized commercially available medium for cellulose-degrading bacteria inoculated with the cellulose-degrading bacteria. By using a commercially available medium as described above, it is possible to grow the cellulose-degrading bacteria more easily.

<CNF-containing water>
The CNF-containing water (water containing CNF) added to the initial medium is not particularly limited as long as it contains CNF and water.
For example, the CNF-containing water may contain other components that do not fall under any of these, in addition to CNF and water.

The CNF-containing water is usually an aqueous dispersion.

[Cellulose Nanofiber (CNF)]
The CNF used in the present invention is not particularly limited and may be a known one.
More specifically, the CNF includes, for example, cellulose or a derivative thereof, which is a microfibril or an aggregate of microfibrils having a fiber width of 3 to 200 nm.

Examples of the CNF include defibrated cellulose nanofibers (defibrated CNF) and TEMPO oxidized cellulose nanofibers (TEMPO oxidized CNF).
The defibrated CNF is manufactured by having a step of obtaining a cellulose nanofiber dispersion liquid (CNF dispersion liquid) by performing a defibration treatment on a cellulose nanofiber precursor (CNF precursor) in a dispersion medium such as water. CNF manufactured by the method.
TEMPO Oxidized CNF is a CNF obtained by a chemical denaturation method of cellulose catalyzed by 2,2,6,6-tetramethyl-1-piperidinyloxy, radical (TEMPO).

The CNF precursor is a cellulose that has not been defibrated, and is composed of, for example, an aggregate of microfibrils.
As the CNF precursor, for example, cellulose oxide, that is, one in which a carboxy group is introduced into at least a part of the glucopyranose ring in the cellulose molecule by the oxidation treatment of cellulose may be used.

The cellulose source (raw material containing cellulose) for obtaining the CNF precursor is not particularly limited as long as it contains cellulose, and may be cellulose itself.
Examples of the cellulose source include those containing naturally-derived cellulose having a crystalline structure of cellulose I, and more specifically, for example, various wood pulps, non-wood pulps, bacterial celluloses, waste paper pulps, cottons, and baronia. Examples thereof include cellulose and squirrel cellulose.
Various commercially available products such as cellulose powder and microcrystalline cellulose powder can also be used as a cellulose source.

The method for defibrating the CNF precursor is not particularly limited. As a specific defibration treatment method, for example, an ultrasonic homogenizer, a low-pressure homogenizer, a high-pressure homogenizer, a counter-collision homogenizer, an ultra-high pressure homogenizer, a ball mill, a planetary mill, a high-speed rotary mixer, a grinding machine, or the like was used. Examples thereof include a mechanical defibration treatment method (in this specification, a CNF obtained by performing a mechanical defibration treatment method is referred to as “mechanical defibration CNF”).
The fact that the treated product obtained by the defibration treatment of the CNF precursor is CNF can be confirmed by observing the fibers of the treated product using, for example, an atomic force microscope (AFM).

The CNF-containing water may contain only one type, two or more types, or two or more types, and the combination and ratio thereof can be arbitrarily adjusted.

The CNF content of the CNF-containing water may be appropriately adjusted so that the growth of the cellulose-degrading bacteria is good, and is not particularly limited.
Among them, the CNF content of the CNF-containing water is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and 0.01 to 1% by mass. Is more preferable, and 0.05 to 0.6% by mass is particularly preferable. When the CNF content is at least the lower limit, the growth rate of the cellulose-degrading bacteria is further improved. When the content of CNF is not more than the upper limit, the handleability of CNF-containing water is further improved. If the content of CNF is too large, the water containing CNF becomes a highly viscous gel, but if the content of CNF is 5% by mass or less, the water containing CNF should be sufficiently infiltrated into the initial medium. Can be done.

[Other ingredients]
The other components in the CNF-containing water can be arbitrarily selected depending on the intended purpose, and are not particularly limited.

The other components contained in the CNF-containing water may be only one kind, may be two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be arbitrarily adjusted.

The content of the other components in the CNF-containing water can be appropriately adjusted according to the type of the initial medium, the type of cellulose-degrading bacteria, and the like, and is not particularly limited.

CNF-containing water can be produced, for example, by mixing CNF in a pure state by withdrawal or purification with water.
Further, CNF-containing water can also be produced by mixing a mixture of CNF and a component other than CNF obtained at the time of producing CNF with water.
Further, the liquid mixture containing CNF and water obtained at the time of producing CNF may be used as it is as CNF-containing water, or the liquid mixture obtained by performing an arbitrary post-treatment operation is contained in CNF. It may be used as water. Examples of the liquid mixture include a CNF dispersion obtained by subjecting a CNF precursor to a defibration treatment (dispersion of defibrated CNF).

When the cellulolytic bacteria are microorganisms, the CNF-containing water is preferably sterilized.
The sterilized CNF-containing water can be obtained by sterilizing the CNF-containing water by a known method such as sterilization treatment by filtration using a sterilization filter or sterilization treatment by ultraviolet irradiation.
The sterilized CNF-containing water can also be obtained by mixing sterilized CNF with sterilized water under sterile conditions such as in a clean bench.

When the cellulose-degrading bacterium is a mushroom, the CNF-containing water is preferably sterilized or not sterilized. Here, the sterilized CNF-containing water is the same as when the above-mentioned cellulose-degrading bacterium is a microorganism.

The method of adding the CNF-containing water to the initial medium is not particularly limited. For example, CNF-containing water can be added by injecting it into the initial medium in a liquid state using a liquid substance injection means such as a dropper or a tube. Further, the CNF-containing water can also be added by atomizing it into a mist and spraying (spraying) it on the initial medium by using a means for atomizing a liquid substance such as a mist.

The amount of CNF added to the initial medium by adding the CNF-containing water to the initial medium may be appropriately adjusted so as to improve the growth of the cellulose-degrading bacteria, and is not particularly limited.
In particular, the amount of CNF added to the initial medium is preferably 0.1 to 10 parts by mass, preferably 0.2 to 7 parts by mass, based on 100 parts by mass of the inoculated amount of the cellulose-degrading bacteria in the initial medium. It is more preferably 0.3 to 5 parts by mass, and particularly preferably 0.4 to 3 parts by mass. When the amount of CNF added is equal to or greater than the lower limit, the growth rate of cellulose-degrading bacteria is further improved. When the amount of CNF added is not more than the upper limit, overuse of CNF is suppressed.

The temperature of the CNF-containing water added to the initial medium is not particularly limited as long as the effect of the present invention is not impaired.
The temperature of the CNF-containing water at the time of addition is preferably 180 ° C. or lower, more preferably 150 ° C. or lower, further preferably 120 ° C. or lower, for example, 100 ° C. or lower, 70 ° C. or lower, 50. It may be either ℃ or less and 30 ℃ or less. When the temperature of the CNF-containing water is equal to or lower than the upper limit, the degeneration of CNF in the CNF-containing water is suppressed, and the growth rate of the cellulose-degrading bacteria is further improved.

The lower limit of the temperature of the CNF-containing water added to the initial medium is not particularly limited as long as the CNF-containing water is not frozen.
The temperature of the CNF-containing water at the time of addition is preferably 0 ° C. or higher.

The temperature of the CNF-containing water added to the initial medium can be appropriately adjusted within a range set by any combination of the above-mentioned preferable lower limit values and upper limit values. For example, the temperature is preferably 0 to 180 ° C, more preferably 0 to 150 ° C, still more preferably 0 to 120 ° C, and for example, 0 to 100 ° C, 0 to 70 ° C, 0 to 50 ° C, and 0. It may be any of ~ 30 ° C. However, these are examples of the above temperatures.

When the initial medium is solid, CNF is likely to be unevenly distributed on the surface of the initial medium due to the addition of CNF-containing water. On the other hand, when the initial medium is liquid, CNF easily diffuses over the entire area of the initial medium due to the addition of CNF-containing water. That is, when the initial medium is solid, the added CNF is unevenly distributed on the surface of the initial medium, which is the main growth site of the cellulose-degrading bacteria. Therefore, the cellulose-degrading bacteria can be grown with a smaller amount of CNF added. It can be grown and has high growth efficiency.

The method for growing the cellulose-degrading bacterium in the CNF-containing medium (medium obtained by adding CNF-containing water to the initial medium) may be a known method, and is appropriately used depending on the type of the cellulose-degrading bacterium and the like. It can be adjusted and is not particularly limited.

For example, when the cellulose-degrading bacterium is a microorganism, its growth can be carried out by applying normal culturing conditions of the microorganism. For example, in this case, the microorganism is preferably grown under sterile, sterile conditions.

When the CNF-containing medium is liquid, the medium may be allowed to stand or shake (for example, shake culture) when the microorganism (cellulose-degrading bacterium) grows. When the CNF-containing medium is in a solid state, this medium may be left to stand during the growth of microorganisms (cellulose-degrading bacteria).
The temperature at the time of growth of the microorganism (cellulose-degrading bacterium) may be, for example, 18 to 60 ° C., and the growth time may be, for example, 2 hours to 10 days. However, these are examples of temperature and growth time.

When the cellulose-degrading bacterium is a mushroom, its growth can be carried out by applying normal mushroom cultivation conditions. For example, in this case, the mushroom may be grown under sterile, sterile conditions, but may be grown under non-sterile conditions (non-sterile conditions).

The temperature at the time of growth of mushrooms (cellulose-degrading bacteria) may be, for example, 10 to 30 ° C., the relative humidity at the time of growth may be, for example, 65 to 95%, and the growth time may be, for example, 15 to. It can be 30 days. However, these are examples of temperature, relative humidity, and growth time.

Traditional methods of growing mushrooms may usually be subject to specific conditions. Such conditions may also be applied to the growing method of the present invention.
That is, in the growth method of the present invention, the cells (mushrooms, cellulose-degrading bacteria) after inoculation are grown to some extent in the initial medium, and the growth is not clearly observed in the form of mushrooms. A so-called "mushroom" is performed to remove a part of the bacterial cells in the initial medium. This fungal scraping is also applied to conventional growth methods. Next, CNF-containing water is added to the initial medium after scraping the bacteria. In the conventional growth method, water (also referred to as “bacterial scraping water”) is added to the initial medium after scraping the fungus, but in the growth method of the present invention, CNF-containing water is added instead of this water. In the growth method of the present invention, the growth of mushrooms is remarkably promoted by applying such specific conditions.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

[Example 1]
<Manufacturing of sterilized medium>
Sawdust (294 g), rice bran (123 g) and water (184 g) were mixed to obtain a medium (601 g).
The entire amount of this medium was then filled into a transparent mushroom growing bottle, four holes were formed near the center of the exposed surface above the medium, and the bottle was capped.
Next, the medium was placed in an autoclave device together with the bottle, and the medium was pre-sterilized at 98 ° C. for 1 hour, and then the medium was sterilized at 120 ° C. for 45 minutes.
Then, after the temperature in the autoclave apparatus was lowered to 80 ° C., the bottle was moved into the clean bench and allowed to stand until the temperature of the bottle (medium) reached 15 ° C.
From the above, a sterilized medium was obtained.

<Manufacturing of initial medium>
In the clean bench, the lid of the bottle filled with the sterilized medium obtained above is opened, the mouth of the bottle is disinfected with alcohol, and the exposed surface is uniform on the exposed surface above the sterilized medium. The inoculum of Oyster Mushroom (about 5 g) was placed to the extent that it could be hidden in.
Then, the bottle was immediately covered, and the inoculated sterilized medium was placed in the incubator together with the bottle, and the inoculum was grown under the conditions of a temperature of 20 ° C. and a relative humidity of 70%.
From the above, an initial medium was obtained.

<Growth of cellulose-degrading bacteria>
Then, the bottle was taken out of the incubator, the lid was removed, and the surface of the medium was scraped with a disinfected spoon to remove about 12 g of the grown bacteria.
Next, a 20 ° C. CNF aqueous dispersion (CNF-containing water) (about 10 g) having a hole in the center of the exposed surface above the medium and containing CNF at a concentration of 0.3% by mass as fungal scraping water. ) Was added to this hole and the bottle was covered.
Next, this medium was placed in an incubator together with the bottle, and the fungus (Oyster Mushroom) was grown for 22 days under the conditions of a temperature of 15 ° C. and a relative humidity of 90%. During this time, the oyster mushrooms were grown in the shade for the first 14 days. From the 15th day, for the first 15 minutes, light the lights to grow the oyster mushrooms, then shade them to grow the oyster mushrooms, and when the height of the oyster mushrooms grows by 3 cm, turn the lights on again to grow the oyster mushrooms. Then, the oyster mushrooms were grown in the light of light, and then the oyster mushrooms were grown for a total of 8 days by repeating this light and dark growth cycle. Then, the state of growth of Oyster Mushroom was observed on the 16th, 18th, 19th, 20th, 21st and 22nd days from the start of growth. The imaging data acquired at this time is shown in FIG. In this example, the above-mentioned growth of Oyster Mushroom is carried out in three bottles, and FIG. 1 shows all the results in these three bottles. In FIG. 1, the results in one bin are shown side by side in one vertical column.

[Comparative Example 1]
<Manufacturing of sterilized medium>
A sterilized medium was produced in the same manner as in Example 1.

<Growth of cellulose-degrading bacteria>
Cellulolytic bacteria (sulfur-degrading bacteria (about 10 g) were added in the same manner as in Example 1 except that water (about 10 g) was added instead of CNF-containing water (about 10 g) having a concentration of 0.3% by mass as the fungus scraping water. Hiratake) was grown. The imaging data acquired at this time is shown in FIG. In this comparative example as well, the growth of Oyster Mushroom was carried out in three bottles, and FIG. 2 shows all the results in these three bottles. Also in FIG. 2, the results in one bin are shown side by side in one vertical column.

As is clear from the results of FIGS. 1 to 2, the growth rate of Oyster Mushroom was significantly faster in Example 1 than in Comparative Example 1. As described above, it was confirmed that the cellulose-degrading bacteria can be grown in a short time by adding the CNF-containing water to the initial medium.

The present invention can be used for short-term growth of cellulose-degrading bacteria.

Claims (3)

A method for growing a cellulolytic bacterium, which comprises adding water containing cellulose nanofibers to a solid medium having a cellulolytic bacterium and sterilized, and then growing the cellulolytic bacterium in the solid medium. The method for growing a cellulolytic bacterium according to claim 1, wherein the cellulolytic bacterium is a mushroom. The cellulose-degrading bacterium is grown in a solid medium having the cellulose-degrading bacterium and sterilized, and then a part of the cellulose-degrading bacterium is removed from the solid medium, and then the cellulose nano is placed in the solid medium. The method for growing a cellulolytic bacterium according to claim 2, wherein the cellulolytic bacterium is grown in the solid medium after adding water containing a fiber.

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