WO2024166182A1 - Method for producing spherical algal body - Google Patents

Abstract

The present invention addresses the problem of providing a new culture technology for red algae.　The present invention provides a method for producing a spherical algal body, the method including: an algal body preparation step for obtaining cut algal bodies from red algae; and a culture step for culturing the cut algal bodies, wherein the culture step is performed while performing aeration so that the cut algal bodies rotate.

Description

Method for producing spherical algae

The present invention relates to a method for producing spherical algae.

In recent years, climate change due to global warming has had a major, adverse effect on the environment.
Greenhouse gases are known to be a cause of global warming.

Methane (CH ₄ ) is a gas that is emitted by cows when they burp, and is known to have a significantly high greenhouse effect among greenhouse gases.

On the other hand, it has been found that adding the red algae Asparagopsis taxiformis to cattle feed can suppress methane emissions from cattle (for example, Non-Patent Document 1).

PLoS One. 2014 Jan 22;9(1):e85289. doi: 10.1371/journal. bone. 0085289. eCollection 2014

Because of the expected effects of suppressing methane emissions as described above, there is a growing need for efficient red algae cultivation techniques.

The present invention was made in consideration of the above situation, and aims to provide a new culture technique for red algae.

The inventors discovered the novel finding that, in culturing red algae, spherical algae can be obtained by culturing the algae in a rotating manner, and have completed the present invention. Specifically, the present invention provides the following:

(1) a step of preparing algal bodies by obtaining sliced algal bodies from red algae;
A culturing step of culturing the sliced algal bodies,
The culture step is carried out while aerating the sliced algal bodies so as to rotate them.
A method for producing spherical algae bodies.

(2) The method according to (1), in which the red algae is Undaria pinnatifida.

(3) The method according to (1), in which the sliced algae is the tip of a lateral branch of a red alga.

(4) The method of (1), wherein in the culture step, the sliced algae rotates at a rotation speed of 1 to 50 rpm in the horizontal direction and/or 6 to 20 rpm in the vertical direction.

(5) The method according to (1), wherein the aeration is carried out for 240 hours or more in the culture process.

The present invention provides a novel culture technique for red algae.

FIG. 2 is a diagram showing the upright algal bodies of the Uncaria arborescens used in the Examples. FIG. 2 shows a portion (within the dashed frame) of the tip of the upright algae of Uncaria arborescens used in the examples that was cut out as a slice algae. FIG. 2 is a diagram showing coccoid algae obtained in an example. This figure shows the change in size over time of the coccoid algae obtained in the examples as they were further cultured.

The following describes in detail an embodiment of the present invention. Note that the present invention is not limited to the following embodiment.

<Method of manufacturing spherical algae>
The method for producing spherical algae bodies of the present invention (also simply referred to as the "production method of the present invention") comprises an algae body preparation step of obtaining sliced algae bodies from red algae, and a culture step of culturing the sliced algae bodies, in which the culture step is carried out while aerating the sliced algae bodies so as to rotate them.

The gametophyte (female or male gametophyte) of red algae is usually an erect alga (Figure 1A).
As a method for culturing erect algae, a method is known in which the tip of the algae is cut off and the resulting sliced algae is cultured in a medium.
However, the conventional methods did not necessarily provide good culture efficiency.

As a result of the inventors' investigations, they made the extremely unexpected discovery that when the sliced algae are cultured while aerating them so that the sliced algae rotate, they can produce spherical algae (Figure 2).

The present inventors also found that even when a large number of sliced algae are cultured in an aquarium used for mass production, coccoid algae are successfully formed from each sliced algae.
From this, it was also found that the production method of the present invention is suitable for a large-scale culture system.

The manufacturing method of the present invention is described in detail below.

(1) Algal Body Preparation Step The algal body preparation step is a step of obtaining algal body slices from red algae.

In the present invention, "red algae" includes any algae belonging to the division Rhodophyta.

Red algae include, but are not limited to, Asparagopsis taxiformis, algae of the Asparagopsis genus (Asparagopsis svedellii, Asparagopsis armata, etc.), etc.

The red algae Asparagopsis taxiformis (scientific name: Asparagopsis taxiformis) is preferred because it is easy to obtain spherical algae and has a high effect of suppressing methane gas emissions.

The red algae used in the production method of the present invention may be in any form, but from the viewpoint of facilitating efficient cultivation, it is preferable that the algae be erect.

In the present invention, the term "erect algae" includes both female and male gametophytes. Whether or not a red alga is an erect algae can be determined by visually observing the morphology.
In the production method of the present invention, both or either of the female gametophyte and the male gametophyte can be used.

In the present invention, "section algae" includes any part of red algae.

From the viewpoint of easiness in obtaining coccoid algae, the sliced algae are preferably from the tip of a lateral branch (a branching portion from the main branch) of an upright algae of a red alga.
In the present invention, the "tip of a lateral branch of a red alga" may be a portion within 2 to 200 mm from the tip of the lateral branch.
The tip of a side branch of red algae is, for example, the area shown within the dashed line frame in Figure 1B.

The sliced algae may be a portion detached from the obtained coccoid algae. The present inventors have confirmed that the small coccoid algae detached from the coccoid algae can also grow independently to form coccoid algae.
In this embodiment, for example, a portion detached from the coccoid algae and having a length of about 2 to 20 mm can be used as the algal slice.

The means for obtaining sliced algae is not particularly limited, but examples include cutting them out of upright red algae or coccoid algae using a cutter or the like.

The amount of sliced algae to be prepared is not particularly limited, and can be adjusted according to the size of the culture vessel and the amount of coccoid algae to be obtained.

The obtained sliced algae may be directly subjected to the culture process, or may be stored under conditions that do not inhibit the growth of the algae before being subjected to the culture process.

(2) Cultivation Step The cultivation step is a step of culturing the sliced algal bodies obtained in the algal body preparation step to obtain spherical algal bodies.
The culture step is carried out by placing the sliced algae and a medium in a culture vessel and aerating the medium.

The main technical feature of the culture step in the present invention is that the culture step is carried out while aerating the sliced algal bodies so as to rotate them.
The present inventors have unexpectedly found that such rotation significantly changes the shape of the sliced algae, turning them into spherical algae.

In the present invention, the term "spherical algae" includes algae in which the number of branches increases radially from the main axis of the sliced algae, and which are generally spherical as a whole. Spherical algae have, for example, the shape shown in Figure 2.

The size of the spherical algae may vary depending on the size of the sliced algae used and the length of aeration time, but may be, for example, 2 to 20 mm in maximum diameter.

(2-1) Culture Vessel The culture vessel is not particularly limited as long as it has a size and shape sufficient to allow the sliced algae in the medium to rotate by aeration.

The material of the culture vessel can be glass, resin, etc.

The culture vessel is filled with culture medium so that the entire slice of algae is submerged along with the slice.

For small-scale culture, the culture vessel may be a flask (round-bottom flask, Erlenmeyer flask, etc.), a beaker, a bottle, a plastic tube, a plastic bag, etc.
Small scale cultures include cultures in tanks with volumes of 0.001 to 0.01 ^m3 .

For large-scale cultivation, the cultivation vessel may be a fiber-reinforced plastic (FRP) tank, a resin (e.g., polyethylene) tank, a stainless steel tank, a tarpaulin tank (including prefabricated ones), a concrete tank, or the like.
Large-scale culture includes culture in tanks with volumes of 0.1 to 200 ^m3 .

(2-2) Aeration Conditions The sliced algal bodies in the culture vessel are cultured while rotating by aeration.

In the present invention, the term "rotation of the sliced algae" includes both rotation in accordance with the flow of the medium and rotation caused by the sliced algae themselves.
In a preferred embodiment of the present invention, during cultivation, the sliced algae simultaneously rotates in accordance with the flow of the medium and due to the sliced algae's own rotation.

The rotation speed of the sliced algae is preferably adjusted in the horizontal and/or vertical direction in order to obtain spherical algae more efficiently.

In the present invention, the "horizontal direction" means a direction perpendicular to the earth's gravity.
In the present invention, the "vertical direction" means the direction of the earth's gravity.

The lower limit of the horizontal rotation speed of the algal slices is preferably 1 rpm or more, more preferably 2 rpm or more, and even more preferably 5 rpm or more.
The upper limit of the horizontal rotation speed of the sliced algal bodies is preferably 50 rpm or less, more preferably 25 rpm or less, and further preferably 10 rpm or less.
The horizontal rotation speed of the algal slices is preferably 1 to 50 rpm, and more preferably 5 to 10 rpm.

The lower limit of the vertical rotation speed of the algal slices is preferably 6 rpm or more, more preferably 8 rpm or more, and even more preferably 10 rpm or more.
The upper limit of the vertical rotation speed of the algal slices is preferably 20 rpm or less, more preferably 15 rpm or less, and further preferably 12 rpm or less.
The vertical rotation speed of the algal slices is preferably 6 to 20 rpm, more preferably 10 to 12 rpm.

The rotation speed of the sliced algae can be determined based on images taken with a video camera, etc.

The aeration time can be adjusted appropriately depending on the size of the spherical algae to be obtained. The longer the aeration time, the larger the spherical algae can be.

The aeration time is preferably 240 hours or more, more preferably 100 hours or more.
The upper limit of the aeration time is not particularly limited, but from the viewpoint of energy efficiency and the like, it is preferably 360 hours or less.
Aeration may be carried out continuously or intermittently, provided that the total aeration time is preferably within the above range.

The aeration means is not particularly limited as long as it can achieve aeration sufficient to rotate the sliced algae, but examples include an air pump and agitator.

The flow rate of the medium in the culture vessel achieved by aeration is not particularly limited, but from the viewpoint of making it easier to efficiently obtain spherical algae, it is preferable to aerate the medium at a rate of 1 to 3 cm/sec, and more preferably 1.5 to 2.0 cm/sec, in both the horizontal and vertical directions.

The flow rate of the medium in the culture vessel can be measured using any flow rate meter (for example, a two-dimensional electromagnetic flow rate meter ("ACM-200A", manufactured by JFE Advantech Co., Ltd.)).

The gas supplied to the sliced algae by aeration is not particularly limited as long as it does not inhibit the growth of the sliced algae or the culture process, but examples include air and low-concentration carbon dioxide gas (e.g., 800 to 1600 ppm).

The amount of gas supplied to the sliced algal bodies by aeration varies depending on the aeration time, etc., but may be, for example, 30 to 60 L/min/ ^m3 .

(2-3) Other Conditions Other conditions in the culture step are not particularly limited, and normal culture conditions for red algae can be adopted.

The amount of sliced algae used is not particularly limited, but is preferably 500 to 3000 mg/L, more preferably 1000 to 2000 mg/L per medium.

The culture temperature can be, for example, 10 to 30°C.

The light intensity may be, for example, 5 to 100 μmol/m ² /s (light/dark cycle of 6 to 18 hours light and 18 to 6 hours dark).

Any medium that does not inhibit the growth of red algae can be used, such as one that contains seawater, a nitrogen source, minerals, etc.

(3) Uses of the Coccoid Algae The uses of the coccoid algae are not particularly limited, and they can be used in the same way as conventional red algae.
For example, since the spherical algae bodies of the present invention can be efficiently mass-produced, it is expected that by adding them to cattle feed, they will continuously contribute to reducing methane emissions from cattle.

The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

Red algae were cultured using the following method to obtain coccoid algae.

(1) Preparation of Algal Slices Erect algal slices (female gametophyte or male gametophyte) of Asparagopsis taxiformis (scientific name: Asparagopsis taxiformis) were prepared as red algae for culture (see FIG. 1A).
The tip of a lateral branch (a branching portion from the main branch) of the upright alga was cut by 2 to 200 mm from the tip (see the dotted frame in FIG. 1B), and this was used as an alga slice for culture and subjected to the following culture process.

(2) Cultivation of sliced algal cells The sliced algal cells (about 1 g) were placed in a single-necked round-bottom flask (volume: 100 mL) containing medium (50 mL) in advance, so that the sliced algal cells were entirely immersed in the medium.
Next, the inside of the flask was aerated using an air pump so that the entire sliced algae in the round-bottom flask was rotated, and cultivation was started. The conditions in the cultivation process were as follows.

(2-1) Aeration conditions Aeration was performed from the mouth of the round-bottom flask fixed in an upright position toward the bottom. Aeration was performed continuously without interruption during the culture period. Therefore, in this test, the aeration time was the same as the culture time.
Aeration was adjusted so that the flow rate of the medium was 1 to 3 cm/sec in both the horizontal and vertical directions. The flow rate was continuously monitored using a two-dimensional electromagnetic current meter ("ACM-200A", manufactured by JFE Advantec Co., Ltd.).
Aeration created a water current, causing the sliced algal bodies to rotate up and down and side to side within the round-bottom flask.
The rotation speed of the sliced algal bodies was 1 to 50 rpm in the horizontal direction and 6 to 20 rpm in the vertical direction. The rotation speed was continuously confirmed based on the images captured by a video camera.
The sliced algae rotated both in accordance with the flow of the medium and on its own axis.

(2-2) Other Culture Conditions The conditions other than the aeration conditions in the culture step are as follows.
Culture temperature: 10-30℃
Light intensity: 5 to 100 μmol/m ² /s (light/dark cycle: 6 to 18 hours light, 18 to 6 hours dark)
Culture medium: Seawater (1 L) supplemented with a nitrogen source (10-50 mg/L), a phosphorus source (1-5 mg/L), and a mineral source (2-0.2 mg/L) was used.
Culture time: 2 weeks (336 hours)

(3) Results After the cultivation was completed, the number of branching parts radially increased from the main axis of the sliced algae, and coccoid algae that were roughly spherical overall were obtained (Figure 2).
The change in shape of the sliced algal bodies was clearly observed from about 240 hours after the start of the culture.

After completion of the cultivation, the cultivation was continued for another 2 to 4 weeks under the same conditions as above, and the coccoid algae changed to a larger size while maintaining a roughly spherical shape, as shown in Figure 3. At the same time, the density of the filaments (branching parts from the main axis) that make up the coccoid algae also clearly increased.
In addition, small algae that detached from the spherical algae that had grown to a certain size also grew independently to form larger spherical algae.
Therefore, according to the production method of the present invention, by adjusting the culture time and culturing the detached small spherical algae, it is possible to obtain spherical algae of various sizes, as indicated by the directions of the arrows in Figure 3.

Although the data is not shown, even at a larger cultivation scale (aquarium volume: 1 to 100 m ³ ), coccoid algae were similarly obtained.
In addition, spherical algae have been cultivated not only in large scale indoors under electric lighting, but also outdoors under natural light. In these cases, the algae could be cultivated successfully in tanks of any shape (spherical, rectangular, etc.).

Although data is not shown, when the cultivation was carried out in the same manner as above, except that aeration was performed during the cultivation process to prevent the sliced algae from rotating, the sliced algae did not become roughly spherical, and their morphology showed almost no change compared to before cultivation.

Claims (5)

A step of preparing algae bodies by obtaining sliced algae bodies from red algae;
A culturing step of culturing the sliced algal bodies,
The culture step is carried out while aerating the sliced algal bodies so as to rotate them.
A method for producing spherical algae bodies. The method of claim 1, wherein the red algae is Uncaria nigra. The method of claim 1, wherein the sliced algae is the tip of a side branch of a red alga. The method according to claim 1, wherein in the culturing step, the sliced algae rotates at a rotation speed of 1 to 50 rpm in the horizontal direction and/or 6 to 20 rpm in the vertical direction. The method of claim 1, wherein the aeration is carried out for 240 hours or more during the culture process.