Molded article of microalgae and method for producing same

Abstract

[Problem] To provide a molded article of microalgae as a non-fossil-resource-derived plastic alternative, and a method for producing the same. [Solution] The present invention provides a molded article that comprises 90-100 mass% microalgae and that has a durometer hardness of 25-72 as determined with a type D durometer. Furthermore, a method for producing the molded article according to the present invention comprises a powder compression step for compressing, under heating, a compression raw material that contains a dried powder of microalgae, wherein the compression raw material contains 90-100 mass% microalgae and has an average particle size of 1 μm to 1 mm.

Description

Molded body of microalgae and method for producing the same

[0001] The present invention relates to a formed body made primarily from microalgae and a method for producing the same.

[0002] In recent years, in the context of the Sustainable Development Goals (SDGs) adopted by United Nations member states, there has been a demand to reduce the use of petroleum-derived raw materials and indirectly reduce carbon dioxide emissions. Currently, plastic products are used for a variety of purposes and are indispensable in our daily lives. However, they are manufactured from petroleum-derived raw materials and have the drawback of not being biodegradable. Therefore, there is a demand for plastic substitutes derived from non-fossil resources, such as plant-based materials produced by photosynthesis. Against this background, Patent Document 1 listed below describes a method for producing a molded product by heating and pressurizing food waste or seaweed.

[0003] Japanese Patent Application Laid-Open No. 2022-180165

[0004] The above-mentioned Patent Document 1 proposes a method of using food waste or seaweed. However, there are issues with ensuring a stable supply of these raw materials, and it is difficult to steadily secure a sufficient amount to replace plastic products. This is because the amount of food waste generated varies greatly depending on the production area, season, and collection system, and seaweed is considered to be a food supply priority amid the worsening global food shortage.

[0005] Microalgae are a raw material that can solve the above problems. Microalgae can be produced stably even in non-agricultural land if water, nutrients, and equipment are available, and photosynthetic organic compounds can be produced efficiently. They can solve the problems of stable supplies of food waste and seaweed without directly competing with edible resources. Due to these advantages, research is being conducted into using microalgae as a plastic substitute. However, with previous plastic substitutes using microalgae, molded bodies could only be produced by kneading microalgae with other substances. Therefore, the present invention aims to provide a molded body from microalgae, particularly a molded body that can be made solely from microalgae, and a method for producing such a molded body.

[0006] According to a first aspect of the present invention, there is provided a molded article containing 90% by mass or more and 100% by mass or less of microalgae, and having a durometer hardness of 25 or more and 72 or less as measured by a type D durometer.

[0007] Furthermore, according to a second aspect of the present invention, there is provided a method for producing a molded body, which includes a powder compression step in which a compressed raw material containing a dry powder of microalgae is compressed under heat, wherein the compressed raw material contains 90% by mass or more and 100% by mass or less of microalgae, and has an average particle size of 1 μm or more and 1 mm or less.

[0008] According to the present invention, a molded product of microalgae is provided, and in particular, a molded product that does not contain any materials other than microalgae can be provided. The molded product of the present invention is a sustainable plastic alternative that can reduce the amount of petroleum-derived raw materials used. Furthermore, since it can be decomposed or edible by microorganisms and animals in nature, it is a highly biodegradable product with a low environmental impact. Furthermore, according to the manufacturing method of the present invention, a method for manufacturing a molded product of microalgae, in particular, a molded product that does not contain any materials other than microalgae, is provided.

[0009] FIG. 1 is a photograph of the molded articles obtained in Example 1 and Comparative Examples 1 to 3.

[0010] The following describes embodiments of the present invention. The present invention is not limited to the embodiments described below, and also includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art.

[0011] [Molded Article] The molded article of the present invention contains 90% by mass or more and 100% by mass or less of microalgae and has a durometer hardness of 25 to 72 using a type D durometer. The molded article will be described in detail below. The molded article can be molded into a plate, rectangular parallelepiped, cylindrical, or other shape depending on the shape of the mold or other shape used during molding.

[0012] Microalgae refer to minute algae whose individual existence cannot be distinguished with the naked eye. Examples of microalgae used in the present invention include microalgae belonging to the divisions Cyanophyta, Glaucophyta, Rhodophyta, Chlorophyta, Cryptophyta, Haptophyta, Heterokontophyta, Dinophyta, Euglenophyta, and Chlorarachniophyta. These may be used alone or in combination of two or more. Among these, preferred microalgae belong to the divisions Chlorophyta and Cyanobacteria, and more preferred microalgae belong to the divisions Chlorophyta, Trebouxiophyta, and Cyanophyta. Among these, the microalgae of the genus Haematococcus, Chlamydomonas, Chlorococcum, Botryococcus, Scenedesmus (also known as rock stalk), Chlorella, and Arthrospira are preferred. For forming a molded body, at least one of Chlamydomonas, rock stalk, Chlorella, Botryococcus, and Spirulina is particularly preferred.

[0013] The molded article of the present invention contains 90% by mass or more and 100% by mass or less of microalgae. The microalgae content may be 95% by mass or more and 100% by mass or less, 97% by mass or more and 100% by mass or less, or even 100% by mass. By containing 90% by mass or more and 100% by mass of microalgae, the molded article of the present invention becomes a sustainable plastic alternative that further reduces the use of petroleum-derived raw materials. Because the molded article of the present invention is mostly made of microalgae, it is highly biodegradable and has a low environmental impact. The molded article may also contain raw materials other than microalgae, such as fiber materials, wood, wood chips, grass, paper, cloth, glass, and clay. However, the molded article of the present invention can be provided that is composed solely of microalgae. Such molded articles are preferable because they do not use petroleum-derived raw materials and have a particularly low environmental impact. Since the molded article does not contain harmful additive compounds or organic solvents and is made solely of microalgae, it is safe for the human body. Furthermore, if edible microalgae are used, it can be used for food.

[0014] The composition of microalgae may be 8 to 18% by mass lipids, 20 to 33% by mass carbohydrates, 0 to 7% by mass ash, and 45 to 70% by mass protein. The composition of microalgae may be 10 to 16% by mass lipids, 23 to 30% by mass carbohydrates, 1 to 6% by mass ash, and 52 to 65% by mass protein. The composition of microalgae may be 8 to 15% by mass lipids, 4 to 8% by mass carbohydrates, 1 to 8% by mass ash, and 50 to 80% by mass protein. The composition of microalgae can be determined by removing water from the microalgae to dry algae, and then measuring the lipid content by acid hydrolysis, the ash content by direct incineration, and the protein content by combustion. The carbohydrate content can be determined by subtracting the total mass percentage of the protein, lipid, and ash.

[0015] The molded article of the present invention has a Type D durometer hardness of 25 or more and 72 or less, as measured in accordance with JIS K 7215-1986. The Type D durometer hardness may be 30 or more and 70 or less, 40 or more and 70 or less, 50 or more and 60 or less, or 30 or more and 60 or less. When the Type D durometer hardness is within this range, a self-supporting product can be manufactured using the molded article of the present invention alone, making it a good substitute for plastic products. For example, it can be used for container materials, agricultural materials, sporting goods, construction materials, materials for electrical and electronic devices, household goods, etc. Several molded articles of the present invention can also be combined and bonded to produce processed products.

[0016] The molded article of the present invention may have a thickness of 0.1 mm or more and 10 cm or less. This thickness range makes it easy to provide a substitute for a variety of plastic products. The thickness of the molded article may be 0.5 mm or more and 8 cm or less, 1 mm or more and 6 cm or less, 3 mm or more and 5 cm or less, or 3 mm or more and 3 cm or less.

[0017] The molded article of the present invention has a surface area of ​​1 cm ２ 4m or more ２ If the surface area of ​​the molded article is within this range, it is easy to provide a substitute for a variety of plastic products. ２ 2m or more ２ It may be less than 5 cm ２ More than 1m ２It may be less than 10 cm ２ More than 90cm ２ It may be the following:

[0018] The molded article of the present invention may have a coating film of oil derived from microalgae on the surface. As described above, microalgae contain lipids, and therefore, the lipids may ooze out onto the surface of the molded article of the present invention to form a coating film. Furthermore, the presence of such an oil film makes it easier to remove the molded article from the mold used for molding after molding.

[0019] [Manufacturing method] The method for manufacturing a molded body of the present invention includes a powder compression step in which a compressed raw material containing a dry powder of microalgae is compressed under heat, and is characterized in that the compressed raw material contains 90% by mass or more and 100% by mass or less of microalgae and has an average particle size of 1 μm or more and 1 mm or less.

[0020] Any of the above-mentioned microalgae can be used as the microalgae. The method for obtaining the microalgae is not particularly limited and can be appropriately selected depending on the purpose. For example, there are methods such as collecting from nature, using commercially available products, and obtaining from preservation institutions or depositories. Furthermore, the microalgae obtained by these methods may be further cultured. Furthermore, the microalgae may have been subjected to a purification process for the purpose of obtaining a single species of microalgae.

[0021] There are no particular limitations on the method for culturing microalgae, and they can be cultured using conventional methods. For example, the following method is used. First, to culture the seed algae, a medium and a microalgae culture solution are placed in a container. While maintaining the temperature at 20-35°C, the container is aerated at a flow rate of 0.1-0.3 vvm with a carbon dioxide concentration of 0.5-5% per liter of culture solution, and exposed to light for 10-24 hours per day for 4-10 days. The medium composition for the seed algae can be appropriately selected from synthetic freshwater algae media such as BG11 liquid medium and TAP medium, and media containing large amounts of nutrients. The resulting seed algae are placed in a photobioreactor together with the medium, and while maintaining the temperature at 20-35°C, the culture solution is aerated at a flow rate of 0.1-0.3 vvm with a carbon dioxide concentration of 0.5-5% per liter of culture solution, and exposed to light for 10-24 hours per day for an additional 4-10 days.

[0022] Next, the cultured microalgae are recovered from the culture solution. There are no particular limitations on the recovery method, and for example, a centrifuge can be used. The microalgae obtained by centrifugation are concentrated wet algae bodies, which are then dried. There are no particular limitations on the drying method, and vacuum drying, freeze drying, drying by heating in a heating device such as an oven or a hot air device, etc. can be used. For example, the wet algae bodies can be spread out in a flat container and left to stand, and then dried in a dryer at 50 to 70°C.

[0023] The obtained dried algae had a moisture content of 100 g kg －１ The water content may be 10 g kg or less (meaning that 1 kg of dry algae contains 100 g of water). －１ More than 90g / kg －１ It may be less than 10 g kg －１ 80g / kg or more －１ The moisture content can be measured using a heat-drying moisture meter. The dried algal cells are preferably stored in a sealed container to prevent them from absorbing moisture from the air.

[0024] Moisture content is 100g / kg －１ If the moisture content exceeds this value, voids may form in the compact due to evaporation of moisture during the heating process, which may change the physical properties, and microorganisms other than microalgae, such as bacteria, may grow during powder storage. The moisture content of dried algae affects the flowability of the powder during the compression process, which is thought to change the strength of the compact. On the other hand, moisture contained on the surface and inside of the powder during powder processing is thought to be preferable, as it acts as a plasticizer to prevent structural changes such as thermal flow, to a certain extent.

[0025] The obtained dried algae cells are pulverized to obtain a dry powder. There are no particular limitations on the method for pulverizing the dried algae cells, and a general-purpose household mill, blender, disk mill, ball mill, jet mill, high-speed pulverizer, or the like can be used. For example, the algae can be pulverized using a high-speed pulverizer at a rotation speed of 10,000 to 30,000 rpm for 10 to 50 seconds. The dried powder is pulverized to an average particle size of 1 μm to 1 mm. The pulverized dry powder may be sieved to an average particle size of 1 μm to 1 mm. Alternatively, the powder may be re-dried after pulverization. The average particle size refers to the particle size at 50% of the integrated value in the particle size distribution determined by laser diffraction / scattering. The average particle size may be 50 μm to 500 μm, or 100 μm to 300 μm.

[0026] The dry powder is an aggregate of microalgae cell length (several μm to several tens of μm). When the average particle size is within the above range, it is believed that heat transfer to the remaining moisture and constituent substances of the algae cells is uniformly propagated during the compression process described below. Furthermore, the voids between the powder particles during molding can be reduced, resulting in a uniform molded product. Here, the shape of the dry powder particles is not particularly important. The molded product of the present invention can be obtained regardless of the shape.

[0027] The compressed raw material used in the present invention contains 90% by mass or more and 100% by mass or less of the dry powder of microalgae obtained as described above. Therefore, the compressed raw material can be made from the dry powder alone. However, other materials such as fiber materials, wood, wood chips, grass, paper, cloth, glass, and clay may also be included. In this case, the materials other than microalgae can also be made into powder with an average particle size of 1 μm or more and 1 mm or less, and mixed with the dry powder of microalgae to make the compressed raw material. There are no limitations on the mixing method, and any method can be used.

[0028] Next, a powder compression process is carried out using the raw material to be compressed under heat. As long as the raw material can be compressed under heat, there are no particular limitations on the method used. For example, a pressure molding machine, powder molding machine, or electric press machine equipped with a temperature control function can be used. For example, the processing machines described in Japanese Patent No. 7321069 and Japanese Patent No. 6840615 can be used. Such a processing machine may include, for example, a lower mold section mounted on a base having a support and an upper mold section that moves along the support by a slide above the lower mold section. A mold containing the raw material is placed in the lower mold section, and the upper mold section is lowered toward the lower mold section by a motor-driven slide, thereby pressing the raw material. A metal plate or the like may be placed on the mold to ensure uniform pressing.

[0029] First, the raw material for compression is placed in a mold of a desired shape and heated to 80 to 150° C. The heating temperature may be 90 to 140° C. or 100 to 130° C. When the heating temperature is within this range, the raw material for compression exhibits appropriate fluidity when pressurized, making it easy to form a uniform molded body.

[0030] While heating, a pressure of 30 MPa to 500 MPa is uniformly applied to the upper part of the raw material using the above-mentioned device, and the raw material is subjected to heat and pressure molding. The pressure may be 35 MPa to 450 MPa, or 40 MPa to 400 MPa. When the pressure is in the range of 30 MPa to 500 MPa, the sugar chains that make up the cell wall and other algae constituents can be structurally changed, resulting in appropriate fluidity in the powder and making it easier to stably obtain a uniform molded body.

[0031] In the powder compression process, pressure can be applied to the compressed raw material by bringing an upper mold section, which compresses the compressed raw material, close to a lower mold section containing the compressed raw material. Oil derived from microalgae may be applied to either or both of the surfaces of the lower mold section and the upper mold section. Because microalgae contain lipids, the lipids ooze out when pressure is applied, resulting in the surface of the molded body being coated with oil. The application of oil makes the molded body easier to release. Furthermore, it is believed that using a compressed raw material containing lipids makes the resulting molded body less likely to crack.

[0032] In the powder compression process, the raw material to be compressed may be vibrated and compressed under heat. By applying vibration, the raw material can be compressed while degassing, improving moldability. There are no particular restrictions on how the compressed material is vibrated, and a conventional pressure molding machine equipped with a function to vibrate the raw material in a mold, such as a vibration press, can be used.

[0033] The present invention will be described in detail below with reference to examples.

[0034] Example 1 Chlamydomonas (UTEX90, Chlamydomonas reinhardtii) purchased from an algae storage institution was used. For microalgae cultivation, 4.5 L of BG11 medium (Table 1 below) and 500 mL of green algae culture solution (biomass concentration per dry weight: 1 g / mL) were placed in a 6 L plastic bottle, and the 6 L plastic bottle was irradiated with a 60 W LED bulb to obtain a concentration of 100 to 500 μmol m －２ ・s －１ The culture was carried out for one week at a temperature of 25 to 30°C (irradiation time: 12 hours / day) while aerating with 3% carbon dioxide.

[0035]

[0036] In Table 1, BG11 Medium Recipe means the BG11 medium recipe, Component means the composition, Amount means the amount, Final Concentration means the final concentration, and Citric Acid·H ２ O means citric acid monohydrate, Ferric Ammonium Citrate means ferric ammonium citrate, Trace Metals Solution means trace metals solution, see recipe means see recipe, Sodium Thiosulfate Pentahydrate means sodium thiosulfate, Trace Metals Solution Recipe means trace metals solution recipe, Bring Total Volume to 1 Liter with dH ２ O is dH ２ ​Then, 22.5 L of medium and 2.5 L of the cultivated seed algae were added to several photobioreactors measuring 5 cm thick, 200 cm wide, and 110 cm high, and the resulting mixture was heated to 1500 μmol / L using an LED light bulb. －２ ・s －１ The cells were irradiated (12 hours / day) and cultured at a temperature of 25-30°C with 3% carbon dioxide aeration for one week.

[0037] The cultured liquid was centrifuged at 10,000 rpm for 30 minutes to separate it from the filtrate, and concentrated wet algae (1 kg dry weight) were collected. －１ The algal bodies were transferred to a flat container and dried in a dryer set at 60° C. The degree of dryness of the algal body powder was confirmed by measuring the moisture content using a heat-drying moisture meter (MX-50, manufactured by A&D Co., Ltd.).

[0038] The dried algae were placed in a high-speed grinder and ground at a rotation speed of 20,000 rpm for 30 seconds to prepare an algae powder. The moisture content of the resulting powder was measured using a heat-dry moisture meter (MX-50, manufactured by A&D Co., Ltd.). The moisture content after grinding was 78 g kg －１ The algal powder was stored in a sealable plastic bag to prevent it from absorbing moisture from the air.

[0039] The average particle size of this powder at 50% cumulative particle size distribution determined by laser diffraction / scattering method was 200 μm. The dried algae bodies were used as a raw material for compression.

[0040]

[0041] An electric press machine (ZENFormer Torque, manufactured by Electrical Discharge Precision Machining Laboratory) equipped with a temperature control device was used for press molding of powder. The mold for powder injection was a 300 mm x 150 mm x 8 mm square plate mold. 250 g of algae powder was fed into the recessed part of the mold and the powder was smoothed.

[0042] The temperature was set to 120°C to increase the fluidity of the moisture and algae constituents, and the compressed raw material was heated in a mold. A metal plate was then placed on top, and a load of 2,205 kN ± 10 kN (49 MPa ± 0.22 MPa) was applied to heat and press the dried algae powder. The mold and the molded product were then cooled at a constant rate and released from the mold, resulting in a 5 mm thick, smooth, black-brown molded plate. The molded product had a Type D durometer hardness of 57.

[0043] The results are shown in the lower right of Figure 1. It was confirmed that a plastic-like plate was molded in Example 1. The molded body obtained had dimensions of 300 mm x 150 mm x 5 mm (surface area 0.045 m). ２ It is believed that a molded body with a larger surface area or a thicker thickness can be formed by appropriately increasing the amount of compressed raw material and the weight, and by using a larger mold.

[0044] [Comparative Example 1] The dried algae bodies in Example 1 were extracted with acetone to produce a defatted powder, which was used as a compressed raw material. This compressed raw material was subjected to hot and pressure molding in a mold set at 80°C, except that a load of 90 tons (882 kN, 20 MPa) was applied. The results obtained in Comparative Example 1 are shown in the upper left of Figure 1. The compressed raw material did not successfully form into a molded body due to the occurrence of cracks.

[0045] [Comparative Example 2] The dried algae bodies in Example 1 were defatted powder and used as a compressed raw material in the same manner as in Comparative Example 1. This compressed raw material was used to perform hot and pressure molding in the same manner as in Example 1, except that a load of 135 tons (1323 kN, 30 MPa) was applied in a mold set at 150°C. The results obtained in Comparative Example 2 are shown in the lower left of Figure 1. Although a molded body was produced, a uniform molded body was not obtained because the fluidity of part of the raw material was too high.

[0046] Comparative Example 3 The dried algae bodies in Example 1 were subjected to hot and pressure molding in the same manner as in Example 1, except that a load of 225 tons (2205 kN, 49 MPa) was applied in a mold set at 160 to 180°C. The results obtained in Comparative Example 3 are shown in the upper right corner of Figure 1. The compressed raw material did not successfully form into a molded body due to the occurrence of cracks.

[0047] The molded article of the present invention is made from microalgae and can be biodegraded and consumed as food by terrestrial microorganisms and animals over a certain period of time. Because it is environmentally friendly and has little environmental impact upon disposal, it can be used for container materials such as tableware, cups, and PET bottle caps; soil management and agricultural materials such as stakes and potted planters; activity materials such as golf balls, golf pins, and surfboards; building materials such as tiles, concrete, walls, and roofing tiles; materials for electrical and electronic devices such as keyboards; and household materials such as makeup brush handles.

[0048] Furthermore, since the molded article of the present invention is made from microalgae, it can be biodegraded and consumed as food by microorganisms and animals in the natural sea over a certain period of time. Furthermore, since it can suppress marine pollution, it can also be used as fishing equipment such as lures and fishing tackle, and underwater structures.

[0049] Furthermore, the molded product of the present invention does not contain harmful additive compounds or organic solvents and can be molded solely from microalgae, making it safe for the human body. Furthermore, the use of edible microalgae makes it suitable and useful for toys such as puzzles and blocks for young children that comply with the Food Sanitation Act. It is also suitable and useful for tableware, cutlery, cups, trays, and other products that comply with the Food Sanitation Act. It can also be applied to edible tableware and cooking utensils. It can also be used for solid fertilizers and feed for aquaculture and livestock that have been given high added value by being molded into unique shapes.

Claims

1. A molded body containing 90% by mass or more and 100% by mass or less of microalgae and having a durometer hardness of 25 or more and 72 or less according to a Type D durometer.

2. The molded article according to claim 1, having a thickness of 0.1 mm or more and 10 cm or less.

3. The molded article according to claim 1, having a surface area of ​​1 cm ２ 4m or more ２ The following is a molded body.

4. The molded body according to claim 1, wherein the microalgae is one or more of Chlamydomonas, Fructus reinhardtii, Chlorella, Spirulina, and Botryococcus.

5. The molded body according to claim 1, which is biodegradable.

6. A method for producing a molded body, comprising a powder compression step of compressing a compressed raw material containing a dry powder of microalgae under heat, wherein the compressed raw material contains 90% by mass or more and 100% by mass or less of microalgae, and has an average particle size of 1 μm or more and 1 mm or less.

7. The method according to claim 6, wherein the powder compression step includes a step of applying a pressure of 30 MPa or more and 500 MPa or less to the compressed raw material.

8. A method according to claim 6, wherein the powder compression step includes a step of applying pressure to the compressed raw material by bringing an upper mold section that compresses the compressed raw material close to a lower mold section that has the compressed raw material loaded thereon, and oil derived from microalgae is applied to one or both of the surfaces of the lower mold section and the upper mold section.

9. The method according to claim 6, wherein the powder compression step includes a step of compressing the powder material under heat while vibrating the powder material.

10. The method according to claim 6, wherein the molded body contains 90% by mass or more and 100% by mass or less of microalgae, and has a durometer hardness of 25 or more and 72 or less according to a type D durometer.

11. The method according to claim 9, wherein the molded body has a thickness of 0.1 mm or more and 10 cm or less and a surface area of ​​1 cm or less. ２ 4m or more ２ The following is a method.

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