JP2017038538A - Method for producing microalgal-derived protein composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for separating a microalgal protein useful as a protein material for agriculture/aquatic feed from unused resources microalga-derived biomass.SOLUTION: A method for producing a microalgal-derived protein composition comprises: concentrating the microalgal-derived biomass from a slurry containing microalga-derived biomass using a separation membrane with an effective pore size of 2 to 200 μm, and then subjecting the microalgal-derived biomass to an alkaline treatment under the condition of pH 10 to 13. In the method, preferably, the microalgae is a genus Botryococcus.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a microalgae-derived protein composition useful as a protein raw material for agricultural and aquatic feeds from microalgae-derived biomass.

Hydrocarbons produced by algae are considered promising as biofuels, and research for industrialization is underway. Among the algae, microalgae belonging to the genus Botryococcus are attracting attention as algae from which liquid fuel can be efficiently obtained because they produce hydrocarbons having properties equivalent to heavy oil. The hydrocarbons produced from the microalgae of the genus Botryococcus are divided into four groups, Race-A, Race-B, Race-L and Race-S, based on the structural features, and in particular, C _n H _2n The strain of the Race-B group that produces hydrocarbons having a triterpene structure represented by ₋₁₀ (n = 30 to 37) often produces 30 to 40% by mass of hydrocarbons (for example, non-patent literature) 1).

  A microalga of the genus Botryococcus forms an aggregate (colony) of several to several hundred cells during the growth process, and is a biopolymer (arginane) that is a polymerization compound such as hydrocarbons produced by itself. The colony structure is maintained. The hydrocarbons produced as described above are retained and accumulated up to about 30 to 40% by mass in this arginane. The hydrocarbons accumulated in this way are used as raw materials for biofuels and biorefinery through processes such as solvent extraction, but a large amount of residue from which hydrocarbons have been removed becomes waste, and algae-derived biofuels It has become a foothold for industrialization (see, for example, Non-Patent Document 2), and development of a method for effectively using various useful components contained in the residue is desired. In particular, the protein contained in the residue is expected to be a new protein raw material in response to the recent problems of depletion of fish meal for feed and the price increase due to the competition with bioethanol for feed raw materials such as corn and soybean. Has been.

  The microalgae of the genus Botryococcus consist of 40-60% alginate, which is a polymerized product of the hydrocarbons described above, 20-30% protein, and cell walls as components other than hydrocarbons. However, since the protein content of the protein raw material for feed is essential to be 40% or more, the use value is poor as it is. Furthermore, arginane, cell walls, and the like are poorly digestible, and it was essential to separate the protein from these components in order to increase the utility value of the microalgae-derived protein.

  On the other hand, microalgae that produce fatty acid esters and the like that can be converted into hydrocarbons and fuels have extremely low concentrations in the culture solution (about 1-2 g / L). Therefore, when the protein component is recovered by concentrating the culture solution, the hydrocarbon components are removed because the polysaccharide component secreted into the culture solution and the cell walls and dead bodies of microalgae are also concentrated and aggregated together. The protein content in the subsequent residue was reduced to about 10 to 20%, which was a cause of lowering the utility value of the protein fraction derived from microalgae.

Microbiol. Cult. Coll. 26 (1). 1-10 (2010) p. 4 2011 Rural and Mountainous Village Sixth Industrialization Measures Project “Survey Report on Practical Use of Algal Biomass Farms in Rural and Mountainous Villages” p. 7 Phytochemistry 22 (2). 389-97 (1983) p. 395 Microbiol. Cult. Coll. 26 (1). 1-10 (2010) p. 5-7

  An object of the present invention is to provide a method for producing a microalga-derived protein composition useful as a protein raw material for agricultural and aquatic feed from microalgae-derived biomass.

  As a result of intensive studies for solving the above-mentioned problems, the present inventors derived from a microalgae obtained after concentrating the microalgae-derived biomass by a specific membrane treatment from a slurry of microalgae-derived biomass as a raw material The present inventors have found that by subjecting biomass to alkali treatment under specific conditions, a protein composition derived from microalgae that is useful as a protein raw material for agricultural and aquatic feed with an increased protein content can be obtained.

That is, the gist of the present invention is the following (1) to (3).
(1) After concentrating the microalgae-derived biomass from the slurry containing the microalgae-derived biomass using a separation membrane having an effective pore size of 2 to 200 μm, the alkali-treatment of the microalgae-derived biomass under conditions of pH 10-13 A method for producing a protein composition derived from microalgae,
(2) The method for producing a protein composition derived from microalgae according to (1), wherein the microalga is genus Botryococcus.
(3) A microalga-derived protein composition obtained by the method for producing a microalga-derived protein composition according to (1) or (2).

  According to the present invention, after concentrating the microalgae-derived biomass from the slurry of the microalgae-derived biomass as a raw material by a specific membrane treatment, the resulting microalgae-derived biomass is alkali-treated under specific conditions, thereby obtaining a protein content. It is possible to obtain a microalga-derived protein composition useful as a protein material for agricultural and aquatic feeds with improved yield in a high yield.

  Hereinafter, the present invention will be described in detail.

  The microalga-derived biomass of the present invention refers to biomass derived from microalgae that mainly produces biofuel, and specific examples include biomass derived from green algae and diatoms. More specifically, Botryococcus braunii, Chlorella spp., Cryptothecodinium chonii, Cylindrotheca spp. Dunaliella primorecta, Isochrysis spp. , Monallanthus salina, Nannochloris spp. , Nannochloropsis spp. , Neochloris spp. , Nitzschia spp. , Phaeodactylum tricornutum, Schizochytrium spp. And biomass derived from Tetraselmis suieia.

  Among these, biomass derived from the genus Botryococcus that produces hydrocarbons equivalent to heavy oil is preferable.

  The biomass derived from the microalga may be either the microalgae itself or a product obtained by drying the microalgae, but is more preferably an extraction residue after the hydrocarbons are further extracted from the microalgae with an organic solvent. .

  Specifically, the microalgae is one or more selected from a group of organic solvents consisting of hexane, chloroform, methanol, ethanol, diethyl ether and acetone, or a mixed solvent of hexane / acetone, a mixed solvent of chloroform / methanol, ethanol. An extraction residue obtained by dispersing in a mixture of organic solvents exemplified by a mixed solvent of / diethyl ether and extracting hydrocarbons in microalgae can be used as biomass derived from microalgae.

  In the present invention, the microalgae-derived biomass can be used as it is as a raw material for the separation membrane concentration step, but it is preferably processed in advance into a powder form, a lump form or the like in order to further increase the protein separation efficiency. As used herein, the powder form includes those that have been fined to a particle size of about 0.1 to 5 mm by a pulverizer (cutter, hammer, etc.) or various mills (stone mill type, mortar type, ball mill, etc.). The thing of a nonuniform shape of about 5 mm-30 mm is mentioned.

  The slurry containing the microalga-derived biomass in the present invention refers to a slurry obtained by dispersing the aforementioned microalgae-derived biomass in a solvent. The solvent is not particularly limited, and examples thereof include water, saline, alkaline aqueous solution or a mixture thereof, and a culture solution of microalgae.

  In the production method of the present invention, it is necessary to concentrate the microalgae-derived biomass from the slurry containing the microalgae-derived biomass using a separation membrane having an effective pore diameter of 2 to 200 μm. Specifically, the effective pore size of the separation membrane is 2 to 200 μm, and from the viewpoint of more effective separation, 3 to 30 μm is preferable, and 5 to 10 μm is more preferable. Although the effect of the effective pore size in the membrane separation is not clear, by using a separation membrane having an effective pore size of 2 μm or more, the secreted polysaccharide is allowed to pass through the separation membrane and a single cell or a plurality of single cells of microalgae are connected ( It is considered that separation and concentration can be achieved by effectively retaining colonies.

Next, the alkali treatment process will be described.
In the present invention, the alkali treatment is performed on the microalga-derived biomass concentrated from the slurry containing the microalga-derived biomass by a specific separation membrane. In the alkali treatment, the biomass derived from the microalgae is treated with an aqueous solution containing a hydroxide such as an alkali metal or an alkaline earth metal, an alcohol solution, or the like. Sodium oxide, potassium hydroxide, and calcium hydroxide are preferably used. In these alkali treatments, from the viewpoint of efficient protein release, it is necessary to adjust the addition amount of the alkali agent so that the pH of the alkali treatment solution is 10 or more and 13 or less, and 11 or more and 12.5 or less. Is preferred.

  In the alkali treatment in the present invention, various stirring, mixing, and pulverization treatments may be used in combination in order to increase the protein release efficiency by the alkali treatment. Specifically, stirring with a propeller-type stirring blade or the like, circulation of treatment liquid with various pumps, pulverization with a ball mill, bead mill, homogenizer, or the like.

  In the alkali treatment in the present invention, the solid-liquid ratio is not particularly limited, but from the viewpoint of fluidity of the microalgae-derived biomass, the solvent amount is preferably 3 to 20 parts by mass with respect to 1 part by mass of the microalgae-derived biomass. It is more preferable to set it as 5-10 mass parts. High protein release efficiency can be obtained while ensuring fluidity by setting it as 3-20 mass parts.

  The protein composition thus obtained is prepared as a dry powder that has undergone steps such as solid-liquid separation, concentration, drying, and pulverization, and then as a microalgae-derived protein useful as a protein raw material for agricultural and aquatic feeds. Can be used.

  Next, the present invention will be described in more detail by way of examples. In addition, this invention is not limited to an Example.

  For the protein quantification and content (purity) measurement in the examples of the present invention, the protein free alkaline treatment to the solution after solid-liquid separation, or the dried protein powder obtained through the drying and pulverization processes are targeted. The Lowry method (manufactured by Nacalai Tesque, Protein Assay Lowry Kit) was used. In the present invention, the protein purity in the obtained microalgal protein composition was 40% by mass or more, and the protein yield (protein recovery rate relative to the raw material) was 15% or more.

<Comparative Example 1>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was concentrated to 1 L with a hollow fiber membrane (manufactured by Asahi Kasei, Microza MF, ULP-143, effective pore size: 0.45 μm). The concentrated solution was spread on a vat and dried under ventilation to obtain approximately 58 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 11.6. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 38 mL of an alkali treatment liquid. Of these, 30 mL was lyophilized to obtain approximately 3.1 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 1.1 g and the protein purity was 29.3%.

<Comparative Example 2>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was concentrated to 1 L with a hollow fiber membrane (manufactured by Asahi Kasei, Microza MF, ULP-143, effective pore size: 0.45 μm). 10 mL of polysilica iron (manufactured by Seiko Kiko Co., Ltd., PSI-025) was added dropwise to the stirred concentrated solution to aggregate the biomass. Aggregates were collected with a metal sieve (pore size 100 μm), spread on a vat, and dried under ventilation to obtain approximately 60 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 11.8. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 37 mL of an alkali treatment solution. Of these, 30 mL was freeze-dried to obtain approximately 2.9 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 0.9 g and the protein purity was 25.2%.

<Comparative Example 3>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 5 μm) and concentrated to 1 L with shaking. The concentrated solution was spread on a vat and dried under ventilation to obtain approximately 30 g of dry biomass. The dried biomass was chopped into 5 mm pieces with scissors, 10 g of which was swollen with 50 mL of water (indicating pH 5.6), stirred for 16 hours, solid-liquid separation was performed, and about 47 mL of the processing solution was added. Obtained. Of these, 40 mL was freeze-dried to obtain approximately 0.8 g of powder. When the protein release amount was measured using the treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 1.1 g and the protein purity was 89.1%.

<Comparative example 4>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 5 μm) and concentrated to 1 L with shaking. The concentrated solution was spread on a vat and dried under ventilation to obtain approximately 30 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and 4N sodium hydroxide was added dropwise to adjust the pH to 8.6. After stirring for 16 hours, solid-liquid separation was performed to obtain about 47 mL of a processing solution. Of these, 40 mL was freeze-dried to obtain approximately 1.3 g of powder. When the protein release amount was measured using the treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 1.4 g and the protein purity was 88.9%.

<Example 1>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 5 μm) and concentrated to 1 L with shaking. The concentrated solution was spread on a vat and dried under ventilation to obtain approximately 32 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 10.2. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 46 mL of an alkali treatment liquid. Of these, 40 mL was freeze-dried to obtain approximately 2.5 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount: 2.6 g, protein purity: 90.1%.

<Example 2>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 5 μm) and concentrated to 1 L with shaking. The concentrated solution was spread on a vat and dried under ventilation to obtain approximately 32 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 11.7. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 48 mL of an alkali treatment solution. Of these, 40 mL was freeze-dried to obtain approximately 2.6 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 2.8 g, and the protein purity was 90.9%.

<Example 3>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 5 μm) and concentrated to 1 L with shaking. 10 mL of polysilica iron (manufactured by Seiko Kiko Co., Ltd., PSI-025) was added dropwise to the stirred concentrated solution to aggregate the biomass. Aggregates were collected with a metal sieve (pore size 100 μm), spread on a vat, and dried under ventilation to obtain approximately 35 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 11.5. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 47 mL of the alkali treatment liquid. Of these, 40 mL was freeze-dried to obtain approximately 2.7 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the freeze-dried powder, the protein release amount was 2.7 g and the protein purity was 85.7%.

<Example 4>
40 L of Botryococcus culture solution (approximately 1.5 g / L as biomass) was put into a nylon mesh bag (effective pore size: 25 μm) and dehydrated by shaking to obtain approximately 650 g of wet biomass. The obtained wet biomass was spread on a vat and dried under ventilation to obtain approximately 32 g of dry biomass. The dried biomass was shredded into 5 mm drawings with scissors, 10 g of which was swollen with 50 mL of water, and then 4N sodium hydroxide was added dropwise to adjust the pH to 11.5. After stirring for 16 hours (alkali treatment), solid-liquid separation was performed to obtain approximately 48 mL of an alkali treatment solution. Of these, 40 mL was freeze-dried to obtain approximately 2.6 g of powder. When the protein release amount was measured using the alkaline treatment liquid and the protein content (purity) was measured using the lyophilized powder, the protein release amount was 2.9 g and the protein purity was 92.3%.

  As shown in Table 1, a microalgae-derived protein composition having an increased protein content by alkali treatment of microalgae-derived biomass concentrated by a specific membrane treatment from a slurry of microalgae-derived biomass as a raw material It was found that can be obtained in high yield. In addition, if the effective pore diameter at the time of membrane concentration of biomass is appropriate from the result of Example 3, even if the biomass recovered using a flocculant is used as a raw material, a microalgae protein useful as a protein raw material for agriculture / fishery feed It turns out that it is possible to obtain.

Claims (3)

After concentrating the microalgae-derived biomass from a slurry containing microalgae-derived biomass using a separation membrane having an effective pore diameter of 2 to 200 μm, the microalgae-derived biomass is alkali-treated under a condition of pH 10-13. A method for producing a microalgae-derived protein composition. The method for producing a protein composition derived from a microalgae according to claim 1, wherein the microalgae is a genus Botryococcus. A microalgae-derived protein composition obtained by the method for producing a microalgae-derived protein composition according to claim 1 or 2.