Methods of processing seaweed

Abstract

The present invention relates to a method for processing macroalgae in which superheated water is used in an initial pretreatment step prior to extraction of polysaccharides. In particular, the present invention relates to a method for obtaining polysaccharides (e.g., alginate) from macroalgae or parts thereof. Certain aspects of the present invention relate to methods for obtaining polysaccharides from macroalgae that enhance polysaccharide yields and / or shorten processing times compared to conventional extraction methods.

Description

Technical Field

[0001] The present invention relates to a method for processing macroalgae. In particular, the present invention relates to a method for obtaining polysaccharides from macroalgae or parts thereof. Certain aspects of the present invention relate to methods for obtaining polysaccharides from macroalgae, which methods improve polysaccharide quality and / or yield and / or reduce processing time compared to conventional extraction methods. The present invention further relates to polysaccharides obtainable, obtained or directly obtained from macroalgae by such methods.

[0002] In particular, the present invention relates to a method for obtaining an alginate selected from alginic acid, alginate and alginate derivatives from the macroalga Laminaria hyperborea. Background Art

[0003] Seaweed, also known as macroalgae, is a versatile product that is widely used as food for direct human consumption, but also as a source of a variety of commercial products in the food, cosmetic and pharmaceutical industries, and in agriculture as a source of fertilizer and animal feed. In particular, macroalgae are known to be a rich source of bioactive substances, including carotenoids (such as fucoxanthin), polyphenols and hydrocolloids, such as alginates. Structurally, certain species of macroalgae are composed of leaf, bark and petiole components, and different bioactive substances are known to be concentrated in these components at different levels.

[0004] Carotenoids are a class of naturally occurring pigments synthesized by plants, algae, bacteria and some fungi through photosynthesis, and make many foods yellow and red. In particular, carotenoids can be extracted from macroalgae and are known to have beneficial light protection and antioxidant properties. An example of a carotenoid is fucoxanthin, a xanthophyll present in the chloroplasts of brown algae and particularly abundant in brown macroalgae, which is brown or green. Although fucoxanthin can be found in the leaves, skins and petioles of macroalgae, it is particularly concentrated in the epidermis and is present in the petioles at much lower levels. Fucoxanthin has been found to have useful biologically active properties, including promoting weight loss, improving blood lipid profiles and reducing insulin resistance in animal models of obesity. Therefore, carotenoids in general and fucoxanthin in particular are widely used commercially as active pharmaceutical ingredients, dietary supplements, health supplements, food additives, for cosmetics and as additives in animal feed. There are also studies suggesting that fucoxanthin and its metabolite fucoxanthinol may be effective in treating and / or preventing cancer (Martin, Mar Drugs, 2015 Jul 31;13(8)4784-98).

[0005] Polyphenols are secondary metabolites of plants that are known to be abundant micronutrients in the mammalian diet. Polyphenols have been shown to exhibit antioxidant activity, and their role in preventing degenerative diseases such as cancer and cardiovascular disease is emerging. In macroalgae, polyphenols are found at high levels in the bark and leaves.

[0006] Hydrocolloids are a heterogeneous group of long-chain polymers, polysaccharides and proteins, characterized by their ability to form viscous dispersions in water. Alginate, agar and carrageenan are water-soluble carbohydrates that can be extracted from macroalgae. Agar and carrageenan are derived from red macroalgae, while alginates can be extracted from brown macroalgae and are present in high concentrations in the stipe.

[0007] Alginate has many beneficial uses in a wide range of industries including pharmaceuticals, cosmetics, food and textile printing. For example, alginate is used in dental impression molds and wound dressings because of its hypoallergenic properties. Other uses include as a thickener in food for both humans and animals, and as a weight loss supplement. In addition, alginate is also incorporated into fertilizers to improve fertilizer utilization and reduce environmental pollution by developing nitrogen slow-release products (Ind. Eng. Chem. Res., 2012, 51 (3), pp. 1413–1422). Similarly, alginate is a product that can be used for papermaking and printing.

[0008] Brown macroalgae commonly used as a source of alginate are Ascophyllum species, Durvillaea species, Ecklonia species, Laminaria species, Lessonia species, Macrocytis species, and Sargassum species. In particular, alginate is extracted from Laminaria japonica. However, the chemical structure of alginate varies from genus to genus, and similar variability is found in the properties of its alginate.

[0009] Alginate is usually extracted from brown macroalgae as a sodium salt. Alginate extraction methods aim to obtain dry alginate powder, especially sodium alginate. The method of extracting alginate from macroalgae involves first soaking the macroalgae in an alkaline solution, such as sodium carbonate, over a period of several hours to dissolve the alginate, thereby forming a thick gel. High quality alginates are found to be able to form strong gels.

[0010] Alginate extracts require "diluting" by conventional filtration methods to remove algal residues, usually by diluting in water. Dissolved alginates are usually recovered from aqueous solutions by adding an acid to precipitate alginic acid, by adding a calcium salt to precipitate calcium alginate, or by adding an antisolvent such as ethanol.

[0011] The choice of acid can result in the formation of alginic acid, which is insoluble in water and is therefore separated in the form of a gel. Optionally, after recovery, the acid can be converted into a salt, such as a sodium salt, by adding a suitable carbonate or hydroxide solution, such as sodium carbonate or sodium hydroxide. The salt can then be precipitated by adding an antisolvent such as ethanol. The precipitate can be separated from the mixture by a filtration method and then dried and ground for commercial use.

[0012] In contrast, extraction of alginate by addition of calcium salts such as calcium chloride produces insoluble calcium alginate fibers which, upon addition of acid, are converted to alginate fibers. Optionally, addition of sodium carbonate converts the alginate fibers to sodium alginate.

[0013] Since macroalgae are a rich source of useful products such as alginate, which has high commercial value, various pretreatment processes have been used to improve the yield and quality of macroalgae products. For example, pretreatment of macroalgae with saturated steam, such as by positioning the macroalgae or parts thereof near the surface of boiling water, increases the yield of alginate. However, steam pretreatment requires long treatment times and can result in low-quality alginate.

[0014] Alginate is concentrated in the stipes of macroalgae, so slicing macroalgae into portions is useful for the extraction of alginate. Another benefit of slicing macroalgae compared to processing whole macroalgae is avoiding products with undesirable properties. For example, polyphenols provide dark pigments primarily to brown macroalgae, and during processing of whole macroalgae, polyphenols are often incorporated during the alginate extraction process to form irreversible dark alginate solutions. Alginate would be more valuable if it were colorless. Therefore, methods are desired to remove substances in the stipe that might otherwise cause the alginate to discolor.

[0015] WO 2015067971 A1 describes washing the stem portion with hot water at up to 90°C, however, this is done only to remove polyphenols that might otherwise cause an unwanted browning of the alginate. A disadvantage of pre-treating macroalgae or parts thereof with hot water (or steam, as discussed above) is the long treatment time required to obtain a suitable alginate yield.

[0016] Formaldehyde has also been used to reduce the brown color of alginate. Some prior art methods use formaldehyde to preserve macroalgae after collection and before processing. In this case, formaldehyde acts as a preservative and removes the color of the macroalgae, ultimately producing a "whiter" alginate. The disadvantage of formaldehyde pretreatment is the use of environmentally unfriendly hazardous substances. Formaldehyde is a volatile organic compound (VOC) that can cause irritation and breathing difficulties in humans and animals. In aquatic environments, formaldehyde is persistent and toxic, with a half-life of 1 to 10 days. It has been found that marine algae are particularly sensitive to formaldehyde at concentrations of 0.1 mg / l to 1 mg / l. Therefore, it would be desirable if macroalgae processing could be performed without the use of formaldehyde.

[0017] There is a continuing need in the art for improved methods to produce higher quality alginates, such as alginates that do not discolor or discolor less. Therefore, it would be beneficial if methods could be provided to facilitate the extraction of higher quality alginates by removing substances in macroalgae that may cause discoloration of the alginate during subsequent alginate extraction. It would also be beneficial to obtain the alginate in a more environmentally friendly method, and it would also be beneficial if such methods reduced processing time.

[0018] Other pretreatment processes have used acids, and a reduction in the viscosity of the solution produced by alginate extraction has been observed upon acid pretreatment, which is believed to be due to a reduction in polymer chain length. Generally, the higher the acid concentration and the longer the treatment time, the greater the reduction in viscosity. Since reduced viscosity is an indicator of an unstable product, indicating increased vulnerability to degradation, there is a need for improved methods by which alginates with increased viscosity can be obtained from macroalgae.

[0019] Acid pretreatment has also been shown to increase the yield of alginate. The method used has been reviewed by Hernandez-Carmona et al. (J. Applied Phycology, 1999, 10, 507-513), who observed that 0.1 M hydrochloric acid was usually used, but in some cases the concentration could be reduced to 0.006 M without observing a difference in yield.

[0020] The disadvantage of acid pretreatment is the use of harmful substances that are not environmentally friendly.

[0021] It would be advantageous if a method could be provided for extracting macroalgae products such as alginate that was more environmentally friendly than existing methods.

[0022] It would also be advantageous if a process could be provided which enabled the extraction of useful substances such as alginate from macroalgae on a commercially viable scale and with improved yields.

[0023] It would be advantageous if a process could be provided that exhibited increased alginate yield and quality while having reduced processing time.

[0024] The inventors have successfully devised a method to address one or more of these problems.

[0025] Unexpectedly and surprisingly, it has been found that useful substances such as alginate can be extracted from macroalgae using a simplified method utilizing superheated solvents such as water. As described herein, superheated solvents are used in a pre-treatment step to reduce the molecular weight of target substances such as alginate, thereby helping to extract the target substance from macroalgae in a subsequent extraction step. The method of the present invention can be more environmentally friendly than prior art methods. In particular, the subsequent extraction step can be carried out under milder conditions than the conditions currently used for industrial processing of macroalgae to produce alginate. For example, low concentrations of highly corrosive substances such as sodium carbonate can be used, resulting in reduced CO2 emissions. In addition, the method is used to remove materials in macroalgae that may cause alginate to discolor during subsequent alginate extraction. Unexpectedly, it has been found that the method used to extract substances such as alginate results in shortened processing time and extraction of alginate with high viscosity.

[0026] Certain embodiments of the present invention are directed to at least partially alleviating the problems associated with the prior art.

[0027] It is an aim of certain embodiments of the present invention to increase the yield of alginate, provide methods for reducing processing time and / or improving product quality. Summary of the invention

[0028] Certain aspects of the present invention are intended to provide and herein provided is a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof, the method comprising the steps of:

[0029] exposing macroalgae or parts thereof to superheated solvents; and

[0030] Extracting polysaccharides from said macroalgae or parts thereof.

[0031] In the method of the present invention, the step of exposing the macroalgae to a superheated solvent is performed as a "pre-treatment", ie, the step is performed prior to the extraction and recovery of the desired polysaccharides.

[0032] The term "solvent" when used herein with respect to a superheated solvent is not intended to place any limitation on its function in the methods described herein. Although a superheated solvent will be a substance with dissolving power, it is not used in the present invention for solubilization, and therefore is not used for extracting target polysaccharides from tissues of macroalgae. During the pretreatment step of the method, due to the conditions under which the superheated solvent is employed, the extraction of polysaccharides by the superheated solvent will be minimal.

[0033] By selecting appropriate reaction conditions during this particular step of the method, such as the temperature of the superheated solvent and the pre-treatment duration, the polysaccharide extracted by the superheated solvent in the pre-treatment stage is minimized (e.g., substantially prevented). Without wishing to be bound by theory, it is believed that the limited pre-treatment step duration and the temperature range of the selected superheated solvent cause the limited hydrolysis of the polysaccharide (e.g., alginate) chain to form shorter polymer chains. It is believed that this partial depolymerization that reduces the molecular weight of the polysaccharide helps its solubilization and extracts in the subsequent extraction steps of the method. During the pre-treatment step, the superheated solvent will not dissolve (and therefore extract) the target polysaccharide material to any significant extent.

[0034] Optionally, the macroalgae or part thereof exposed to the superheated solvent has not undergone any previous processing steps other than collection, storage and / or transportation. Optionally, the macroalgae or part thereof exposed to the superheated solvent has not undergone any previous bleaching steps. Optionally, the macroalgae or part thereof exposed to the superheated solvent has not undergone any previous bleaching steps by exposure to chemical agents. Optionally, the macroalgae or part thereof exposed to the superheated solvent, such as superheated water, is unbleached macroalgae.

[0035] Therefore, the present invention also provides and provided herein is a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof as described herein, provided that the macroalgae or parts thereof exposed to the superheated solvent have not undergone any previous bleaching step.

[0036] The present invention also provides and provided herein is a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof as described herein, provided that the macroalgae or parts thereof exposed to the superheated solvent is unbleached.

[0037] It is believed that the use of the method removes materials from the macroalgae that may cause the alginate to discolor during subsequent alginate extraction, to the extent that bleaching of the macroalgae or parts thereof may not be required prior to alginate extraction. For example, any naturally occurring pigments such as polyphenols that may be present in the macroalgae may be dissolved to some extent in or decomposed by the superheated solvent. In this way, for example, these pigments can be easily removed by washing the macroalgae after the pretreatment step and prior to extracting the target polysaccharide. This can result in an increased yield of higher quality polysaccharides (e.g., alginate).

[0038] Optionally, the macroalgae or part thereof exposed to the superheated solvent may be dried prior to exposure to the superheated solvent. Suitably, the macroalgae or part thereof may be air dried at ambient or elevated temperature. Alternatively, the macroalgae or part thereof exposed to the superheated solvent may be fresh, i.e. not dehydrated to any significant extent.

[0039] Therefore, the present invention also provides and provides herein a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof, the method comprising the following steps:

[0040] Drying the macroalgae or parts thereof ("drying step");

[0041] exposing the macroalgae or parts thereof to a superheated solvent (a "pre-treatment step"); and

[0042] - Extracting polysaccharides from said macroalgae or a part thereof ("extraction step").

[0043] Suitably, the macroalgae is divided into portions prior to the drying step.

[0044] It is believed that drying the macroalgae or parts thereof after harvesting may allow for the extraction of better quality alginate. It is believed that drying the macroalgae or parts thereof after harvesting may allow for the extraction of alginate without the need for chemical preservatives such as formaldehyde.

[0045] Suitably, the polysaccharide is an alginate selected from: alginic acid; alginate; and / or alginate derivatives thereof. In a preferred embodiment, the product produced by the methods described herein will be sodium alginate, such as dried sodium alginate.

[0046] Suitably, the macroalgae is brown algae.

[0047] Suitably, the macroalgae or part thereof exposed to the superheated solvent, such as superheated water, is unbleached macroalgae, such as unbleached brown macroalgae.

[0048] As described herein, superheated solvents are employed to achieve a limited degree of hydrolysis of the polysaccharide material, and thus facilitate subsequent extraction. It is not intended that the superheated solvent should result in extensive hydrolysis of the polysaccharide chains, as this will unduly affect the quality of the extracted material (e.g., it will reduce the viscosity of the material). As will be appreciated, the superheated solvents used in the methods of the present invention should therefore be substantially free of (e.g., free of) other substances that can hydrolyze the polysaccharides. For example, the superheated solvent will be substantially free of any acidic or alkaline substances, such as any mineral acid or sodium carbonate.

[0049] Suitably, the superheated solvent is water.

[0050] The pH of water used in the present invention is generally in the range of about 5 to about 8, for example, about 7.

[0051] The water used in the process of the invention will typically be deionized water. This can be prepared using any method known in the art, for example by passing the drinking water through a reverse osmosis system to remove most of the dissolved ions, and then removing any remaining ions by contact with a deionizer resin. The conductivity of the deionized water will be low, for example it may be less than about 10 μS, preferably in the range of 3 μS to 5 μS.

[0052] In another embodiment, the superheated solvent is an alcohol, such as C 1-3 Alcohols, such as methanol, ethanol or propanol. The alcohol solvent may be substantially free of water, but need not be. In the presence of any water, it is typically deionized water as described herein.

[0053] In another embodiment, the superheated solvent is a mixture of water and alcohol, such as a mixture of deionized water and alcohol. 1-3 Alcohol mixtures. Suitable water / alcohol mixtures for use in the present invention can be readily determined by those skilled in the art, but may for example contain up to 30 wt.% alcohol, preferably 15 to 30 wt.%, more preferably 10 to 15 wt.% alcohol and the remainder water.

[0054] Suitably, the macroalgae or part thereof is exposed to a superheated solvent, such as superheated water, superheated alcohol or a superheated alcohol / water mixture, preferably at a temperature of about 101°C to 150°C, such as 105°C to 130°C, such as 110°C to 125°C, such as 112°C to 118°C, such as about 115°C, such as 110°C to 130°C, such as about 125°C.

[0055] Suitably, the superheated solvent, e.g. superheated water, superheated alcohol or superheated alcohol / water mixture is maintained in a liquid state by applying pressure, e.g. at a pressure of about 105 kPa to 500 kPa, e.g. 120 kPa to 300 kPa, e.g. 140 kPa to 240 kPa, e.g. 150 kPa to 190 kPa, e.g. 165 kPa to 170 kPa, e.g. 140 kPa to 270 kPa, e.g. 130 kPa to 235 kPa.

[0056] Suitably, the superheated solvent, e.g. superheated water, superheated alcohol or superheated alcohol / water mixture is maintained in a liquid state by applying pressure at a temperature of about 101°C to 150°C, for example by applying a pressure of about 105 kPa to 500 kPa, for example by applying a pressure of about 105 kPa to 500 kPa at a temperature of 105°C to 130°C, for example by applying a pressure of about 120 kPa to 300 kPa at a temperature of 110°C to 125°C, for example by applying a pressure of about 140 kPa to 240 kPa at a temperature of 112°C to 118°C, for example by applying a pressure of about 150 kPa to 190 kPa at a temperature of 115°C, for example by applying a pressure of about 165 kPa to 170 kPa at a temperature of 110°C to 130°C, for example by applying a pressure of about 130 kPa to 235 kPa at a temperature of 125°C.

[0057] Suitably, the macroalgae are exposed to the superheated solvent, such as superheated water, superheated alcohol or a superheated alcohol / water mixture for a period of about 30 seconds to 60 minutes, such as 2 to 40 minutes, such as 5 to 25 minutes, such as 5 to 20 minutes, such as 7 to 15 minutes, such as 7 to 13 minutes.

[0058] Suitably, the macroalgae or part thereof is immersed in water, alcohol or an alcohol / water mixture contained in a suitable vessel. The water, alcohol or alcohol / water mixture may already be in the vessel and heated after the macroalgae or part thereof is added. Alternatively, the macroalgae or part thereof may be placed in a vessel and a superheated solvent, such as superheated water, superheated alcohol or a superheated alcohol / water mixture, may be added.

[0059] Suitably, the macroalgae or parts thereof may be continuously added to a vessel containing a superheated solvent, such as superheated water, superheated alcohol or a superheated alcohol / water mixture, by means of an extruder, a screw drive or a dual drive system.

[0060] Following the pretreatment step of the method, the macroalgae or part thereof is subjected to an extraction step in which the target polysaccharide is extracted from the macroalgae or part thereof and optionally recovered. Suitably, the macroalgae or part thereof is separated from the superheated solvent and cooled prior to the extraction step. Removal of the macroalgae or part thereof from the superheated solvent will have the effect of terminating the pretreatment step and preventing further hydrolysis of the polysaccharide material.

[0061] Prior to the extraction step, the pre-treated macroalgae or parts thereof may be washed (eg with water).

[0062] Suitably, prior to extraction, the macroalgae or part thereof may be contacted with an acid, for example a mineral acid such as hydrochloric acid. This serves to remove residual calcium and other multivalent cations.

[0063] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof comprises contacting the macroalgae or part thereof with an alkaline solution to produce an alginate composition. Suitably, the alkaline solution is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and sodium carbonate.

[0064] The extraction method can be carried out according to any known method, for example, as described by Hernandez-Carmona et al. (Journal of Applied Phycology, 1999, 10, 507-513).

[0065] Suitably, the step of extracting the polysaccharides from the macroalgae or part thereof comprises contacting the macroalgae or part thereof with carbonate ions. Suitably, the alkaline solution comprises carbonate ions.

[0066] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof comprises contacting the macroalgae or part thereof with an alkaline solution, such as sodium carbonate. Suitably, the alkaline solution comprises sodium carbonate.

[0067] Suitably, the step of extracting polysaccharides from macroalgae or parts thereof comprises contacting the macroalgae or parts thereof with an alkaline solution, such as sodium carbonate at a concentration of 0.1% to 4%, such as 0.5% to 3%, such as 2% to 4%. In one embodiment of the method, a low concentration of alkaline solution (such as sodium carbonate) may be used. For example, the alkaline solution may be contacted with the macroalgae or parts thereof at a concentration of 0.5% to 3%, preferably 1% to 2.5%, more preferably 1.5% to 2.5%.

[0068] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof comprises adding a sodium carbonate solution to the macroalgae, wherein the weight ratio of sodium carbonate solution to macroalgae stipe is from 3:1 to 20:1, such as 5:1 to 18:1, for example 5:1 to 15:1.

[0069] Optionally, the step of extracting polysaccharides from macroalgae or a portion thereof comprises contacting the macroalgae or a portion thereof with a hot alkaline solution to produce an alginate composition. The term "hot" refers to a temperature above room temperature but not so high as to degrade the macroalgae. The temperature required to maintain the hot alkaline solution is known to the skilled person.

[0070] Suitably, the step of extracting polysaccharides from macroalgae or parts thereof further comprises the step of soaking the macroalgae or parts thereof in an alkaline solution for a period of about 2 minutes to 24 hours, such as 30 minutes to 24 hours, such as 2 to 18 hours, such as about 4 to 14 hours, such as 6 to 10 hours. Suitably, the step of extracting polysaccharides from macroalgae or parts thereof comprises mixing the macroalgae or parts thereof with an alkaline solution using an extruder, for example, as described in Vauchel, P, Kaas, R, Arhallas, A, Baron, R. Legrand, J. 2008. Food and Bioprocess Technology, 1 (3) pp. 297-300.

[0071] Suitably, the step of extracting the polysaccharide from the macroalgae or part thereof further comprises the step of separating the alginate composition from the macroalgae or part thereof, for example by dilution (if necessary) and filtration, for example by centrifugation.

[0072] To precipitate alginate from an alginate composition, the alginate composition may be contacted with:

[0073] a. Acid ("acid step"); or

[0074] b. calcium salt ("calcium salt step"); or

[0075] c. Antisolvent ("Antisolvent Step").

[0076] Suitably, the acid step comprises contacting the alginate composition with an acid, preferably hydrochloric acid, to form an alginic acid precipitate. Suitably, the concentration of the acid is sufficient to reduce the pH of the solution to 2 or less. It is believed that the acid complexes with the alginate to form insoluble alginic acid, thereby forming a precipitate.

[0077] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof further comprises the step of isolating the alginic acid precipitate, for example by centrifugation.If desired, the alginic acid precipitate may be converted to a desired alginate, for example an alkali salt of alginic acid.

[0078] Suitably, the calcium step comprises contacting the alginate composition with a calcium salt, such as calcium chloride, to form calcium alginate. Suitably, the calcium step comprises contacting the alginate composition with an excess of a calcium salt, such as calcium chloride at a concentration of about 500 mg / dL.

[0079] Suitably, the calcium step further comprises the step of converting the calcium alginate to alginic acid by contacting the calcium alginate with an acid.

[0080] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof further comprises the step of isolating the alginic acid precipitate, for example by centrifugation.If desired, the alginic acid precipitate may be converted to a desired alginate, for example an alkali salt of alginic acid.

[0081] Suitably, the antisolvent step comprises contacting the alginate composition with an antisolvent, such as ethanol (at a concentration of about 30% to 70%, such as 40% to 60%, such as about 50%), such as acetone (at a concentration of about 30% to 70%, such as 40% to 60%, such as about 50%).

[0082] Suitably, the step of extracting polysaccharides from the macroalgae or part thereof further comprises the step of separating the alginate precipitate, for example by centrifugation.

[0083] Suitably, prior to the pre-treatment step described herein, the method further comprises separating the whole macroalgae into parts, including leaves, skin and stalk. In the case of removing the skin from the stalk, any known method can be used, including both mechanical and chemical methods. For example, mechanical methods include peeling as described in EP 3 068 804. Alternatively, the method may further comprise removing the leaves from the stalk, i.e. separating the whole macroalgae into leaves and skin, and the stalk remains intact. In this embodiment, the stalk is "unpeeled".

[0084] Suitably, the method of the present invention can be carried out on a part of macroalgae, wherein the part is selected from leaves, skins and stalks. Suitably, the part is a stalk. Suitably, the stalk is preferably divided into parts with a size of less than 0.5 cm, for example less than 0.5 mm, by cutting or mixing. Suitably, the stalk is preferably divided into parts with a size of 0.5 cm to 2.0 cm by cutting or mixing. Suitably, the part is an unpeeled stalk (i.e. a stalk with the skin retained). Suitably, the unpeeled stalk is preferably divided into parts with a size of less than 0.5 cm, for example less than 0.5 mm, by cutting or mixing. Suitably, the unpeeled stalk is preferably divided into parts with a size of 0.5 cm to 2.0 cm by cutting or mixing. Suitably, the part is a leaf. Suitably, the leaf is preferably divided into parts with a size of less than 0.5 cm, for example less than 0.5 mm, by cutting or mixing. Suitably, the leaf is preferably divided into parts with a size of 0.5 cm to 2.0 cm by cutting or mixing.

[0085] Suitably, macroalgae selected from the group consisting of Laminaria spp, Ascophyllum spp, Durvillaea spp, Ecklonia spp, Lessonia spp, Macrocytis spp and Sargassum spp, such as Laminaria japonica, can be used in the method of the present invention. In a particular embodiment, the macroalgae or part thereof used in the present invention is Laminaria japonica. It is particularly preferred to use the stalks of Laminaria japonica (peeled or unpeeled).

[0086] Certain aspects of the present invention are intended to provide and herein provided is a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof, the method comprising the steps of:

[0087] Removing the skin of the macroalgae, preferably the stalk portion of the macroalgae, for example by peeling;

[0088] exposing the macroalgae or portion thereof to a superheated solvent, such as superheated water, maintained at a temperature of about 105°C to 130°C in a pressurized vessel;

[0089] Soaking the macroalgae or part thereof in an alkaline solution (e.g., at a concentration of up to 8%, such as up to 4%, such as 0.1% to 2%, such as 0.1% to 0.5%, such as 0.1% to 0.25%) with periodic shaking for about 4 to 20 hours to form an alginate solution (e.g., sodium alginate);

[0090] removing macroalgae residues from the alginate solution using a separation procedure, preferably by centrifugation;

[0091] Forming an alginic acid precipitate or alginate precipitate; and

[0092] • Separate the resulting precipitate, for example by filtration or centrifugation.

[0093] Certain aspects of the present invention are intended to provide and herein provided is a method for obtaining polysaccharides, such as alginate, from macroalgae or parts thereof, the method comprising the steps of:

[0094] Providing macroalgae, preferably unpeeled stipe portions of macroalgae;

[0095] exposing the macroalgae or portion thereof to a superheated solvent, such as superheated water, maintained at a temperature of about 105°C to 130°C in a pressurized vessel;

[0096] Soaking the macroalgae or part thereof in an alkaline solution (e.g., at a concentration of up to 8%, such as up to 4%, such as 0.1% to 2%, such as 0.1% to 0.5%, such as 0.1% to 0.25%) with periodic shaking for about 4 to 20 hours to form an alginate solution (e.g., sodium alginate);

[0097] removing macroalgae residues from the alginate solution using a separation procedure, preferably by centrifugation;

[0098] Forming an alginic acid precipitate or alginate precipitate; and

[0099] • Separate the resulting precipitate, for example by filtration or centrifugation.

[0100] The step of forming alginate precipitate from alginate solution can be as described herein or by any method known to those skilled in the art, for example, by contacting alginate with acid. Optionally, the alginate precipitate is separated and an alkaline solution is added to the alginate precipitate to convert the alginate precipitate back into alginate. The obtained alginate can be converted into a precipitate by adding an antisolvent (e.g., ethanol).

[0101] The step of forming an alginate precipitate from an alginate solution can be performed as described herein or by any method known to those skilled in the art, such as by neutralizing the pH of the alginate solution to 7 by adding an acid and then adding an antisolvent (e.g., ethanol) to directly precipitate the alginate.

[0102] It is believed that certain aspects of the present invention provide methods having:

[0103] Increased alginate yield;

[0104] Improved alginate quality; and / or

[0105] ·The processing time for extracting alginate is shortened.

[0106] In a further aspect, the present invention provides polysaccharides obtainable, obtained or directly obtained from macroalgae or parts thereof by any method described herein. In particular, the present invention provides alginate obtainable, obtained or directly obtained from macroalgae or parts thereof by any method described herein.

[0107] definition

[0108] It should be understood that many of the terms and phrases used within this specification are known to those skilled in the art.The definitions provided herein are intended to serve alone as embodiments of the present invention or in combination with any other embodiments and / or definitions herein.

[0109] As used herein, the term "macroalgae" may also be referred to as "seaweed". The seaweed may be, for example, brown algae, such as kelp. The kelp may be a tangle (Laminaria japonica). The seaweed generally consists of three distinct morphological parts, which are characterized by the thallus (leaves), the stipe (stem), and the root-like appressorium (appressorium). The stipe of the seaweed may be substantially cylindrical and include three distinct regions depending on the radial distance from the central axis: a radially inner portion including a core region of the stipe, referred to as the inner core; a radially middle portion surrounding the core including a tissue region, referred to as the outer core; and a radially outer portion including a protective surface layer, also referred to as an outer layer (referred to herein as skin). Since these regions differ in their physical properties and chemical composition, it may be beneficial to separate these regions. However, in certain embodiments of the present invention, it may not be necessary to separate the skin from the stipe.

[0110] As used herein, the term "superheated solvent" refers to a solvent, such as water, alcohol or water / alcohol mixture, that is heated to a temperature above its normal boiling point but below the critical temperature at a pressure sufficient to maintain a liquid state at atmospheric pressure. In this sense, a superheated solvent has the same meaning as a subcritical solvent. According to the present invention, the pressure must be sufficient to maintain the superheated solvent in a liquid state. According to the present invention, the macroalgae to be processed can be immersed in a solvent, such as water, contained in a suitable pressure vessel. In certain embodiments, the water can already be in the vessel and then heated after the addition of the macroalgae. In another embodiment, the macroalgae can be placed in a vessel and a superheated solvent, such as superheated water, can be added. In one embodiment of the present invention, seaweed is continuously added to a pressure vessel containing a superheated solvent, such as superheated water, by a suitable mechanism such as an extruder, a screw drive or a dual valve system. The superheated solvent used in the method of the present invention is not used to extract the target polysaccharide, but is used to improve the yield and quality of the polysaccharide (such as alginate) obtained from the subsequent extraction step in the pretreatment step.

[0111] As used herein, the term "bleaching" refers to a reactive chemical process in which coloring materials, i.e., colored components, are removed or extracted. Bleaching is the whitening or lightening of a color by exposure to a chemical agent. Examples of such chemical agents include:

[0112] formaldehyde;

[0113] Compounds comprising or serving as a source of peroxides or peroxyacids such as hydrogen peroxide, peroxide salts, peroxyacids, hydroperoxides, carbonates, percarbonates, 6-(phthalimido)peroxycaproic acid (PAP), peracetic acid;

[0114] Oxidation catalysts, such as mononuclear and binuclear transition metal catalysts (e.g., manganese) (e.g., the oxidation catalyst can be selected from one or more groups selected from [(Mn IV )2(uO)3(Me3-TACN)2] 2+ 、[(Mn III )2(uO)(u-CH3COO)2(Me3-TACN2)] 2+ and [Mn III Mn IV (uO)2(u-CH3COO)(Me4-DTNE)] 2+ and suitable salts thereof);

[0115] peroxide activators (i.e., compounds that react with a source of peroxide groups to provide peroxide groups), such as tetraacetylethylenediamine (TAED);

[0116] Peroxyacid activators (i.e., compounds that react with a source of peroxyacid to provide peroxyacid groups), such as tetraacetylethylenediamine (TAED);

[0117] Hypochlorite;

[0118] Compounds including or acting as sources of: chlorite;

[0119] Chlorine dioxide;

[0120] Chlorite salts;

[0121] Chlorine or a compound acting as a source thereof.

[0122] As used herein, the terms "extracting" and "obtaining" are used interchangeably. According to the present invention, the method of extracting polysaccharides refers to obtaining hydrocolloids, particularly alginate, from macroalgae. Methods for extracting polysaccharides, such as alginate, are known to those skilled in the art. The extraction will generally involve the solubilization of polysaccharides present in the macroalgae or parts thereof. For example, the extraction will involve the solubilization of alginate, which is generally present in the macroalgae (e.g., in the stalk) in an insoluble form as calcium alginate. After extraction, the resulting solution will generally be separated (e.g., filtered) from the residual solid components of the macroalgae.

[0123] As used herein, the term "alginate" is used to refer to salts of alginic acid, but may also refer to other derivatives of alginic acid and to alginic acid itself. Alginic acid is a polysaccharide composed of (1-4)-linked blocks of β-D-mannuronic acid (M) and α-L-guluronic acid ester (G). The properties of alginic acid are affected by the relative proportions of the M and G residues and the molecular weight of the polymer. Alginic acid is extracted from the cell walls of brown algae in the form of sodium, calcium and magnesium salts of alginic acid.

[0124] As used herein, the term "solution" refers to an aqueous solution, ie, a substance that dissolves in water.

[0125] As used herein, the term "alkaline solution" refers to an aqueous solution containing an alkali liquid having a pH greater than 7 and having the ability to neutralize an acid. According to certain aspects of the present invention, the alkaline solution may include carbonate ions or sodium carbonate.

[0126] As used herein, the term "acid" refers to a substance with a pH less than 7, or a species that can provide protons in a solution and has the ability to neutralize an alkali. According to certain aspects of the invention, the acid added during the extraction process is complexed with alginate to form insoluble alginic acid. On the one hand, the acid is hydrochloric acid.

[0127] As used herein, the term "precipitate" refers to an insoluble solid material that forms from a liquid solution.

[0128] As used herein, the term "yield increase" refers to an increase in the production of a product (polysaccharide, such as alginate) from macroalgae processing. Yield increase specifically refers to an increase in alginate obtained from macroalgae or a portion thereof.

[0129] As used herein, the term "purity" refers to the percentage of a product (e.g., alginate) obtained from macroalgae processing and extraction in a sample. For example, a purity of about 90% to 100% can be obtained. The term "increased purity" refers to a greater percentage of a product obtained from macroalgae processing in a sample.

[0130] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations thereof mean "including but not limited to", and are not intended to (and do not) exclude other parts, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context requires otherwise. In particular, where the indefinite article is used, the specification should be understood as contemplating plural as well as singularity unless the context requires otherwise.

[0131] Unless incompatible with this document, features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein. All features disclosed in this specification and / or all steps of any method or process so disclosed may be combined in any combination, except for at least some mutually exclusive combinations of the features and / or steps. The present invention is not limited to any details of any of the foregoing embodiments. The present invention extends to any novel feature or novel combination of features disclosed in this specification or to any novel step or any novel combination of steps in the steps of any method or process so disclosed.

[0132] The contents of all previously published documents mentioned in this application are incorporated herein by reference.

[0133] Certain embodiments of the invention include:

[0134] 1. A method for obtaining polysaccharides from macroalgae or parts thereof, the method comprising the following steps:

[0135] exposing macroalgae or parts thereof to superheated solvents; and

[0136] Extracting polysaccharides from said macroalgae or parts thereof.

[0137] 2. The method according to embodiment 1, wherein the macroalgae or part thereof exposed to the superheated solvent has not undergone any previous bleaching step by exposure to a chemical agent.

[0138] 3. The method of any one of the preceding embodiments, wherein the polysaccharide is an alginate selected from the group consisting of: alginic acid; alginate; and / or alginate derivatives thereof.

[0139] 4. The method of any preceding embodiment, wherein the macroalgae is brown algae.

[0140] 5. The method of any one of the preceding embodiments, wherein the superheated solvent is water.

[0141] 6. The method according to any of the preceding embodiments, wherein the macroalgae or a portion thereof is exposed to superheated water preferably at a temperature of about 101°C to 150°C, such as 105°C to 130°C, such as 110°C to 125°C, such as 112°C to 118°C, preferably 115°C, such as 110°C to 130°C, preferably 125°C.

[0142] 7. The method according to any of the preceding embodiments, wherein the superheated water is maintained in a liquid state by applying a pressure applied at about 105 to 500 kPa, such as 120 to 300 kPa, such as 140 to 240 kPa, such as 150 to 190 kPa, such as 165 to 170 kPa, such as 140 to 270 kPa, such as 130 to 235 kPa.

[0143] 8. The method of any one of the preceding embodiments, wherein the macroalgae is exposed to the superheated water for about 30 seconds to 60 minutes, such as about 2 to 40 minutes, such as 5 to 25 minutes, such as 7 to 15 minutes, such as about 7 to 13 minutes.

[0144] 9. The method of any preceding embodiment, wherein the step of extracting polysaccharides from macroalgae or a portion thereof comprises contacting the macroalgae or a portion thereof with an alkaline solution to produce an alginate composition.

[0145] 10. The method of embodiment 9, wherein the alkaline solution is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, and sodium carbonate.

[0146] 11. The method of embodiment 9 or embodiment 10, wherein the weight ratio of the alkaline solution, such as sodium carbonate, to the handle is 3:1 to 20:1, such as 10:1 to 20:1, such as 5:1 to 15:1.

[0147] 12. The method of any one of embodiments 9 to 11, wherein the macroalgae or portion thereof is immersed in the alkaline solution for a period of about 2 minutes to 24 hours, such as 30 minutes to 24 hours, such as 2 to 18 hours, such as about 4 to 14 hours, such as 6 to 10 hours.

[0148] 13. The method of any one of embodiments 9 to 12, wherein the step of extracting polysaccharides from macroalgae or a portion thereof further comprises contacting the alginate composition with an acid, such as hydrochloric acid, wherein the concentration of the acid is sufficient to reduce the pH of the solution to 2 or less to form an alginate precipitate.

[0149] 14. The method of any one of embodiments 9 to 12, wherein the step of extracting polysaccharides from macroalgae or a portion thereof further comprises contacting the alginate composition with an excess of a calcium salt, such as calcium chloride at a concentration of about 500 mg / dL.

[0150] 15. The method of any one of embodiments 9 to 12, wherein the step of extracting polysaccharides from macroalgae or a portion thereof further comprises contacting the alginate composition with an antisolvent, such as ethanol at a concentration of about 30% to 70%, such as 40% to 60%, such as about 50%, such as acetone at a concentration of about 30% to 70%, such as 40% to 60%, such as about 50%.

[0151] 16. The method of any preceding embodiment, wherein the macroalgae is a part thereof, and the part is selected from the group consisting of leaves, bark, and petioles.

[0152] 17. The method according to embodiment 16, wherein the portion is a stem, and wherein the stem is divided into portions having a size of less than 2 cm, preferably by cutting or blending.

[0153] 18. The method according to embodiment 16, wherein the parts are leaves, and wherein the leaves are divided into parts having a size of less than 2.0 cm, preferably by cutting or blending.

[0154] 19. The method of any preceding embodiment, wherein the macroalgae is selected from the group consisting of Laminaria japonica, Ascophyllum nodosum, Bull algae, Laminaria edulis, Giant kelp, Laminaria japonica, and Sargassum, such as Laminaria japonica.

[0155] 20. The method according to any one of the preceding embodiments, comprising the steps of:

[0156] Removing the skin of the macroalgae, preferably the stalk portion of the macroalgae, for example by peeling;

[0157] exposing the macroalgae or portion thereof to superheated water maintained at a temperature of about 105°C to 130°C in a pressurized vessel;

[0158] Soaking the macroalgae or part thereof in an alkaline solution having a concentration of about 2% to 8% with periodic shaking for about 4 to 20 hours to form an alginate solution, such as sodium alginate;

[0159] removing macroalgae residues from the alginate solution, preferably by centrifugation;

[0160] Formation of alginic acid precipitate or alginate precipitate;

[0161] • Separate the resulting precipitate, for example by filtration or centrifugation.

[0162] Further details of certain embodiments are provided below. DETAILED DESCRIPTION

[0163] Figure 1 A bar graph showing the amount of alginate (depicted as a percentage) extracted from peeled and rinsed Laminaria japonica stems is presented. Figure 1 The data shown in was generated as described in Example 1.

[0164] Figure 2 The percentage of alginate recovered from Laminaria japonica stems after pretreatment with steam at 115°C for 13 minutes, 26 minutes, and 52 minutes is shown. Figure 2 The data shown in was generated as described in Example 2.

[0165] Figure 3 The percentage of alginate recovered from dry and fresh samples of Laminaria japonica after pretreatment with superheated water at 115°C for 0, 7, 13, and 26 minutes is shown. Figure 3 The data shown in was generated as described in Example 3.

[0166] Figure 4 The viscosity of alginate recovered from dried and fresh samples of Laminaria japonica after pretreatment with superheated water at 115 °C for 0, 7, 13, and 26 minutes is shown. Figure 4 The data shown in was generated as described in Example 3.

[0167] Examples

[0168] All examples used Laminaria japonica. Examples 1 and 2 used peeled stems that had been washed in water to provide a standard starting material. The preparation of the sample used in Example 3 is described below. The extraction yield is related to the dry matter obtained from the washed stem portion. The water content of the stem was determined by loss on drying at 105°C, thereby determining the dry matter content of the stem.

[0169] All examples used water for superheated water treatment, which was prepared as follows: first, drinking water (tap water) was passed through a reverse osmosis system to remove most of the dissolved ions. The resulting water was then passed through a mixed bed of deionizer resins to remove the remainder of the dissolved ions and reduce the conductivity to a low level. In this way, the conductivity of the drinking water (tap water) was reduced from about 500 μS to between about 3 μS and 5 μS.

[0170] Example 1

[0171] a. Preprocessing

[0172] The petiole of Laminaria japonica was peeled, cleaned and divided into about 0.5 cm large parts by cutting. The petiole parts were subjected to a pretreatment process, specifically exposing the petiole to: superheated water (115°C for 13 minutes or 125°C for 30 minutes), boiling water (100°C for 30 minutes) or acid (8 to 24 hours), or without treating the petiole.

[0173] Superheated water is produced by heating water above its normal boiling point (over 100°C) and maintained as a liquid by applying pressure. The stem portion is immersed in a suitable vessel containing water. The water may be heated after the macroalgae portion is added, or alternatively the macroalgae may be placed into a pressurized vessel and then the superheated water added.

[0174] Alternatively, the handle portions were treated with sulfuric acid (0.04 M) overnight, or the handles were exposed to boiling water (100° C.).

[0175] b. extract

[0176] The handle portion (2-3 g) was extracted by periodically shaking it overnight in a 4% sodium carbonate solution (15:1 sodium carbonate solution to handle) to form a solution containing water-soluble sodium alginate. The liquid was separated from the undissolved solids in the solution by centrifugation. Hydrochloric acid was added to an aliquot of the liquid to precipitate the water-insoluble alginic acid from the solution. The mixture was then subjected to centrifugation and the pellet was washed with water to remove soluble impurities and residual acid and re-centrifuged. The pellet was then dried for collection and the weight of the precipitate was expressed as a percentage of the dry matter in the original handle.

[0177] Example 2 - Comparison

[0178] The stems of Kombu (Kelp) were peeled, cleaned and divided into about 0.5 cm large parts by cutting. The stem parts were subjected to a pretreatment process, specifically, the stems were exposed to saturated steam at 115° C. for 13 minutes, 26 minutes and 52 minutes.

[0179] The stem portion (2-3 g) was extracted as described in Example 1b (Extraction). Each time point experiment was analyzed in triplicate. Results (% alginate) Figure 2 Shown in.

[0180] The yield of alginate measured after 115°C steam pretreatment increased with increasing treatment time from 13, 26 and 52 minutes, with the highest yield of alginic acid found at 52 minutes of steam pretreatment. The yield of alginate extracted from the stipes of macroalgae after 52 minutes of steam pretreatment was comparable to the recovery of alginate after 13 minutes of superheated water pretreatment (see Figure 1 ). Thus, pretreatment of macroalgae stipes with superheated water resulted in high alginate yields within a short treatment time period.

[0181] The quality of the alginate product was evaluated by measuring the viscosity of a solution of alginate in water. The viscosity of a 0.5 wt% sodium alginate solution was measured by the falling ball viscometer method. After 13 minutes of superheated water pretreatment, the pretreatment gave a viscosity of about 2.6 mPa.s for the alginate, and after 13 minutes of steam pretreatment, the pretreatment gave a viscosity of 1.5 mPa.s for the alginate. The lower viscosity of the steam-treated alginate indicates more degradation of the alginate product. Due to the low concentration of the sodium alginate solution used in the evaluation, the ball did not reach the terminal velocity and therefore the viscosity values ​​measured were not absolute. However, the higher values ​​after pretreatment with superheated water indicate a reduced degree of degradation of the recovered alginate product.

[0182] in conclusion

[0183] Compared to overnight treatment with boiling water or acid, pretreatment with superheated water produces higher yields. Compared to steam pretreatment, pretreatment with superheated water requires shorter treatment times and produces higher quality products.

[0184] Example 3

[0185] Dried flaked northern kelp and fresh chopped northern kelp stalks with skin were subjected to a pretreatment process using superheated water, and then alginate was extracted.

[0186] Preparation of dried flaked northern kelp: The leaves and epiphytes are removed, but the skin is retained, then chopped and dried. The dried northern kelp stalks are then rehydrated and then pre-treated with superheated water.

[0187] Fresh chopped northern kelp stalks were prepared by removing leaves and epiphytes and soaking the stalks with skin in demineralized water to remove salts so that the solution conductivity was less than 200 μS. The soaked stalks were then blended using a Tefal BlendforceII BL42 blender with a 600W motor at the highest power setting.

[0188] The particle size of the stems ranged from approximately 500 μm to 1000 μm for both dry and fresh material.

[0189] The sample of the material was transferred to a pressure cooker and subjected to a pretreatment process using superheated water at a temperature of 115°C and a pressure of 168.8 kPa for 0 minutes, 7 minutes, 13 minutes and 26 minutes. The handle (50 g to 75 g) was extracted by periodically shaking it for 60 minutes in a 0.25% sodium carbonate solution (sodium carbonate solution to handle is 5:1) to form a solution containing water-soluble sodium alginate. The liquid was separated from the undissolved solid in the solution by filtering through a 100 μm nylon filter. Hydrochloric acid was added to an aliquot of the liquid to precipitate water-insoluble alginic acid from the solution. The mixture was then subjected to filtration through a 100 μm nylon filter, and the gel was washed with water to remove soluble impurities and residual acid and refiltered. The washed gel was then converted to the sodium form, precipitated with alcohol and dried. The weight of the recovered alginate was expressed as the percentage of dry matter in the salt-depleted handle.

[0190] Each time point experiment was analyzed in triplicate. The results (% alginate) are shown in Figure 3 Neutralize in Table 1 below.

[0191] Table 1

[0192]

[0193] Superheated water pretreatment of dried and fresh skinned stems produced high yields of alginate. Alginate obtained from unpeeled stems (both dried and fresh samples) was found to be essentially colorless, confirming that the quality of the alginate was not adversely affected by the presence of pigmented skin in the initial samples.

[0194] The quality of the alginate products obtained from the dried and fresh starting materials was also evaluated by measuring the viscosity of 1% alginate solutions in water. The viscosity was measured by the falling ball viscometer method and the values ​​measured were Figure 4 and are shown in Table 2 below.

[0195] Table 2

[0196]

[0197] For both dry and fresh materials, the viscosity of the extracted alginate decreased with increasing superheated water pretreatment time, and the viscosity results were similar regardless of the initial state of the sample. Lower viscosity than expected was observed in the fresh sample at 7 minutes SHW time, which may be due to the age of the sample at the time of testing, and may be the result of microbial degradation.

Claims

1. A method for obtaining polysaccharides from macroalgae fractions, the method comprising the following steps: a pretreatment step of exposing the macroalgae portion to superheated water having a temperature of 110° C. to 130° C. for a period of 5 to 25 minutes, wherein the superheated water is maintained in a liquid state by applying pressure, the superheated water being substantially free of any acidic or alkaline substances; ● contacting the pre-treated macroalgae fraction with a mineral acid; and - a subsequent extraction step of extracting polysaccharides from said macroalgae fraction; wherein the polysaccharide is an alginate selected from the group consisting of alginic acid, alginate and alginate derivatives; wherein the macroalgae portion is an unpeeled stalk of Laminaria hyperborea; The portion of macroalgae exposed to superheated water did not undergo any prior bleaching step; as well as Wherein the step of extracting polysaccharides from the macroalgae portion comprises contacting the macroalgae portion with an alkaline solution to produce an alginate composition.

2. The method of claim 1, wherein the macroalgae portion is exposed to the superheated water at a temperature of 110°C to 125°C.

3. The method of claim 1, wherein the macroalgae portion is exposed to the superheated water at a temperature of 112°C to 118°C.

4. The method of claim 1, wherein the macroalgae portion is exposed to the superheated water at a temperature of 115°C or 125°C.

5. The method according to claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 105 to 500 kPa.

6. The method according to claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 120 to 300 kPa.

7. The method of claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 140 to 240 kPa.

8. The method of claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 150 to 190 kPa.

9. The method of claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 165 to 170 kPa.

10. The method of claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 140 to 270 kPa.

11. The method of claim 1, wherein the superheated water is maintained in a liquid state by applying a pressure of 130 to 235 kPa.

12. The method of claim 1, wherein the macroalgae portion is exposed to the superheated water for a period of 7 to 15 minutes.

13. The method of claim 1, wherein the macroalgae portion is exposed to the superheated water for a period of 7 to 13 minutes.

14. The method of claim 1, wherein the alkaline solution is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and sodium carbonate.

15. The method according to claim 14, wherein the concentration of the alkaline solution is 0.1% to 3%.

16. The method of claim 1, wherein the weight ratio of the alkaline solution to the macroalgae stipe is 3:1 to 20:

1.

17. The method of claim 1, wherein the alkaline solution is sodium carbonate.

18. The method of claim 1, wherein the weight ratio of the alkaline solution to the macroalgae stipe is 10:1 to 20:

1.

19. The method of claim 1, wherein the weight ratio of the alkaline solution to the macroalgae stipe is 5:1 to 15:

1.

20. The method of claim 1, wherein the macroalgae portion is soaked in the alkaline solution for a period of time ranging from 2 minutes to 24 hours.

21. The method of claim 1, wherein the macroalgae portion is soaked in the alkaline solution for a period of time ranging from 30 minutes to 24 hours.

22. The method of claim 1, wherein the macroalgae portion is soaked in the alkaline solution for a period of time ranging from 2 to 18 hours.

23. The method of claim 1, wherein the macroalgae portion is soaked in the alkaline solution for a period of time of 4 to 14 hours.

24. The method of claim 1, wherein the macroalgae portion is soaked in the alkaline solution for a period of 6 to 10 hours.

25. The method of any one of claims 1-24, wherein the step of extracting polysaccharides from the macroalgae portion further comprises contacting the alginate composition with an acid, wherein the concentration of the acid is sufficient to reduce the pH of the solution to 2 or less to form an alginate precipitate.

26. The method of claim 25, wherein the acid is hydrochloric acid.

27. The method of any one of claims 1-24, wherein the step of extracting polysaccharides from the macroalgae fraction further comprises contacting the alginate composition with an excess of a calcium salt.

28. The method of claim 27, wherein the calcium salt is calcium chloride at a concentration of 500 mg / dL.

29. The method of any one of claims 1-24, wherein the step of extracting polysaccharides from the macroalgae fraction further comprises contacting the alginate composition with an antisolvent.

30. The method of claim 29, wherein the antisolvent is ethanol at a concentration of 30% to 70%.

31. The method of claim 29, wherein the antisolvent is ethanol at a concentration of 40% to 60%.

32. The method of claim 29, wherein the antisolvent is ethanol at a concentration of 50%.

33. The method of claim 29, wherein the antisolvent is acetone at a concentration of 30% to 70%.

34. The method of claim 29, wherein the antisolvent is acetone at a concentration of 40% to 60%.

35. The method of claim 29, wherein the antisolvent is acetone at a concentration of 50%.

36. The method of any one of claims 1-24, wherein the stem is divided into portions less than 2 cm in size by cutting or blending.

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