JPH1180204A - Method for hydrolyzing alginic acid and hydrolyzed material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrolyzed material holding the function of an alginic acid by hydrolyzing an alginic acid, its salt or its ester using a phosphoric acid. SOLUTION: An alginic acid, its salt or its ester is hydrolyzed using 50-90 wt.% phosphoric acid at 0-60 deg.C for 1 hr-1 month. The hydrolyzed material is refined by dissolving the obtained hydrolyzed material into water 0.2-100 times as much, separating the solution from the residue, depositing the hydrolyzed material by mixing the solution with a hydrophilic organic solvent and separating out the deposit. As the alginic acid, a commercial alginic acid extracted from brown algae such as kelp, wakame seaweed and hijiki seaweed can be used. An alkali (alkaline earth) metal of an alginic acid and an ester of an alginic acid also can be used. By this process, a hydrolyzed material of an alginic acid which is easily soluble to water and which does not exhibit a high viscosity when it is dissolved in water is easily prepared industrially.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hydrolyzing alginic acid and a hydrolyzate of alginic acid which can be used as a raw material for various foods and pharmaceuticals. In particular, the present invention relates to a method for hydrolyzing alginic acid with phosphoric acid and the degradation products obtained by such a hydrolysis method.

[0002]

2. Description of the Related Art Alginic acid contained in brown algae such as kelp, seaweed and hijiki has a pyranose ring type in which D-mannuronic acid and L-guluronic acid are linked by β-1,4, and has a molecular weight of 20,000.グ リ 200,000 linear glycuronoglycan, blocks of only D-mannuronic acid (MM blocks), blocks of only L-guluronic acid (GG blocks), and alternately D-mannuronic acid and L-guluronic acid Block (MG block) is a complex block copolymer arbitrarily linked. L in GG block
-Guluronic acid adopts a 1C conformation, and a divalent metal ion and L
-The carboxyl group of guluronic acid and the oxygen atom of the sugar ring are easily coordinated, and Egg Box Junction
forming a crosslinked region called n. For this reason, it has the property that the higher the proportion of the GG block, the more easily it gels.

Alginic acid is well known to have various excellent physiologically active functions. However, since it exhibits high viscosity when dissolved in water, it is used as an emulsion stabilizer, a thickener, etc. Mainly, dyeing, textile, food, paper, medical, photography,
In the field of cosmetics and the like, it is only used as a paste, a stabilizer, a thickener, and the like), and it is generally extremely difficult to use it as a material for foods, pharmaceuticals, and the like.

[0004] For this reason, various attempts have been hitherto reported to solve these problems by decomposing alginic acid to retain alginic acid oligosaccharides which retain functions such as physiological activity and do not exhibit viscosity increase (for example, Kitamikado et a
l., (1989) Journal of the Japanese Society of Fisheries Science 55 (4) 709-713
etc). However, these reports all use an alginate-degrading enzyme produced by a microorganism, and have the drawback that industrial implementation is difficult and equipment costs are high.

[0005] On the other hand, hydrolysis with sulfuric acid is used for thorough hydrolysis in determining the composition of D-mannuronic acid / L-guluronic acid in alginic acid. However, it is difficult to control the reaction and the hydrolysis is difficult. Is colored, and there is a problem that monomers (D-mannuronic acid and L-guluronic acid) are decomposed.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a hydrolyzed alginic acid which is easily dissolved in water while maintaining the function of alginic acid and does not exhibit high viscosity even when dissolved in water, and an industrially useful alginic acid hydrolyzate. An object is to provide an easy manufacturing method.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a hydrolyzate of alginic acid by phosphoric acid retains the function of alginic acid and is easily dissolved in water. Furthermore, they have found that they do not exhibit high viscosity even when dissolved in water, and have completed the present invention based on this finding.

That is, the present invention provides a method for hydrolyzing alginic acid or a salt or ester thereof using phosphoric acid, and a decomposition product obtained by the method. The present invention also provides, after hydrolyzing alginic acid or a salt or ester thereof with phosphoric acid, adding water to the obtained hydrolysis mixture to dissolve the decomposition product, separating the obtained solution, Then, the solution is mixed with a hydrophilic organic solvent to precipitate a decomposition product, and the precipitate is collected.
A method for purifying a decomposition product of alginic acid or a salt or ester thereof and a decomposition product obtained thereby are provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The phosphoric acid used in the present invention is preferably a phosphoric acid having a concentration of 50 to 90% by weight. In a preferred embodiment of the present invention, alginic acid or a salt or ester thereof is prepared by using phosphoric acid at a concentration of 50 to 90% by weight at 0 to 60 ° C, more preferably 20 to 90% by weight.
Hydrolyze at a temperature of 40 ° C. for 1 hour to 1 month. Further, 0.2 to 100 times the amount of water is added to and dissolved in the thus obtained hydrolysis mixture, the obtained solution is separated, and then this solution is mixed with a hydrophilic organic solvent. Decomposition products may be deposited, and the precipitation products may be collected.

The alginic acid used in the present invention includes commercially available alginic acid extracted from brown algae such as kelp, wakame, and hijiki, and salts of alginic acid (eg, alkali salts such as sodium salt and potassium salt). Metal salts, alkaline earth metal salts such as calcium salts, magnesium salts, etc.) or alginic acid esters (eg, propylene glycol ester, ethylene glycol ester, ethyl ester, methyl ester, etc.) may be used (hereinafter, Examples , Except these are collectively referred to as alginic acid).

According to the above-mentioned method of the present invention, a high-yield alginic acid decomposition product which is easily soluble in water and does not show high viscosity when dissolved in water, that is, gives a low-viscosity solution. Can be. At this time, the molecular weight and the molecular weight distribution can be controlled by adjusting the phosphoric acid concentration, the reaction temperature and / or the reaction time.
In addition, according to the method of the present invention, the decomposed product is once dissolved in water and then reprecipitated in a water-soluble organic solvent (eg, methanol, ethanol, isopropanol, etc.), so that it is more easily dissolved and contains a metal component such as calcium. Can be obtained. At this time, the amount of water used for the decomposed product is 0.1.
The amount is preferably 2 to 100 times the amount. If the amount is 0.2 times or less, the viscosity may be so high that it becomes difficult to handle. If the amount is 100 times or more, reprecipitation in a water-soluble organic solvent becomes difficult, and the aqueous solution is once concentrated. It may be necessary to take a method of re-precipitation after completion.

Further, even when, for example, alginic acid having a high calcium content is used as a raw material, the decomposed product of alginic acid obtained by the purification method of the present invention has a very low calcium content. Therefore, conventionally, such a metal component (metal salt) has been removed by an operation such as dialysis, but such an operation is not required for the alginate decomposition product obtained by the method of the present invention.

The decomposed product of alginic acid obtained by the present invention can be suitably used as a metal ion dispersant and the like.
It retains the same bioactive function as alginic acid as a raw material, and can be used as a material for foods, pharmaceuticals and the like.

[0014]

Next, the present invention will be further described with reference to examples, but the present invention is not limited to these examples. The measurement of the molecular weight [number average molecular weight (hereinafter abbreviated as Mn) and weight average molecular weight (hereinafter abbreviated as Mw)] in Examples was performed by gel permeation chromatography system [manufactured by Tosoh Corporation, high-speed GPC HLC-812].
0]. As columns, TSK-gel G5000PW _XL and G
3000PW _XL was used with sodium polyacrylate as standard and 0.025M phosphate buffer as eluent.

Example 1 5.0 g of alginic acid (commercial product A) was added to 60% by weight of phosphoric acid 9
It was dissolved in 0 ml and left at 40 ° C. for 3 days. To this, 100 ml of methanol was added, and the mixture was stirred and left to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality and dried, and then the alginic acid decomposed product was obtained. 3 g (86.0% yield) was obtained. As a result of measuring the molecular weight, Mn /
Mw = 8200 / 20,000.

Example 2 5.0 g of alginic acid (commercially available product A) was mixed with 85% by weight of phosphoric acid 9
It was dissolved in 0 ml and 5 ml of ion-exchanged water, and allowed to stand at 20 ° C. for 3 days. To this, 100 ml of methanol was added, and the mixture was stirred and left to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality and dried, and then the alginic acid decomposed product was obtained. 0 g (80.0% yield) was obtained. As a result of measuring the molecular weight, it was Mn / Mw = 4700/13000.

Example 3 5.0 g of alginic acid (commercial product A) was added to 85% by weight phosphoric acid 4
It was dissolved in 5 ml and left at 40 ° C. for 3 days. To this, 100 ml of methanol was added, and the mixture was stirred and allowed to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality, and then dried to obtain a decomposed product of alginic acid. 1 g (82.0% yield) was obtained. As a result of measuring the molecular weight, Mn /
Mw = 4300/11000.

Example 4 5.0 g of alginic acid (commercial product A) was added to 85% by weight phosphoric acid 4
It was dissolved in 5 ml and left at 20 ° C. for 3 days. After adding 100 ml of distilled water under vigorous stirring and allowing to stand for 2 hours, the precipitated solid is separated by filtration, and the obtained filtrate is added to 1 l of methanol with stirring. Thereafter, the mixture was allowed to stand for 4 hours, and the precipitated solid was filtered to obtain a solid (filtration residue). The solid was washed with neutrality, and then dried.
(62.0% yield). As a result of measuring the molecular weight, M
n / Mw = 3400/7200.

Example 5 Propylene glycol alginate (commercially available product C)
5.0 g was dissolved in 45 ml of 85% by weight phosphoric acid and allowed to stand at 40 ° C. for 3 days. 100 ml of methanol was added thereto, and the mixture was stirred and allowed to stand for 2 hours. The precipitated solid was filtered, and the solid (filter cake) obtained was washed with neutrality and dried.
Alginate propylene glycol ester decomposition product 1.3
g (26.0% yield). As a result of measuring the molecular weight,
Mn / Mw = 3200/24000.

Example 6 Propylene glycol alginate (commercially available product C)
5.0 g was dissolved in 50 ml of 50% by weight phosphoric acid and allowed to stand at 40 ° C. for 3 days. 100 ml of methanol was added thereto, and the mixture was stirred and allowed to stand for 2 hours. The precipitated solid was filtered, and the solid (filter cake) obtained was washed with neutrality and dried.
3.3 Decomposition of propylene glycol alginate
g (66.0% yield). As a result of measuring the molecular weight,
Mn / Mw = 30000 / 240,000.

COMPARATIVE EXAMPLE 1 5.0 g of alginic acid (commercially available product A) was mixed with 85% by weight of formic acid 45
The resulting solution was dissolved in ml and left at 20 ° C. for 3 days. To this, 100 ml of methanol was added, and the mixture was stirred and left to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality and dried, and then the alginic acid decomposed product was obtained. 3 g (86.0% yield) was obtained. As a result of measuring the molecular weight, Mn / M
w = 4000/9600.

COMPARATIVE EXAMPLE 2 5.0 g of alginic acid (commercial product A) was mixed with 85% by weight of formic acid 45
The mixture was dissolved in ml and left at 40 ° C. for 7 days. After adding 100 ml of distilled water under vigorous stirring and allowing to stand for 2 hours, the precipitated solid is separated by filtration, and the obtained filtrate is added to 1 l of methanol with stirring. Thereafter, the mixture was allowed to stand for 4 hours, and the precipitated solid was filtered to obtain a solid (filtration residue). The solid was washed until it became neutral, and then dried, and 1.0 g of an alginic acid decomposition product (yield: 20.0%) was obtained. I got As a result of measuring the molecular weight, Mn /
Mw = 2000/5000.

Comparative Example 3 5.0 g of alginic acid (commercially available product A) was added to 50% by weight sulfuric acid 45
The resulting solution was dissolved in ml and left at 20 ° C. for 3 days. 100 ml of methanol was added thereto, and the mixture was stirred and allowed to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality, and then dried. 5 g (30.0% yield) was obtained. As a result of measuring the molecular weight, Mn / M
w = 5300/22000. The obtained alginic acid decomposition product was colored brown.

COMPARATIVE EXAMPLE 4 5.0 g of alginic acid (commercial product A) was added to 25% by weight sulfuric acid 45
The mixture was dissolved in ml and left at 40 ° C. for 1 day. 100 ml of methanol was added thereto, and the mixture was stirred and allowed to stand for 2 hours. The precipitated solid was filtered to obtain a solid (filtration residue), which was washed with neutrality, and then dried. 7 g (34.0% yield) was obtained. As a result of measuring the molecular weight, Mn / M
w = 5900/14000. The obtained alginic acid decomposition product was colored brown.

Comparative Example 5 Raw material alginic acid (commercially available product A) (Mn / Mw = 52000)
Comparative Example 6 Ethylenediaminetetraacetic acid / 2Na salt (hereinafter referred to as EDTA / 2
Comparative Example 7 Sodium polyacrylate (Mn / Mw = 3300/820)
0) Comparative Example 8 Alginic acid (commercially available product B) (Mn / Mw = 220,000 /
Comparative Example 9 Propylene glycol alginate (commercially available product C)
(Mn / Mw = 63000/3400000) Evaluation test 1 (Metal ion dispersing power) As a dispersant, an aqueous solution in which the products of Examples 1 to 4 and Comparative examples 1 to 7 were adjusted to an active ingredient of 0.6% by weight was used. To prepare a solution having the following composition,
After treatment at 0 ° C. for 30 minutes, the mixture was rapidly cooled to 30 ° C.
C) Filtration was performed, and the results of evaluation based on the criteria of ○ to × based on the presence or absence of filtration residue are shown in Table 1.

Solution composition Ion-exchanged water 170 ml 4 wt% aqueous sodium hydroxide solution 10 ml 400 ppm iron ion aqueous solution or 2000 ppm calcium ion aqueous solution 10 ml dispersant 10 ml total 200 ml Evaluation criteria ○: Good dispersibility, no filtration residue △ : Slightly poor dispersibility, little filtration residue ×: Poor dispersibility, large amount of filtration residue

[0027]

[Table 1]

It can be seen that the alginic acid hydrolyzate prepared by hydrolysis with phosphoric acid has a metal ion dispersibility equal to or higher than that of a commercially available dispersant. Also, EDTA-2Na
Synthetic dispersing agents (chelating agents) such as polyacrylic acid and polyacrylic acid have low biodegradability, whereas alginic acid decomposed products have good biodegradability. Evaluation Test 2 (Regioselectivity of Hydrolysis) The ¹³ C-NMR of the alginic acid hydrolyzate obtained in Example 1 was measured and the sequence was analyzed. It was found that the content of the GG block was smaller than that of the raw alginic acid. In addition, it was confirmed that the GG block was selectively hydrolyzed in the hydrolysis with phosphoric acid.

Evaluation Test 3 (Measurement of Ash Content of Alginic Acid Decomposition Product) A sample was precisely weighed in a crucible having a constant weight, heated and decomposed at 800 ° C. for 8 hours in an electric furnace, cooled, and the ash content was determined. Write.

[0030]

[Table 2]

The alginic acid decomposed product obtained by purification according to the method of Example 4 contained almost no metal salt. The main component of the ash was calcium. Evaluation Test 4 (Measurement of Viscosity of Alginic Acid Decomposed Product) Decomposed products of Examples 1 to 4 obtained according to the present invention and Comparative Examples 2, 3, 5, and 8
1% by weight of product neutralized with caustic soda
The viscosities of the concentrated aqueous solutions were measured at 30 ° C. for the decomposition products of Examples 5 and 6 and the product of Comparative Example 9, respectively, at 1% by weight aqueous solution. The measurement was performed using a B-type viscometer (Tokyo Keiki Co., Ltd.), and particularly for low viscosity samples, the measurement was performed at 60 rpm using a BL adapter.
Table 3 shows the results.

[0032]

[Table 3]

The decomposition products of the present invention (Examples 1 to 4, 5 and 6) have a very low viscosity as compared with before decomposition (Comparative Examples 5 and 9) and are easily dissolved in water. Met. In particular, the decomposed product of alginic acid obtained in Example 4 contained Ca
Dissolved quickly in water due to low ²⁺ ions.

[0034]

The hydrolysis method of the present invention can be easily carried out in a conventional industrial plant, and is suitable for large-scale production. The hydrolyzate of alginic acid obtained by the hydrolysis method of the present invention retains the function of alginic acid, is easily dissolved in water, and does not exhibit high viscosity even when dissolved in water, so that it is suitably used as a material for pharmaceuticals and the like. can do.

Further, according to the purification method of the present invention, it is possible to obtain an alginic acid decomposed product having extremely low calcium content even from alginic acid having a high calcium content obtained by the calcium method. Further, the hydrolysis method of the present invention,
Since the L-guluronic acid-L-guluronic acid bond in the sugar chain of alginic acid is more selectively hydrolyzed, the alginate oligosaccharide obtained by the present method has a low GG block content,
It has the characteristic that the viscosity is lower than that of the alginic acid oligomer obtained by another method, and it is easy to handle.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mikio Kajiyama 3-30-1 Kitasenzoku, Ota-ku, Tokyo (72) Inventor Akio Takemura 2-17-1-207, Kasuya, Setagaya-ku, Tokyo (72) Inventor Ono 13-5 Onogawa 13-5, Tsukuba, Ibaraki, Japan (72) Inventor Hiroshi Mizumachi B-102, 1-24-18, Sakai, Musashino

Claims (6)

[Claims] 1. A method for hydrolyzing alginic acid or a salt or ester thereof using phosphoric acid. 2. A method for hydrolyzing alginic acid or a salt or ester thereof with phosphoric acid, comprising the steps of:
The method according to claim 1, wherein the hydrolysis is carried out at a temperature of 0 to 60C for 1 hour to 1 month using phosphoric acid at a concentration of% by weight. 3. After hydrolyzing alginic acid or a salt or ester thereof with phosphoric acid, water is added to the obtained hydrolysis mixture to dissolve the decomposition product, and the obtained solution is separated. A method for purifying a decomposition product of alginic acid or a salt or ester thereof, comprising mixing the solution with a hydrophilic organic solvent to precipitate a decomposition product, and separating the precipitate. 4. An alginic acid or a salt or ester thereof is prepared by using phosphoric acid at a concentration of 50 to 90% by weight,
After hydrolysis for 1 hour to 1 month at a temperature of 0 ° C., the obtained hydrolysis mixture is dissolved by adding 0.2 to 100 times the amount of water, and the obtained solution is separated. The purification method according to claim 3, wherein the solution is mixed with a hydrophilic organic solvent to precipitate a decomposed product, and the separated product is separated. 5. A decomposition product obtained by the hydrolysis method according to claim 1 or 2. 6. A decomposition product obtained by the purification method according to claim 3 or 4.