JPH0576481B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to the production of acidic polysaccharides from an aqueous solution of acidic polysaccharides obtained by extraction from substances containing acidic polysaccharides or by introducing acidic groups into polysaccharides. This invention relates to a method for recovering polysaccharides.

[Prior Art] Acidic polysaccharides have unique physical properties such as developing high viscosity or gelation when dissolved in water, and are used in a wide range of fields such as foods, textiles, paper manufacturing, cosmetics, and pharmaceuticals.

Polysaccharides, including acidic polysaccharides, are generally recovered from the extraction filtrate obtained by extracting the polysaccharides from raw materials containing the polysaccharides into water using an appropriate method and, if necessary, filtering the extraction residue. Becomes a product. Recovery methods include (1) direct removal of water from the extraction filtrate, such as spray drying, drum drying, and (2) addition of a water-miscible organic solvent to the extraction filtrate to precipitate polysaccharides, followed by separation. (3) A method of adding certain cations to the extraction filtrate to precipitate the polysaccharide, redissolving it with an acid or alkali, precipitating it again with a water-miscible organic solvent, and separating and drying it. (4) There is a method in which polysaccharides are precipitated by adding certain cations to the extraction filtrate, and aluminum is removed by washing with a water-miscible organic solvent containing acid or alkali.

Method (1) is not only economically disadvantageous as it requires a large amount of latent heat to evaporate dozens of times more water than the recovered polysaccharide, but also leaves water-soluble impurities remaining in the polysaccharide. Therefore, it has the disadvantage of low product purity.

Method (2) can solve the drawbacks of method (1) to some extent, but it requires several tens of times more water-miscible organic solvent than the polysaccharide, and it requires a recovery process to recover this organic solvent. This method has the disadvantage that the costs associated with equipment and recovered heat are large.

The polysaccharides that can be applied to method (3) are limited to acidic polysaccharides; however, acidic polysaccharides precipitate with extremely high selectivity, resulting in high quality products; Even if an organic solvent is used in combination, the amount of water-miscible organic solvent used is significantly reduced, so it is also economically advantageous. In particular, aluminum ions are excellent as cations because they are non-toxic.
However, in this method, the acid or alkali used must have a concentration of 1 to 6 normal;
Acidic polysaccharides deteriorate significantly due to such a strongly acidic or strongly alkaline atmosphere. Additionally, a neutralization step is required to obtain the final product. Recovery of acidic polysaccharides for handling strong acids or strong alkalis,
Furthermore, it has the disadvantage that recovery operations for water-miscible organic solvents are difficult, and despite being an excellent method as mentioned above, it has only been put into practical use in very few cases. be.

Method (4) has the same advantages as (3), and also has the advantage of dissolving and
It is excellent in that acidic polysaccharides can be solubilized simply by washing without reprecipitation, but as in (3), it is necessary that the acid or alkali used be at a concentration of 1 to 6N. However, acidic polysaccharides deteriorate significantly due to such a strongly acidic or strongly alkaline atmosphere. Additionally, a neutralization step is required to obtain the final product. There is a drawback that recovery of acidic polysaccharides and further recovery of water-miscible organic solvents becomes difficult due to the handling of strong acids or strong alkalis.

[Object of the invention] In view of the current situation, the above method using aluminum
The object of the present invention is to provide a method for recovering polysaccharides which is superior in quality and economy by eliminating the drawbacks while retaining the advantages of the recovery method (3).

[Structure of the Invention] That is, the gist of the present invention is to add a water-soluble aluminum salt to an aqueous solution of an acidic polysaccharide, and then convert the precipitate formed by using one or more aluminum solubilizing reagents selected from polyphosphates, hydroxypolycarboxylic acids, or salts thereof. A method for recovering an acidic polysaccharide, which comprises redissolving the acidic polysaccharide in an aqueous solution containing the acidic polysaccharide, and then adding a water-miscible organic solvent to precipitate the acidic polysaccharide.

That is, the present invention has the following features: (1) When an aluminum solubilizing reagent is added to a dispersion of aluminum hydroxide precipitates formed when an aqueous solution containing aluminum ions is adjusted to pH 4 to 11, aluminum hydroxide precipitates are dissolved regardless of the pH range. (2) We discovered that when an aqueous solution of an aluminum solubilizing reagent is added to an acidic polysaccharide precipitated with aluminum ions, the acidic polysaccharide precipitate dissolves. This method is applied to a method for recovering acidic polysaccharides, which involves washing the precipitate formed by adding the acidic polysaccharide.

The acidic polysaccharide used in the present invention is a polysaccharide containing an acidic group in its chemical structure,
Examples of acidic groups include carboxyl groups, sulfate groups, and phosphoric acid groups. In the present invention, acidic polysaccharides include agar, furcerelan, carrageenan, sodium alginate, pectin, gum arabic, xanthan gum, and chondroitin sulfate.
Mucopolysaccharides such as heparin, and polysaccharides into which acidic groups have been chemically introduced, such as carboxymethylated cellulose, carboxymethylated starch, carboxymethylated guar, sulfated cellulose, sulfated starch, sulfated agar, and phosphorus. Examples include oxidized cellulose and phosphorylated starch.

As the water-soluble aluminum salt used in the present invention, aluminum chloride, aluminum sulfate, or aluminum potassium sulfate is used.
Moreover, the aluminum solubilizing reagent means a reagent that does not precipitate aluminum ions as aluminum oxide in any pH range. In other words, aluminum ions become aluminum oxide and precipitate in the neutral pH range of 4 to 11, but it refers to a reagent that prevents this from precipitating. Such reagents include polyphosphates, hydroxypolycarboxylic acids, or salts thereof. Examples of polyphosphates include water-soluble salts of hexametaphosphoric acid, tetrametaphosphoric acid, and pyrophosphoric acid, such as sodium salts and potassium salts. Alternatively, as the hydroxypolycarboxylic acid or its salt, citric acid, tartaric acid, malic acid, or a water-soluble salt thereof such as sodium salt or potassium salt can be used. As the aluminum solubilizing reagent, two or more of these can also be used in combination. The concentration of the reagent in the aluminum solubilizing reagent aqueous solution is often 0.5 to 30% by weight; polysaccharides are not sufficiently dissolved at concentrations lower than this range, and even if the concentration exceeds 30% by weight, there is no improvement in the effect. It is difficult to see, and it is economically disadvantageous. The amount of the aqueous reagent solution added to the acidic polysaccharide precipitated with aluminum is at least 1 times the amount per 1 part by weight of the acidic polysaccharide, but there is no improvement in the effect even if it is added at least 5 times the amount.

The water-miscible organic solvent used in the present invention may include methanol, ethanol, isopropanol, acetone, tetrahydrofuran, or a combination thereof. The amount of water-miscible organic solvent used is 10 to 300% of the amount of the aluminum solubilizing reagent aqueous solution used, but it is preferably as small as possible. If it is less than 10%, the reprecipitation effect is poor, and if it is used more than 300%, it will only be economically disadvantageous.

The stable PH range of acidic polysaccharides differs depending on the type, but in the method of the present invention, the pH of the aqueous solution when redissolving the acidic polysaccharides precipitated with aluminum can be set completely arbitrarily. The solubilization effect of is not affected by pH, and a subsequent neutralization step is required, so it has the characteristic of being able to prevent deterioration of acidic polysaccharides.

[Examples] The present invention will be described in more detail below with reference to Examples.

In the Examples, the viscosity was measured using a B-type viscometer at 30 rpm, and the breaking strength of the gel was measured using a Neocard meter.

Example 1 Add 2000 parts of water to 100 parts of Yukiyuma cotoni
60 parts of aluminum chloride hexahydrate was added to 2,050 parts of Katupa carrageenan solution obtained by heating and extraction at 95°C and filtration to obtain 170 parts of carrageenan precipitate. 10 parts of this was added to 20 parts of an 8% aqueous solution of dipotassium citrate adjusted to pH 8, stirred to re-dissolve the carrageenan, and then 20 parts of isopropanol was added to precipitate, which was repeated three times. After drying, 2.82 parts of Katupa carrageenan was obtained. The aluminum content of the carrageenan is 420 ppm,
The viscosity of its 1.5% aqueous solution was 115 centipoise at 75°C. In addition, the breaking strength of the gel is 430g/
It was warm in ^cm2 .

Comparative Example 1 Using 10 parts of the carrageenan precipitate obtained in Example 1, this was redissolved in 20 parts of a 2N hydrochloric acid aqueous solution, and then 20 parts of isopropanol was added to precipitate it.
The mixture was further neutralized with a 1% caustic potash aqueous solution and dried to obtain 2.65 parts of Katupa carrageenan. The aluminum content of the carrageenan was 1200 ppm, the viscosity of its 1.5% aqueous solution was 2 centipoise at 75°C, and the breaking strength of the gel was 23 g/cm ² .

Example 2 5000 parts of water and 1 part of caustic soda were added to 100 parts of Laminaria digitata, extracted by heating at 80°C, and filtered to obtain 5080 parts of a sodium alginate aqueous solution. 55 parts of aluminum chloride hexahydrate was added to the solution to obtain 185 parts of precipitate. This whole amount was redissolved in 370 parts of a 10% aqueous solution of disodium citrate adjusted to pH 7, and 230 parts of isopropanol was added thereto, and the resulting precipitate was dried to obtain 39 parts of sodium alginate. The sodium alginate contained 390 ppm aluminum.

Example 3 350 g of dried squeezed fruit peel of a summer mandarin orange was stirred in 0.02 N aqueous hydrochloric acid solution 4 at room temperature for 30 minutes. After repeating this operation twice, the washed pericarp was placed in 80°C of water, adjusted to pH 2.0 with hydrochloric acid, and stirred at 90°C for 30 minutes to extract pectin. Next, the undissolved residue was separated using gauze, and 0.5% diatomaceous earth filter aid was added to and mixed with the separated liquid, followed by precision filtration. 0.5% aluminum chloride hexahydrate was dissolved and added to the obtained clear filtrate to obtain 500 g of precipitate. 500 ml of a 15% aqueous solution of sodium hexametaphosphate was added to the precipitate, the pH was adjusted to 2.0 with a 1% aqueous hydrochloric acid solution, and the precipitate was redissolved. 1000 ml of isopropanol was added to the solution to precipitate and collect pectin, which was then compressed, dried and ground to obtain 46 g of powdered pectin. The pectin contained 460 ppm aluminum.

Claims (1)

[Scope of Claims] 1. A precipitate formed by adding a water-soluble aluminum salt to an aqueous solution of an acidic polysaccharide, 1 selected from polyphosphates, hydroxypolycarboxylic acids, or salts thereof.
A method for recovering an acidic polysaccharide, which comprises redissolving the acidic polysaccharide in an aqueous solution containing at least one aluminum solubilizing reagent, and then adding a water-miscible organic solvent to precipitate the acidic polysaccharide. 2. The method for recovering polysaccharides according to claim 1, wherein the polyphosphate is a water-soluble salt of an acid selected from the group consisting of hexametaphosphoric acid, tetrametaphosphoric acid, and pyrophosphoric acid. 3. Recovery of the acidic polysaccharide according to claim 1, wherein the hydroxypolycarboxylic acid or its salt is a sodium salt or potassium salt of an acid selected from the group consisting of citric acid, tartaric acid, and malic acid. Method. 4. The method for recovering acidic polysaccharides according to claim 1, wherein the water-miscible organic solvent is methanol, ethanol, isopropanol, acetone, or tetrahydrofuran.