JPS644521B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently and smoothly forming a precipitate from an aqueous solution of a polysaccharide using a hydrophilic organic solvent, thereby increasing the purification and dehydration efficiency of the polysaccharide. Polysaccharides are water-soluble polymers extracted from naturally occurring seeds, seaweed, etc., and their aqueous solutions exhibit high viscosity, unique flow characteristics, and some have gelling ability. Food for a reason,
It has an extremely wide range of uses including cosmetics, paints, civil engineering, and oil drilling. In general, polysaccharides are manufactured in the form of powder, and for example, when polysaccharides contained in the endosperm of seeds include guar gum, locust bean gum, tamarind gum, etc., they are heated or chemically treated to remove the outer skin. After peeling, the germ is removed and a powder is obtained by crushing and sieving. However, the gums produced by this method contain fibers, fats and oils, and proteins resulting from residual germ, and have the drawback that the aqueous solutions of these gums have poor transparency, and are usually called crude products. In order to improve these drawbacks, these gum powders are purified by dissolving them in water or hot water, filtering them, and then precipitating them with a hydrophilic organic solvent. On the other hand, polysaccharides that exist between cells in seaweed include carrageenan, furcerelan, agar aldinate, etc. To make polysaccharides from these, the raw material seaweed is extracted with hot water, and after filtration, hydrophilic A method of precipitating with an organic solvent, dehydrating and purifying, and then drying and pulverizing is adopted. Furthermore, polysaccharides such as xanthan gum, which are produced by the fermentation action of microorganisms, are known, and their production involves centrifugation and removal of bacterial cells from an intermediate product obtained as a dilute aqueous solution of the gum by the fermentation action of the Xanthomonas campestrifus bacterium. Later, a method of precipitation using a hydrophilic organic solvent was adopted. As is clear from the above description, in the production or purification of polysaccharides, a common step is to precipitate an aqueous solution with a hydrophilic organic solvent, and the concentration of the aqueous solution is extremely low, 0.1 to 3%. However, it goes without saying that efficient purification, dehydration, and smooth formation of gum precipitate are very important for their production. Although this process is in principle an extremely simple method in which polysaccharides are precipitated by adding a poor solvent to a solution of a good solvent, industrially, the uniformity of the precipitation is the key to the efficiency of its purification and dehydration effects. It is important to determine this and how to create a precipitate that satisfies this. Furthermore, the produced precipitates may adhere to each other, form lumps, or accumulate on the parts of the mixer, making it impossible to proceed smoothly with the process. The reason for this is the rapid change in the solvent composition of the polysaccharide aqueous solution. The present invention provides a method for smoothly and continuously producing homogeneous precipitates. The key point is to add in advance 50 to 80% of the amount of hydrophilic organic solvent required to precipitate the polysaccharide to be precipitated, stir well and mix, and completely dissolve in the mixed solvent of water and hydrophilic organic solvent. After that, the remaining hydrophilic organic solvent is added to form a precipitate, which not only makes it possible to obtain an extremely homogeneous and highly purified dehydrated polysaccharide, but also avoids the above-mentioned troubles. The two-stage addition of the solvent can very easily be made into a continuous process by using two mixers arranged in series. In the first step, 50 to 80% of the amount of hydrophilic organic solvent required to precipitate the polysaccharide is added to the polysaccharide aqueous solution stirred under high shear conditions, so the polysaccharide is rapidly dissolved without precipitation. Since a solution of the polysaccharide in a hydrophilic organic solvent and water is formed in the step, inconveniences such as the formation of lumps due to the heterogeneity of the system due to the subsequent addition of a water-soluble organic solvent can be avoided. be. Next, in the second step, while stirring the solution, the amount of hydrophilic organic solvent required for precipitation of the polysaccharide is added to the solution. At this stage, the polysaccharide forms a precipitate for the first time, but since the solvent composition changes extremely slowly, the polysaccharide precipitates very uniformly. In other words, if the solvent composition changes rapidly, a polysaccharide film will be firmly formed at the boundary between the added hydrophilic organic solvent and the polysaccharide aqueous solution, thereby inhibiting further mixing of the two. In this case,
Not only does dehydration not proceed, but the removal of polysaccharide impurities contained in the aqueous solution is hindered, and no purification effect can be expected. Moreover, it becomes a string-like precipitate, which tends to adhere to each other or stick to the inside of the mixer. On the other hand, in the method of the present invention, the solvent composition changes slowly, and all of the above-mentioned problems are solved. In the method of the present invention, the amount of hydrophilic organic solvent mixed in the first step is set to 50 to 80% of the amount of solvent to precipitate polysaccharides. On the other hand, if too much of the hydrophilic organic solvent is mixed beyond this range, the concentration change of the hydrophilic organic solvent in the subsequent second stage of mixing will be too large, and the features of the present invention will not be realized. The features of the method will not be realized. As the solvent used in carrying out the present invention, any water-soluble solvent can be used, such as alcohols such as methanol, ethanol, and isopropanol, ethers such as methyl ether and ethyl ether, dioxane, acetone, Examples include tetrahydrofuran. The present invention will be specifically described below according to Example 1. Example 1 Euchyuma spinosum was extracted with hot water and then filtered.
A carrageenan aqueous solution with a concentration of 1.9 was obtained. A 100 parts of the aqueous solution and 150 parts of isopropyl alcohol
The components were mixed using a rotary blade stirrer to obtain carrageenan precipitate. (Sample (A)) B When 100 parts of the aqueous solution was mixed with 80 parts of the 150 parts of isopropyl alcohol necessary for the precipitation of carrageenan using a rotary blade stirrer, no precipitate was formed and a solution state was observed. . The remaining 70 parts of isopropyl alcohol was further added to this solution and mixed in the same manner, resulting in carrageenan precipitate. (Sample (B)) Sample (A) contained the same amount of water as before mixing with isopropyl alcohol inside the precipitate, and a large amount of water that had not been dehydrated and purified was present. In addition, a large number of coils were observed to be wrapped around the stirring blades. On the other hand, the state of precipitation of sample (B) was uniform, and no wrapping around the stirring blade was observed. Sample (A) obtained as above was subjected to gravitational acceleration of 1500G.
Sample (C) was obtained by centrifugation under the conditions of
was treated in the same manner to obtain sample (D). The results of analyzing each sample are shown in Table 1.

[Table] It can be seen that the method according to the present invention has a large dehydration and purification effect on carrageenan. Example 2 Euchyuma spinosum was extracted and filtered with hot water to obtain an aqueous carrageenan solution with a concentration of 1.97%. A: The aqueous solution was continuously fed to a rotary blade stirrer at a rate of 10/min and isopropyl alcohol necessary for precipitation of carrageenan was continuously fed at a rate of 15/min, and at the same time, the aqueous solution was continuously discharged at a rate of 25/min. Although carginan was precipitated, Example 1
Similar to sample (A), the precipitate was non-uniform and the entanglement of the precipitate around the stirring blades was very noticeable. B Two rotary blade stirrers are arranged separately, and the first stage stirrer supplies the aqueous solution at a rate of 10/min and isopropyl alcohol at a rate of 8/min.
/min. The liquid discharged from the first-stage stirrer was immediately sent to the second-stage stirrer, where isopropyl alcohol was supplied and mixed at a rate of 7 min. The carrageenan was not substantially precipitated in the first stage stirrer and was sent in a solution state to the second stage stirrer. The carrageenan was precipitated in the second-stage stirrer, and the state of the precipitation was extremely uniform, and no coiling or adhesion to the stirring blades or the like was observed at all. Example 3 Crude locust bean gum was dissolved in hot water and filtered to obtain an aqueous solution with a concentration of 0.87%. A: The aqueous solution was continuously fed to a rotary blade stirrer at a rate of 10/min, and isopropyl alcohol was continuously fed at a rate of 7.5/min, and simultaneously discharged at a rate of 17.5/min. The effluent contained locust bean gum precipitate. In addition, a large amount of precipitate was found to be wrapped around and attached to the blades in the stirrer. The precipitate in the effluent was centrifuged under conditions of gravitational acceleration of 1500G. (Sample (E)) B Two rotary blade stirrers are arranged in series, and the first stage stirrer supplies the aqueous solution at a rate of 10/min and isopropyl alcohol at a rate of 4/min.
/min. The liquid discharged from the first-stage stirrer was immediately sent to the second-stage stirrer, where isopropyl alcohol was supplied and mixed at a rate of 3.5 min. The locust bean gum was not substantially precipitated in the first stage stirrer and was sent in a solution state to the second stage stirrer. The locust bean gum was uniformly precipitated in the second stage stirrer, and no wrapping or adhesion to the stirring blades was observed at all. The locust bean gum precipitate contained in the liquid discharged from the second stage stirrer was centrifuged under the condition of gravitational acceleration of 1500G. (Sample (F)) The results of chemical analysis of samples (E) and (F) obtained in Example 3 are shown in Table 2.

[Table] It was shown that the method of the present invention is excellent in terms of dehydration effect and purification effect.

Claims (1)

[Claims] 1. In a method for precipitating and purifying and dehydrating polysaccharides from an aqueous polysaccharide solution using a hydrophilic organic solvent, the amount of the hydrophilic organic solvent required for precipitation and separation from the aqueous solution is 50 to 90%. % to form a homogeneous solution, and then the remainder of the hydrophilic organic solvent is added to precipitate the polysaccharide. 2. The method for producing a polysaccharide according to claim 1, wherein the polysaccharide is carrageenan, furceleran, agar, locust bean gum, guar gum, xanthan gum, scleroglucan, or pullulan. 3. The method for producing a polysaccharide according to claim 1, wherein the hydrophilic organic solvent is an alcohol. 4. The method for producing a polysaccharide according to claim 3, wherein the hydrophilic organic solvent is isopropyl alcohol.