CN109776626B - A kind of method for preventing discoloration of sialic acid aqueous solution - Google Patents

Abstract

The present invention provides a method for preventing discoloration of an aqueous solution of sialic acid. The method includes the following steps: adjusting the pH of the sialic acid aqueous solution to 5.0-12.0. After using the method of the present invention, the treated sialic acid aqueous solution is placed in a low temperature environment, a normal temperature environment or a high temperature environment, and the sialic acid aqueous solution will always remain a colorless solution, and is very stable, at least two years in the normal temperature environment.

Description

A kind of method for preventing discoloration of sialic acid aqueous solution

technical field

The invention relates to the field of industrialized production, and more particularly, to a method for preventing discoloration of an aqueous solution of sialic acid.

Background technique

Sialic acid has the functions of improving intelligence, memory, antibacterial and antivirus, and is widely used in medicine, food and cosmetics. In these application fields, sialic acid samples are often used in the form of aqueous solutions, which requires that the sialic acid aqueous solution samples must be very stable, not only in content, but also in other aspects such as appearance and color. The sialic acid aqueous solution is colorless and transparent, but the sialic acid aqueous solution is unstable. With the extension of time, if the storage conditions are not suitable, the color of the aqueous solution will gradually change from colorless to light yellow, and then gradually deepen. It seriously affects the application of sialic acid.

SUMMARY OF THE INVENTION

In view of the above problems, the first object of the present invention is to provide a method for preventing the discoloration of an aqueous solution of sialic acid, the method comprising the steps of:

The pH of the aqueous sialic acid solution was adjusted to 5.0 to 12.0.

After using the method of the present invention, the treated sialic acid aqueous solution is placed in a low temperature environment, a normal temperature environment or a high temperature environment, and the sialic acid aqueous solution will always remain a colorless solution, and is very stable, at least two years in the normal temperature environment.

In a preferred embodiment of the present invention, the pH of the aqueous sialic acid solution is adjusted to 6.0-8.0.

In a preferred embodiment of the present invention, the sialic acid aqueous solution is prepared by dissolving sialic acid in water; the purity of the sialic acid is 80% to 99%.

In the present invention, the sialic acid is preferably the sialic acid obtained by the extraction method disclosed in CN201811372637.8. Among them, all solutions disclosed in CN201811372637.8 are included in the present invention.

Wherein, preferably, the sialic acid extraction method of the present invention is obtained by adjusting pH, concentrating and purifying, heating and concentrating, and acidifying a sialic acid solution obtained by pretreatment of a sialic acid monomer source; the sialic acid monomer source is: Polysialic acid or bird's nest.

The sialic acid monomer is preferably polysialic acid, and the pretreatment is hydrolysis. The hydrolysis reaction of the polysialic acid further includes: adding an acid to the polysialic acid until the pH of the solution is 1-2, and reacting at a temperature of 80-90° C. for 2-4 hours. Wherein, adopt 50-300nm ceramic membrane to 10-30g/L of polysialic acid fermentation broth filtration treatment, and then use ultrafiltration membrane with specification of 8-12KDa to filter until the solid content of the solution is less than 3 times of the polysialic acid content to obtain the above-mentioned Polysialic acid solution. Wherein, the pH adjustment is preferably as follows: adding sodium hydroxide until the pH of the solution is 5-7 and obtaining a sialic acid salt solution. Concentration and purification specifically include: ultrafiltration treatment and nanofiltration treatment. The ultrafiltration treatment includes: using a 0.5-2KDa ultrafiltration membrane to filter the decolorizing solution to remove the unhydrolyzed polysialic acid. The nanofiltration treatment is as follows: the 200-400Da nanofiltration membrane is used to desalt the sialic acid salt solution, so that the solid content of the sialic acid salt solution is less than 3 times of the sialic acid content. The heating concentration preferably includes: heating and concentrating the nanofiltrate 8-12 times in a vacuum so that the concentration of sodium sialate in the concentrated solution reaches about 200-500 g/L. Acidizing crystallization and drying include: adding an acidic substance to the concentrated solution after heating and concentration until the pH of the solution is 1-2, crystallizing at 0-10 ° C for 5-10 hours to obtain crystals, filtering the crystals, washing, and vacuum drying to obtain saliva acid.

In a preferred embodiment of the present invention, the concentration of the sialic acid aqueous solution is 1% to 20%, preferably 2% to 5%. In a preferred embodiment of the present invention, the pH of the aqueous sialic acid solution is adjusted to 5.0-12.0 using an alkaline solution. Wherein, the alkaline solution is sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.

In the present invention, the pH value of the sialic acid aqueous solution is set to 5.0-12.0, and it is placed in a low temperature or normal temperature environment, and it will not change color for at least 2 years. It will not change color when placed at 60℃ for at least 12 months.

Description of drawings

Fig. 1 is the situation that the sialic acid aqueous solution after the treatment of Experimental Example 1 of the present invention is placed at room temperature for 2 years;

Fig. 2 is the situation that the sialic acid aqueous solution after the treatment of comparative example 1 of the present invention is placed at room temperature for 2 years

Fig. 3 is the situation that the sialic acid aqueous solution after the treatment of Example 2 of the present invention is sealed and placed at 80 ℃;

Fig. 4 is the situation that the sialic acid aqueous solution after the treatment of comparative example 2 of the present invention is sealed and placed at 80 ℃;

Fig. 5 is the situation where the sialic acid aqueous solution treated in Example 3 of the present invention is sealed and placed at 60°C

FIG. 6 shows the situation where the treated sialic acid aqueous solution in Comparative Example 3 of the present invention is sealed and placed at 60°C.

Detailed ways

The specific embodiments of the present invention will be further described in detail below with reference to the examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

The raw material components used in the present invention are all commercially available, and the reagents used in the examples of the present invention are all chemically pure.

The preparation method of sialic acid used in the embodiments of the present invention is the method disclosed in Example 4 in CN201811372637.8, and the details are as follows:

The 25g/L polysialic acid fermentation broth was filtered with a 200nm ceramic membrane, and then filtered with a 11KDa ultrafiltration membrane until the solid content of the solution was less than 3 times the polysialic acid content to obtain a polysialic acid solution. Sulfuric acid was added to the polysialic acid solution until the pH of the solution was 1, and the reaction was carried out at a temperature of 86° C. for 3.0 h to obtain a sialic acid solution. To the sialic acid solution, add activated carbon with a mass ratio of 2% to the sialic acid solution for decolorization to obtain a decolorized solution, add sodium hydroxide to a pH of 5 to obtain a sialic acid salt solution, and use a 1.2KDa ultrafiltration membrane to decolorize the solution. The unhydrolyzed polysialic acid was removed by filtration. A 350Da nanofiltration membrane is used to filter the sialic acid salt solution to obtain a nanofiltrate, so that the solid content in the nanofiltrate is less than 3 times of the sialic acid content. The nanofiltrate was concentrated by vacuum heating, then 33% perchloric acid was added to make the solution pH 2, crystallized at 6° C. for 8 h to obtain crystals, and the crystals were filtered and vacuum dried to obtain sialic acid.

In the present invention, the present invention is described in detail with the sialic acid obtained in Example 4 in CN201811372637.8. The sialic acid obtained in other embodiments disclosed in CN201811372637.8 is consistent with the result of the sialic acid obtained in Example 4. In the present invention I will not repeat them one by one.

The obtained sialic acid was dissolved in water to prepare sialic acid aqueous solutions of different concentrations in the following examples.

Example 1

A 2% sialic acid aqueous solution was prepared, the pH was 2.0, and then the pH value of the sialic acid aqueous solution was adjusted to 7.0 with sodium hydroxide, and the solution was sealed and placed in a normal temperature environment. Placed for 2 years without discoloration.

Example 2

A 5% sialic acid aqueous solution was prepared, the pH was 1.8, the pH value of the sialic acid aqueous solution was adjusted to 8.0 with potassium hydroxide, and the solution was sealed and placed in an environment of 80°C.

Example 3

Adjust the pH value of the N-acetylneuraminic acid aqueous solution to 9.0 with an alkaline substance such as sodium hydroxide or sodium carbonate, and place it in a sealed environment at 60°C.

Comparative Example 1

Comparative Example 1 was the same as Example 1, except that the pH of the aqueous sialic acid solution was not adjusted with sodium hydroxide.

Comparative Example 2

Comparative Example 2 was the same as Example 2, except that potassium hydroxide was not used to adjust the pH of the aqueous sialic acid solution.

Comparative Example 2

Comparative Example 3 was the same as Example 3, except that the pH of the sialic acid aqueous solution was not adjusted with an alkaline substance such as sodium hydroxide or sodium carbonate.

The sialic acid aqueous solution in Example 1 did not change color after being placed for 2 years, as shown in FIG. 1 , while the sialic acid aqueous solution in Comparative Example 1 turned light yellow when it was placed for about 6 months, as shown in FIG. 2 .

The sialic acid aqueous solution in Example 2 was placed for 6 months without discoloration, as shown in Figure 3, while the sialic acid aqueous solution in Comparative Example 2 turned light yellow on the 5th day, and the color gradually deepened thereafter, as shown in Figure 4.

The sialic acid aqueous solution in Example 3 did not change color after being placed for 12 months, as shown in Figure 5, while the sialic acid aqueous solution in Comparative Example 2 turned light yellow on the 15th day, and the color gradually deepened thereafter, as shown in Figure 6.

Finally, the method of the present invention is only a preferred embodiment, and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A method for preventing discoloration of an aqueous sialic acid solution, comprising the steps of:

adjusting the pH value of a sialic acid aqueous solution to 6.0-8.0, wherein the sialic acid aqueous solution is prepared by dissolving sialic acid in water; the sialic acid is at least 80% pure.

2. The method of claim 1, wherein the sialic acid is extracted by adjusting the pH of a sialic acid solution obtained by pretreating a sialic acid monomer source, concentrating and purifying, heating and concentrating, and performing acidification and crystallization; the sialic acid monomer source is polysialic acid or cubilose.

3. The method of claim 2, wherein the source of sialic acid monomers is polysialic acid and the pre-treatment is hydrolysis; the hydrolysis reaction of the polysialic acid comprises the following steps: and adding an acid substance into the polysialic acid until the pH value of the solution is 1-2, and reacting for 2-4 hours at the temperature of 80-90 ℃.

4. The method of claim 1, wherein the aqueous sialic acid solution has a concentration of 1% to 20%.

5. The method of claim 4, wherein the aqueous sialic acid solution has a concentration of 2% to 5%.

6. The method according to any one of claims 1 to 5, wherein the aqueous sialic acid solution is adjusted to a pH of 6.0 to 8.0 using an alkaline reagent; the alkaline reagent is sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.

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