CN110872360B - Preparation method of oxidized curdlan - Google Patents
Preparation method of oxidized curdlan Download PDFInfo
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- CN110872360B CN110872360B CN201911147149.1A CN201911147149A CN110872360B CN 110872360 B CN110872360 B CN 110872360B CN 201911147149 A CN201911147149 A CN 201911147149A CN 110872360 B CN110872360 B CN 110872360B
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- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
- C08B37/0024—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Glucans; (beta-1,3)-D-Glucans, e.g. paramylon, coriolan, sclerotan, pachyman, callose, scleroglucan, schizophyllan, laminaran, lentinan or curdlan; (beta-1,6)-D-Glucans, e.g. pustulan; (beta-1,4)-D-Glucans; (beta-1,3)(beta-1,4)-D-Glucans, e.g. lichenan; Derivatives thereof
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Abstract
The invention discloses a preparation method of oxidized curdlan, belonging to the field of biomass materials. The invention adds hydrogen peroxide in batches, strictly controls the oxidation time, and leads-CH in the molecular structure of the curdlan2OH groups are all converted into-COONa or COOH, and no other byproducts are generated. The preparation method has the advantages of high reaction efficiency, mild reaction conditions, simple operation, low price of the used reagent, greenness and no pollution.
Description
Technical Field
The invention belongs to the field of biomass materials, and particularly relates to a preparation method of oxidized curdlan.
Background
Curdlan, also known as thermogel, curdlan, is produced by microbial fermentation, a water-insoluble glucan consisting of beta-1, 3-glycosidic linkages, having a relative molecular weight of about 50 to 200 million. The curdlan belongs to natural biological molecules, has no toxic or side effect and is wide in source. Compared with numerous natural polysaccharides, the polysaccharide has numerous potential advantages in development: 1) the curdlan has very good biodegradability, biocompatibility and biological nontoxicity; 2) can be dissolved in alkaline water, so as to be convenient for the homogeneous reaction; 3) the molecular structure of the material contains a plurality of active-OH which are ideal sites for structural modification.
In recent years, oxidized polysaccharides have received much attention. Such as oxidized regenerated cellulose, oxidized starch, oxidized soybean polysaccharide, etc., can be used as green antibacterial agent. The oxidant for the polysaccharide is periodate, sodium hypochlorite and hydrogen peroxide. Because of the specific molecular structure of curdlan, hydrogen peroxide can only be used as an oxidizing agent to oxidize the curdlan. As the oxidation time increases, not only the hydroxyl group on the primary carbon is oxidized to a carboxyl group, but also the hydroxyl group on the secondary carbon C on the five-membered ring is likely to be oxidized, resulting in a decrease in the strength of the molecule. In addition, the carbon electron cloud density is decreased by the action of the charge absorption property of the carboxyl group, and thus, in an alkaline aqueous solution, a nucleophilic substitution reaction with a hydroxyl group in a water molecule is likely to occur, and a glycoside bond is cleaved.
The existing literature reports that the water-soluble curdlan obtained by hydrolysis with hydrogen peroxide, for example, the Food Chemistry283(2019) 302-304 reports that the product obtained by hydrolysis with hydrogen peroxide contains aldehyde group; the document Food Chemistry 135(2012) 2436-2438 reports that the product obtained after hydrolysis with hydrogen peroxide contains aldehyde groups and carboxyl groups. None of these methods can achieve oxidized curdlan that is fully carboxylated at the 6-position. The current method for obtaining oxidized curdlan with 6-position complete carboxylation is to use sodium hypochlorite as an oxidant, however, chlorine-containing substances released in the process of oxidizing curdlan by sodium hypochlorite can affect the health of operators. Therefore, there is an urgent need to develop an oxidized curdlan which is non-toxic and environmentally friendly and is completely carboxylated at the 6-position by oxidation.
Disclosure of Invention
In order to solve the problems, the invention takes hydrogen peroxide as an oxidant, and the oxidant is green and clean; however, the oxidation efficiency is not very high due to the one-time addition of hydrogen peroxide, and the consumption of hydrogen peroxide is very large, so the invention adopts a specific addition mode and environmental control in a matching manner, and adds hydrogen peroxide in batches, so that the 6-site of the curdlan can be completely carboxylated, and simultaneously, the consumption of hydrogen peroxide is reduced.
The invention adds hydrogen peroxide in batches, strictly controls the oxidation time, and leads-CH in the molecular structure of the curdlan2OH groups are all converted into-COONa or-COOH, and no other byproducts are generated. The preparation method has the advantages of high reaction efficiency, mild reaction conditions, simple operation, low price of the used reagent, greenness and no pollution.
The invention aims to provide a preparation method of oxidized curdlan, which comprises the following steps:
(1) pretreatment: dissolving curdlan in an alkali solution to form a mixed solution; wherein the pH of the alkali solution is 11-13;
(2) and (3) oxidation reaction: adding 30% hydrogen peroxide into the mixed solution obtained in the step (1), and reacting for 0.5-1.5 h; then adding 30% hydrogen peroxide, and reacting for 0.5-1.5 h; wherein the addition amount of 30% hydrogen peroxide to the curdlan is (1-4) mL/g each time;
or adding 30% hydrogen peroxide into the mixed solution obtained in the step (1), reacting for 0.5-1.5, then adding 30% hydrogen peroxide, reacting for 0.5-1.5, and then adding 30% hydrogen peroxide, reacting for 0.5-1 h; wherein the addition amount of 30% hydrogen peroxide to the curdlan is (1-4) mL/g each time;
(3) after the reaction in the step (2) is finished, adjusting the reaction to be neutral by using acid; cooling, performing solid-liquid separation, taking clear liquid, and drying to obtain the oxidized curdlan powder product.
In one embodiment of the invention, the mass concentration of curdlan in the mixed solution in the step (1) is 10-25 mg/mL. Preferably 20 mg/mL.
In one embodiment of the present invention, the alkali solution in the step (1) is 2mol/L NaOH solution or KOH solution.
In one embodiment of the present invention, the pretreatment in step (1) is a treatment at room temperature for 2 to 3 hours.
In one embodiment of the present invention, the temperature of the oxidation reaction in the step (2) is 50 to 60 ℃.
In one embodiment of the invention, the addition amount of 30% hydrogen peroxide to curdlan in step (2) is preferably (1-2) mL/g.
In one embodiment of the present invention, the drying in the step (3) is freeze-drying.
In one embodiment of the present invention, the solid-liquid separation in step (3) is to separate the precipitate and the supernatant by centrifugation.
In one embodiment of the present invention, the acid in the step (3) is 2mol/L hydrochloric acid.
In one embodiment of the present invention, the specific process steps are as follows:
(1) dissolving 1g of curdlan in 50mL of 2mol/L aqueous alkali, and stirring at room temperature for 2-3 h; wherein the alkali can be NaOH or KOH;
(2) preheating the solution obtained in the step (1) to 50-60 ℃, adding 2mL of 30% hydrogen peroxide, stirring, mixing, reacting for one hour, then adding 2mL, and reacting for 1 hour; or adding 2ml of hydrogen peroxide, stirring and reacting for 1 hour, then adding 1ml of hydrogen peroxide, reacting for 1 hour, and then adding 1ml of hydrogen peroxide to react for half an hour;
(3) adjusting the solution obtained in the step (2) to be neutral by acid; then cooling to room temperature, and filtering the supernatant by using a centrifugal machine; freeze drying the supernatant to obtain oxidized curdlan powder product.
In one embodiment of the present invention, the molecular structure of the oxidized curdlan is as follows:
wherein R ═ COONa or COOH.
The invention has the beneficial effects that:
the oxidized curdlan is prepared by adopting a specific hydrogen peroxide oxidative decomposition method, so that carboxyl groups are completely introduced into C-6 in a molecular structure, the selectivity of the C-6 carboxylated curdlan can reach 100%, other oxidation byproducts are not generated, and the yield is high and can reach more than 89%. The obtained oxidized curdlan has good water solubility and excellent bacteriostatic effect, and can be used in daily chemicals and food industry.
Drawings
FIG. 1 is an infrared spectrum of curdlan compared with oxidized curdlan obtained in example 1.
Detailed Description
Example 1:
(1) dissolving 1g of curdlan in 50mL of 2mol/L NaOH solution, and stirring at room temperature for 2h to obtain a curdlan aqueous solution A;
(2) heating the solution A to 60 ℃, adding 2ml of hydrogen peroxide, stirring and reacting for 1 hour, and then adding 2ml of hydrogen peroxide to react for 1 hour;
(3) adjusting the pH value of the solution obtained in the step (2) to 7 by using 2mol/L hydrochloric acid;
(4) and (4) cooling the solution obtained in the step (3) to room temperature, filtering the solution by using a centrifugal machine to obtain supernatant, and freeze-drying the supernatant to obtain 0.98g of curdlan oxide powder product. (yield: 90%)
As can be seen from FIG. 1, the distance is 3360cm-1A very wide absorption peak is arranged nearby and corresponds to the stretching vibration of a large number of-OH on the curdlan main chain. At 2875 and 2921cm-1The absorption peak corresponds to-CH2The CH symmetric stretching vibration group. The oxidized curdlan prepared by the invention is prepared at 2875-2921cm-1Disappearance of the peak indicating-CH2OH groups are all converted to-COOH, 1579cm-1At 1405cm-1A new characteristic absorption peak appears, corresponding to the characteristic peak of the carboxylate, 1685cm-1The vicinity is the characteristic peak of aldehyde group, and the absence of the characteristic peak in figure 1 indicates that no aldehyde group exists in the product, which indicates that the completely carboxylated oxidized curdlan is successfully synthesized. The other characteristic absorption peaks are not changed, which indicates that the preparation method of the invention does not destroy the structure of the curdlan and obtains the oxidized curdlan product with completely carboxylated C6-position.
Example 2:
(1) dissolving 1g of curdlan in 50mL of 2mol/L NaOH solution, and stirring at room temperature for 3h to obtain a curdlan aqueous solution A;
(2) heating the solution A to 50 ℃, adding 2ml of hydrogen peroxide, stirring and reacting for 1 hour, then adding 1ml of hydrogen peroxide, reacting for one hour, and then adding 1ml of hydrogen peroxide to react for half an hour;
(3) adjusting the pH value of the solution obtained in the step (2) to 7 by using 2mol/L hydrochloric acid;
(4) and (4) cooling the solution obtained in the step (3) to room temperature, filtering the solution by using a centrifugal machine to obtain supernatant, and freeze-drying the supernatant to obtain the curdlan oxide powder product.
The oxidized curdlan powder product is an oxidized curdlan product with complete carboxylation at the C6-position, and the yield is as follows: 91 percent.
Example 3:
(1) dissolving 1g of curdlan in 50mL of 2mol/L NaOH solution, and stirring at room temperature for 2h to obtain a curdlan aqueous solution A;
(2) heating the solution A to 60 ℃, adding 5ml of hydrogen peroxide, stirring and reacting for 1 hour, then adding 5ml of hydrogen peroxide, and continuing to react for one hour;
(3) adjusting the pH value of the solution obtained in the step (2) to 7 by using 2mol/L hydrochloric acid;
(4) and (4) cooling the solution obtained in the step (3) to room temperature, filtering the solution by using a centrifugal machine to obtain supernatant, and freeze-drying the supernatant to obtain the curdlan oxide powder product.
The oxidized curdlan powder product is an oxidized curdlan product with complete carboxylation at the C6-position, and the yield is as follows: 89 percent.
Comparative example 1
Referring to example 1, the addition mode of hydrogen peroxide in step (2) is replaced by adding 5ml of hydrogen peroxide at a time, and other conditions are not changed, so that the curdlan oxide powder product is prepared. As a result, it was found that the oxidation degree of the obtained product was incomplete and the product contained an aldehyde group.
Comparative example 2
Referring to example 1, step (2) was replaced with: heating the solution A to 60 ℃, adding 2ml of hydrogen peroxide, stirring and reacting for 2 hours, then adding 2ml of hydrogen peroxide, reacting for 2 hours, and then adding 1ml of hydrogen peroxide to react for 1 hour; other conditions are unchanged, and the oxidized curdlan powder product is prepared. As a result, the molecular weight of the obtained product is remarkably reduced, and the glucan molecular skeleton of curdlan is destroyed and decomposed.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (32)
1. The preparation method of oxidized curdlan is characterized by comprising the following steps:
(1) pretreatment: dissolving curdlan in an alkali solution to form a mixed solution;
(2) and (3) oxidation reaction: adding 30% hydrogen peroxide into the mixed solution obtained in the step (1), and reacting for 0.5-1.5 h; then adding 30% hydrogen peroxide, and reacting for 0.5-1.5 h; wherein the addition amount of 30% hydrogen peroxide to the curdlan is (1-4) mL/g each time;
or adding 30% hydrogen peroxide into the mixed solution obtained in the step (1), reacting for 0.5-1.5, then adding 30% hydrogen peroxide, reacting for 0.5-1.5, and then adding 30% hydrogen peroxide, reacting for 0.5-1 h; wherein the addition amount of 30% hydrogen peroxide to the curdlan is (1-4) mL/g each time;
(3) after the reaction in the step (2) is finished, adjusting the reaction to be neutral by using acid; cooling, performing solid-liquid separation, taking clear liquid, and drying to obtain the curdlan oxide.
2. The method according to claim 1, wherein the temperature of the oxidation reaction in the step (2) is 50 to 60 ℃.
3. The method according to claim 1, wherein the addition amount of 30% hydrogen peroxide to curdlan in step (2) is (1-2) mL/g.
4. The method according to claim 2, wherein the addition amount of 30% hydrogen peroxide to the curdlan in step (2) is (1-2) mL/g.
5. The method as claimed in any one of claims 1 to 4, wherein the mass concentration of curdlan in the mixed solution in step (1) is 10 to 25 mg/mL.
6. The method according to any one of claims 1 to 4, wherein the pretreatment in step (1) is carried out at room temperature for 2 to 3 hours.
7. The method according to claim 5, wherein the pretreatment in step (1) is a treatment at room temperature for 2-3 h.
8. The method according to any one of claims 1 to 4, wherein the pH of the alkali solution in the step (1) is 11 to 13.
9. The method according to claim 5, wherein the pH of the alkali solution in the step (1) is 11 to 13.
10. The method according to claim 6, wherein the pH of the alkali solution in the step (1) is 11 to 13.
11. The method according to any one of claims 1 to 4, wherein the alkali solution in the step (1) is a 2mol/L NaOH solution or a KOH solution.
12. The method of claim 5, wherein the alkali solution in the step (1) is 2mol/L NaOH solution or KOH solution.
13. The method as claimed in claim 6, wherein the alkali solution in the step (1) is 2mol/L NaOH solution or KOH solution.
14. The method according to claim 8, wherein the alkali solution in the step (1) is 2mol/L NaOH solution or KOH solution.
15. The method according to any one of claims 1 to 4, wherein the drying in step (3) is freeze-drying.
16. The method according to claim 5, wherein the drying in step (3) is freeze-drying.
17. The method according to claim 6, wherein the drying in step (3) is freeze-drying.
18. The method according to claim 8, wherein the drying in step (3) is freeze-drying.
19. The method according to claim 11, wherein the drying in step (3) is freeze-drying.
20. The method according to any one of claims 1 to 4, wherein the solid-liquid separation in step (3) is to obtain a precipitate and a supernatant by centrifugal separation.
21. The method according to claim 5, wherein the solid-liquid separation in step (3) is to obtain the precipitate and the supernatant by centrifugation.
22. The method according to claim 6, wherein the solid-liquid separation in step (3) is to obtain the precipitate and the supernatant by centrifugal separation.
23. The method according to claim 8, wherein the solid-liquid separation in step (3) is to obtain the precipitate and the supernatant by centrifugation.
24. The method according to claim 11, wherein the solid-liquid separation in step (3) is centrifugal separation to obtain the precipitate and the supernatant.
25. The method according to claim 15, wherein the solid-liquid separation in step (3) is centrifugal separation to obtain the precipitate and the supernatant.
26. The method according to any one of claims 1 to 4, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
27. The method according to claim 5, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
28. The method according to claim 6, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
29. The method according to claim 8, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
30. The method according to claim 11, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
31. The method according to claim 15, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
32. The method as claimed in claim 20, wherein the acid in the step (3) is 2mol/L hydrochloric acid.
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