Preparation method for improving deacetylation degree of chitosan and application

Abstract

The invention discloses a preparation method for improving the deacetylation degree of chitosan, which comprises the following steps: step S1, crushing crab shells, cleaning the processed eriocheir sinensis shells, drying at 65 DEG C, grinding the dried crab shells, and sieving with a 100-mesh sieve to prepare crab shell powder; s2, plasma pretreatment: mixing the crab shell powder with distilled water according to the ratio of 1: 20 (w / v), performing pretreatment by adopting atmospheric pressure plasma jet, putting a beaker loaded with a crab shell powder solution into a 180 rpm magnetic stirrer, treating for 60 minutes under the conditions that the power is 750 W and the gas flow is 1.2 L / min, washing to be neutral, and drying at 65 DEG C to obtain the plasma pretreated crab shell powder, the deacetylation degree of chitosan is increased by 4-7% through plasma pretreatment, the product purity is equivalent to that of commercial chitosan, and the production cost is saved; the performance of the chitosan extracted by the method is superior to that of chitosan extracted by a traditional chemical extraction method.

Description

Technical Field

[0001] This invention relates to the field of biomass processing technology, and more specifically, to a method for preparing chitosan with increased deacetylation degree and its application. Background Technology

[0002] Global fisheries processing generates millions of tons of biomass waste annually, with crustacean exoskeletons accounting for a significant proportion (approximately 30%–70%). This biomass waste is rich in chitin, whose natural reserves are second only to cellulose, making it the second largest natural polysaccharide resource on Earth. However, the highly ordered crystal structure formed by strong hydrogen bonds between chitin molecules and its dense supramolecular assembly result in poor solubility and low accessibility to reaction sites, severely restricting its high-value conversion.

[0003] Industrially, a deacetylation process catalyzed by high temperature and concentrated alkali (such as NaOH) is commonly used to convert chitin into its water-soluble derivative, chitosan. The application efficiency of chitosan is highly dependent on its degree of deacetylation (DD). However, industrial-scale chitosan production mainly employs a chemical deacetylation process under high temperature (>100°C) and high-concentration alkaline solution (50% NaOH) conditions. These harsh reaction conditions, while hydrolyzing N-acetamide bonds, may also trigger random breakage of β-(1→4)-glycosidic bonds in the chitin backbone. This leads to a decrease in the degree of polymerization, destruction of the crystal structure, and loss of mechanical properties, thus limiting its application potential in high-end materials.

[0004] To overcome the shortcomings of chemical extraction processes, a series of green alternative technologies (such as microbial fermentation, enzyme catalysis, and ionic liquid / deep eutectic solvent methods) have been developed. While these methods demonstrate advantages in reaction selectivity and mild conditions, they are generally limited by challenges such as low efficiency, long cycle times, and difficulties in reagent recovery, and their stability for large-scale scaling is insufficient. Therefore, within the existing framework of chemical deacetylation technology, achieving greening and efficiency optimization through innovative process enhancement strategies has become a key breakthrough for promoting the upgrading of the chitosan industry. This invention discloses an extraction method that is simple in process, relatively mild in extraction, and yields chitosan products with a higher degree of deacetylation. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing chitosan with improved deacetylation degree, thereby solving the problems of low deacetylation degree, high production cost, and serious pollution associated with traditional chemical methods.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing chitosan with increased deacetylation degree, comprising the following steps:

[0009] Step S1: Crab shell crushing. Wash the processed Chinese mitten crab shells, dry them at 60-65℃, grind the dried crab shells, and pass them through a 100-mesh sieve to make crab shell powder.

[0010] Step S2, plasma pretreatment: Mix crab shell powder with distilled water at a ratio of 1:15 to 1:20 (w / v), and pretreat using atmospheric pressure plasma jet (APPJ). Place the beaker containing the crab shell powder solution on a magnetic stirrer at 180 rpm and treat for 55 to 60 min at a power of 700 to 750 W and a gas flow rate of 1.2 L / min. Wash until neutral and dry at 60 to 65 °C to obtain plasma-pretreated crab shell powder.

[0011] Step S3, demineralization: Mix plasma-pretreated crab shell powder with 2M HCl solution at a ratio of 1:15 to 1:20 (w / v);

[0012] Step S4, protein removal: wash the demineralized solids until neutral.

[0013] Step S5, decolorization: Wash the deproteinized solid material until neutral, add 100 mL of 6% H2O2 solution, and stir in a 60℃ water bath for 1~5 h.

[0014] Step S6, plasma post-treatment: The decolorized solid material is washed until neutral and dried at 65°C to obtain a white solid product, which is crab chitin. The crab chitin is mixed with distilled water at a ratio of 1:20 (w / v) and treated with atmospheric pressure plasma jet (APPJ). The beaker containing the crab chitin solution is placed on a magnetic stirrer at 180 rpm and treated for 55-60 min at a power of 700-750 W and a gas flow rate of 1.2 L / min. After washing until neutral, it is dried at 60-65°C to obtain plasma-treated crab chitin.

[0015] Step 7, deacetylation: Mix plasma-treated crab chitin with 10%~50% NaOH (w / w) solution at a ratio of 1:20 (w / v);

[0016] Step 8, Chitosan preparation: Wash the deacetylated solid material until neutral, dry at 65°C, and the resulting white solid product is crab shell chitosan.

[0017] As a preferred embodiment, the demineralization process in step S3 is as follows: weigh 5 g of plasma-pretreated crab shell powder into a beaker, add 100 mL of HCl solution, and stir in a 60°C water bath for 1-5 h.

[0018] As a preferred embodiment, step 4, the protein removal process, involves adding 100 mL of 1M NaOH solution and stirring in a water bath at 80-120°C for 1-5 hours.

[0019] As a preferred embodiment, in step 7, the ratio of sodium hydroxide to distilled water is 40%~50% (w / v); the temperature range is 100~120℃; and the stirring time is 3~5 h.

[0020] The above preparation method is applied in the deacetylation process of chitosan.

[0021] (III) Beneficial Effects

[0022] Compared with the prior art, the present invention provides a preparation method and application for improving the degree of deacetylation of chitosan, which has the following beneficial effects:

[0023] This invention utilizes atmospheric pressure plasma jet (APPJ) treatment as an auxiliary process for extracting chitosan from crab shells. First, the crab shell powder is pretreated, then demineralized with HCl and deproteinized with NaOH. The resulting chitin product is then subjected to plasma post-treatment, followed by deacetylation with NaOH. Its advantages include: plasma treatment increases the degree of deacetylation of chitosan by 4%–7%, resulting in product purity comparable to commercial chitosan and saving production costs; the chitosan extracted by this invention exhibits superior performance compared to chitosan extracted using traditional chemical extraction methods. Attached Figure Description

[0024] Figure 1 Nuclear magnetic resonance spectroscopy of chitosan extracted from crab shells using traditional chemical methods;

[0025] Figure 2 Viscosity-average molecular weight (Mη, Ubbelohde viscosity method) of crab shell chitosan extracted by traditional chemical methods.

[0026] Figure 3 Nuclear magnetic resonance spectrum of crab shell chitosan extracted by plasma pretreatment;

[0027] Figure 4 Viscosity-average molecular weight (Mη, Ubbelohde viscosity method) of chitosan extracted from crab shells by plasma pretreatment.

[0028] Figure 5 Nuclear magnetic resonance spectrum of crab shell chitosan extracted by plasma post-processing;

[0029] Figure 6Viscosity-average molecular weight (Mη, Ubbelohde viscosity method) of chitosan extracted from crab shells by plasma post-processing. Detailed Implementation

[0030] The present invention will be further described and illustrated below with reference to specific embodiments and the accompanying drawings:

[0031] Example 1

[0032] This invention relates to a method for preparing chitosan with increased degree of deacetylation, comprising the following steps:

[0033] (1) Crab shell crushing: Wash the Chinese mitten crab shells processed in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0034] (2) Demineralization: Mix crab shell powder with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, weigh 5 g of crab shell powder into a beaker, add 100 mL of HCl solution, and stir in a 60℃ water bath for 1 h.

[0035] (3) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1M NaOH solution, and stir in a 95℃ water bath for 1 h.

[0036] (4) Decolorization: Wash the deproteinized solids until neutral, add 100 mL of 6% H2O2 solution, and stir in a 60℃ water bath for 1 h.

[0037] (5) Deacetylation: Wash the decolorized solid material until neutral, dry at 65°C, and the white solid product obtained is crab chitin; mix crab chitin with 50% NaOH (w / w) solution at a ratio of 1:20 (w / v), specifically: weigh 5g of crab chitin into a beaker, add 100 mL of NaOH solution, and stir in an oil bath at 100°C for 3 h.

[0038] (6) Chitosan preparation: Wash the deacetylated solid material until neutral, dry at 65°C, and the resulting white solid product is crab shell chitosan.

[0039] Depend on Figure 1 Nuclear magnetic resonance spectroscopy shows that the degree of deacetylation of chitosan prepared by traditional chemical extraction method is 67%.

[0040] Depend on Figure 2 It can be seen that the viscosity-average molecular weight of chitosan prepared by traditional chemical extraction method is 5.19 × 10⁻⁶. 5 g / mol.

[0041] Example 2

[0042] This invention relates to a method for preparing chitosan with increased degree of deacetylation, comprising the following steps:

[0043] (1) Crab shell crushing: Wash the Chinese mitten crab shells processed in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0044] (2) Plasma pretreatment: Crab shell powder and distilled water were mixed at a ratio of 1:20 (w / v) and pretreated using plasma jet (APPJ). Specifically, the beaker containing the crab shell powder solution was placed on a magnetic stirrer at 180 rpm and treated for 60 min at a power of 750W and a gas flow rate of 1.2 L / min. The mixture was then washed until neutral and dried at 65℃ to obtain plasma-pretreated crab shell powder.

[0045] (3) Demineralization: The plasma-pretreated crab shell powder was mixed with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, 5 g of plasma-pretreated crab shell powder was weighed into a beaker, 100 mL of HCl solution was added, and the mixture was stirred in a water bath at 60°C for 1 h.

[0046] (4) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1M NaOH solution, and stir in a 95℃ water bath for 1 h.

[0047] (5) Decolorization: Wash the deproteinized solids until neutral, add 100 mL of 6% H2O2 solution, and stir in a 60℃ water bath for 1 h.

[0048] (6) Deacetylation: Wash the decolorized solid material until neutral, dry at 65°C, and the white solid product obtained is crab chitin; mix crab chitin with 50% NaOH (w / w) solution at a ratio of 1:20 (w / v), specifically: weigh 5g of crab chitin into a beaker, add 100 mL of NaOH solution, and stir in an oil bath at 100°C for 3 h.

[0049] (7) Chitosan preparation: Wash the deacetylated solid material until neutral, dry at 65°C, and the resulting white solid product is crab shell chitosan.

[0050] Depend on Figure 3 Nuclear magnetic resonance spectroscopy showed that the degree of deacetylation of the chitosan extracted by plasma pretreatment was 71%.

[0051] Depend on Figure 4 It can be seen that the viscosity-average molecular weight of chitosan extracted by plasma pretreatment is 4.80 × 10⁻⁶. 5 g / mol.

[0052] Example 3

[0053] This invention relates to a method for preparing chitosan with increased degree of deacetylation, comprising the following steps:

[0054] (1) Crab shell crushing: Wash the Chinese mitten crab shells processed in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0055] (2) Plasma pretreatment: The crab shell powder and distilled water were mixed at a ratio of 1:20 (w / v) and pretreated using plasma jet (APPJ). Specifically, the beaker containing the crab shell powder solution was placed on a magnetic stirrer at 180 rpm and treated for 60 min at a power of 750W and a gas flow rate of 1.2 L / min. The mixture was then washed until neutral and dried at 65℃ to obtain plasma-pretreated crab shell powder.

[0056] (3) Demineralization: The plasma-pretreated crab shell powder was mixed with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, 5 g of plasma-pretreated crab shell powder was weighed into a beaker, 100 mL of HCl solution was added, and the mixture was stirred in a water bath at 60°C for 1 h.

[0057] (4) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1M NaOH solution, and stir in a 95℃ water bath for 1 h.

[0058] (5) Decolorization: Wash the deproteinized solids until neutral, add 100 mL of 6% H2O2 solution, and stir in a 60℃ water bath for 1 h.

[0059] (6) Plasma post-treatment: The decolorized solid material was washed until neutral and dried at 65°C. The resulting white solid product was crab chitin. The crab chitin was mixed with distilled water at a ratio of 1:20 (w / v) and treated with plasma jet (APPJ). Specifically, the beaker containing the crab chitin solution was placed on a magnetic stirrer at 180 rpm and treated for 60 min at a power of 750 W and a gas flow rate of 1.2 L / min. The mixture was washed until neutral and dried at 65°C to obtain plasma-treated crab chitin.

[0060] (7) Deacetylation: The plasma-treated crab chitin was mixed with 50% NaOH (w / w) solution at a ratio of 1:20 (w / v). Specifically, 5 g of crab chitin was weighed into a beaker, 100 mL of NaOH solution was added, and the mixture was stirred in an oil bath at 100°C for 3 h.

[0061] (8) Chitosan preparation: Wash the deacetylated solid material until neutral, dry at 65°C, and the resulting white solid product is crab shell chitosan.

[0062] Depend on Figure 5 Nuclear magnetic resonance spectroscopy showed that the degree of deacetylation of chitosan extracted by plasma post-processing was 74%.

[0063] Depend on Figure 6 It can be seen that the viscosity-average molecular weight of chitosan extracted by plasma post-processing is 4.76 × 10⁻⁶. 5 g / mol.

[0064] Chitosan prepared by traditional chemical extraction method has a degree of deacetylation of 67% and a viscosity-average molecular weight of 5.19 × 10⁻⁶. 5 g / mol;

[0065] The degree of deacetylation of chitosan extracted by plasma pretreatment was 71%, and the viscosity-average molecular weight was 4.80 × 10⁻⁶. 5 g / mol;

[0066] The degree of deacetylation of chitosan extracted by plasma post-treatment was 74%, and the viscosity-average molecular weight was 4.76 × 10⁻⁶. 5 g / mol.

[0067] High-energy particles in plasma can directionally bombard the hydrogen bond network between chitin molecules, causing controlled dissociation in the crystalline region. This change in microstructure makes subsequent alkaline treatment reagents more easily penetrate, increasing the acetylamino group removal efficiency by 4%–7%. Simultaneously, the active particles in the plasma preferentially act on the amorphous regions of chitin, inducing local depolymerization of the polymer backbone, resulting in a decrease in molecular weight from 5.19 × 10⁻⁶. 5 g / mol decreased to 4.76 × 10 5 g / mol. Plasma technology enables precise control of material structural parameters, expanding the application potential of chitosan in multiple fields. In tissue engineering, increased deacetylation enhances the interaction between the material and cell receptors; in functional packaging materials, lower molecular weight chitosan helps form denser barrier coatings.

[0068] The present invention relates to a method for improving the degree of deacetylation of chitosan, which increases the degree of deacetylation by 4% to 7% during the extraction of chitosan from crab shells. The process is simple, green and environmentally friendly, and the chitosan produced has better performance than chitosan prepared by traditional chemical extraction methods.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for increasing the degree of deacetylation of chitosan, characterized by, The method comprises the following steps: Step S1, crushing crab shells, washing the processed Chinese mitten crab shells, drying at 60-65°C, grinding the dried crab shells, and passing through a 100-mesh sieve to obtain crab shell powder; Step S2, plasma pretreatment, mixing the crab shell powder with distilled water at a ratio of 1:15-1:20 (w / v), pretreating the mixture by atmospheric pressure plasma jet (APPJ), placing the beaker containing the crab shell powder solution on a 180 rpm magnetic stirrer, and treating the mixture at a power of 700-750 W and a gas flow of 1.2 L / min for 55-60 min, washing the mixture to neutral, and drying the mixture at 60-65°C to obtain plasma pretreated crab shell powder; Step S3, demineralization, mixing the plasma pretreated crab shell powder with a 2M HCl solution at a ratio of 1:15-1:20 (w / v); Step S4, deproteinization, washing the demineralized solid material to neutral; Step S5, decolorization, washing the deproteinized solid material to neutral, adding 100 mL of a 6% H2O2 solution, and stirring the mixture in a 60°C water bath for 1-5 h; Step S6, plasma post-treatment, washing the decolorized solid material to neutral, drying the mixture at 65°C, and obtaining white solid product, which is crab shell chitin; mixing the crab shell chitin with distilled water at a ratio of 1:20 (w / v), treating the mixture by atmospheric pressure plasma jet (APPJ), placing the beaker containing the crab shell chitin solution on a 180 rpm magnetic stirrer, and treating the mixture at a power of 700-750 W and a gas flow of 1.2 L / min for 55-60 min, washing the mixture to neutral, and drying the mixture at 60-65°C to obtain plasma-treated crab shell chitin; Step 7, deacetylation, mixing the plasma-treated crab shell chitin with a 10%-50% NaOH (w / w) solution at a ratio of 1:20 (w / v); Step 8, chitosan preparation, washing the deacetylated solid material to neutral, and drying the mixture at 65°C to obtain white solid product, which is crab shell chitosan.

2. The method for increasing the degree of deacetylation of chitosan according to claim 1, characterized in that In the demineralization process of step S3, 5 g of plasma pretreated crab shell powder is placed in a beaker, 100 mL of an HCl solution is added, and the mixture is stirred in a 60°C water bath for 1-5 h.

3. The method of claim 1, wherein the degree of deacetylation of chitosan is increased. In the deproteinization process of step 4, 100 mL of a 1M NaOH solution is added, and the mixture is stirred in an 80-120°C water bath for 1-5 h.

4. The method of claim 1, wherein the degree of deacetylation of chitosan is increased. In step 7, the ratio of sodium hydroxide to distilled water is 40%-50% (w / v), the temperature range is 100-120°C, and the stirring time is 3-5 h.

5. The method of any one of claims 1-4 for use in the deacetylation of chitosan.

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