CN115141291A - Method for extracting chitosan from snow crab shells - Google Patents
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- 229920001661 Chitosan Polymers 0.000 title claims abstract description 69
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- 239000000463 material Substances 0.000 claims abstract description 47
- 229920002101 Chitin Polymers 0.000 claims abstract description 39
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- 238000003381 deacetylation reaction Methods 0.000 claims abstract description 17
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- 238000002844 melting Methods 0.000 claims abstract description 12
- 230000008018 melting Effects 0.000 claims abstract description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 93
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- 239000008236 heating water Substances 0.000 claims description 8
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- 150000001412 amines Chemical class 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 3
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- 239000002253 acid Substances 0.000 claims description 2
- 239000003929 acidic solution Substances 0.000 claims description 2
- CBMPTFJVXNIWHP-UHFFFAOYSA-L disodium;hydrogen phosphate;2-hydroxypropane-1,2,3-tricarboxylic acid Chemical compound [Na+].[Na+].OP([O-])([O-])=O.OC(=O)CC(O)(C(O)=O)CC(O)=O CBMPTFJVXNIWHP-UHFFFAOYSA-L 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 9
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- 238000002360 preparation method Methods 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
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- ZPWVASYFFYYZEW-UHFFFAOYSA-L dipotassium hydrogen phosphate Chemical compound [K+].[K+].OP([O-])([O-])=O ZPWVASYFFYYZEW-UHFFFAOYSA-L 0.000 description 1
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- WZZVUHWLNMNWLW-UHFFFAOYSA-N n-[5-[3-acetamido-5-[3-acetamido-4,5-dihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy-4-hydroxy-6-(hydroxymethyl)oxan-2-yl]oxy-2,4-dihydroxy-6-(hydroxymethyl)oxan-3-yl]acetamide Chemical compound OC1C(NC(=O)C)C(O)OC(CO)C1OC1C(NC(C)=O)C(O)C(OC2C(C(O)C(O)C(CO)O2)NC(C)=O)C(CO)O1 WZZVUHWLNMNWLW-UHFFFAOYSA-N 0.000 description 1
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- FYKDNWHPKQOZOT-UHFFFAOYSA-M sodium;dihydrogen phosphate;2-hydroxypropane-1,2,3-tricarboxylic acid Chemical compound [Na+].OP(O)([O-])=O.OC(=O)CC(O)(C(O)=O)CC(O)=O FYKDNWHPKQOZOT-UHFFFAOYSA-M 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- 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
- C08B37/0027—2-Acetamido-2-deoxy-beta-glucans; Derivatives thereof
- C08B37/003—Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0003—General processes for their isolation or fractionation, e.g. purification or extraction from biomass
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- Chemical Kinetics & Catalysis (AREA)
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Abstract
The invention relates to a method for extracting chitosan from snow crab shells. The invention relates to the steps of the pretreatment, decalcification reaction, deproteinization, deacetylation, acidolysis melting and the like of the shell of the snow crab, and the invention performs acidolysis and deproteinization treatment on chitin in the shell of the snow crab, thereby reducing the dosage of alkali, having mild reaction conditions, good flocculation effect, more than 99% of chitin conversion rate and more than 95% of product yield. The reaction conditions of the invention are mild, the integrity of chitosan molecules can be ensured below 100 ℃, and the viscosity of the chitosan molecules is above 500mPaS when the chitosan molecules are dissolved to form 1% solution. The chemical materials can be recycled, and the generated waste water, waste gas and waste liquid are less, so that the method is suitable for further industrial mass production.
Description
Technical Field
The invention relates to a method for preparing chitosan, in particular to a method for extracting chitosan from snow crab shells.
Background
Chitin (Chitin) is the second largest natural macromolecule widely existing in shells of shrimps, crabs and insects and cell walls of algae and fungi, with annual output inferior to cellulose, estimated to be as high as 100 hundred million tons of biosynthetic resources every year, and is the only natural basic polysaccharide discovered so far, with the chemical name of beta- (1, 4) -2-acetamido-2-deoxy-D-glucose.
Chitosan (Chitsotan) is a deacetylated product of chitin and is a copolymer composed of beta- (1, 4) -2-amino-2-deoxy-beta-D-glucose units and beta- (1, 4) -2-acetamido-2-deoxy-beta-D-glucose units. In general, chitosan is obtained by removing more than 55% of the N-acetyl group of chitin. Because the inner hydrogen bond and the outer hydrogen bond in the chitin molecule are interacted to form an ordered macromolecular structure, the solubility performance is poor, and the application of the chitin molecule in many aspects is limited; the chitosan has greatly improved solubility due to the existence of a large amount of free ammonia in a molecular structure, has unique physicochemical property and physiological function, greatly expands the application field, and is known as the sixth vital element after sugar, protein, lipid, vitamin and mineral substances.
The preparation method of chitosan mostly consumes long time, has high requirements on equipment and generally has low yield. The research on the preparation method of the chitosan with simple process, strong operability, suitability for industrial production, high yield and high purity has obvious economic and social benefits.
The disadvantages of extracting chitosan from shells are: the required treatment time is long, and the deacetylation degree of the obtained chitosan is low; the energy consumption is high, and the viscosity of the chitosan product is low; intermittent operation is not beneficial to continuous production, and large-scale production is limited.
Disclosure of Invention
The invention aims to provide a preparation method capable of continuously and uninterruptedly producing chitosan, in particular to a method for extracting chitosan from snow crab shells, which has simple preparation process, adopts an alkaline reagent containing alcohol, can obviously shorten the time of deproteinization, reduces the requirement on temperature, has the conversion rate of chitin of more than 99 percent and the product yield of more than 95 percent, and solves the problems of low conversion rate and low yield of the prior art.
A method for extracting chitosan from snow crab shells, the method comprising the steps of:
step (1), decalcification reaction: directly putting the shell of the snow crab into a reaction kettle, adding an acid solution, adjusting the pH value, soaking for 1-2 hours, filtering, washing with water for 2-3 times until the shell is neutral, and drying to obtain a product for later use;
step (2), deproteinization: adding alkaline solution I into the reaction kettle until the concentration is 5-15%, heating to 90-110 deg.C, reacting for 1-3 hr with aeration amount of 0.5-1.5m 3 The chitin is washed to be neutral, filtered, naturally dried and the water content is detected to obtain the chitin for later use;
and (3) deacetylation: adding an alkaline reagent II into the reaction kettle in the step (2), soaking for 5-20 hours, heating to 60-70 ℃, preserving heat for reaction for 5-10 hours, filtering, washing with water, filtering, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
acid hydrolysis and melting: putting the chitosan into 30% hydrochloric acid solution, heating the chitosan to 85-110 ℃ by steam, keeping the temperature for reaction for 1-5 hours, and heating the chitosan to a solution state material for later use;
flocculation in step (5): transferring the solution-state material to a flocculation tank, adding an alkaline solution III, reacting for 0.5-2 hours, filtering, and washing for 2-3 times by adding water;
and (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
The alkaline solution I, the alkaline solution II and the alkaline solution III are selected from aqueous solutions of sodium hydroxide and sodium bicarbonate.
The acidic solution in the step (1) is one selected from hydrochloric acid solution, formic acid-sodium formate buffer solution and citric acid-disodium hydrogen phosphate buffer solution, and the pH value is adjusted to 3.0-3.5.
The step (2) is to add sodium hydroxide into the reaction kettle until the concentration is 10 percent, heat the mixture to 100 ℃, keep the temperature for 2 hours, and ensure that the aeration quantity is 1m 3 /min, washing to neutral, filtering, air drying, and detecting water content below 20% to obtain chitin
Calculated by weight-volume ratio, the chitin obtained in the step (3): 50% sodium hydroxide =1, the conversion of chitin is more than 99%, and the product yield is more than 95%.
The step (4) is to put 5kg of the chitosan into a reaction kettle according to the weight-volume ratio, and then add 1m of chitosan 3 Heating water and 30% hydrochloric acid solution 15kg by steam to 95 deg.C, reacting for 2 hr, and heating to obtain solution state material. The method of claim 1, wherein the ratio is calculated as a weight to volume ratioThe material in the solution state is transferred to a flocculation tank, 3kg of 50% sodium hydroxide is added, the reaction time is 1 hour, and after filtration, water is added for washing for 2 times.
Further, the method comprises the following steps:
step (1), decalcification reaction: directly putting the shell of the snow crab into a reaction kettle, adding 30% hydrochloric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing with water for 2 times until the shell is neutral, and drying to obtain a product for later use;
step (2) deproteinization: adding sodium hydroxide into the reaction kettle, adjusting the concentration to 10%, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration amount is 1m 3 The chitin is washed to be neutral, filtered and naturally dried, and the chitin is obtained after the water content is detected to be qualified for later use;
step (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 5-20 hours, heating to 60-70 ℃, keeping the temperature for reaction for 5-10 hours, filtering, washing with water, filtering, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: adding chitin amine into a reaction kettle, and adding 1m 3 Heating the water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under the condition of heat preservation, and heating the solution to obtain a solution material for later use;
and (5) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Compared with the prior art, the method for preparing chitosan by using the snow crab shells as the raw material has the advantages that:
the method carries out acidolysis and deproteinization on the chitin in the shell of the snow crab by two steps of deproteinization and deacetylation, and adopts the mode of alcohol-containing solution for treatment, thereby shortening the process flow, reducing the using amount of alkali, having mild reaction conditions, having the chitin conversion rate of more than 99 percent and the product yield of more than 95 percent.
The reaction conditions of the invention are mild, the integrity of chitosan molecules can be ensured at the temperature of below 100 ℃, and the viscosity of 1% solution formed by dissolving the chitosan molecules is above 500 mPaS.
Drawings
FIG. 1: effect of different flocculants on flocculation Effect
FIG. 2: influence of different flocculants on flocculation effect at different times
FIG. 3: effect of different sodium hydroxide contents on flocculation Effect at different times
FIG. 4: percentage of degree of deacetylation of crustacean in examples of the invention
FIG. 5: conversion of chitin in examples of the invention
FIG. 6: results of viscosity measurements in various embodiments of the invention
Detailed Description
The present invention is not limited to the following embodiments, and based on the technical solutions disclosed in the present invention, a person skilled in the art may make some substitutions and modifications to some technical features without creative efforts based on the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.
Example 1: a method for extracting chitosan from snow crab shells, said method comprising the steps of:
step (1), decalcification reaction: laying 10kg of shell of the snow crab by 5cm-10cm, putting the shell of the snow crab into a reaction kettle, adding 15kg of 30% hydrochloric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing for 2 times by using clear water to be neutral, and drying to obtain a product for later use;
step (2), deproteinization: adding 15kg of sodium hydroxide solution into the reaction kettle, adjusting the concentration to be 10 percent, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration amount is 1m 3 Min, then washing to be neutral, filtering, naturally drying, and detecting the water content to be below 30% to obtain chitin for later use;
and (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 10 hours, heating to 65 ℃, preserving heat, reacting for 8 hours, filtering, washing with water, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Heating water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under heat preservation, and heating to a solution state for later use;
and (5) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) filter pressing: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Example 2: a method for extracting chitosan from snow crab shells, said method comprising the steps of:
step (1), decalcification reaction: laying 10kg of shell of the snow crab in a flat state for 5cm-10cm, putting the shell of the snow crab into a reaction kettle, adding 15kg of 30% hydrochloric acid solution, adjusting the pH value to 3.5, soaking for 1 hour, filtering, washing with water for 3 times until the shell is neutral, and drying to obtain a product for later use;
step (2) deproteinization: adding 15kg of sodium hydroxide solution into the reaction kettle, adjusting the concentration to 10%, heating to 90 ℃, keeping the temperature and reacting for 2 hours, wherein the aeration amount is 0.5m 3 Min, then washing to be neutral, filtering, naturally drying, and detecting the water content to be below 30% to obtain chitin for later use;
and (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 5 hours, heating to 60 ℃, keeping the temperature for reaction for 5 hours, filtering, washing with water, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Water and 30% hydrochloric acid solution, heating with steam to raise temperatureReacting at 85 ℃ for 1 hour, and heating to obtain a solution state material for later use;
and (5) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 0.5 hour, filtering, and adding water for washing for 2 times.
And (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Example 3: a method for extracting chitosan from snow crab shells, the method comprising the steps of:
step (1), decalcification reaction: putting 10kg of snow crab shell into a reaction kettle, adding 30% hydrochloric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing with water for 2 times until the mixture is neutral, and drying to obtain a product for later use;
step (2) deproteinization: adding sodium hydroxide into the reaction kettle, adjusting the concentration to be 10%, heating to 100 ℃, keeping the temperature for reaction for 3 hours, wherein the aeration amount is 1.5m 3 The chitin is washed to be neutral, filtered and naturally dried, and the chitin is obtained after the water content is detected to be qualified for later use;
and (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 20 hours, heating to 70 ℃, preserving heat for reaction for 10 hours, filtering, washing with water, filtering, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
acid hydrolysis and melting: adding chitin amine into a reaction kettle, adding 1m 3 Heating water and 30% hydrochloric acid solution with steam to 110 deg.C, reacting for 5 hr, and heating to obtain solution state material;
and (5) transferring the material in the solution state into a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Example 4: a method for extracting chitosan from snow crab shells, said method comprising the steps of:
step (1), decalcification reaction: laying 10kg of snow crab shells by 5cm-10cm, putting the snow crab shells into a reaction kettle, adding 15kg of 30% hydrochloric acid solution, adjusting the pH value to be 3.5, soaking the snow crab shells in citric acid-sodium dihydrogen phosphate buffer solution for 8 hours, filtering, washing the snow crab shells with water for 2 times until the snow crab shells are neutral, and drying the snow crab shells to obtain a product for later use;
step (2) deproteinization: adding 15kg of disodium hydrogen phosphate solution into a reaction kettle, adjusting the concentration to 10%, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration rate is 1m 3 Min, then washing to be neutral, filtering, naturally airing, and detecting that the water content is below 30 percent to obtain chitin for later use;
and (3) deacetylation: adding 50% disodium hydrogen phosphate into the reaction kettle in the step (2), soaking for 10 hours, heating to 65 ℃, keeping the temperature for reaction for 8 hours, filtering, washing with water, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Heating water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under heat preservation, and heating to a solution state for later use;
and (5) transferring the solution-state material to a flocculation tank, adding 3kg of 50% disodium hydrogen phosphate, reacting for 1 hour, filtering, and washing with water for 2 times.
And (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Comparative example 1: a method for extracting chitosan from snow crab shells, said method comprising the steps of:
step (1), decalcification reaction: laying 10kg of shell of snow crab in 5-10cm flat, putting into a reaction kettle, adding 15kg of 30% sulfuric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing with water for 2 times until the shell is neutral, and drying to obtain a product for later use;
step (2) deproteinization: adding 15kg of potassium hydroxide solution into the reaction kettle, adjusting the concentration to be 10 percent, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration amount is 1m 3 Min, then washing to be neutral, filtering, naturally drying, and detecting the water content to be below 30% to obtain chitin for later use;
and (3) deacetylation: adding 50% of potassium hydroxide into the reaction kettle in the step (2), soaking for 10 hours, heating to 65 ℃, preserving heat, reacting for 8 hours, filtering, washing with water, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Heating the water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under the condition of heat preservation, and heating the solution for later use;
and (5) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) filter pressing: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Comparative example 2: a method for extracting chitosan from snow crab shells, the method comprising the steps of:
step (1), decalcification reaction: laying 10kg of shell of the snow crab by 5cm-10cm, putting the shell of the snow crab into a reaction kettle, adding 15kg of 30% hydrochloric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing for 2 times by using water until the shell is neutral, and drying to obtain a product for later use;
step (2), deproteinization: adding 15kg of sodium hydroxide solution into a reaction kettle, adjusting the concentration to be 10 percent, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration quantity is1m 3 Min, then washing to be neutral, filtering, naturally drying, and detecting the water content to be below 30% to obtain chitin for later use;
step (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 10 hours, heating to 65 ℃, keeping the temperature for reaction for 8 hours, filtering, washing with water, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Heating water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under heat preservation, and heating to a solution state for later use;
and (5) transferring the material in the solution state into a flocculation tank, adding 5kg of 30% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
Comparative example 3: a method for extracting chitosan from snow crab shells, the method comprising the steps of:
pretreating the shell of the snow crab: 10kg of the shell of the snow crab is directly led into a reaction kettle and is paved to be about 5-10cm thick. Step (1), decalcification of the shell of the snow crab: adding a formic acid-sodium formate buffer solution with the pH value of 3.5 into the shell of the snow crab, soaking for 8 hours, and filtering for later use;
step (2), washing the shell of the snow crab with water: washing the snow crab shells in the step (1) with water until the snow crab shells are neutral, and measuring the water content to be 71.3 percent, wherein the snow crab shells are reserved;
deproteinizing in step (3): adding 10% sodium bicarbonate ethanol solution into the mixture (2), heating to 70 deg.C, reacting for 3 hr with aeration amount of 1m 3 Per min, once every 30min, filtering and washing for later use;
and (4) deacetylation: adding 50% sodium bicarbonate methanol solution, heating to 70 deg.C, reacting for 8 hr, and drying for 2 hr;
step (5), acid hydrolysis and melting: adding the crude product of chitosan into a reaction kettle, and adding 1m 3 Heating water and 30% sulfuric acid solution with steam to 95 deg.C, reacting for 2 hr, and heating to obtain solution state material;
and (6) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
Step (7), filter pressing: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (8) drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
1. Physical Property measurement
The chitosan prepared in the above examples was measured for the appearance, degree of deacetylation of chitin, viscosity, conversion of chitin, and the like.
And (3) viscosity measurement: the chitosans of examples 1-4 and comparative examples 1-3 were dissolved to form a 1% solution, and then the viscosity was measured.
The results are shown in FIGS. 4-6.
By comparing fig. 4-6 with the comparative examples, the appearance, chitin deacetylation degree, viscosity, conversion rate of chitin of examples 1-4 of the present invention are superior to each other to different degrees, especially the solution adopted in example 1 is optimized, and the inventors consider that it is possible to obtain the final result by finding out the key techniques of temperature, alcohol concentration, etc. through continuous experiments, in contrast: comparative example 1, which employs different acidifying agents, is not complete except for calcium, and differs from the present invention in appearance and final conversion. The technical effects of the invention cannot be finally achieved by adopting different proportions of materials and alkalizing agents in the comparative examples 2, 3 and 4.
2) Detection of flocculation Effect
The inventor screens related flocculation materials, selects a crude product of the chitosan in the embodiment 1 of the invention to flocculate, calculates the optimal dosage, the optimal material and other conditions by calculating the flocculation rate, selects an aqueous solution of sodium hydroxide, sodium bicarbonate and dipotassium hydrogen phosphate to detect the flocculation effect, and extracts the solution for 5 times; in order to determine the amount of flocculating agent, the amount of flocculating agent was screened for sodium hydroxide and subsequently extracted 5 times, see in particular fig. 1 and 2.
Claims (8)
1. A method for extracting chitosan from snow crab shells is characterized by comprising the following steps:
step (1), decalcification reaction: directly putting the shell of the snow crab into a reaction kettle, adding an acid solution, adjusting the pH value, soaking for 1-2 hours, filtering, washing with water for 2-3 times until the shell is neutral, and drying to obtain a product for later use;
step (2) deproteinization: adding alkaline solution I into the reaction kettle until the concentration is 5-15%, heating to 90-110 deg.C, reacting for 1-3 hr with aeration amount of 0.5-1.5m 3 The chitin is washed to be neutral, filtered, naturally dried and the water content is detected to obtain the chitin for standby;
step (3) deacetylation: adding an alkaline reagent II into the reaction kettle in the step (2), soaking for 5-20 hours, heating to 60-70 ℃, preserving heat for reaction for 5-10 hours, filtering, washing with water, filtering, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
step (4), acid hydrolysis and melting: putting the chitosan into 30% hydrochloric acid solution, heating the chitosan to 85-110 ℃ by steam, carrying out heat preservation reaction for 1-5 hours, and heating the chitosan to a solution state material for later use;
flocculation in step (5): transferring the solution-state material to a flocculation tank, adding an alkaline solution III, reacting for 0.5-2 hours, filtering, and washing for 2-3 times by adding water;
and (6) pressure filtration: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
2. The method of claim 1, wherein the alkaline solution I, the alkaline solution II and the alkaline solution III are selected from the group consisting of aqueous solutions of sodium hydroxide and sodium bicarbonate.
3. The method of claim 1, wherein the acidic solution in step (1) is one selected from the group consisting of a hydrochloric acid solution, a sulfuric acid solution, a formic acid-sodium formate buffer solution, and a citric acid-disodium hydrogen phosphate buffer solution, and the pH is adjusted to 3.0 to 3.5.
4. The method of claim 1, wherein the step (2) comprises adding sodium hydroxide to the reaction kettle to a concentration of 10%, heating to 100 ℃, maintaining the temperature for 2 hours, and aerating with an amount of 1m 3 And/min, washing to be neutral, filtering, naturally drying, and detecting the water content to be below 20% to obtain the chitin for later use.
5. The method according to claim 1, wherein said chitin of step (3): 50% sodium hydroxide = 1.
6. The method of claim 1, wherein in step (4), 5kg of chitosan is added to the reaction vessel at a weight/volume ratio of 1m 3 Heating water and 30% hydrochloric acid solution 15kg by steam to 95 deg.C, reacting for 2 hr, and heating to obtain solution state material.
7. The method according to claim 1, wherein the step (5) transfers the material in the solution state to a flocculation tank, adds 3kg of 50% sodium hydroxide, reacts for 1 hour, and filters and then washes 2 times with water, calculated as a weight to volume ratio.
8. The method of claim 1, wherein the method comprises the steps of:
step (1), decalcification reaction: directly putting the shell of the snow crab into a reaction kettle, adding 30% hydrochloric acid solution, adjusting the pH value to 3.0, soaking for 2 hours, filtering, washing with water for 2 times until the shell is neutral, and drying to obtain a product for later use;
step (2), deproteinization: adding sodium hydroxide into the reaction kettle, adjusting the concentration to be 10%, heating to 100 ℃, keeping the temperature for reaction for 2 hours, wherein the aeration amount is 1m 3 The chitin is washed to be neutral, filtered and naturally dried, and the chitin is obtained after the water content is detected to be qualified for later use;
and (3) deacetylation: adding 50% of sodium hydroxide into the reaction kettle in the step (2), soaking for 5-20 hours, heating to 60-70 ℃, keeping the temperature for reaction for 5-10 hours, filtering, washing with water, filtering, drying until the water content is below 1%, and crushing to obtain a crude product of the chitosan;
acid hydrolysis and melting: adding chitin amine into a reaction kettle, and adding 1m 3 Heating water and 30% hydrochloric acid solution by steam to 95 ℃, reacting for 2 hours under heat preservation, and heating to a solution state for later use;
and (5) transferring the material in the solution state to a flocculation tank, adding 3kg of 50% sodium hydroxide, reacting for 1 hour, filtering, and then adding water to wash for 2 times.
And (6) filter pressing: carrying out filter pressing on the flocculate through a plate frame, and detecting the moisture of the material to be below 60%;
step (7), drying and outsourcing: drying the filter-pressed materials by a dryer until the water content is less than 1%, and then packaging to obtain the chitosan.
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