RU2330670C1 - Method of chitosan production - Google Patents

Abstract

FIELD: medicine; pharmacology.

SUBSTANCE: offered invention concerns medicine and pharmacology, exactly to method of Chitosan production. Method includes milling of natural chitin-containing raw material, alternating by turn three stages of raw material deproteinisation, and three stages of decalcification, deproteinisation stages are carried out by sodium hydroxide solution of concentration 3-5% produced by diaphragm electrolysis method within 3-4 hours at temperature 60-65°C; decalcification stages are performed by 3-5% hydrochloric acid solution at temperature 20-25°C within 1-3 hours; deacetylation is performed by 49-55% sodium hydroxide produced by diaphragm electrolysis method; deproteinisation and decalcification stages are performed in series connected six steel devices with internal glass-enamel coating, equipped with stirrers, thermopools, connections for reagents feeding and disposal, jackets for reactionary mass cooling and heating. Afterwards deacetylation follows with 49-55% sodium hydroxide produced by diaphragm electrolysis method. Process is conducted at temperature 95-105°C within 7-9 hours and followed by washing, spinning and drying of finished Chitosan.

EFFECT: production of high-clean Chitosan.

Description

The present invention relates to pharmacology and allows to obtain the natural compound chitosan, widely used in pharmacology.

A known method of producing chitosan, including a one-time deproteinization with a 3.5% sodium hydroxide solution for 2 hours at t = 65 ° C, filtering the suspension, washing the solid phase, demineralization (decalcification) with a 3.65% HCl solution per 30 minutes at room temperature, filtering, washing, extraction with acetone, drying, bleaching with a 0.315% sodium hypochlorite solution, washing and drying the obtained chitin, deacetylation with 50% sodium hydroxide solution at 100 ° C for 30 minutes, washing and drying the obtained chitosan . (Meyers S.P., No N.K., Lee K.S. Isolation and characterization of chitin from crabfish shell waste J. Agric. Food Chem. 1989, 37, 575).

The disadvantages of this method are a large number of operations performed manually, because the process is framed by a periodic method; the inability to remove most of the proteins and calcium hydroxide due to too short a time for the process of deproteinization and decalcification; completely insufficient time for the deacetylation step; excessive phase of the extraction, plus a flammable and explosive and toxic reagent - acetone; bleaching the finished chitin with sodium hypochlorite, the active chlorine of which to some extent destroys the chitin molecule; the appearance of active chlorine in wastewater after prolonged washing of chitin to a complete absence of chlorine in the product. The result is chitosan with a degree of deacetylation not higher than 60-70%, with a high content of proteins and mineral impurities, as well as with a low viscosity.

The closest analogue of the proposed invention is a method for producing chitosan, including grinding natural chitin-containing raw materials to particles with a size of 100-200 microns; powder extraction with liquid carbon dioxide for 1-3 hours; the first decalcification of the powder with a 5-10-fold excess of 0.8-2.5% hydrochloric acid at 35-50 ° C for 0.5-2 hours; washing the solid phase with water at 50-75 ° C to a pH of 5.4; conducting the first deproteinization at 4-7 times the volume of water and a pH of 9.0-10.5 by adding solid sodium hydroxide to the water. An enzyme is added to the resulting suspension in an amount of 0.1-0.5% by weight of the dry powder; draining the liquid phase; washed the residue with water; conduct second decalcification with 5-7 times the weight of dry powder in an amount of 0.8-2.5% hydrochloric acid at a temperature of 35-50 ° C for 0.5-2 hours; washed the reaction mass; add a 4-7-fold volume of water and adjust its pH to 9.0-10.5 by adding solid sodium hydroxide and 0.1-0.5% by weight of the dry powder of the enzyme. Deproteinization is 2-4 hours at a temperature of 50-70 ° C; the mother liquor is drained, 2-4 volumes by weight of dry chitin of 45-50% sodium hydroxide are added and deacetylation is carried out at a temperature of 85-95 ° C for 2-4 hours; washed chitosan with water at a temperature of 60-80 ° C to a pH of 6.5-7.4; chitosan is centrifuged; dried and ground (US Pat. RF No. 2221811).

The disadvantages of this method are:

a large number of operations (8) in the production of a product performed manually, as the process is framed as periodic;

an excessively high degree of grinding of the feedstock, as a result of which the loss of the processed material will be large and will increase as proteins (up to 40%) and CaCO ₃ (up to 30%) are removed from the feedstock and the additional reduction in grain size is associated with this;

a dangerous operation of extracting powder with liquid carbon dioxide, which retains a liquid state only under pressure above 60 kgf / cm ² . The operation is possible only in an autoclave and becomes supervised by the Gosgortekhnadzor;

difficulties in stirring up powder sediment deposited on the bottom of industrial reactors after removal of the mother liquors and the probable failure of the gearboxes when the stirrer motors are switched on;

the need for devices to ensure safe bleeding of CO ₂ pressure from the reactor;

too high decalcification process temperature and

the associated increased destruction of the chitin molecule;

hydrogen chloride contained in the hydrochloric acid introduced for decalcification is not sufficient to completely remove calcium carbonate;

washing the resulting calcined chitin-protein complex (CBCH) from hydrogen chloride to pH 5.4 requires a large flow of water and is long in time;

the use of drinking water for washing is associated with an increase in the content of hardness salts (fireproof residue) in the finished product;

preparing an alkaline solution for deproteinization directly in the reactor by adding solid alkali to the suspension is a dangerous technique, associated with a spontaneous increase in temperature and local overheating at the place where the alkali enters water;

the temperature, time and duration of deacetylation are insufficient to achieve a high degree of deacetylation.

In order to obtain high-quality chitosan suitable for use in medicine, as well as to avoid the above-mentioned disadvantages of the known method, the following method for producing chitosan, which is carried out by a continuous method and includes three stages of deproteinization and three stages of decalcification, performed alternately, replacing deproteinization by decalcification, thus simulating counterflow principle, in which the processed material is in contact with fresh reagents as the process progresses. Depending on the quality and composition of the feedstock (crushed crab shell - hereinafter referred to as “crab crumbs”), the number, order and duration of the application of the stages of decalcification and deproteinization can be changed. If the amount of fraction minus 3 mm exceeds 3% in the crab crumbs, the amount and time of decalcification and deproteinization are reduced. When the content of CaCO ₃ in the crab grains is more than 40% or proteins more than 45%, the amount and time of deproteinization or decalcification are reduced, respectively.

The result is a white chitin that is practically free of CaCO ₃ and with very little protein residue. The isolated chitin is subjected to deacetylation with high percent sodium hydroxide at elevated temperature. All reactions are carried out in a nitrogen atmosphere, in a chain of standard steel devices with a high-quality glass-enamel coating, with a capacity of 6.3-2.5 m ³ , equipped with stirrers, thermowells, fittings for introducing and removing reacting components, shirts for heating and cooling the reaction masses, as well as in an apparatus made of X18H10T steel, since during deacetylation the glass-enamel coating of the reactors is destroyed by high temperatures and alkali concentrations.

The operations of loading components, reagents, removing mother liquors and washing water are mechanized. They are carried out due to the vacuum created in each of the devices.

In contrast to the known methods, in the proposed as an alkaline agent, a liquid solution of sodium hydroxide obtained by the method of diaphragm electrolysis is used. Thanks to the use of caustic diaphragm liquid soda, the need for dangerous and laborious crushing and dissolution of solid alkali has disappeared.

All devices are filled with nitrogen before loading reagents and the processed material into them.

The essence of the method is as follows.

1st deproteinization. The reactor A-1 is filled with nitrogen and 800 kg of crushed crab shell are loaded into it. 4000 liters of a 3% NaOH solution obtained by the method of diaphragm electrolysis are also fed here at 60-65 ° C. Withstand the pulp with stirring and t = 60-65 ° C for 3-4 hours. After 10-20 minutes of sediment, the mother liquor is removed into the collection. The remaining calcined chitin-protein complex (KHBC) is washed with 2400 liters of water at a temperature of 60-65 ° C, the pulp is mixed for 30-40 minutes, allowed to settle for 10-20 minutes and the washing water is removed into the collector. The operation is carried out twice.

1st decalcification. Reactor A-2 was filled with nitrogen, pulp from A-1 was fed and stirred for 10 minutes. They are allowed to stand for 10 minutes, water is removed from reactor A-2, and 4000 liters of a 5% HCl solution with t = 10-20 ° C. are fed. Withstand the pulp with stirring and t = 20-25 ° C for 1-1.5 hours. After 10 min of sediment, the mother liquor is removed into the collection. The remaining CBCC is washed with 2400 liters of water at a temperature of 60-65 ° C, the pulp is stirred for 30 minutes, allowed to stand for 10 minutes and the washing water is removed into the collector. The operation is carried out twice.

2nd deproteinization. Reactor A-3 is filled with nitrogen, pulp from A-2 is fed and stirred for 10 minutes. It is allowed to stand for 10 minutes, water is removed from reactor A-3 and 4000 liters of a 4% NaOH solution obtained by diaphragm electrolysis are supplied t = 55- 60 ° C. Withstand the pulp with stirring and t = 55-60 ° C for 4 hours. After 10 min of sediment, the mother liquor is removed into the collection. The remaining CBCC is washed with 2400 liters of water at a temperature of 60-65 ° C, the pulp is stirred for 30 minutes, allowed to stand for 10 minutes and the washing water is removed into the collector. The operation is carried out twice.

2nd decalcification. Reactor A-4 is filled with nitrogen, pulp from A-3 is fed and stirred for 10 minutes. It is allowed to stand for 10 minutes, water is removed from reactor A-4 and 2400 liters of 4% HCl solution with t = 20-25 ° C are fed. Withstand the pulp with stirring and t = 20-25 ° C for 2 hours. After 10 min of sediment, the mother liquor is removed into the collection. The remaining CBCC is washed with 2400 liters of water at a temperature of 60-65 ° C, the pulp is stirred for 30 minutes, allowed to stand for 10 minutes and the washing water is removed into the collector. The operation is carried out twice.

3rd deproteinization. Reactor A-5 is filled with nitrogen, pulp from A-4 is fed and stirred for 10 minutes. It is allowed to stand for 10 minutes, water is removed from reactor A-5 and 2400 liters of 5% NaOH solution obtained by diaphragm electrolysis are fed t = 50- 55 ° C. Withstand the pulp with stirring and t = 55-60 ° C for 2 hours. After 10 min of sediment, the mother liquor is removed into the collection. The remaining calcined chitin (KX) is washed with 2000 liters of water at a temperature of 60-65 ° C, the pulp is stirred for 30 minutes, allowed to stand for 10 minutes and the washing water is removed into the collection tank. The operation is carried out twice.

3rd decalcification. The reactor A-6 is filled with nitrogen, the pulp from A-5 is fed and stirred for 20 minutes. Allow 10 minutes to stand, remove water from reactor A-6 and supply 2400 liters of a 3% HCl solution with t = 20 ° C. Withstand the pulp with stirring and t = 20 ° C for 2 hours. After 10 min of sediment, the mother liquor is removed into the collection. The remaining chitin is washed with 1600 liters of water at a temperature of 40-45 ° C, the pulp is stirred for 30 minutes, allowed to stand for 10 minutes and the washing water is removed into the collection tank. The operation is carried out until a pH of 6.0 is obtained. Chitin is obtained in white, practically does not contain CaCO ₃ and proteins.

Deacetylation Reactor A-7 is filled with nitrogen, pulp from A-6 is fed and stirred for 20 minutes. It is allowed to stand for 10 minutes, water is removed from reactor A-7 and 2700 liters of 49-55% NaOH solution obtained by diaphragm electrolysis are fed. The process is carried out at t = 95-105 ° C for 7-9 hours. After the reaction time, the mother liquor is removed in a separate collection, and the finished chitosan is washed.

Jointing. First, moisture from chitosan is removed by centrifuge at 1400 rpm for 25-40 minutes.

Drying chitosan. Raw chitosan removed from a centrifuge contains about 60% water. It is dried in a vacuum drum dryer at a residual pressure of 90-120 mm RT. Art. and t = 60-65 ° C.

In the proposed method for producing chitosan, the yield of the finished product is 94-95%, and its quality indicators are expressed by the following figures:

- mass fraction of water%, no more 6 - dynamic viscosity of 1% solution of chitosan in 1% solution 10-1000 acetic acid cp, within - degree of deacetylation%, not less 90 - mass fraction of insoluble residue 1% chitosan solution 0.1 in 1% acetic acid solution%, not more than - mass fraction of residue after calcination%, no more 0.1 - protein content%, no more 0.15 - heavy metal content (Hg, As, Pb, Sb) ppm, no more 3 - pH of the aqueous extract, within 6-7.3 - microflora MAFAnM, no more 1 × 10 ^-3

Due to the gradual and layer-by-layer processing of the feedstock, it is possible to minimize damage to the chitin molecule, to virtually completely remove all impurities, since the counterflow principle is simulated here, in which it meets fresh reagents in each of the devices as the processed crab grain moves from the device to the device.

Claims (1)

A method of producing chitosan, characterized in that it involves grinding natural chitin-containing raw materials, carrying out alternately three stages of deproteinization of the raw material and three stages of decalcification, the deproteinization stage is carried out with a solution of sodium hydroxide concentration of 3-5%, prepared by the method of diaphragm electrolysis, for 3-4 hours at a temperature of 60-65 ° C; the stage of decalcification is carried out with a 3-5% solution of hydrochloric acid, at a temperature of 20-25 ° C for 1-3 hours; deacetylation with 49-55% sodium hydroxide obtained by the method of diaphragm electrolysis; the stages of deproteinization and decalcification are carried out in six steel devices in series connected with an internal glass enamel coating, with stirrers, thermowells, fittings for introducing and removing reagents, shirts for cooling and heating the reaction masses, followed by deacetylation with a 49-55% sodium hydroxide solution, obtained by the method of diaphragm electrolysis, the process is conducted at a temperature of 95-105 ° C for 7-9 hours; washing, jointing and drying the finished chitosan.