A preparation device and preparation method of oligomolecular chitosan

Abstract

The present application relates to a preparation device and a preparation method of oligomolecular chitosan, wherein the preparation device comprises a separation tank, a feed pipe and a discharge pipe are arranged on the separation tank, a vortex partition is arranged in the separation tank, the vortex partition divides the inner cavity space of the separation tank into a vortex channel, the feed pipe is connected to the outer ring inlet of the vortex channel, and the discharge pipe is connected to the inner ring outlet of the vortex channel; a plurality of filter plates extending in the spiral direction of the vortex channel are fixedly connected on the inner arc side of the vortex partition, a filter membrane is embedded on the filter plate, a sealing plate is fixedly connected to the free end of the filter plate, the sealing plate, the filter plate and the vortex partition form a closed filtrate space, a suction filter pipe connected to the filtrate space is arranged on the separation tank; there is a gap between the free end of the filter plate and the outer arc side of the vortex channel located in the inner circle. The present application continuously flushes the filter membrane on the filter plate with a degradation solution, which can greatly reduce the probability of foam adhering to the filter membrane and affecting the filtration and separation efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of oligomolecular chitosan, and in particular to a preparation device and a preparation method of oligomolecular chitosan. Background Art

[0002] Chitosan oligosaccharides, also known as chitosan oligosaccharides, are short-chain derivatives of chitosan, composed of 2-10 aminoglucose units connected by β-(1→4) glycosidic bonds. It has good solubility in water, and due to its unique chemical structure and biological activity, chitosan oligosaccharides are widely used in food, feed, medicine, cosmetics and agriculture. There are three main preparation methods: enzymatic hydrolysis, chemical degradation and physical degradation, all of which use different means to degrade chitosan.

[0003] In the related art, a Chinese patent application numbered CN200810056488.4 proposes a process for preparing oligomolecular chitosan by complex enzyme degradation, comprising: (1) first mixing chitosan with water, then adding glacial acetic acid to dissolve the chitosan to obtain a chitosan solution with a concentration of 20 to 25 g / L, and then adjusting the pH value of the solution to 4.5 to 5.0 with glacial acetic acid; (2) adding a complex enzyme to the chitosan solution obtained in the first step for degradation to obtain a chitosan degradation solution; (3) using the degradation solution in the second step as a feed solution and subjecting it to microfiltration to remove various enzyme residues therein; (4) subjecting the microfiltration permeate obtained in the third step to nanofiltration to separate salts and monosaccharides and to concentrate; and (5) spray drying the nanofiltration retentate obtained in the fourth step to obtain oligomolecular chitosan.

[0004] The above-mentioned related technologies have the following defects: the mixed solution after the degradation reaction is completed still contains a small amount of undegraded chitosan and other macromolecular impurities, and the oligochitosan molecules contain a large number of hydroxyl groups and amino groups. These functional groups can reduce the surface tension of water and make the mixed solution have a certain surface activity. Therefore, during the centrifugal separation process, these surfactants can aggregate to form foams attached to the filter membrane, seriously affecting the filtration and separation effects of the filter membrane; and the surface activity of some enzymes and proteins present in the mixed solution will further promote the generation of these foams, aggravating the impact on the filtration and separation effects. Summary of the invention

[0005] In order to improve the problem that a degraded oligomolecular chitosan mixed liquid is prone to generate foam during filtration separation, thereby affecting the separation efficiency, the present application provides a preparation device and a preparation method of oligomolecular chitosan.

[0006] The first aspect of the present application provides a preparation device for oligosaccharides using the following technical solution:

[0007] A preparation device for oligomolecular chitosan, comprising a separation tank, wherein a feed pipe and a discharge pipe are arranged on the separation tank, a vortex baffle is arranged in the separation tank, the vortex baffle divides the inner cavity space of the separation tank into a vortex channel, the feed pipe is connected to the outer ring inlet of the vortex channel, and the discharge pipe is connected to the inner ring outlet of the vortex channel;

[0008] A plurality of filter plates extending in the spiral direction of the vortex channel are fixedly connected to the inner arc side of the vortex baffle, a filter membrane is embedded in the filter plate, a sealing plate is fixedly connected to the free end of the filter plate, the sealing plate, the filter plate and the vortex baffle form a closed filtrate space, and a suction filter pipe connected to the filtrate space is provided on the separation tank;

[0009] There is a gap between the free end of the filter plate and the outer arc side of the vortex channel located on the inner circle.

[0010] Furthermore, the filter plate extends in a streamlined manner toward the spiral direction of the vortex channel, and the distance between the filter plate and the outer arc side of the vortex channel located in the inner circle gradually decreases along the spiral direction of the vortex channel.

[0011] Furthermore, a breathable membrane is embedded in the sealing plate, and an exhaust pipe with one end extending into the filtrate space is provided on the separation tank, and an outlet of the exhaust pipe is higher than an outlet of the suction filtration tube.

[0012] Furthermore, the plurality of exhaust pipes are commonly connected to a negative pressure exhaust device.

[0013] Furthermore, the sealing plate is arranged in an arc shape, and its outer arc side is arranged close to the filtrate space.

[0014] Furthermore, the exhaust pipe is arranged in a position in the filtrate space close to the sealing plate, and the suction filter pipe is arranged in a position in the filtrate space far from the sealing plate.

[0015] Furthermore, a filter port is formed through the filter plate, the filter membrane is embedded in the filter port, and the surface area of ​​the filter membrane after being flattened is larger than the opening area of ​​the filter port.

[0016] Furthermore, the exhaust pipe is connected to a pulse air supply device.

[0017] Furthermore, the filter holes of the plurality of filter membranes tend to decrease along the spiral direction of the vortex channel.

[0018] The second aspect of the present application provides a method for preparing oligosaccharide using the following technical solution:

[0019] A method for preparing oligomolecular chitosan, based on the above-mentioned device for preparing oligomolecular chitosan, comprises the following steps:

[0020] S1. Mixing chitosan with water, and then adding glacial acetic acid to dissolve the chitosan to obtain a chitosan solution;

[0021] S2. Adding a complex enzyme to the chitosan solution in S1 for degradation to obtain a chitosan degradation solution;

[0022] S3. The degradation solution in S2 is passed as a feed liquid through the feed pipe into the separation tank for multiple single-stage or multi-stage filtration, and the monosaccharide filtrate is extracted from the filtrate space by the suction tube;

[0023] S4. The monosaccharide filtrate in S3 is spray-dried to obtain oligosaccharide chitosan.

[0024] In summary, the beneficial technical effects of this application are:

[0025] 1. When the degradation solution passes through the vortex channel of the separation tank at a high speed, it passes through multiple filter spaces in sequence. Part of the oligosaccharide and water in the degradation solution passes through the filter membrane on the filter plate and enters the filtrate space. Since the degradation solution needs to pass through multiple filter spaces, the degradation solution can be filtered multiple times in the separation tank, which can greatly improve the filtering effect of the degradation solution; and when the degradation solution passes through the filter space, the filter membrane on the filter plate can be continuously washed, which can not only filter and separate, but also rinse the filter membrane, so the probability of bubbles generated during the filtration and separation process adhering to the filter membrane and affecting the filtration efficiency can be greatly reduced;

[0026] 2. By setting up an exhaust pipe, the upper cavity of the filtrate space can be sucked, so that the filtrate space is as negative pressure as possible, thereby reducing the probability of bubbles adhering to the filter membrane; and when the filtrate space is negative pressure, the filtration efficiency of the filter membrane for the degradation solution can also be improved; at the same time, after the degradation solution passes through the filtration space, a low-pressure area will be formed on the inner arc side of the sealing plate, so that the gas in the degradation solution can overflow, pass through the breathable membrane into the filtrate space, and be discharged by the exhaust pipe, thereby reducing the probability of bubbles adhering to the filter membrane during the filtration process;

[0027] 3. Compared with chemical defoaming that affects the purity of oligomolecular chitosan and mechanical defoaming that requires additional mechanical structure, the preparation method of the present application can independently complete the defoaming operation during the filtration of the degradation solution, which can greatly improve the filtration and separation efficiency and quality of the oligomolecular chitosan degradation solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application;

[0029] Figure 2 It is a schematic diagram of a partial cross-sectional structure of the separation tank of the embodiment of the present application after the top cover is cut off;

[0030] Figure 3 is a top view of the separation tank of the embodiment of the present application with the top cover cut off;

[0031] Figure 4 This is a partial cross-sectional structural schematic diagram mainly used to show the structure in the filtrate space in this application.

[0032] Description of reference numerals:

[0033] 1. Separation tank; 11. Feed pipe; 12. Discharge pipe; 13. Vortex channel; 14. Filtrate space; 15. Filtration space;

[0034] 2. Vortex baffle;

[0035] 3. filter plate; 31. filter membrane; 32. filter port;

[0036] 4. Sealing plate; 41. Breathable membrane;

[0037] 51. Filter pipe; 52. Filtrate main pipe; 53. Suction pump; 54. Liquid storage tank;

[0038] 6. Exhaust pipe;

[0039] 7. Float valve; 71. Ring; 72. Plug; 73. Float block. DETAILED DESCRIPTION

[0040] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0041] The present application discloses a device for preparing oligomolecular chitosan. Figure 1 , Figure 2 and Figure 3 , which includes a separation tank 1 mainly used for filtering and separation, and the other equipment used, such as a dissolving tank, a reactor, a dryer, etc., are conventional technologies and will not be described here. A feed pipe 11 and a discharge pipe 12 are provided on the separation tank 1, and a vortex baffle 2 is provided in the separation tank 1. The two ends of the vortex baffle 2 are respectively fixed to the axial inner top wall and the inner bottom wall of the separation tank 1. The vortex baffle 2 divides the inner cavity space of the separation tank 1 to form a vortex channel 13. The feed pipe 11 is connected to the outer ring inlet of the vortex channel 13, and the discharge pipe 12 is connected to the inner ring outlet of the vortex channel 13 and is located at the lower end surface of the separation tank 1.

[0042] A plurality of filter plates 3 extending in the spiral direction of the vortex channel 13 are fixedly connected to the inner arc side of the vortex partition 2, and a gap is provided between the free end of the filter plate 3 and the outer arc side of the vortex channel 13 located in the inner circle, and a filter membrane 31 is embedded in the filter plate 3. Specifically, a filter port 32 is provided through the filter plate 3, and the filter membrane 31 is embedded and installed in the filter port 32. A sealing plate 4 is fixedly connected to the free end of the filter plate 3, and the two opposite sides are respectively fixed to the inner top wall and the inner bottom wall. The sealing plate 4, the filter plate 3 and the vortex partition 2 enclose a closed filtrate space 14, and one side of the filter plate 3 is the filtrate space 14, and the other side is the filtration space 15, and the filtration space 15 gradually narrows along the spiral direction from the outer circle to the inner circle of the vortex channel 13; a suction filter pipe 51 connected to the filtrate space 14 is provided on the separation tank 1, and the plurality of suction filter pipes 51 are commonly connected to a filtrate main pipe 52, and the filtrate main pipe 52 is connected to a suction pump 53 and a liquid storage tank 54.

[0043] In this way, when the degradation of the chitosan solution is completed, the degradation solution is pumped into the separation tank 1 through the feed pipe 11. When the degradation solution passes through the vortex channel 13 of the separation tank 1 at a high speed, it passes through multiple filter spaces 15 in sequence. Part of the oligomeric chitosan and water in the degradation solution passes through the filter membrane 31 on the filter plate 3 and enters the filtrate space 14, and then is discharged through the suction pipe 51 under the suction of the suction pump 53. The filtered and separated oligomeric chitosan solution can be collected in the liquid storage tank 54. In this process, since the degradation solution needs to pass through multiple filter spaces 15, the degradation solution can be filtered multiple times in the separation tank 1, which can greatly improve the filtering effect of the degradation solution.

[0044] When the degradation solution passes through the filter space 15, the filter membrane 31 on the filter plate 3 can be continuously washed, which can not only filter and separate, but also rinse the filter membrane 31, thereby greatly reducing the probability of bubbles generated during the filtration and separation process adhering to the filter membrane 31 and affecting the filtration efficiency. At the same time, when the degradation solution passes through the filter space 15, the flow channel becomes narrower, resulting in an accelerated flow rate of the degradation solution, which can reduce the pumping pressure of the degradation solution and reduce the filtration and separation costs.

[0045] It should be further explained that when the degradation solution circulates in the vortex channel 13, part of the water in it will also pass through the filter membrane 31 and enter the filtrate space 14, resulting in a reduction in the residual solution entering the inner circle, which will affect the filtering effect of the downward flow channel in the vortex channel 13 to a certain extent. Therefore, the size of the filter ports 32 opened on the multiple filter plates 3 gradually increases from the outer circle to the inner circle of the vortex channel 13 to reduce the amount of water passing through the outer circle filter ports 32; at the same time, the suction force of the suction pump 53 on the multiple suction filter tubes 51 also gradually decreases from the outer circle to the inner circle of the vortex channel 13, and the total suction flow rate of the multiple suction filter tubes 51 is less than the inlet flow rate of the feed pipe 11.

[0046] If necessary, in one embodiment, the discharge pipe 12 can also be connected to the lower half channel of the vortex channel 13 close to the innermost circle (not shown in the figure), so that the final residual degradation solution can re-enter the vortex channel 13 for fewer times of re-filtration, thereby improving the separation and filtration efficiency of the separation tank 1.

[0047] Furthermore, in order to improve the separation quality of the degradation solution in the separation tank 1, the filter holes of the multiple filter membranes 31 tend to decrease along the spiral direction from the outer circle to the inner circle of the vortex channel 13, that is, the filter membrane 31 close to the outer circle of the vortex channel can be set as a microfiltration membrane or an ultrafiltration membrane, and the filter membrane 31 close to the inner circle of the vortex channel can be set as an ultrafiltration membrane or a nanofiltration membrane, and the multi-stage filtration of the degradation solution can be achieved with the help of multiple filter membranes 31. However, it should be clear that the filtrate sucked out of the filtrate space 14 corresponding to the microfiltration membrane and the ultrafiltration membrane shall not be directly discharged into the liquid storage tank 54, but needs to be re-transported to the lower half channel of the vortex channel 13 close to the innermost circle, and deep purification is carried out with the help of the filter membrane 31 composed of multiple ultrafiltration membranes and nanofiltration membranes to ensure the filtration quality, and at the same time, the water flow in the lower half channel of the vortex channel 13 close to the innermost circle can also be increased to ensure the washing effect of the filter membrane 31 and the filtering effect of the filter membrane 31.

[0048] When setting up the specific Figure 2 and Figure 3 The filter plate 3 extends linearly in the spiral direction of the vortex channel 13, and the distance between the filter plate 3 and the outer arc side of the vortex channel 13 located in the inner circle gradually decreases along the spiral direction of the vortex channel 13, which can reduce the direct impact of the degradation solution on the filter membrane 31 to ensure the service life of the filter membrane 31 as much as possible.

[0049] And refer to Figure 2 , Figure 3 and Figure 4 A breathable membrane 41 is embedded in the sealing plate 4, and an exhaust pipe 6 with one end extending into the filtrate space 14 is provided on the separation tank 1. The outlet of the exhaust pipe 6 is higher than the outlet of the suction pipe 51, and multiple exhaust pipes 6 are commonly connected to a negative pressure suction device; and the sealing plate 4 is arranged in an arc shape, and its outer arc side is arranged close to the filtrate space 14, the exhaust pipe 6 is arranged in a position close to the sealing plate 4 in the filtrate space 14, and the suction pipe 51 is arranged in a position away from the sealing plate 4 in the filtrate space 14.

[0050] In this way, when the degradation solution circulates in the filter space 15, the exhaust pipe 6 sucks the upper cavity of the filtrate space 14 through the negative pressure exhaust device, so that the filtrate space 14 is as negatively pressurized as possible, thereby reducing the probability of bubbles adhering to the filter membrane 31; and when the filtrate space 14 is negatively pressurized, the filtration efficiency of the filter membrane 31 for the degradation solution can also be improved. At the same time, after the degradation solution passes through the filter space 15, a low-pressure area will be formed on the inner arc side of the sealing plate 4, so that the gas in the degradation solution can overflow, pass through the breathable membrane 41 into the filtrate space 14, and be discharged by the exhaust pipe 6, thereby reducing the probability of bubbles adhering to the filter membrane 31 during the filtration process.

[0051] In one embodiment, a liquid level sensor may be provided in the filtrate space 14, and a solenoid valve connected to the sensor may be provided on the exhaust pipe 6. When the liquid level in the filtrate space 14 rises to about to cover the bottom of the exhaust pipe 6, the solenoid valve is controlled to close the exhaust pipe 6 to prevent the exhaust pipe 6 from extracting the filtrate in the filtrate space 14; or refer to Figure 4 A sliding float valve 7 is sleeved on the lower end of the exhaust pipe 6. When the liquid level in the filtrate space 14 rises, the lower end of the exhaust pipe 6 is closed by the float valve 7, which can also prevent the exhaust pipe 6 from extracting the filtrate in the filtrate space 14. The float valve 7 includes a ring 71 sleeved on the outer periphery of the exhaust pipe 6, a sealing plug 72 fixedly connected to the ring 71 at an interval, and a floating block 73 fixedly connected to the bottom of the sealing plug 72.

[0052] In another feasible embodiment, it is further configured that the surface area of ​​the filter membrane 31 after flattening is larger than the opening area of ​​the filter port 32, and the exhaust pipe 6 is connected to a pulse gas supply device. In this way, after the filtration is completed, high-speed gas can be pulsed into the filtrate space 14 through the pulse gas supply device, and the filter membrane 31 can be cleaned by shaking the filter membrane 31 on the filter plate 3, so as to reduce the probability of foam adhesion during subsequent filtration.

[0053] The present application discloses a method for preparing oligomolecular chitosan. Based on the above-mentioned preparation device for oligomolecular chitosan, Figure 1 and Figure 2 , which comprises the following steps:

[0054] S1. Mixing chitosan with water, and then adding glacial acetic acid to dissolve the chitosan to obtain a chitosan solution;

[0055] S2. Adding a complex enzyme to the chitosan solution in S1 for degradation to obtain a chitosan degradation solution;

[0056] S3. The degradation solution in S2 is passed as a feed liquid through the feed pipe 11 into the separation tank 1 for multiple single-stage or multi-stage filtration, and the monosaccharide filtrate is extracted from the filtrate space 14 by the suction tube 51;

[0057] S4. The monosaccharide filtrate in S3 is spray-dried to obtain oligosaccharide chitosan.

[0058] Therefore, by passing the degradation solution into the separation tank 1 for multiple single-stage or multi-stage filtration, the degradation solution can continuously rinse the filter membrane 31 on the filter plate 3, thereby greatly reducing the probability of foam adhering to the filter membrane 31 and affecting the filtration and separation efficiency. Compared with chemical defoaming that affects the purity of oligomolecular chitosan and mechanical defoaming that sets an additional mechanical structure, the preparation method of the present application can independently complete the defoaming operation during the filtration of the degradation solution, which can greatly improve the filtration, separation efficiency and quality of the oligomolecular chitosan degradation solution.

[0059] The implementation principle of the preparation device of oligomolecular chitosan in the embodiment of the present application is:

[0060] When the degradation of the chitosan solution is completed, the degradation solution is pumped into the separation tank 1 through the feed pipe 11. When the degradation solution passes through the vortex channel 13 of the separation tank 1 at a high speed, it passes through multiple filter spaces 15 in sequence. Part of the oligomeric chitosan and water in the degradation solution passes through the filter membrane 31 on the filter plate 3 and enters the filtrate space 14, and then is discharged through the suction pipe 51 under the suction of the suction pump 53. The filtered and separated oligomeric chitosan solution can be collected in the liquid storage tank 54. In this process, since the degradation solution needs to pass through multiple filter spaces 15, the degradation solution can be filtered multiple times in the separation tank 1, which can greatly improve the filtering effect of the degradation solution.

[0061] When the degradation solution passes through the filter space 15, the filter membrane 31 on the filter plate 3 can be continuously washed, which can not only filter and separate, but also rinse the filter membrane 31, thereby greatly reducing the probability of bubbles generated during the filtration and separation process adhering to the filter membrane 31 and affecting the filtration efficiency. At the same time, when the degradation solution passes through the filter space 15, the flow channel becomes narrower, resulting in an accelerated flow rate of the degradation solution, which can reduce the pumping pressure of the degradation solution and reduce the filtration and separation costs.

[0062] Unless otherwise defined, the technical terms or scientific terms used in this application should be understood by people with ordinary skills in the field to which this application belongs. The words "first", "second", "third" and similar words used in the specification and claims of this application do not indicate any order, quantity or importance, but are only used to distinguish different components. "One" or "one" and similar words do not indicate a quantitative limit, but indicate that there is at least one. "Include" or "comprise" and similar words mean that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0063] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A preparation device for oligochitosan, characterized in that: The invention comprises a separation tank (1), wherein the separation tank (1) is provided with a feed pipe (11) and a discharge pipe (12), wherein a vortex baffle (2) is provided in the separation tank (1), wherein the vortex baffle (2) divides the inner cavity space of the separation tank (1) into a vortex channel (13), wherein the feed pipe (11) is connected to an outer ring inlet of the vortex channel (13), and the discharge pipe (12) is connected to an inner ring outlet of the vortex channel (13); A plurality of filter plates (3) extending in the spiral direction of the vortex channel (13) are fixedly connected to the inner arc side of the vortex baffle (2); a filter membrane (31) is embedded in the filter plate (3); a sealing plate (4) is fixedly connected to the free end of the filter plate (3); the sealing plate (4), the filter plate (3) and the vortex baffle (2) enclose a closed filtrate space (14); and a suction filter pipe (51) communicating with the filtrate space (14) is provided on the separation tank (1); There is a gap between the free end of the filter plate (3) and the outer arc side of the vortex channel (13) located on the inner circle; The filter plate (3) extends in a streamlined manner in the spiral direction of the vortex channel (13), and the distance between the filter plate (3) and the outer arc side of the vortex channel (13) located in the inner circle gradually decreases along the spiral direction of the vortex channel (13).

2. The preparation device of oligochitosan according to claim 1, characterized in that: A breathable membrane (41) is embedded in the sealing plate (4), and an exhaust pipe (6) having one end extending into the filtrate space (14) is provided on the separation tank (1), wherein the outlet of the exhaust pipe (6) is higher than the outlet of the suction filtration pipe (51).

3. The preparation device of oligochitosan according to claim 2, characterized in that: The plurality of exhaust pipes (6) are commonly connected to a negative pressure exhaust device.

4. The preparation device of oligochitosan according to claim 1, characterized in that: The sealing plate (4) is arranged in an arc shape, and its outer arc side is arranged close to the filtrate space (14).

5. The preparation device of oligochitosan according to claim 2, characterized in that: The exhaust pipe (6) is arranged in the filtrate space (14) at a position close to the sealing plate (4), and the suction filter pipe (51) is arranged in the filtrate space (14) at a position away from the sealing plate (4).

6. The preparation device of oligochitosan according to claim 1, characterized in that: The filter plate (3) is provided with a filter port (32) extending therethrough, the filter membrane (31) being embedded and installed in the filter port (32), and the surface area of ​​the filter membrane (31) after being flattened is larger than the opening area of ​​the filter port (32).

7. The preparation device of oligochitosan according to claim 2, characterized in that: The exhaust pipe (6) is connected to a pulse air supply device.

8. The preparation device of oligochitosan according to claim 1, characterized in that: The filter holes of the plurality of filter membranes (31) tend to decrease along the spiral direction of the vortex channel (13).

9. A method for preparing oligomolecular chitosan, based on the preparation device for oligomolecular chitosan according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Mixing chitosan with water, and then adding glacial acetic acid to dissolve the chitosan to obtain a chitosan solution; S2. Adding a complex enzyme to the chitosan solution in S1 for degradation to obtain a chitosan degradation solution; S3. The degradation solution in S2 is passed as a feed liquid into the separation tank (1) through the feed pipe (11) for multiple single-stage or multi-stage filtration, and the monosaccharide filtrate is extracted from the filtrate space (14) through the suction filtration pipe (51); S4. The monosaccharide filtrate in S3 is spray-dried to obtain oligosaccharide chitosan.

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