A method for preparing gamma-cyclodextrin by a precipitation technique separation enzyme method

Abstract

The application discloses a method for preparing gamma-cyclodextrin by precipitation technology and enzyme method, and comprises the following steps: taking gamma-cyclodextrin mother liquor prepared by a solvent method and enzyme method as a sample solution; under high-temperature conditions, first, a complex formed by the gamma-cyclodextrin and a reaction aid is dissociated; then, a precipitation separation technology is used; and finally, an inorganic salt precipitant is added to effectively separate a reaction agent, so that the purification of a target product is realized, and a high-efficiency and simple gamma-cyclodextrin separation and purification method is established. By using the method, the total conversion rate of the gamma-cyclodextrin can reach about 53.89%, the recovery rate of the gamma-cyclodextrin after separation can reach 82.76% to 90.84%, the purity is 92.56% to 95.63%, and the residual amount of the reaction aid is 0.02%.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation and purification technology, specifically relating to a method for preparing γ-cyclodextrin by precipitation separation of enzymes. Background Technology

[0002] Cyclodextrins are a class of cyclic oligomers composed of D-glucanopyranoside units linked by α-1,4-glycosidic bonds. Their spatial structure is a hollow cylindrical shape, thus possessing both a hydrophilic surface and a hydrophobic cavity structure. They are promising encapsulation materials with broad applications and have been used in pharmaceuticals, food, cosmetics, and materials science. Cyclodextrins can be classified according to the number of glucose units they comprise; the most common types, composed of 6, 7, and 8 glucose units, are named α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, respectively.

[0003] Compared to α- and β-cyclodextrins, γ-cyclodextrins have a larger lumen, enabling them to encapsulate larger or more complex molecules, thus showing broad application prospects in pharmaceuticals, food, and cosmetics. Due to their good water solubility (25 g / 100 mL water at 25°C) and biocompatibility, γ-cyclodextrins exhibit higher solubility when forming complexes with poorly water-soluble guest molecules, further expanding their application potential in food and pharmaceuticals. However, the preparation and purification of γ-cyclodextrins present significant challenges, primarily due to the difficulty in separating them from reaction auxiliaries.

[0004] Currently, the production of γ-cyclodextrin mainly utilizes starch as a substrate and is catalyzed by γ-cyclodextrin glucosyltransferase. However, during the production process, organic reagents such as macrocyclic ketones are often added to improve the yield. A commonly used reaction aid is cyclododecanone, as described in patents CN201310036791 and CN102827900B. In these patents, the removal of the reaction aid primarily employs steam distillation, but this method is energy-intensive and time-consuming, making it unsuitable for industrial-scale production. Furthermore, CN109400760A reports a method for purifying γ-cyclodextrin using cyclodextrin hydrolase, but this method requires strict control over enzyme selection and reaction conditions, easily leading to enzyme inactivation and hindering industrial scale-up. Therefore, there is an urgent need to develop an efficient and rapid separation and purification method to reduce costs and improve production efficiency. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing γ-cyclodextrin by separating enzymes using precipitation technology.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing γ-cyclodextrin by precipitation separation enzyme method, characterized in that it includes,

[0009] The complex formed by γ-cyclodextrin and reaction aids was diluted and dissociated at high temperature. After adding a precipitant, stirring and filtering, a solution was obtained. The solution was desalted using an ion exchange resin, and then concentrated and dried to obtain high-purity γ-cyclodextrin.

[0010] In a preferred embodiment of the preparation method described in this invention, the precipitant is a soluble potassium salt solution, including one or more of potassium phosphate, potassium hydroxide, potassium acetate, potassium chloride solution, and potassium dihydrogen phosphate.

[0011] In a preferred embodiment of the preparation method described in this invention, the reaction aid is a phenyl-substituted borate or a phenyl-substituted borate derivative, including one or more of 2-fluorophenylboronic acid, methylphenylboronic acid, 4-nitrophenylboronic acid, and sodium tetraphenylborate.

[0012] As a preferred embodiment of the preparation method of the present invention, the complex formed by γ-cyclodextrin and the reaction aid is diluted and dissociated at high temperature, wherein the dilution factor is 2 to 10 times, the temperature is 60 to 95°C, and the time is 1 to 2 hours.

[0013] In a preferred embodiment of the preparation method described in this invention, the concentration of the precipitant is 20-50%.

[0014] In a preferred embodiment of the preparation method described in this invention, the addition of the precipitant and stirring are carried out at a temperature of 70–95°C, a stirring rate of 150–200 rpm, and a stirring time of 1–60 min.

[0015] As a preferred embodiment of the preparation method described in this invention, the ion exchange resin includes anion exchange resin and cation exchange resin, wherein the anion exchange resin includes macroporous weak-base styrene-based anion exchange resin, and the cation exchange resin includes macroporous strong-acid styrene-based cation exchange resin.

[0016] As a preferred embodiment of the preparation method described in this invention, the desalination conditions are as follows: the conductivity of the material at the outlet of the ion exchange resin column is less than 50 μs / cm, the feeding is stopped, and the ion exchange resin is regenerated; the temperature of the filtrate is 10–50°C, the pH is 4.0–8.0, and the injection flow rate is 1–2 BV / h.

[0017] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing γ-cyclodextrin by separating γ-cyclodextrin using precipitation technology and enzymatic methods.

[0018] The recovery rate of the γ-cyclodextrin was 82.76%–90.84%, and the purity was 92.56%–95.63%.

[0019] Beneficial effects of this invention:

[0020] (1) This invention uses the mother liquor of γ-cyclodextrin prepared by solvent enzymatic methods as the sample solution and establishes a new, efficient, and simple method for separating and purifying γ-cyclodextrin by salt precipitation. The process involves high-temperature dissociation of the complex followed by inorganic salt precipitation, simplifying the entire operation, eliminating cumbersome purification steps, and significantly reducing equipment requirements and operational difficulty. Furthermore, this method is suitable for large-scale production, contributing to improved operability and stability in industrial applications. The method ultimately achieved a γ-cyclodextrin recovery rate of 90.84% ​​and a product purity of up to 95.63%.

[0021] (2) This invention uses ion exchange resin to desalt the separated stock solution, resulting in a final conductivity of less than 50 μS / cm, which significantly reduces the impurity content in the product and further improves the quality of γ-cyclodextrin. This desalting process simplifies subsequent purification steps while ensuring high product purity, effectively reducing production costs. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 This is the HPLC chromatogram of the original solution obtained by using 15% (w / w) cassava starch as a substrate in this invention.

[0024] Figure 2 This is the HPLC chromatogram of the product after separation by precipitation method according to the present invention.

[0025] Figure 3This invention relates to the effect of temperature on precipitation separation.

[0026] Figure 4 This invention relates to the effect of potassium chloride addition on precipitation separation. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available. See Table 1 for details.

[0031] Table 1

[0032]

[0033] The γ-cyclodextrin glucosyltransferase was derived from a genetically engineered strain of Bacillus subtilis containing the gene sequence of this enzyme. (Published literature on γ-cyclodextrin glucosyltransferase: Wang Lei. Recombinant expression and application of Bacillus clarkii 7364 γ-cyclodextrin glucosyltransferase [D]. Jiangnan University, 2013.; doi number of the literature on the construction of genetically engineered strains of Bacillus subtilis: 10.1021 / acs.jafc.2c08320)

[0034] The anion exchange resin used in the examples was specifically D354 anion exchange resin from Hangzhou Zhengguang Resin Co., Ltd.; the cation exchange resin was specifically D001 cation exchange resin from Hangzhou Zhengguang Resin Co., Ltd.; and sodium tetraphenylborate was purchased from Shanghai Titan Technology Co., Ltd.

[0035] In the embodiments and comparative examples of this invention, the detection method for cyclodextrin employs high-performance liquid chromatography (HPLC): the reaction solution is boiled in a water bath for 30 min to inactivate the enzyme, diluted 10-fold with the mobile phase, allowed to stand for 30 min, centrifuged (10,000 × g, 10 min), and the supernatant is filtered through a 0.22 μm organic filter membrane before HPLC analysis of the product. The HPLC conditions are: Waters 1525 HPLC system (equipped with a differential refractive index detector), ChemCore NH2 column (4.6 × 250 mm), column temperature 40 °C, mobile phase 70% (v / v) acetonitrile aqueous solution, and flow rate 1 mL / min.

[0036] Example 1

[0037] (1) Using a 15% (w / w) dry cassava starch solution as the substrate, the mixture was first prepared at 55°C for 10 min. Then, γ-cyclodextrin glucosyltransferase was added at a concentration of 3 U enzyme solution / g starch, and the mixture was heated to 90°C for starch gelatinization and liquefaction. Next, the enzyme was inactivated at 90°C for 30 min, followed by cooling to 55°C. At 55°C, γ-cyclodextrin glucosyltransferase was added again to the reaction system at a concentration of 5 U enzyme solution / g starch, along with 2% sodium tetraphenylborate (a reaction auxiliary agent) of the total system mass. The reaction was carried out for cyclization, and after 12 h, the enzyme was inactivated in a boiling water bath for 30 min to obtain the original solution to be treated.

[0038] (2) Dilute the original solution to be treated with pure water 5 times to obtain a material solution with a concentration of 1.5%, and heat it to 90°C at a heating rate of 5°C / min, and keep it at that temperature for 60 min.

[0039] (3) After the heat preservation is completed, maintain the temperature at 90℃ and gradually add 8.72 mL of 20% potassium chloride solution (the molar ratio of sodium tetraphenylborate to potassium chloride is 1:2) to the reaction system. The stirring speed is controlled at 150 rpm to ensure that the mixture is fully mixed and the precipitation reaction is carried out for 1 hour. After the precipitation reaction is completed, filter the solution while it is still hot and collect the filtrate.

[0040] (4) The filtrate from step (3) is desalinated. Specifically, the cation exchange resin column and the anion exchange resin column are connected in series. The filtrate is adjusted to pH 5.0 with sodium hydroxide at room temperature and fed into the cation exchange resin column at a flow rate of 2 BV / h. The effluent from the cation exchange resin column then enters the anion exchange resin column, and the effluent from the anion exchange resin column is collected. When the conductivity of the effluent from the anion exchange resin column is less than 50 μS / cm, the feeding is stopped and the ion exchange resin is regenerated.

[0041] (5) The desalted liquid collected in step (4) was concentrated using a rotary evaporator at a water bath temperature of 80°C and a negative pressure of -0.088MPa to 20% of its original volume. After concentration, the concentrate was freeze-dried to obtain a powdered high-purity γ-cyclodextrin product.

[0042] The experimental results showed that the purity of γ-cyclodextrin reached 95.21%, the recovery rate was 90.52%, and the residual amount of sodium tetraphenylborate was 0.02%.

[0043] Example 2

[0044] The difference between this embodiment and Example 1 is that the addition of 8.72 mL of 20% potassium chloride solution at 50°C in step (3) is adjusted. The rest of the preparation process is the same as in Example 1.

[0045] Example 3

[0046] The difference between this embodiment and Example 1 is that in step (3), 8.72 mL of 20% potassium chloride solution is gradually added at 70°C. The rest of the preparation process is the same as in Example 1.

[0047] Example 4

[0048] The difference between this embodiment and Example 1 is that 11.48 mL of 20% potassium acetate solution (the molar ratio of sodium tetraphenylborate to potassium acetate is 1:2) is gradually added in step (3). The rest of the preparation process is the same as in Example 1.

[0049] Example 5

[0050] The difference between this embodiment and Example 1 is that 6.56 mL of 20% potassium hydroxide solution (sodium tetraphenylborate to potassium hydroxide molar ratio of 1:2) is gradually added in step (3), while the rest of the preparation process is the same as in Example 1.

[0051] Example 6

[0052] The difference between this embodiment and embodiment 1 is that the dilution process is not performed in step (2), while the rest of the preparation process is the same as in embodiment 1.

[0053] Example 7

[0054] The difference between this embodiment and embodiment 1 is that the dilution factor in step (2) is adjusted to 2 times, while the rest of the preparation process is the same as in embodiment 1.

[0055] Example 8

[0056] The difference between this embodiment and Example 1 is that 2.18 mL of a 20% potassium chloride solution (the molar ratio of sodium tetraphenylborate to potassium chloride is 2:1) is gradually added in step (3). The rest of the preparation process is the same as in Example 1.

[0057] Example 9

[0058] The difference between this embodiment and Example 1 is that 4.36 mL of 20% potassium chloride solution (sodium tetraphenylborate and potassium chloride in a molar ratio of 1:1) is gradually added in step (3). The rest of the preparation process is the same as in Example 1.

[0059] Table 2. Separation of γ-cyclodextrin in different embodiments

[0060]

[0061]

[0062] Table 2 shows that temperature, type of precipitant, and dilution factor have a significant impact on the recovery rate and purity of γ-cyclodextrin. Specifically, increasing the temperature significantly improves the recovery rate and purity of γ-cyclodextrin, as high temperature facilitates the dissociation of sodium tetraphenylborate, thus promoting separation. The choice of different precipitants affects the purity and recovery rate of the final product, with potassium chloride showing superior performance as a precipitant. Appropriate dilution factors can significantly improve the separation effect, aiding in the dissociation and precipitation of reaction auxiliaries. At higher temperatures (e.g., 90℃), the γ-cyclodextrin-sodium tetraphenylborate complex is more easily dissociated. High temperatures increase molecular kinetic energy, weakening the weak intermolecular interactions within the complex, thereby breaking the bond between γ-cyclodextrin and sodium tetraphenylborate, releasing sodium tetraphenylborate. Appropriate dilution factors (e.g., 5 times) reduce the ion concentration in the system, weakening the stability of the sodium tetraphenylborate-γ-cyclodextrin complex, making γ-cyclodextrin more easily dissociate and release sodium tetraphenylborate. At lower dilution factors (e.g., undiluted or 2-fold dilution), the ion concentration in the solution is high, the stability of the complex is enhanced, and sodium tetraphenylborate is difficult to separate completely, reducing the separation efficiency. At higher dilution factors, the dissociation of the complex is enhanced, and K... + It is more likely to form a precipitate with sodium tetraphenylborate. Therefore, appropriate dilution and temperature can optimize reaction conditions and effectively improve the separation efficiency and purity of γ-cyclodextrin.

[0063] Comparative Example 1

[0064] Using a 15% (w / w) dry cassava starch solution as the substrate, the mixture was first prepared at 55°C for 10 min. Then, γ-cyclodextrin glucosyltransferase was added at a concentration of 3 U enzyme solution / g starch, and the mixture was heated to 90°C for starch gelatinization and liquefaction. Next, the enzyme was inactivated at 90°C for 30 min, followed by cooling to 55°C. At 55°C, γ-cyclodextrin glucosyltransferase was added again to the reaction system at a concentration of 5 U enzyme solution / g starch, with 2% (by weight) of ultrapure water added as a control. The cyclization reaction was then carried out for 12 h, followed by enzyme inactivation in a boiling water bath for 30 min to obtain the original solution to be treated.

[0065] Comparative Example 2

[0066] (1) Using a 15% (w / w) dry cassava starch solution as the substrate, the mixture was first prepared at 55°C for 10 min. Then, γ-cyclodextrin glucosyltransferase was added at a concentration of 3 U enzyme solution / g starch, and the mixture was heated to 90°C for starch gelatinization and liquefaction. Next, the enzyme was inactivated at 90°C for 30 min, followed by cooling to 55°C. At 55°C, γ-cyclodextrin glucosyltransferase was added again to the reaction system at a concentration of 5 U enzyme solution / g starch, along with cyclododecanone, a reaction auxiliary agent equivalent to 2% of the total mass of the system, to carry out the cyclization reaction. After reacting for 12 h, the enzyme was inactivated in a boiling water bath for 30 min to obtain the original solution to be treated.

[0067] (2) Dilute the original solution to be treated with pure water by 2 times, then use a steam distillation apparatus to distill off the cyclododecanone, collect the distillate, and use a rotary evaporator to concentrate the distillate back to the original volume.

[0068] Comparative Example 3

[0069] The difference between this comparative example and comparative example 2 is that the reaction aid in step (1) is changed to 5-cyclohexadecene-1-one, while the rest of the preparation process is the same as that of comparative example 2.

[0070] Comparative Example 4

[0071] The difference between this comparative example and comparative example 2 is that the reaction aid in step (1) is changed to cyclopentadecanone, while the rest of the preparation process is the same as that of comparative example 2.

[0072] Comparative Example 5

[0073] The difference between this comparative example and comparative example 2 is that the reaction aid in step (1) is changed to potassium tetraphenylborate, while the rest of the preparation process is the same as that of comparative example 2.

[0074] Comparative Example 6

[0075] The difference between this comparative example and Example 1 is that in step (3), 8.72 mL of a 20% potassium chloride solution (the molar ratio of sodium tetraphenylborate to potassium chloride is 1:2) is gradually added at room temperature (25°C).

[0076] The recovery rate of γ-cyclodextrin obtained in Comparative Example 6 was only 1.2%. This indicates that at room temperature, the complex structure formed by γ-cyclodextrin and the reaction aid is stable, resulting in poor precipitation separation. High-temperature conditions (such as 90°C in Example 1) can disrupt the structure of the complex, releasing the reaction aid. Adding a precipitant can then effectively separate γ-cyclodextrin. Therefore, precipitation reactions at room temperature cannot effectively remove the reaction aid, leading to a significant decrease in the recovery rate of γ-cyclodextrin.

[0077] Comparative Example 7

[0078] The difference between this comparative example and Example 1 is that, in step (3), 6.84 mL of a 20% sodium chloride solution (sodium tetraphenylborate to sodium chloride in a molar ratio of 1:2) is gradually added at 90°C. The rest of the preparation process is the same as in Example 1.

[0079] Comparative Example 8

[0080] The difference between this comparative example and Example 1 is that, in step (3), 12.98 mL of a 20% concentration calcium chloride solution (the molar ratio of sodium tetraphenylborate to calcium chloride is 1:2) is added at 90°C. The rest of the preparation process is the same as in Example 1.

[0081] Table 3. Conversion rate and separation of γ-cyclodextrin in different comparative proportions.

[0082]

[0083] Note: (ND = not dected)

[0084] Table 3 shows that the conversion and recovery rates of γ-cyclodextrin differed when using different reaction auxiliaries. For example, the recovery rates of γ-cyclodextrin using large-ring reaction auxiliaries such as cyclododecanone, 5-cyclohexadecen-1-one, and cyclopentadecanone reached over 85%, but the product purity and conversion rates were low. Potassium tetraphenylborate had no significant effect on the production of the system, but sodium tetraphenylborate could increase the conversion rate of γ-cyclodextrin by 169.7%, with a residual amount of only 0.02% after separation. The recovery rate and purity of γ-cyclodextrin showed significant differences at different temperatures. The recovery rate of Comparative Example 6 (reaction at room temperature) was only 1.2%, while the recovery rate was significantly improved at 90℃. This indicates that temperature is an important factor affecting the separation and purification of γ-cyclodextrin; high temperature can effectively promote the dissociation of the complex, causing sodium tetraphenylborate to precipitate and separate, thus improving the purity of γ-cyclodextrin. Compared with other ions such as sodium and calcium, potassium ions showed the best effect in the separation process. Sodium and calcium ions have low reactivity, making it difficult to form stable precipitates, which leads to decreased separation efficiency and product purity. The unique chemical reactivity of potassium ions ensures the efficiency of sodium tetraphenylborate precipitation separation, making it a superior precipitant choice.

[0085] Figure 1 The image shown is a high-performance liquid chromatography (HPLC) chromatogram of the stock solution obtained using 15% tapioca starch as a substrate. Figure 1 Multiple peaks were observed in the stock solution, indicating complex components in the system, including the target product γ-cyclodextrin and the reaction auxiliary sodium tetraphenylborate. This result shows that the system contains a high level of impurities before precipitation separation, requiring further purification to obtain high-purity γ-cyclodextrin. Figure 2 The image shown is the HPLC chromatogram of γ-cyclodextrin after precipitation and separation. Figure 1 compared to, Figure 2 The peak of γ-cyclodextrin was significantly enhanced, while the peak of sodium tetraphenylborate essentially disappeared. This indicates that using potassium chloride as a precipitant, the dissociation reaction of sodium tetraphenylborate under high temperature conditions generates a precipitate, removing unwanted byproducts from the system and achieving a significant purification effect. This method is not only simple and easy to operate, but also helps to improve product purity and recovery rate, making it suitable for large-scale applications. Figure 3 and Figure 4 The results together validated the importance of optimizing the potassium ion molar ratio and reaction temperature for the separation of γ-cyclodextrin. Figure 4 In the study, the separation effect was optimal when the molar ratio of potassium ions to sodium tetraphenylborate was 1:2, indicating that this ratio of potassium ion supply was most suitable for precipitation formation. Figure 3In this study, high temperatures (e.g., 90°C) promoted the dissociation of the complex and facilitated the formation of efficient potassium ion precipitates, thereby maximizing the purity and recovery rate of γ-cyclodextrin. Overall, the combined effect of a suitable potassium ion ratio and high-temperature conditions provides an optimized solution for improving the separation purity and recovery rate of γ-cyclodextrin, and this method is suitable for industrial application.

[0086] 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 it. 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 spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing γ-cyclodextrin by precipitation separation of enzymes, characterized in that: include, (1) Using a 15% (w / w) dry cassava starch solution as the substrate, the slurry was first prepared at 55℃ for 10 min; then γ-cyclodextrin glucosyltransferase was added at a rate of 3 U enzyme solution / g starch, and the mixture was heated to 90℃ for starch gelatinization and liquefaction; then, the enzyme was inactivated at 90℃ for 30 min, and then cooled to 55℃; at 55℃, γ-cyclodextrin glucosyltransferase was added to the reaction system again at a rate of 5 U enzyme solution / g starch, and sodium tetraphenylborate, a reaction aid equivalent to 2% of the total mass of the system, was added to carry out the cyclization reaction. After 12 h of reaction, the enzyme was inactivated in a boiling water bath for 30 min to obtain the original solution to be treated. (2) Dilute the original solution to be treated with pure water 5 times to obtain a material solution with a concentration of 1.5%, and heat it to 90°C at a heating rate of 5°C / min, and keep it at that temperature for 60 min. (3) After the heat preservation is completed, keep the temperature at 90℃ and gradually add 8.72 mL of 20% potassium chloride solution to the reaction system. The molar ratio of sodium tetraphenylborate to potassium chloride is 1:

2. The stirring speed is controlled at 150 rpm to ensure that the mixture is fully mixed and the precipitation reaction is carried out for 1 h. After the precipitation reaction is completed, filter the solution while it is still hot and collect the filtrate. (4) The filtrate in step (3) is desalinated. Specifically, the cation exchange resin column and the anion exchange resin column are connected in series. The filtrate is adjusted to pH 5.0 with sodium hydroxide at room temperature and fed into the cation exchange resin column at a flow rate of 2 BV / h. The material from the cation exchange resin column outlet enters the anion exchange resin column and the material from the anion exchange resin column outlet is collected. When the conductivity of the material from the anion exchange resin column outlet is less than 50 μs / cm, the feeding is stopped and the ion exchange resin is regenerated. (5) The desalted liquid separated is concentrated in a rotary evaporator at a water bath temperature of 80°C and a negative pressure of -0.088 MPa to 20% of the original volume. After concentration, the concentrated liquid is freeze-dried to finally obtain a powdered high-purity γ-cyclodextrin product. The experimental results showed that the purity of γ-cyclodextrin reached 95.21%, the recovery rate was 90.52%, and the residual amount of sodium tetraphenylborate was 0.02%.

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