A method for preparing a pharmaceutical sweetener

Abstract

This disclosure relates to the field of pharmaceutical excipients and additives, specifically a method for preparing a pharmaceutical sweetener. The method includes the following steps: preparing modified microalgae polysaccharides; adding the modified microalgae polysaccharides, a first sweetener, a second sweetener, dietary fiber, and an acidity regulator to water, mixing thoroughly, and then spray-drying to obtain the pharmaceutical sweetener. This disclosure solves the problem of poor palatability of microalgae polysaccharides; enabling microalgae polysaccharides, as a filler sweetener, to be compounded with high-intensity sweeteners, other filler sweeteners, dietary fiber, and acidity regulators, thereby possessing both good tableting performance and antioxidant activity.

Description

Technical Field

[0001] This disclosure relates to the field of pharmaceutical excipient additives technology, specifically a method for preparing a pharmaceutical sweetener. Background Technology

[0002] Existing pharmaceutical sweeteners mostly use single synthetic sweeteners or sugar alcohols, resulting in monotonous taste, limited functionality, and a noticeable bitter aftertaste. Microalgae-derived polysaccharides offer advantages such as sustainable sources and diverse functional activities; however, polysaccharides extracted from microalgae like Chlorella generally suffer from a strong algal odor and poor palatability, limiting their application in pharmaceutical excipients. Traditional deodorization methods, such as activated carbon adsorption, have limited effectiveness, organic solvent extraction poses safety risks, and strong oxidant treatment easily leads to polysaccharide degradation and loss of activity. Furthermore, existing sweetener formulations lack multifunctional integration of tableting performance, lyophilization protection, and antioxidant functions, failing to meet the complex excipient requirements of modern pharmaceutical preparations. Therefore, developing a microalgae-derived compound sweetener with good palatability and multifunctional pharmacological activity, along with its mild and efficient preparation method, has significant industrial application value. Summary of the Invention

[0003] This disclosure provides a method for preparing a pharmaceutical sweetener to address the shortcomings of related technologies.

[0004] According to a first aspect of the present disclosure, a method for preparing a pharmaceutical sweetener is provided, the method comprising the following steps: Step 1: Preparation of modified microalgal polysaccharides; Step 2: Add the modified microalgae polysaccharide, the first sweetener, the second sweetener, dietary fiber, and the acidity regulator to water, mix evenly, and then spray dry to obtain the pharmaceutical sweetener.

[0005] In one aspect of the present disclosure, the mass ratio of the modified microalgae polysaccharide, the first sweetener, the second sweetener, the dietary fiber, and the acidity regulator is selected from (20-40):(0.2-1):(25-50):(5-20):(0.3-1).

[0006] In one aspect of this disclosure, the first sweetener is selected from at least one of steviol glycosides, mogrosides, sucralose, and acesulfame potassium.

[0007] In one aspect of the present disclosure, the second sweetener is selected from at least one of erythritol, xylitol, maltitol, mannitol, sorbitol, trehalose, and lactitol.

[0008] In one aspect of this disclosure, the dietary fiber is selected from at least one of fructooligosaccharides, inulin, galactooligosaccharides, polydextrose, resistant dextrin, and oat β-glucan.

[0009] In one aspect of the embodiments of this disclosure, the acidity regulator is selected from at least one of citric acid, malic acid, tartaric acid, lactic acid, ascorbic acid, and gluconic acid.

[0010] In one aspect of this disclosure, the modified microalgal polysaccharide is a deodorized Chlorella polysaccharide; the deodorized Chlorella polysaccharide is prepared through the following steps: Step 1-a: Prepare crude extract of Chlorella polysaccharides; Step 2-a: The crude Chlorella polysaccharide extract is subjected to chemical oxidation to remove odor; a chemically oxidized and deodorized Chlorella polysaccharide extract is obtained. Step 3-a: The chemically oxidized and deodorized Chlorella polysaccharide extract is subjected to biotransformation to obtain a biotransformed and deodorized Chlorella polysaccharide extract; Step 4-a: The deodorized Chlorella polysaccharide fermentation broth after bioconversion is subjected to Maillard reaction to mask the odor, thereby obtaining crude deodorized Chlorella polysaccharide extract; Step 5-a: The crude extract of Chlorella polysaccharide after deodorization is purified by membrane separation to obtain the deodorized Chlorella polysaccharide.

[0011] In one aspect of this disclosure, step 2 includes: Step 1-b: Add 30% hydrogen peroxide aqueous solution dropwise to the crude Chlorella polysaccharide extract until the final concentration is 2-5 g / L; then stir the reaction for 20-45 min. Step 2-b: Then raise the temperature to 80℃-90℃ and hold for 10-20 minutes; Step 3-b: Add 1.5%-3% activated carbon by weight of the system, stir at 50℃-55℃ for 45-70 minutes, and then filter to obtain the chemically oxidized and deodorized Chlorella polysaccharide extract.

[0012] In one aspect of this disclosure, step 3 includes: Step 1-c: Adjust the pH of the chemically oxidized and deodorized Chlorella polysaccharide extract to 6.0-6.5, maintain the temperature at 37℃-40℃, inoculate with 1%-2% Lactobacillus plantarum and 0.5%-1% Lactobacillus casei; then ferment in a sealed container for 12-24 hours. Step 2-c: Heat to 75℃-80℃ and maintain for 20-30 minutes. Then remove the precipitate by centrifugation to obtain the deodorized Chlorella polysaccharide extract after biotransformation.

[0013] In one aspect of this disclosure, step 4 includes: Step 1-d: Adjust the pH of the biotransformed and deodorized Chlorella polysaccharide extract to 7.0-7.5, and then add 0.3%-0.8% lysine or arginine; Step 2-d: Heat to 85℃-95℃ and react for 30-45 minutes; after the reaction is complete, quickly cool to below 50℃ to obtain the crude Chlorella polysaccharide extract after deodorization treatment.

[0014] In one aspect of this disclosure, step 5 includes: Step 1-e: Filter the deodorized Chlorella polysaccharide extract crude product through a 0.1-0.2μm microfiltration membrane; Step 2-e: The solution is then concentrated using an ultrafiltration membrane with a molecular weight cutoff of 10-30 kDa to 1 / 5 to 1 / 8 of its original volume, yielding the ultrafiltration concentrate. Step 3-e: The ultrafiltration retentate concentrate is then treated with a nanofiltration membrane with a molecular weight cutoff of 200-500 Da. The nanofiltration retentate is collected and freeze-dried to obtain the deodorized Chlorella polysaccharide.

[0015] In one aspect of this disclosure, the pharmaceutical sweetener is selected from any of the following components in parts by weight: Component a: 35 parts by weight of deodorized Chlorella polysaccharide, 0.3 parts by weight of steviol glycosides, 20 parts by weight of erythritol, 20 parts by weight of trehalose, 12 parts by weight of fructooligosaccharides and 0.4 parts by weight of citric acid; Component b: 37.5 parts by weight of deodorized Chlorella polysaccharide, 0.45 parts by weight of mogroside, 25 parts by weight of xylitol, 15 parts by weight of maltitol, 8 parts by weight of inulin, 5 parts by weight of resistant dextrin and 0.5 parts by weight of malic acid. Component c: 37.5 parts by weight of deodorized Chlorella polysaccharide, 0.5 parts by weight of sucralose, 25 parts by weight of mannitol, 20 parts by weight of sorbitol, 6 parts by weight of oat β-glucan, 6 parts by weight of resistant dextrin, and 0.5 parts by weight of ascorbic acid.

[0016] In one aspect of this disclosure, the crude extract of Chlorella polysaccharides is prepared by the following steps: Step 1-f: Weigh the Chlorella powder; add it to water at a material-to-liquid ratio of 1:(20-30), and extract in a water bath at 80℃-85℃ for 2-3 hours; then centrifuge and collect the supernatant. Step 2-f: Add an equal volume of 10% trichloroacetic acid solution to the supernatant obtained in step 1-f, stir, and let stand overnight at 4°C; then centrifuge and collect the supernatant. Step 3-f: Add 3 times the volume of anhydrous ethanol to the supernatant obtained in step 2-f, stir and let stand overnight at 4°C; then centrifuge and collect the precipitate; dry the precipitate and dissolve it in water to obtain the crude extract of Chlorella polysaccharide.

[0017] Compared with the prior art, the beneficial effects of this disclosure are: This disclosure utilizes a three-stage deodorization process involving chemical oxidation, biotransformation, and Maillard reaction to effectively remove the algal odor from Chlorella polysaccharides, thus solving the problem of poor palatability of microalgal polysaccharides. As a filler sweetener, it can be compounded with high-intensity sweeteners, other filler sweeteners, dietary fiber, and acidity regulators, thereby possessing good tableting performance, freeze-drying protection properties, and antioxidant activity. The raw materials are sustainable, the process is mild and low-cost, and it is suitable for various dosage forms such as oral liquids, chewable tablets, and freeze-dried preparations. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0019] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0020] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0021] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0022] Unless otherwise stated, the terms used in this disclosure have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this disclosure).

[0023] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0024] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0025] In this disclosure, the Chlorella polysaccharide prepared in this disclosure is less sweet than sucrose and exists as a filler sweetener; it needs to be used in combination with other high-intensity sweeteners and filler sweeteners.

[0026] The present disclosure is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure.

[0027] Example 1: Example 1 includes the following steps: Weigh 150g of Chlorella powder; add it to water at a material-to-liquid ratio of 1:20, and extract in a water bath at 80℃ for 3 hours; then centrifuge (4000rpm, 5min) and collect the supernatant; add an equal volume of 10% trichloroacetic acid solution to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 5min) and collect the supernatant; add 3 times the volume of anhydrous ethanol to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 10min) and discard the supernatant to collect the precipitate; dry the precipitate and dissolve it in 10 times its mass of water to obtain the crude Chlorella polysaccharide extract of this embodiment.

[0028] Add 30% hydrogen peroxide solution dropwise to the crude Chlorella polysaccharide extract until the final concentration is 3.5 g / L; then stir the reaction for 30 min; then raise the temperature to 85°C and maintain it for 15 min; then add 2.5% activated carbon by mass of the system, stir at 50°C for 60 min, and then filter to obtain the chemically oxidized and deodorized Chlorella polysaccharide extract of this embodiment; then adjust the pH value to 6.2, maintain the temperature at 40°C, and inoculate with 1.2% Lactobacillus plantarum and 0.8% Lactobacillus casei; then seal. Ferment for 24 hours; heat to 80℃ and maintain for 30 minutes, then centrifuge (3000 rpm, 4 minutes) to remove the precipitate, obtaining a deodorized Chlorella polysaccharide extract through bioconversion; adjust the pH of the deodorized Chlorella polysaccharide extract to 7.2, then add 0.5% lysine; heat to 90℃ and react for 45 minutes; after the reaction, add 3 times the volume of deionized water to rapidly cool the system to below 50℃, obtaining the crude deodorized Chlorella polysaccharide extract.

[0029] The crude extract of Chlorella polysaccharides after deodorization was filtered through a 0.15 μm microfiltration membrane; then concentrated through an ultrafiltration membrane with a molecular weight cutoff of 10 kDa to 1 / 8 of the original volume, yielding an ultrafiltration concentrate; the ultrafiltration concentrate was then treated through a nanofiltration membrane with a molecular weight cutoff of 200 Da, and the nanofiltration concentrate was collected and freeze-dried to obtain deodorized Chlorella polysaccharides.

[0030] 35 parts by weight of the aforementioned freeze-dried and deodorized Chlorella polysaccharide, 0.3 parts by weight of steviol glycoside, 20 parts by weight of erythritol, 20 parts by weight of trehalose, 12 parts by weight of fructooligosaccharide, and 0.4 parts by weight of citric acid were added to 200 parts by weight of deionized water, mixed evenly, and spray-dried (inlet air temperature 170°C, outlet air temperature 75°C) to obtain the pharmaceutical sweetener of this embodiment.

[0031] Comparative Example 1: Comparative Example 1 includes the following steps: 0.3 parts by weight of steviol glycosides, 30 parts by weight of erythritol, 45 parts by weight of trehalose, 12 parts by weight of fructooligosaccharides and 0.4 parts by weight of citric acid were added to 200 parts by weight of deionized water, mixed evenly, and spray-dried (inlet air temperature 170°C, outlet air temperature 75°C) to obtain the pharmaceutical sweetener of this comparative proportion.

[0032] Example 2: Example 2 includes the following steps: Weigh 150g of Chlorella powder; add it to water at a material-to-liquid ratio of 1:20, and extract in a water bath at 80℃ for 3 hours; then centrifuge (4000rpm, 5min) and collect the supernatant; add an equal volume of 10% trichloroacetic acid solution to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 5min) and collect the supernatant; add 3 times the volume of anhydrous ethanol to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 10min) and discard the supernatant to collect the precipitate; dry the precipitate and dissolve it in 10 times its mass of water to obtain the crude Chlorella polysaccharide extract of this embodiment.

[0033] Add 30% hydrogen peroxide aqueous solution dropwise to the crude Chlorella polysaccharide extract until the final concentration is 3.5 g / L; then stir the reaction for 30 min; then heat to 85℃ and maintain for 15 min; then add 2.5% activated carbon by mass of the system, stir at 50℃ for 60 min, and then filter to obtain the chemically oxidized and deodorized Chlorella polysaccharide extract of this embodiment; filter the chemically oxidized and deodorized Chlorella polysaccharide extract through a 0.15 μm microfiltration membrane; then treat it through a nanofiltration membrane with a molecular weight cutoff of 200 Da, collect the nanofiltration retentate, and freeze-dry it to obtain the deodorized Chlorella polysaccharide of this embodiment.

[0034] 35 parts by weight of the aforementioned freeze-dried and deodorized Chlorella polysaccharide, 0.3 parts by weight of steviol glycoside, 20 parts by weight of erythritol, 20 parts by weight of trehalose, 12 parts by weight of fructooligosaccharide, and 0.4 parts by weight of citric acid were added to 200 parts by weight of deionized water, mixed evenly, and spray-dried (inlet air temperature 170°C, outlet air temperature 75°C) to obtain the pharmaceutical sweetener of this embodiment.

[0035] The main difference between Example 2 and Example 1 is that Example 2 only includes the chemical oxidation deodorization step, and does not include biotransformation and Maillard reaction deodorization.

[0036] Comparative Example 2: Comparative Example 2 includes the following steps: Weigh 150g of Chlorella powder; add it to water at a material-to-liquid ratio of 1:20, and extract in a water bath at 80℃ for 3h; then centrifuge (4000rpm, 5min) and collect the supernatant; add an equal volume of 10% trichloroacetic acid solution to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 5min) and collect the supernatant; add 3 times the volume of anhydrous ethanol to the supernatant, stir and let stand overnight at 4℃; then centrifuge (4000rpm, 10min) and discard the supernatant to collect the precipitate; dry the precipitate to obtain the Chlorella polysaccharide of this comparative example.

[0037] 35 parts by weight of the aforementioned Chlorella polysaccharide, 0.3 parts by weight of steviol glycoside, 20 parts by weight of erythritol, 20 parts by weight of trehalose, 12 parts by weight of fructooligosaccharide and 0.4 parts by weight of citric acid were added to 200 parts by weight of deionized water, mixed evenly, and spray-dried (inlet air 170°C, outlet air 75°C) to obtain the pharmaceutical sweetener of this comparative example.

[0038] The main difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not include a deodorization step.

[0039] Performance testing: Palatability testing: Sensory evaluation was used to test the palatability of Examples 1-2 and Comparative Examples 1-2. A panel of 10 evaluators scored the samples on a 9-point scale, with 1 point representing extremely fishy smell and 9 points representing no fishy smell. Blind testing was conducted on the samples from Examples 1-2 and Comparative Examples 1-2. The results showed that the average score for Example 1 was 8.5 points; the average score for Comparative Example 1 was 9 points; the average score for Example 2 was 5.6 points; and the average score for Comparative Example 2 was 2.3 points. Furthermore, more than half of the evaluators reported that the sample from Example 1 had an aroma similar to that of a lactic acid bacteria beverage.

[0040] Tableting performance testing and antioxidant activity testing: The tableting performance was determined by testing the disintegration time of the samples: The disintegrator was turned on, water was added to the disintegration tank, and the water bath temperature was adjusted to stabilize the disintegration medium temperature at 37±1℃. Six test samples from Examples 1-2 and Comparative Examples 1-2 were taken and placed in six transparent glass tubes of the disintegration basket, one sample per tube. The position of the disintegration basket was adjusted so that the sieve was exactly 15 mm from the bottom of the disintegration tank at its lowest position and 15 mm below the water surface at its highest position. The disintegrator was started, with a lifting frequency of 30 to 32 times per minute and a stroke of 55 ± 2 mm. Timing was started from the start time, and the time it took for each sample to disintegrate and pass through the sieve was observed and recorded; the average disintegration time was calculated; the results are shown in Table 1.

[0041] Antioxidant activity was determined by testing the scavenging of DPPH free radicals: Sample solutions of Examples 1-2 and Comparative Examples 1-2 were prepared at 30 mg / mL. 500 μL of each solution was added to a 96-well plate, and 100 μL of 0.04 mg / mL DPPH ethanol solution was added to each. The solutions were reacted at room temperature in the dark for 30 min. In the control group, 100 μL of anhydrous ethanol was used instead of the DPPH ethanol solution. In the blank group, 100 μL of deionized water was used instead of the sample solution. In the positive control group, 100 μL of ascorbic acid was used instead of the sample solution. The preparation methods were the same as for the test solutions. Absorbance was measured at 517 nm, and three parallel experiments were performed. Scavenging rate (%) = [1 - [Sample A - Control A] / Blank A] × 100%; the results are shown in Table 1.

[0042] Table 1 Example Mean disintegration time (s) DPPH removal rate (%) Example 1 481 59.67 Comparative Example 1 78 32.21 Example 2 462 60.18 Comparative Example 2 451 58.63

[0043] As can be seen, Chlorella polysaccharide, as a filler sweetener, can simultaneously possess good tableting performance and antioxidant activity; while Example 1 uses a three-stage deodorization process of chemical oxidation-biotransformation-Maillard reaction to remove the algal odor of Chlorella polysaccharide itself. The biotransformation deodorization process also imparts an aroma similar to that of lactic acid bacteria beverages, resulting in good palatability.

[0044] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for preparing a pharmaceutical sweetener, characterized in that, The preparation method of the sweetener for the drug includes the following steps: Step 1: Preparation of modified microalgal polysaccharides; Step 2: Add the modified microalgae polysaccharide, the first sweetener, the second sweetener, dietary fiber, and the acidity regulator to water, mix evenly, and then spray dry to obtain the pharmaceutical sweetener.

2. The method for preparing the pharmaceutical sweetener according to claim 1, characterized in that, The mass ratio of the modified microalgae polysaccharide, the first sweetener, the second sweetener, dietary fiber, and the acidity regulator is selected from (20-40):(0.2-1):(25-50):(5-20):(0.3-1).

3. The method for preparing the pharmaceutical sweetener according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The first sweetener is selected from at least one of steviol glycosides, mogrosides, sucralose, and acesulfame potassium; (2) The second sweetener is selected from at least one of erythritol, xylitol, maltitol, mannitol, sorbitol, trehalose, and lactitol; (3) The dietary fiber is selected from at least one of fructooligosaccharides, inulin, galactooligosaccharides, polydextrose, resistant dextrin, and oat β-glucan; (4) The acidity regulator is selected from at least one of citric acid, malic acid, tartaric acid, lactic acid, ascorbic acid, and gluconic acid.

4. The method for preparing the pharmaceutical sweetener according to claim 1, characterized in that, The modified microalgae polysaccharide is a deodorized Chlorella polysaccharide; the deodorized Chlorella polysaccharide is prepared through the following steps: Step 1-a: Prepare crude extract of Chlorella polysaccharides; Step 2-a: The crude Chlorella polysaccharide extract is subjected to chemical oxidation to remove odor; a chemically oxidized and deodorized Chlorella polysaccharide extract is obtained. Step 3-a: The chemically oxidized and deodorized Chlorella polysaccharide extract is subjected to biotransformation to obtain a biotransformed and deodorized Chlorella polysaccharide extract; Step 4-a: The deodorized Chlorella polysaccharide fermentation broth after bioconversion is subjected to Maillard reaction to mask the odor, thereby obtaining crude deodorized Chlorella polysaccharide extract; Step 5-a: The crude extract of Chlorella polysaccharide after deodorization is purified by membrane separation to obtain the deodorized Chlorella polysaccharide.

5. The method for preparing the pharmaceutical sweetener according to claim 4, characterized in that, Step 2 includes: Step 1-b: Add 30% hydrogen peroxide aqueous solution dropwise to the crude Chlorella polysaccharide extract until the final concentration is 2-5 g / L; then stir the reaction for 20-45 min. Step 2-b: Then raise the temperature to 80℃-90℃ and hold for 10-20 minutes; Step 3-b: Add 1.5%-3% activated carbon by weight of the system, stir at 50℃-55℃ for 45-70 minutes, and then filter to obtain the chemically oxidized and deodorized Chlorella polysaccharide extract.

6. The method for preparing the pharmaceutical sweetener according to claim 4, characterized in that, Step 3 includes: Step 1-c: Adjust the pH of the chemically oxidized and deodorized Chlorella polysaccharide extract to 6.0-6.5, maintain the temperature at 37℃-40℃, inoculate with 1%-2% Lactobacillus plantarum and 0.5%-1% Lactobacillus casei; then ferment in a sealed container for 12-24 hours. Step 2-c: Heat to 75℃-80℃ and maintain for 20-30 minutes. Then remove the precipitate by centrifugation to obtain the deodorized Chlorella polysaccharide extract after biotransformation.

7. The method for preparing the pharmaceutical sweetener according to claim 4, characterized in that, Step 4 includes: Step 1-d: Adjust the pH of the biotransformed and deodorized Chlorella polysaccharide extract to 7.0-7.5, and then add 0.3%-0.8% lysine or arginine; Step 2-d: Heat to 85℃-95℃ and react for 30-45 minutes; after the reaction is complete, quickly cool to below 50℃ to obtain the crude Chlorella polysaccharide extract after deodorization treatment.

8. The method for preparing the pharmaceutical sweetener according to claim 4, characterized in that, Step 5 includes: Step 1-e: Filter the deodorized Chlorella polysaccharide extract crude product through a 0.1-0.2μm microfiltration membrane; Step 2-e: The solution is then concentrated using an ultrafiltration membrane with a molecular weight cutoff of 10-30 kDa to 1 / 5 to 1 / 8 of its original volume, yielding the ultrafiltration concentrate. Step 3-e: The ultrafiltration retentate concentrate is then treated with a nanofiltration membrane with a molecular weight cutoff of 200-500 Da. The nanofiltration retentate is collected and freeze-dried to obtain the deodorized Chlorella polysaccharide.

9. The method for preparing the pharmaceutical sweetener according to any one of claims 1-3, characterized in that, The sweetener used in the pharmaceutical product is selected from any of the following components in parts by weight: Component a: 35 parts by weight of deodorized Chlorella polysaccharide, 0.3 parts by weight of steviol glycosides, 20 parts by weight of erythritol, 20 parts by weight of trehalose, 12 parts by weight of fructooligosaccharides and 0.4 parts by weight of citric acid; Component b: 37.5 parts by weight of deodorized Chlorella polysaccharide, 0.45 parts by weight of mogroside, 25 parts by weight of xylitol, 15 parts by weight of maltitol, 8 parts by weight of inulin, 5 parts by weight of resistant dextrin and 0.5 parts by weight of malic acid. Component c: 37.5 parts by weight of deodorized Chlorella polysaccharide, 0.5 parts by weight of sucralose, 25 parts by weight of mannitol, 20 parts by weight of sorbitol, 6 parts by weight of oat β-glucan, 6 parts by weight of resistant dextrin, and 0.5 parts by weight of ascorbic acid.

10. The method for preparing the pharmaceutical sweetener according to claim 4, characterized in that, The crude extract of Chlorella polysaccharides was prepared through the following steps: Step 1-f: Weigh the Chlorella powder; add it to water at a material-to-liquid ratio of 1:(20-30), and extract in a water bath at 80℃-85℃ for 2-3 hours; then centrifuge and collect the supernatant. Step 2-f: Add an equal volume of 10% trichloroacetic acid solution to the supernatant obtained in step 1-f, stir, and let stand overnight at 4°C; then centrifuge and collect the supernatant. Step 3-f: Add 3 times the volume of anhydrous ethanol to the supernatant obtained in step 2-f, stir and let stand overnight at 4°C; then centrifuge and collect the precipitate; dry the precipitate and dissolve it in water to obtain the crude extract of Chlorella polysaccharide.