Method for preparing rebaudioside B by separating mother liquor sugar based on simulated moving bed

Abstract

The invention discloses a method for preparing rebaudioside B by separating mother liquor sugar based on a simulated moving bed, which comprises the following steps: dissolving stevia mother liquor sugar to obtain a stevia mother liquor sugar solution, and adjusting the pH value of the stevia mother liquor sugar solution to 7.5-9.5 to obtain a to-be-treated solution; the to-be-treated liquid is pumped into a simulated moving bed separation system to be separated, and an organic phase and an organic salt phase are obtained; concentrating the upper organic salt phase by using a reverse osmosis membrane, and collecting permeate and trapped fluid; heating the trapped fluid, then adding a pH regulator to regulate the pH value of the solution to 4.0-5.5, and carrying out precipitation treatment; and filtering the precipitated solution, and drying the collected filter cake to obtain the high-content rebaudioside B. According to the method, the stevia mother liquor sugar is taken as a raw material, the purity and the yield of rebaudioside B are remarkably improved through accurate pH control and optimized operation of simulated moving bed separation in the whole process, the single-batch treatment capacity is large, a mixed solvent does not need to be used in the treatment process, the amount of generated waste liquid is small, and the whole process is energy-saving and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of stevioside, and in particular to a method for preparing rebaudioside B based on separating mother liquor sugars in a simulated moving bed. Background Art

[0002] Stevioside is a modern new natural sweetener extracted from the leaves of Stevia, a perennial herbaceous plant of the Asteraceae family. It has the characteristics of high sweetness and low caloric energy, and is an ideal sweetener that can replace sucrose. Rebaudioside B (RB) is an effective ingredient isolated from Stevia, and its sweetness is 150 times that of sucrose. Although the sweetness of Rebaudioside B is weaker than that of the main product Rebaudioside A (RA), the bitterness of the latter is significantly weaker than that of the latter, so the taste of RB is significantly better than that of RA. In addition to being a sweetener, studies have found that Rebaudioside B also has the effects of regulating blood sugar and blood lipids, relieving constipation, and promoting metabolism. It can be used as an auxiliary treatment for diseases such as diabetes and hyperlipidemia. It is a steviol glycoside compound with great application potential. How to prepare high-purity Rebaudioside B is of great significance.

[0003] The traditional production process of rebaudioside B is to obtain it by hydrolyzing rebaudioside A. Although this process can obtain a high-content rebaudioside B product, it will greatly affect the yield of the main product rebaudioside A. At present, many stevioside manufacturers will inevitably produce a part of stevioside mother liquor sugar after producing the main product high-content rebaudioside A and other specifications of stevioside. This mother liquor sugar has a low total glycoside content, poor taste, and low economic value, but rebaudioside B is significantly enriched in this type of mother liquor sugar. Therefore, how to recover rebaudioside B in the mother liquor sugar has become one of the urgent problems to be solved by stevioside manufacturers.

[0004] Patent CN102093447B discloses a method for purifying stevioside RB. After the mother liquor sugar is adsorbed on a macroporous adsorption resin column, the stevioside adsorbed on the resin column is eluted with 70-75wt% ethanol, and then the eluate is collected in sections, the eluate is concentrated and precipitated, and the obtained solid and liquid are dried separately to obtain crude stevioside; the crude stevioside obtained by this method contains both rebaudioside B and other steviol glycoside components. If rebaudioside B is refined, it is also necessary to crystallize and purify it with a mixed solvent for 48 hours, and solid-liquid separation is performed to obtain a high-content rebaudioside B product. The above method has the following disadvantages: the single batch processing capacity of the resin is small, the separation is not thorough when the single gradient solvent is segmented to collect rebaudioside B, and the crystallization time is long. The crystallization refining requires separation with a mixed solvent, and the solvent recovery is difficult, which increases the production energy consumption of rebaudioside B. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a method for preparing rebaudioside B based on simulated moving bed separation of mother liquor sugar is provided. The method uses stevia mother liquor sugar as raw material, and significantly improves the purity and yield of rebaudioside B through precise control of pH in the whole process and optimized operation of simulated moving bed separation. The single batch processing volume is large, no mixed solvent is required during the processing process, and the amount of waste liquid generated is small, and the whole process is energy-saving and environmentally friendly.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0008] (1) dissolving stevia mother liquid sugar to obtain a stevia mother liquid sugar solution, and adjusting the pH of the stevia mother liquid sugar solution to 7.5-9.5 to obtain a liquid to be treated;

[0009] (2) pumping the liquid to be treated into a simulated moving bed separation system for separation to obtain an organic phase and an organic salt phase;

[0010] (3) concentrating the organic salt phase using a reverse osmosis membrane to collect a permeate and a retentate;

[0011] (4) heating the retentate, then adding a pH adjuster to adjust the pH of the solution to 4.0-5.5, and performing a precipitation treatment;

[0012] (5) Filter the solution after precipitation, collect the filter cake and dry it to obtain high-content rebaudioside B.

[0013] Preferably, in step (1), the concentration of the stevia mother liquid sugar solution is 15-35wt%; the pH regulator used to adjust the stevia mother liquid sugar solution is one of a sodium salt solution and a potassium salt solution; and / or the concentration of the sodium salt solution is 5-40wt%, and the sodium salt is one of NaOH, NaHCO3, and Na2CO3; and / or the concentration of the potassium salt solution is 5-40wt%, and the potassium salt is one of KOH, KHCO3, and K2CO3.

[0014] Preferably, in step (2), when a simulated moving bed separation system is used for treatment, the stationary phase is a uniform gel cation chromatography resin and the mobile phase is water; and / or the average particle size of the uniform gel cation chromatography resin is 220-320 μm; and / or the uniform gel cation chromatography resin is one of a sodium type resin and a potassium type resin.

[0015] Preferably, in step (2), the simulated moving bed separation system is six chromatographic columns connected in series and connected end to end, and the diameter-to-height ratio of a single column chromatographic column is 2.0:(1-1.5); when the simulated moving bed chromatographic separation system is used to treat the above-mentioned treated liquid, in one circulation process, the feed amount of the treated liquid is 10-15 v / v% of the volume of the single column chromatographic column, the feed amount of water is 30-34 v / v% of the volume of the single column chromatographic column, and the circulating liquid flushing amount is 35-37 v / v% of the volume of the single column chromatographic column.

[0016] Furthermore, in step (2), the separation process includes circulating flushing, water flushing, water analysis, and feeding process, the water analysis and feeding are carried out simultaneously, and the organic salt phase is recovered in the water flushing process and the feeding process, and the organic phase is recovered in the water analysis process.

[0017] Furthermore, the conditions during separation are: circulating flushing flow rate (Va) is 160-170mL / min, water flushing flow rate (Vb) is 160-180mL / min, water analysis flow rate (Vc) is 150-170mL / min, feed flow rate (Vd) is 100-120mL / min, circulating flushing time is 10-12min, water flushing time is 3-4min, water analysis time (feeding time) is 4-8min, and then switch to the next cycle.

[0018] Preferably, in step (2), the organic phase is concentrated and dried to obtain a stevioside product.

[0019] Preferably, in step (3), the conditions for the concentration treatment are: an operating temperature of 30-65° C. and a membrane pressure of 3.0-6.0 MPa.

[0020] Preferably, in step (3), the solid content of the retentate is 10-20 wt %.

[0021] Preferably, in step (3), the permeate is used as the mobile phase in step (2).

[0022] Preferably, in step (4), the temperature of the heating treatment is 70-85°C.

[0023] Preferably, in step (4), the pH regulator is one of hydrochloric acid solution, sulfuric acid solution and citric acid solution; and / or the concentration of the hydrochloric acid solution is 5-35wt%; and / or the concentration of the sulfuric acid solution is 5-35wt%; and / or the concentration of the citric acid solution is 20-50wt%.

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. The present invention uses stevia mother liquor sugar as raw material, and obtains a high-yield and high-purity rebaudioside B product through simulated moving bed chromatography separation, reverse osmosis membrane separation and selective precipitation. The method is simple to operate, has a large single batch processing capacity, good separation effect, and improves the economic value of stevia mother liquor sugar.

[0026] 2. The present invention significantly improves the separation effect of simulated moving bed chromatography by reasonably controlling the solid content and pH of the stevia mother liquor sugar solution and adjusting the conditions of simulated moving bed chromatography, thereby increasing the yield and purity of rebaudioside B.

[0027] 3. The present invention reasonably adjusts the conditions of reverse osmosis membrane separation, thereby effectively controlling the solid content of the retentate, improving the effect of selective precipitation, and thus improving the yield and purity of rebaudioside B.

[0028] 4. The present invention effectively avoids the loss of rebaudioside B and the precipitation of impurities by reasonably adjusting the pH value and temperature during selective precipitation, thereby improving the yield and purity of rebaudioside B.

[0029] 5. The method provided by the present invention has a high degree of automation and a large single batch processing volume, which reduces manual operations, improves production efficiency and product stability, and also recovers other steviol glycosides except rebaudioside B in stevia mother liquor sugar, and the waste liquid is fully utilized, which is energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] Figure 1 It is a schematic diagram of a simulated moving bed chromatography separation system;

[0032] Figure 1 Among them, 1. water pipeline; 2. circulating liquid flushing pipeline, 3. liquid inlet pipeline for treated liquid; 4. organic salt phase discharge pipeline; 5. organic phase discharge pipeline. DETAILED DESCRIPTION

[0033] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0035] Based on the technical problems existing in the background technology, the present invention provides a method for preparing rebaudioside B based on simulated moving bed separation of mother liquor sugar. The method combines simulated moving bed separation, reverse osmosis membrane separation and acid precipitation, and precisely controls the pH and temperature of the solution during the process to obtain a high content of rebaudioside B. In addition, the method has a large single batch processing capacity, simple operation and good separation effect.

[0036] The specific plan is as follows:

[0037] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0038] (1) dissolving stevia mother liquid sugar to obtain a stevia mother liquid sugar solution, and adjusting the pH of the stevia mother liquid sugar solution to 7.5-9.5 to obtain a liquid to be treated;

[0039] (2) pumping the liquid to be treated into a simulated moving bed separation system for separation to obtain an organic phase and an organic salt phase;

[0040] (3) concentrating the organic salt phase using a reverse osmosis membrane to collect a permeate and a retentate;

[0041] (4) heating the retentate, then adding a pH adjuster to adjust the pH of the solution to 4.0-5.5, and performing a precipitation treatment;

[0042] (5) Filter the solution after precipitation, collect the filter cake and dry it to obtain high-content rebaudioside B.

[0043] Regarding step (1):

[0044] In some embodiments, the solid content of the stevia mother liquid sugar solution is 15-35 wt %.

[0045] In the above scheme, the lower the solid content of stevia mother liquor, the more water is used, and both stevia and rebaudioside B are hydrophilic. When the solid content is low, the separation effect is poor, and when the solid content is too high, the material concentration is high when using simulated moving bed separation, which will also reduce the separation effect. Therefore, in order to ensure a good separation effect, the solid content of stevia mother liquor is controlled to be 15-35wt% in the present invention.

[0046] In some embodiments, the pH regulator used to adjust the stevia mother liquid sugar solution is one of a sodium salt solution and a potassium salt solution; and / or the concentration of the sodium salt solution is 5-40wt%, and the sodium salt is one of NaOH, NaHCO3, and Na2CO3; and / or the concentration of the potassium salt solution is 5-40wt%, and the potassium salt is one of KOH, KHCO3, and K2CO3.

[0047] In the above scheme, the present invention uses sodium salt or potassium salt to adjust the pH value of the stevia mother liquid sugar solution. In this process, the rebaudioside B in the stevia mother liquid sugar is combined with sodium ions or potassium ions. The combined rebaudioside B has weak adsorption to the stationary phase in the simulated moving bed, while other steviol glycosides in the stevia mother liquid sugar solution are not ionic and have strong adsorption to the stationary phase, thereby achieving good separation of rebaudioside B. If the pH of the stevia mother liquid sugar solution is too low, the combination of rebaudioside B and sodium ions or potassium ions is not thorough, affecting the separation effect; and if the pH is too high, not only will the amount of auxiliary materials increase, but the sodium ions will also be enriched in the simulated moving bed chromatography system, affecting the separation effect. Therefore, the pH of the stevia mother liquid sugar solution needs to be strictly controlled.

[0048] Regarding step (2):

[0049] In some embodiments, when a simulated moving bed separation system is used for treatment, the stationary phase is a uniform gel cation chromatography resin and the mobile phase is pure water; and / or the particle size of the uniform gel cation chromatography resin is 220-320 μm; and / or the uniform gel cation chromatography resin is one of a sodium type resin and a potassium type resin.

[0050] In the above scheme, in actual operation, the type of resin filled in the chromatographic column of the simulated moving bed separation system must correspond to the salt used when adjusting the pH in step (1). For example, when a sodium salt solution is used to adjust the pH, the resin filled in the chromatographic column of the simulated moving bed separation system is a sodium-type resin. Further, the sodium-type resin can be selected from Lanxiao Technology S1850 sodium-type resin, and the potassium-type resin can be selected from Lanxiao Technology S1850 potassium-type resin.

[0051] In some embodiments, the simulated moving bed separation system is six chromatographic columns connected in series and connected end to end, and the diameter-to-height ratio of a single column chromatographic column is 2.0:(1-1.5); when the simulated moving bed chromatographic separation system is used to treat the above-mentioned treated liquid, the feed amount of the treated liquid is 10-15v / v% of the volume of the single column chromatographic column, the feed amount of water is 30-34v / v% of the volume of the single column chromatographic column, and the circulating liquid flushing amount is 35-37v / v% of the volume of the single column chromatographic column.

[0052] In some embodiments, Figure 1As shown, the simulated moving bed chromatography system consists of six identical chromatographic columns connected in series and connected end to end. The six chromatographic columns are divided into four zones, namely, zone Z1, zone Z2, zone Z3, and zone Z4. In one cycle, the first chromatographic column is zone Z1, zone Z2 is two chromatographic columns connected in series, zone Z3 is two chromatographic columns connected in series, and zone Z4 is the last chromatographic column. When switching to the next cycle, each zone is moved back by one resin column as a whole by switching the feed and discharge valves.

[0053] Specifically, after the system is stable, one cycle includes four processes: circulation flushing, water flushing, water analysis and feeding. Water analysis and feeding are carried out simultaneously. During circulation flushing, the effluent of the chromatographic column in zone Z4 enters from the chromatographic column in zone Z1 to flush the organic salt phase in the chromatographic columns in zone Z1-Z4 connected in series, so that the organic salt phase is initially enriched in the chromatographic column; during water flushing, water enters from the chromatographic column in zone Z1 to flush the organic salt phase in the chromatographic columns in zone Z1-Z3 connected in series and connected. At this time, the organic phase and the organic salt phase are initially separated, the organic phase is concentrated at the front end, and the organic salt phase is concentrated at the rear end of the chromatographic columns in series, so as to achieve the initial collection of the organic salt phase; and the organic salt phase is collected at the organic salt phase outlet in zone Z3; during water analysis, water enters from the chromatographic column in zone Z1, and the organic phase is collected at the bottom of the chromatographic column in zone Z1. Feeding is carried out simultaneously with water analysis, and the liquid to be treated enters from the first chromatographic column in series in zone Z3, and the organic salt phase is collected at the bottom of the second chromatographic column in zone Z3. Then, the next cycle is switched by switching the feeding valve and the discharging valve.

[0054] In some embodiments, the conditions during separation are: the circulating flushing flow rate (Va) is: 160-170mL / min, the water flushing flow rate (Vb) is 160-180mL / min, the water analysis flow rate (Vc) is 150-170mL / min, the feed flow rate (Vd) is 100-120mL / min, the circulating flushing time is 10-12min, the water flushing time is 3-4min, the water analysis time (feeding time) is 4-8min, and then switch to the next cycle. Further, when collecting the organic salt phase and the organic phase, the discharge flow rate of the organic salt phase and the organic phase depends on the influent flow rate, for example, the discharge flow rate of the organic salt phase during the water flushing process is consistent with the water flushing flow rate, the discharge flow rate of the organic phase during the water analysis process is consistent with the water analysis flow rate, and the discharge flow rate of the organic salt phase during the feeding process is consistent with the feed flow rate of the liquid to be treated.

[0055] The present invention effectively controls the conditions of the above process, so that the organic phase and the organic salt phase in the liquid to be treated are effectively separated, and the whole process is carried out continuously, thereby improving the extraction efficiency of rebaudioside B.

[0056] In the above scheme, rebaudioside B has a weaker reaction with the resin in the chromatographic column, has a faster moving speed in the chromatographic column, and will be concentrated in the Z3 area during the cyclic separation process. The other stevioside components in the liquid to be treated except rebaudioside B have a stronger reaction with the resin in the chromatographic column, and will be concentrated in the Z1 area during the cyclic separation process. During the entire separation process, the injection is always maintained at the intersection of the Z2 area and the Z3 area. By switching the valve, the organic phase containing other steviosides and the organic salt phase containing rebaudioside B are obtained in the Z1 area and the Z3 area respectively. The separated components are extracted and collected in time, and the unseparated mixture is always circulated in the chromatographic column.

[0057] In some embodiments, during the simulated moving bed chromatography separation process, the other steviol glycoside components in the treated liquid except rebaudioside B have strong adsorption to the stationary phase and flow out as an organic phase. This part of the steviol glycoside material is concentrated and dried to obtain a steviol glycoside product, further improving the utilization rate of the stevia mother liquor sugar.

[0058] Regarding step (3):

[0059] In some embodiments, the conditions of the concentration treatment are: an operating temperature of 30-65° C. and a membrane pressure of 3.0-6.0 MPa.

[0060] In some embodiments, the retentate has a solid content of 10-20 wt %.

[0061] In the above scheme, the present invention further concentrates and separates the solution containing rebaudioside B (organic salt phase) through a reverse osmosis membrane, effectively controls the solid content of the retentate, and thus makes the acid precipitation process better. If the solid content of the retentate is too low, more products will be dissolved in the water, resulting in a low product yield, and if the solid content of the retentate is too high, impurities will precipitate simultaneously with rebaudioside B during acid precipitation, thereby reducing the purity of the rebaudioside B product.

[0062] In some embodiments, the permeate from the reverse osmosis membrane concentration treatment is used as the mobile phase for the simulated moving bed chromatography separation in step (2), thereby improving the utilization rate of the waste liquid, reducing the amount of waste liquid discharged, and being energy-saving and environmentally friendly.

[0063] Regarding step (4):

[0064] In some embodiments, the temperature of the heat treatment is 70-85°C.

[0065] In some embodiments, the pH adjuster is one of hydrochloric acid solution, sulfuric acid solution, and citric acid solution; and / or the concentration of the hydrochloric acid solution is 5-35wt%; and / or the concentration of the sulfuric acid solution is 5-35wt%; and / or the concentration of the citric acid solution is 20-50wt%.

[0066] In the above scheme, the present invention selectively precipitates rebaudioside B under certain conditions by precisely controlling temperature and pH, thereby obtaining a high content of rebaudioside B. If the pH is too low, the structure of rebaudioside B or impurities may be destroyed, resulting in a simultaneous decrease in the solubility of rebaudioside B and the solubility of impurities, thereby causing rebaudioside B and impurities to precipitate simultaneously, and the purity of rebaudioside B will decrease. If the pH is too high, although the purity of the rebaudioside B product is improved to a certain extent, part of the rebaudioside B is still in a dissolved state, which will reduce the yield of the product.

[0067] In addition, under certain pH conditions, the temperature will also affect the selective precipitation of rebaudioside B. If the temperature is too low, impurities will precipitate together with rebaudioside B, thereby reducing the purity of the product. If the temperature is too high, part of rebaudioside B will be dissolved with the impurities, which will increase the purity of the product but reduce the yield of the product. Therefore, in order to ensure the high purity and high yield of the product, the temperature and pH during the selective precipitation of rebaudioside B need to be strictly controlled.

[0068] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0069] Unless otherwise specified in the following examples, the raw materials are commercially available.

[0070] The yield calculation method of rebaudioside B (RB) in the following examples is as follows:

[0071] RB yield (%) = [(m2 × M2) / (m1 × M1)] × 100%;

[0072] Wherein, m1: mass of stevia mother liquor sugar; M1: content of rebaudioside B in stevia mother liquor sugar;

[0073] m2: the quality of the target product; M2: the content of rebaudioside B in the target product.

[0074] Example 1

[0075] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0076] S1: Pre-processing:

[0077] Dissolve 40 kg of stevia mother liquor sugar (total glycoside content 70.1 wt%, rebaudioside B content 10.7 wt%) in 100 L of pure water to obtain a stevia mother liquor sugar solution; add a 20 wt% KOH solution to adjust the pH of the stevia mother liquor sugar solution to 8.5 to obtain a solution to be treated;

[0078] S2: Simulated Moving Bed Chromatography Separation:

[0079] The simulated moving bed chromatographic separation system comprises 6 chromatographic columns connected in series and end to end (the first chromatographic column is the Z1 zone, the two chromatographic columns connected to the Z1 zone and connected in series are the Z2 zone, the two chromatographic columns connected to the Z2 zone and connected in series are the Z3 zone, and the tail chromatographic column is the Z4 zone), the diameter of the chromatographic column is 22 cm, the height is 13 cm, the chromatographic column is filled with S1850 potassium type resin (Lanxiao Technology) with an average particle size of 300 μm, when feeding, the feed amount of the liquid to be treated is 12 v / v% of the volume of the single column chromatographic column, the feed amount of water is 32 v / v% of the volume of the single column chromatographic column, and the circulation flushing amount is 36 v / v% of the volume of the single column chromatographic column; one cycle comprises circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone, water flushing of the Z1 zone to the Z The process comprises four steps: a chromatographic column in zone 3, a chromatographic column in zone Z1 with water analysis, and feeding from a chromatographic column in zone Z3, wherein feeding and water analysis are performed simultaneously, Va (circulation flushing flow rate) is 160 mL / min, Vb (water flushing flow rate) is 160 mL / min, Vc (water analysis flow rate) is 160 mL / min, and Vd (feeding flow rate) is 100 mL / min. Va, Vb, Vc (Vd) are respectively operated for 11.3 min, 4.0 min, and 6.0 min before switching to the next cycle; the organic phase containing other steviol glycosides is collected from the discharge port of zone Z1 by switching the valve, and the organic salt phase containing rebaudioside B is collected from the discharge port of the 2# chromatographic column in zone Z3; the organic phase is concentrated and dried to obtain a stevioside product;

[0080] S3: Reverse osmosis membrane concentration:

[0081] The organic salt phase in S2 is concentrated by reverse osmosis membrane (operating temperature is 50° C., membrane pressure is 4.5 MPa) to obtain a retentate with a solid content of 15 wt%. The permeate in the concentration process is used as the mobile phase in the simulated moving bed separation system in step (2);

[0082] S4: Selective precipitation:

[0083] The retentate in S3 was heated to 80°C, and a 15wt% hydrochloric acid solution was added to adjust the solution pH to 5.0. The solution was precipitated until no new precipitate was produced. The filter cake was collected and dried to obtain 3972g of the target product, rebaudioside B. The content of rebaudioside B was 96.1wt%, and the effective yield was 89.2%.

[0084] Example 2

[0085] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0086] S1: Pre-processing:

[0087] Dissolve 52 kg of stevia mother liquor sugar (total glycoside content 74.7 wt%, rebaudioside B content 14.1 wt%) in 100 L of pure water to obtain a stevia mother liquor sugar solution; add a 40 wt% NaOH solution to adjust the pH of the stevia mother liquor sugar solution to 9.5 to obtain a solution to be treated;

[0088] S2: Simulated Moving Bed Chromatography Separation:

[0089] The simulated moving bed chromatographic separation system comprises 6 chromatographic columns connected in series and end to end (the first chromatographic column is the Z1 zone, the two chromatographic columns connected to the Z1 zone and connected in series are the Z2 zone, the two chromatographic columns connected to the Z2 zone and connected in series are the Z3 zone, and the tail chromatographic column is the Z4 zone), the diameter of the chromatographic column is 22 cm, the height is 13 cm, the chromatographic column is filled with S1850 sodium type resin (Lanxiao Technology) with an average particle size of 300 μm, when feeding, the feed amount of the liquid to be treated is 15 v / v% of the volume of the single column chromatographic column, the feed amount of water is 34 v / v% of the volume of the single column chromatographic column, and the circulation flushing amount is 35 v / v% of the volume of the single column chromatographic column; one cycle comprises circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone, water flushing of the Z1 zone to the Z4 zone, and the circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone. The process comprises four steps: a chromatographic column in zone 3, a chromatographic column in zone Z1 with water analysis, and feeding from a chromatographic column in zone Z3, wherein feeding and water analysis are performed simultaneously, Va (circulation flushing flow rate) is 170 mL / min, Vb (water flushing flow rate) is 170 mL / min, Vc (water analysis flow rate) is 170 mL / min, and Vd (feeding flow rate) is 110 mL / min. Va, Vb, and Vc (Vd) are respectively operated for 10.3 min, 3.2 min, and 6.8 min before switching to the next cycle; the organic phase containing other steviol glycosides is collected from the discharge port of zone Z1 by switching valves, and the organic salt phase containing rebaudioside B is collected from the discharge port of the 2# chromatographic column in zone Z3; the organic phase is concentrated and dried to obtain a stevioside product;

[0090] S3: Reverse osmosis membrane concentration:

[0091] The organic salt phase in S2 is concentrated by reverse osmosis membrane (operating temperature is 65° C., membrane pressure is 3.0 MPa) to obtain a retentate with a solid content of 20 wt%. The permeate in the concentration process is used as the mobile phase in the simulated moving bed separation system in step (2);

[0092] S4: Selective precipitation:

[0093] The retentate in S3 was heated to 85°C, and a 50wt% citric acid solution was added to adjust the pH of the solution to 5.5. The solution was precipitated until no new precipitate was produced. The solution was filtered and the collected filter cake was dried to obtain 6554g of the target product, high-content rebaudioside B. The content of rebaudioside B was 95.7wt%, and the effective yield was 85.5%.

[0094] Example 3

[0095] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0096] S1: Pre-processing:

[0097] 18 kg of stevia mother liquor sugar (total glycoside content 60.4 wt%, rebaudioside B content 5.8 wt%) was dissolved in 100 L of pure water to obtain a stevia mother liquor sugar solution; 5 wt% NaHCO3 was added to the stevia mother liquor sugar to adjust the pH of the stevia mother liquor sugar solution to 7.5 to obtain a liquid to be treated;

[0098] S2: Simulated Moving Bed Chromatography Separation:

[0099] The simulated moving bed chromatographic separation system comprises 6 chromatographic columns connected in series and end to end (the first chromatographic column is the Z1 zone, the two chromatographic columns connected to the Z1 zone and connected in series are the Z2 zone, the two chromatographic columns connected to the Z2 zone and connected in series are the Z3 zone, and the tail chromatographic column is the Z4 zone), the diameter of the chromatographic column is 22 cm, the height is 13 cm, the chromatographic column is filled with S1850 sodium type resin (Lanxiao Technology) with an average particle size of 300 μm, when feeding, the feed amount of the liquid to be treated is 10 v / v% of the volume of the single column chromatographic column, the feed amount of water is 30 v / v% of the volume of the single column chromatographic column, and the circulation flushing amount is 37 v / v% of the volume of the single column chromatographic column; one cycle comprises circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone, water flushing of the Z1 zone to the Z4 zone, and the circulation flushing of the water. The process comprises four steps: a chromatographic column in zone 3, a chromatographic column in zone Z1 with water analysis, and feeding from a chromatographic column in zone Z3, wherein feeding and water analysis are performed simultaneously, Va (circulation flushing flow rate) is 165 mL / min, Vb (water flushing flow rate) is 180 mL / min, Vc (water analysis flow rate) is 170 mL / min, and Vd (feeding flow rate) is 100 mL / min. Va, Vb, and Vc (Vd) are respectively operated for 11.2 min, 3.6 min, and 5.0 min before switching to the next cycle; the organic phase containing other steviol glycosides is collected from the discharge port of zone Z1 by switching the valve, and the organic salt phase containing rebaudioside B is collected from the discharge port of the 2# chromatographic column in zone Z3; the organic phase is concentrated and dried to obtain a stevioside product;

[0100] S3: Reverse osmosis membrane concentration:

[0101] The organic salt phase in S2 is concentrated by reverse osmosis membrane (operating temperature is 30° C., membrane pressure is 6.0 MPa) to obtain a retentate with a solid content of 10 wt%. The permeate in the concentration process is used as the mobile phase in the simulated moving bed separation system in step (2);

[0102] S4: Selective precipitation:

[0103] The retentate in S3 was heated to 70°C, and a 5wt% hydrochloric acid solution was added to adjust the pH of the solution to 4.0. The solution was precipitated until no new precipitate was produced. The filter cake was collected and dried to obtain 943g of the target product, high-content rebaudioside B. The content of rebaudioside B was 95.9wt%, and the effective yield was 86.6%.

[0104] Example 4

[0105] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0106] S1: Pre-processing:

[0107] Dissolve 45 kg of stevia mother liquor sugar (total glycoside content 67.2 wt%, rebaudioside B content 7.9 wt%) in 100 L of pure water to obtain a stevia mother liquor sugar solution; add a 10 wt% Na2CO3 solution to adjust the pH of the stevia mother liquor sugar solution to 8.0 to obtain a liquid to be treated;

[0108] S2: Simulated Moving Bed Chromatography Separation:

[0109] The simulated moving bed chromatographic separation system comprises 6 chromatographic columns connected in series and end to end (the first chromatographic column is the Z1 zone, the two chromatographic columns connected to the Z1 zone and connected in series are the Z2 zone, the two chromatographic columns connected to the Z2 zone and connected in series are the Z3 zone, and the tail chromatographic column is the Z4 zone), the diameter of the chromatographic column is 22 cm, the height is 13 cm, the chromatographic column is filled with S1850 sodium type resin (Lanxiao Technology) with an average particle size of 300 μm, when feeding, the feed amount of the liquid to be treated is 14 v / v% of the volume of the single column chromatographic column, the feed amount of water is 31 v / v% of the volume of the single column chromatographic column, and the circulation flushing amount is 37 v / v% of the volume of the single column chromatographic column; one cycle comprises circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone, water flushing of the Z1 zone to the Z4 zone, and the circulation flushing of the chromatographic columns in the Z1 zone to the Z4 zone. The process comprises four steps: a chromatographic column in zone 3, a chromatographic column in zone Z1 with water analysis, and feeding from a chromatographic column in zone Z3, wherein feeding and water analysis are performed simultaneously, Va (circulation flushing flow rate) is 160 mL / min, Vb (water flushing flow rate) is 160 mL / min, Vc (water analysis flow rate) is 160 mL / min, and Vd (feeding flow rate) is 120 mL / min. Va, Vb, and Vc (Vd) are respectively operated for 11.6 min, 3.9 min, and 5.8 min before switching to the next cycle; the organic phase containing other steviol glycosides is collected from the discharge port of zone Z1 by switching valves, and the organic salt phase containing rebaudioside B is collected from the discharge port of the 2# chromatographic column in zone Z3; the organic phase is concentrated and dried to obtain a stevioside product;

[0110] S3: Reverse osmosis membrane concentration:

[0111] The organic salt phase in S2 is concentrated by reverse osmosis membrane (operating temperature is 55° C., membrane pressure is 3.5 MPa) to obtain a retentate with a solid content of 13 wt%. The permeate in the concentration process is used as the mobile phase in the simulated moving bed separation system in step (2);

[0112] S4: Selective precipitation:

[0113] The retentate in S3 was heated to 75°C, and a 10wt% sulfuric acid solution was added to adjust the pH of the solution to 4.5. The solution was precipitated until no new precipitate was produced. The solution was filtered and the collected filter cake was dried to obtain 3207g of the target product, high-content rebaudioside B. The content of rebaudioside B was 95.6wt%, and the effective yield was 86.2%.

[0114] Example 5

[0115] A method for preparing rebaudioside B based on separation of mother liquor sugars by a simulated moving bed comprises the following steps:

[0116] S1: Pre-processing:

[0117] Dissolve 30 kg of stevia mother liquor sugar (total glycoside content 63.5 wt%, rebaudioside B content 8.6 wt%) in 100 L of pure water to obtain a stevia mother liquor sugar solution; add a 40 wt% KHCO3 solution to adjust the pH of the stevia mother liquor sugar to 8.0 to obtain a liquid to be treated;

[0118] S2: Simulated Moving Bed Chromatography Separation:

[0119] The simulated moving bed chromatographic separation system comprises 6 chromatographic columns connected in series and end to end (the first chromatographic column is Z1 zone, the two chromatographic columns connected to Z1 zone and connected in series are Z2 zone, the two chromatographic columns connected to Z2 zone and connected in series are Z3 zone, and the tail chromatographic column is Z4 zone), the diameter of the chromatographic column is 22 cm, the height is 13 cm, the chromatographic column is filled with S1850 potassium type resin (Lanxiao Technology) with an average particle size of 300 μm, when feeding, the feed amount of the liquid to be treated is 13 v / v% of the volume of the single column chromatographic column, the feed amount of water is 30 v / v% of the volume of the single column chromatographic column, and the circulation flushing amount is 36 v / v% of the volume of the single column chromatographic column; one cycle comprises circulation flushing of the chromatographic columns in Z1 zone to Z4 zone, water flushing of Z1 zone to Z The process comprises four steps: a chromatographic column in zone 3, a chromatographic column in zone Z1 with water analysis, and feeding from a chromatographic column in zone Z3, wherein feeding and water analysis are performed simultaneously, Va (circulation flushing flow rate) is 170 mL / min, Vb (water flushing flow rate) is 170 mL / min, Vc (water analysis flow rate) is 150 mL / min, and Vd (feeding flow rate) is 100 mL / min. Va, Vb, Vc (Vd) are respectively operated for 10.6 min, 3.1 min, and 6.5 min before switching to the next cycle; the organic phase containing other steviol glycosides is collected from the discharge port of zone Z1 by switching the valve, and the organic salt phase containing rebaudioside B is collected from the discharge port of the 2# chromatographic column in zone Z3; the organic phase is concentrated and dried to obtain a stevioside product;

[0120] S3: Reverse osmosis membrane concentration:

[0121] The organic salt phase in S2 is concentrated by reverse osmosis membrane (operating temperature is 38° C., membrane pressure is 5.5 MPa) to obtain a retentate with a solid content of 12 wt%. The permeate in the concentration process is used as the mobile phase in the simulated moving bed separation system in step (2);

[0122] S4: Selective precipitation:

[0123] The retentate in S3 was heated to 73°C, and a 35wt% citric acid solution was added to adjust the pH of the solution to 4.8. The solution was precipitated until no new precipitate was produced. The solution was filtered and the collected filter cake was dried to obtain 2321g of the target product, high-content rebaudioside B. The content of rebaudioside B was 95.8wt%, and the effective yield was 86.2%.

[0124] In order to better verify the effect of the present invention, the following is a detailed description with reference to Example 1 and combined with a plurality of comparative examples.

[0125] Comparative Example 1

[0126] Compared with Example 1, the difference is that in S1, the solid content of the stevia mother liquid sugar solution is 10wt%, and the other conditions are the same as those in Example 1, and 3472g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 93.2wt%, and the effective yield is 80.1%.

[0127] Comparative Example 2

[0128] Compared with Example 1, the difference is that in S1, the solid content of the stevia mother liquid sugar solution is 45wt%, and the other conditions are the same as those in Example 1, and 3258g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 92.1wt%, and the effective yield is 74.3%.

[0129] Comparative Example 3

[0130] Compared with Example 1, the difference is that in S1, the pH of the liquid to be treated is 6, and the other conditions are the same as in Example 1, and 3330 g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 90.7wt%, and the effective yield is 74.8%.

[0131] Comparative Example 4

[0132] Compared with Example 1, the difference is that in S1, the pH of the liquid to be treated is 10.5, and the other conditions are the same as those in Example 1, and 3521 g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 92.3wt%, and the effective yield is 80.4%.

[0133] Comparative Example 5

[0134] Compared with Example 1, the difference is that in S2, when the simulated moving bed chromatography system is used for separation, the water flushing flow rate is 120 mL / min, and the other conditions are the same as those in Example 1, and 3657 g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 89.3 wt%, and the effective yield is 76.3%.

[0135] Comparative Example 6

[0136] Compared with Example 1, the difference is that in S2, when the simulated moving bed chromatography system is used for separation, the water flushing flow rate is 200 mL / min, and the other conditions are the same as those in Example 1, and 3161 g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 95.1 wt%, and the effective yield is 70.2%.

[0137] Comparative Example 7

[0138] Compared with Example 1, the difference is that in S2, when the simulated moving bed chromatography system is used for separation, the feed flow rate is 150 mL / min, and the other conditions are the same as those in Example 1, and 3452 g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 94.9 wt%, and the effective yield is 76.5%.

[0139] Comparative Example 8

[0140] Compared with Example 1, the difference is that in S4, the temperature of selective precipitation is 60°C, and the other conditions are the same as those in Example 1, and 4185g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 89.8wt%, and the effective yield is 93.0%.

[0141] Comparative Example 9

[0142] Compared with Example 1, the difference is that in S4, the temperature of selective precipitation is 95°C, and the other conditions are the same as those in Example 1, and 3489g of the target product with high content of rebaudioside B is obtained, the content of rebaudioside B is 95.9wt%, and the effective yield is 82.8%.

[0143] Comparative Example 10

[0144] Compared with Example 1, the difference is that in S4, during selective precipitation, the pH of the solution is 3.0, and the other conditions are the same as in Example 1, and 4423g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 85.5wt%, and the effective yield is 93.6%.

[0145] Comparative Example 11

[0146] Compared with Example 1, the difference is that in S4, during selective precipitation, the pH of the solution is 6.5, and the other conditions are the same as in Example 1, and 2981g of the target product high-content rebaudioside B is obtained, the content of rebaudioside B is 96.0wt%, and the effective yield is 70.8%.

[0147] The results of the above comparative examples and embodiments are analyzed as follows:

[0148] Compared with the comparative example, the embodiment of the present invention optimizes the solid content of the liquid to be treated, accurately controls the pH of the solution, adopts simulated moving bed chromatography separation, reverse osmosis membrane separation, selective precipitation treatment, and optimizes the parameters of each process, thereby producing a high content of rebaudioside B, with a significantly improved effective yield, and recovering other steviol glycosides except rebaudioside B in stevia mother liquor sugar, and the waste water in the process is fully utilized, thereby greatly improving the economic value of stevia mother liquor sugar.

[0149] Specifically, it can be seen from Comparative Examples 1-2 and Example 1 that the solid content of the appropriate stevia mother liquor sugar solution has a certain influence on the separation and recovery of rebaudioside B. Within a certain range, as the solid content of the stevia mother liquor sugar solution increases, the higher the purity of the obtained target product rebaudioside B, the higher the yield, but when the solid content exceeds a certain value, the solid content of the stevia mother liquor sugar solution continues to increase, and the content of rebaudioside B in the target product decreases instead. This is mainly because, when the solid content of the stevia mother liquor sugar is too high, the material concentration is too high during simulated moving bed chromatography separation, resulting in a poor separation effect.

[0150] It can be seen from Comparative Examples 3-4 and Example 1 that the pH of the stevia mother liquor sugar solution is also critical during separation. Within a certain pH range, as the pH value increases, rebaudioside B can fully combine with sodium ions or potassium ions, so that in the simulated moving bed chromatography separation process, it can be better separated from other stevioside components, thereby improving the yield of the target product and the content of rebaudioside B in the target product. However, when the pH exceeds a certain range, the pH continues to increase, and the content of rebaudioside B in the target product decreases instead. This is mainly because the pH is too high, which will cause excessive use of the pH adjuster, thereby causing the sodium ions to be enriched in the simulated moving bed chromatography separation system, affecting the separation effect.

[0151] The conditions for separation using a simulated moving bed chromatography system are also extremely critical. The circulating liquid flushing flow, water flushing flow, water desorption flow and feed flow will have a certain impact on the performance of the product. If the circulating liquid flushing flow or water flushing flow is too small, it will affect the separation efficiency and cause the organic phase to be enriched at the front end. If the flow is too fast, the organic salt phase and the organic phase will be enriched at the back end of the simulated moving bed chromatography separation system, affecting the enrichment effect. If the feed flow is too large, the separation effect will also deteriorate.

[0152] It can be seen from Comparative Examples 8-11 that during selective precipitation, the precipitation temperature and the pH of the solution are extremely critical. If the pH is too low or the temperature is too low, impurities will precipitate together with rebaudioside B, thereby reducing the purity of the target product. If the pH or temperature is too high, part of the rebaudioside B will be dissolved and will not precipitate, thereby reducing the yield of the target product.

[0153] In summary, in order to improve the purity and yield of rebaudioside B, the separation conditions need to be strictly controlled.

[0154] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing rebaudioside B based on separation of mother liquor sugar by simulated moving bed, It is characterized in that The following steps are involved: (1) dissolving stevia mother liquid sugar to obtain a stevia mother liquid sugar solution, and adjusting the pH of the stevia mother liquid sugar solution to 7.5-9.5 to obtain a liquid to be treated; (2) pumping the liquid to be treated into a simulated moving bed separation system for separation to obtain an organic phase and an organic salt phase; (3) treating the organic salt phase with a reverse osmosis membrane to concentrate the permeate and the retentate, and using the permeate as a mobile phase in step (2); (4) heating the retentate, then adding a pH adjuster to adjust the pH of the solution to 4.0-5.5, and performing a precipitation treatment; (5) Filter the solution after precipitation, collect the filter cake and dry it to obtain high-content rebaudioside B.

2. A method for preparing rebaudioside B based on separating mother liquor sugars by a simulated moving bed according to claim 1, It is characterized in that In step (1), the solid content of the stevia mother liquor sugar solution is 15-35wt%.

3. A method for preparing rebaudioside B based on separating mother liquor sugars by a simulated moving bed according to claim 1, It is characterized in that In step (1), the pH regulator used to adjust the stevia mother liquor sugar solution is a sodium salt solution or a potassium salt solution; and / or the concentration of the sodium salt solution is 5-40wt%, and the sodium salt is NaOH, NaHCO 3 、Na 2 CO 3 and / or the concentration of the potassium salt solution is 5-40wt%, the potassium salt is KOH, KHCO 3 , K 2 CO 3 One of them.

4. A method for preparing rebaudioside B based on separating mother liquor sugars by a simulated moving bed according to claim 1, It is characterized in that In step (2), when a simulated moving bed separation system is used for treatment, the stationary phase is a uniform gel cation chromatography resin and the mobile phase is water; and / or the average particle size of the uniform gel cation chromatography resin is 220-320 μm; and / or the uniform gel cation chromatography resin is one of a sodium type resin and a potassium type resin.

5. A method for preparing rebaudioside B based on separating mother liquor sugar by simulated moving bed according to claim 1, It is characterized in that In step (2), the simulated moving bed separation system is composed of six chromatographic columns connected in series and connected end to end, and the diameter-to-height ratio of a single chromatographic column is 2.0:(1-1.5).

6. A method for preparing rebaudioside B by separating mother liquor sugars based on a simulated moving bed according to claim 5, It is characterized in that In step (2), when the treated liquid is treated with a simulated moving bed chromatography separation system, one cycle includes circulating flushing, water flushing, water analysis, and feeding, and the water analysis and feeding are carried out simultaneously, and the organic salt phase is collected during the water flushing and feeding processes, and the organic phase is collected during the water analysis; and / or during one cycle, the feed amount of the treated liquid is 10-15 v / v% of the volume of the single column chromatography column, the feed amount of water is 30-34 v / v% of the volume of the single column chromatography column, and the circulating liquid flushing amount is 35-37 v / v% of the volume of the single column chromatography column.

7. A method for preparing rebaudioside B by separating mother liquor sugars based on a simulated moving bed according to claim 6, It is characterized in that In step (2), the separation conditions are as follows: the circulating flushing flow rate is 160-170 mL / min, the water flushing flow rate is 160-180 mL / min, the water analysis flow rate is 150-170 mL / min, the feed flow rate is 100-120 mL / min, the circulating flushing time is 10-12 min, the water flushing time is 3-4 min, the water analysis time is 4-8 min, and then switch to the next cycle.

8. The method for preparing rebaudioside B by separating mother liquor sugars based on a simulated moving bed according to claim 1, It is characterized in that In step (3), the conditions for the concentration treatment are: an operating temperature of 30-65° C., a membrane pressure of 3.0-6.0 MPa; and / or a solid content of the retentate of 10-20 wt %.

9. The method for preparing rebaudioside B by separating mother liquor sugars based on a simulated moving bed according to claim 1, It is characterized in that In step (4), the temperature of the heating treatment is 70-85°C.

10. The method for preparing rebaudioside B by separating mother liquor sugars based on a simulated moving bed according to claim 1, It is characterized in that In step (4), the pH adjusting agent is one of hydrochloric acid solution, sulfuric acid solution, and citric acid solution; and / or the concentration of the hydrochloric acid solution is 5-35wt%; and / or the concentration of the sulfuric acid solution is 5-35wt%; and / or the concentration of the citric acid solution is 20-50wt%.

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