Method for preparing erythritol crystals

Abstract

The present invention relates to the field of erythritol crystallization, and discloses a method for preparing erythritol crystals. The method comprises: (1) mixing erythritol concentrate, erythritol seed crystals and ethanol to obtain a mixed material; (2) pre-crystallizing the mixed material under the intermittent presence of ultrasonic waves, and then cooling and crystallizing to obtain a slurry; (3) performing solid-liquid separation on the slurry to obtain erythritol crystals and a mother liquor. The method has a simple and mild process, low cost, short crystallization time, can avoid agglomeration, crystal scale and cavity formation, and has uniform product particles and high yield.

Description

Technical Field

[0001] The present invention relates to the field of erythritol crystallization, and in particular to a method for preparing erythritol crystals. Background Art

[0002] Erythritol is a natural sugar and functional sweetener widely used in the development of low-calorie health foods, as well as functional foods and beverages for people with diabetes and glucose intolerance. While domestic erythritol production is already among the largest in the world, product quality, particularly in terms of crystal form and particle size distribution, still needs to be improved.

[0003] Industrial production primarily relies on fermentation. After purification, the fermentation broth is evaporated and concentrated, then cooled and crystallized to produce erythritol crystals. Due to the low erythritol concentration in the fermentation broth, atmospheric distillation and concentration require higher operating temperatures, resulting in greater water evaporation and higher energy consumption. While reduced pressure or multi-effect evaporation can reduce energy consumption, they also increase the complexity of the equipment and process. Furthermore, whether using evaporative crystallization or evaporative concentration followed by cooling crystallization, crystal scaling easily forms on heat exchange surfaces such as coils and jackets, significantly reducing heat transfer efficiency. This makes the evaporation rate or cooling rate difficult to control, prolonging the crystallization time and resulting in an uneven particle size distribution in the crystallized product and a low crystallization rate. Furthermore, during the evaporative crystallization process, the solid suspension density within the crystallizer increases, leading to uneven crystal-liquid mixing and crystals easily sinking to the bottom. Furthermore, friction and collision between crystals and between the crystals and the stirring paddles can lead to severe localized supersaturation of the crystals during the crystallization process, which also exacerbates the uneven particle size distribution of the crystallized product. In addition, erythritol has a high solubility in water (200 g / (100 g water) at 65°C and 40 g / (100 g water) at 15°C). Therefore, regardless of evaporative crystallization or cooling crystallization, a large amount of erythritol remains in the mother liquor at the end of the crystallization operation, resulting in low production capacity per unit volume of the crystallizer and low yield.

[0004] In CN104086365B, the utilization rate and overall yield of erythritol are improved by recycling the remaining erythritol in the erythritol crystallization mother liquor. However, the crystallization method of this method is the traditional method of first evaporating and concentrating, and then cooling and crystallizing. The one-time crystallization yield is low, and there are many bubbles in the concentrated liquid, resulting in different crystal particle sizes.

[0005] CN106831337A uses a continuous dissolution membrane crystallization method to achieve fully continuous production of erythritol dissolution crystallization, avoiding the localized supersaturation and excessive nucleation that occurs when the dissolution agent is directly added to the crystallization mother liquor. The dissolution agent can also be recovered for recycling. However, this method has problems such as difficulty in removing bubbles, membrane contamination, and low primary crystallization yield. In addition, the additional distillation tower and membrane wear and tear costs are high, making it difficult to implement industrially.

[0006] Therefore, it is necessary to develop a method for preparing erythritol crystals with simple and mild process, low cost, short crystallization time, avoidance of agglomeration, formation of crystal scale and cavity, and uniform product particles, high yield and high purity. Summary of the Invention

[0007] The present invention aims to overcome the above-mentioned problems existing in the prior art and provide a method for preparing erythritol crystals. The method has simple and mild process, low cost, short crystallization time, can avoid agglomeration, crystal scale and cavity formation, and has uniform product particles and high yield.

[0008] In order to achieve the above object, the present invention provides a method for preparing erythritol crystals, which comprises:

[0009] (1) mixing erythritol concentrate, erythritol seed crystals and ethanol to obtain a mixed material;

[0010] (2) pre-crystallizing the mixed material in the intermittent presence of ultrasonic waves, and then performing cooling crystallization to obtain a slurry;

[0011] (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and mother liquor.

[0012] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0013] 1. The method of the present invention has a short crystallization time, high yield and high purity. In addition, it can avoid agglomeration, crystal scale and cavity formation, and the product has uniform particle size distribution and high quality.

[0014] 2. The method of the present invention has a simple process flow, mild operating conditions, and low requirements for equipment. It avoids the problem of crystal scaling on the heat exchange surface, thereby reducing the heat transfer efficiency, greatly reduces the problem of high energy consumption caused by low heat transfer efficiency, reduces production costs, and is easy to industrialize.

[0015] Biological Deposits

[0016] The strain described in the present invention is classified and named Yarrowia lipolytica, and was deposited in the General Microbiology Center of China Culture Collection Administration (address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code: 100101) on May 28, 2021 (the abbreviation of the depository unit is CGMCC), and the deposit number is CGMCC No. 22632. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0018] The present invention provides a method for preparing erythritol crystals, the method comprising:

[0019] (1) mixing erythritol concentrate, erythritol seed crystals and ethanol to obtain a mixed material;

[0020] (2) pre-crystallizing the mixed material in the intermittent presence of ultrasonic waves, and then performing cooling crystallization to obtain a slurry;

[0021] (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and mother liquor.

[0022] It is understood that ultrasonic waves can be provided to the mixed material by extending an ultrasonic probe below the liquid surface of the mixed material.

[0023] According to the present invention, preferably, the method for obtaining an erythritol concentrate comprises: purifying an erythritol solution to be purified to obtain a purified erythritol solution, and concentrating the purified erythritol solution to obtain an erythritol concentrate;

[0024] The purity of the purified erythritol solution is not less than 88 weight % (for example, 88 weight %, 88.5 weight %, 89 weight %, 90 weight %, 91 weight %, or 92 weight %).

[0025] Wherein, the erythritol solution to be purified can be any one or a mixture of two or three of natural extraction, biological fermentation or chemical synthesis.For example, the erythritol solution to be purified can be saccharified by starch, liquefied into glucose, and then converted by yeast fermentation. However, according to a preferred embodiment of the present invention, the erythritol solution to be purified is fermented by Yarrowia lipolytica, and more preferably, the Yarrowia lipolytica is deposited in the General Microbiology Center of China Committee for the Collection of Microorganisms (Address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code: 100101) on May 28, 2021 (the abbreviation of the depository unit is CGMCC), and the deposit number is CGMCC No.22632. When the fermentation adopts the above-mentioned Yarrowia lipolytica, it is possible to make fermentation by-products and impurities less, and the erythritol output is higher and the yield is higher:

[0026] The Yarrowia lipolytica described above is inoculated into a fermentation medium for fermentation to obtain a fermentation broth containing erythritol. The resulting fermentation broth is subjected to solid-liquid separation to obtain an erythritol solution to be purified. Specifically, the method of the present invention preferably further comprises: inoculating the Yarrowia lipolytica described above into a fermentation medium for fermentation, subjecting the resulting fermentation broth containing erythritol to solid-liquid separation, and using the resulting liquid phase as the erythritol solution to be purified.

[0027] The fermentation conditions may be those commonly used in the art for producing erythritol. Preferably, the fermentation conditions include a fermentation temperature of 30-35°C and a fermentation time of 60-120 hours. Furthermore, preferably, to further increase erythritol production, the fermentation temperature is 30-32°C.

[0028] Preferably, the method further comprises: during the fermentation process, controlling the dissolved oxygen content in the fermentation broth to be 10-35 vol%. The method for controlling the dissolved oxygen content in the fermentation broth can be a commonly used method in the art, for example, by controlling the ventilation volume of the fermenter or the rotation speed of the fermenter, and those skilled in the art can adjust it according to actual conditions.

[0029] Wherein, the fermentation medium can be a medium commonly used in the art for fermenting erythritol. Preferably, the fermentation medium contains a carbon source, a nitrogen source, an optional inorganic nutrient salt, and an optional surfactant. Preferably, relative to 1L of the fermentation medium, the content of the carbon source is 150-350g, the content of the nitrogen source is 5-30g, the content of the inorganic nutrient salt is 0-7g, and the content of the surfactant is 0-2g.

[0030] Preferably, the carbon source is glucose.

[0031] Preferably, the nitrogen source may be at least one of yeast extract powder, yeast extract, corn steep liquor, ammonium citrate, ammonium sulfate and diammonium hydrogen sulfate.

[0032] Preferably, the inorganic nutrient salt is potassium dihydrogen sulfate and / or magnesium sulfate.

[0033] Preferably, the surfactant is Tween 80.

[0034] Preferably, per liter of the fermentation medium, the glucose content is 150-350 g, the nitrogen source content is 5-30 g, the potassium dihydrogen phosphate content is 0-5 g, the magnesium sulfate content is 0-2 g, and the Tween 80 content is 0-2 g. Preferably, the initial pH of the fermentation medium is 5-6.5. The nitrogen source can be any commonly used nitrogen source in the art, for example, at least one of yeast extract powder, yeast extract, corn steep liquor, ammonium citrate, ammonium sulfate, and diammonium hydrogen phosphate.

[0035] Preferably, the initial pH value of the fermentation medium is 5-6.5.

[0036] Preferably, the method may further comprise: when the glucose concentration in the fermentation broth is lower than 100g / L, adding glucose solution to the fermentation broth until the converted total sugar reaches 380-450g / L, stopping the addition, and continuing the fermentation until the glucose concentration in the fermentation broth is lower than 1g / L. Wherein, the "converted total sugar" refers to the ratio of the sum of the initial total amount of glucose (g) in the fermentation medium and the total amount of glucose (g) in the glucose solution added to the total volume (L) of the fermentation broth after the addition of glucose solution is stopped. Wherein, the flow rate of the glucose solution is controlled to maintain the glucose concentration in the fermentation broth at 100-150g / L. There is no requirement for the concentration of the glucose solution, and it can be the concentration of glucose solutions commonly used in the art. Preferably, the concentration of the glucose solution can be 600-800g / L.

[0037] Unless otherwise specified, the solvent of the fermentation medium is deionized water.

[0038] Preferably, the Yarrowia lipolytica is inoculated in the form of seed liquid.

[0039] The seed solution preparation method may be a conventional preparation method in the art, such as primary seed culture or secondary seed culture. Those skilled in the art may select a culture method according to actual conditions.

[0040] The primary seed culture may be a conventional method in the art, for example, the method may include: inoculating glycerol bacteria into an activation culture medium, and culturing at 28-32° C. and 180-240 rpm for 16-30 hours.

[0041] The "glycerol bacteria" mentioned above refers to Yarrowia lipolytica preserved in glycerol, and the number of viable bacteria is generally 10 7 In the present invention, the inoculation amount of the "glycerol bacteria" can be a conventional inoculation amount in the art, for example, 3‰ (v / v).

[0042] The secondary seed culture may be a conventional method in the art. In some embodiments of the present invention, the secondary seed culture is as follows: first, a glycerol strain or a slant-preserved strain is inoculated into an activation medium, cultured at 28-32°C and 180-240 rpm for 12-24 hours, and then inoculated into a fermentation medium at an inoculum size of 5-15% (v / v), cultured at 28-32°C and 180-350 rpm for 12-24 hours to obtain a seed solution.

[0043] The activation medium may be a medium commonly used in the art for activating Yarrowia lipolytica. Preferably, the activation medium contains 50-150 g / L of glucose, 10-30 g / L of yeast extract or yeast paste, and 0.2-1 g / L of potassium dihydrogen phosphate.

[0044] Wherein, the OD of the seed solution 600 The value can be selected in a wide range. Preferably, the OD value of the seed solution is 600 The value is 8-25.

[0045] The inoculation amount of the seed solution can be any commonly used in the art. Preferably, the inoculation amount of the seed solution is 5-15% (v / v).

[0046] Wherein, the purification method can be sequentially passing through a cation exchange resin and an anion exchange resin.

[0047] According to the present invention, in order to further improve the crystallization yield and further ensure that a crystalline product with more uniform particle size distribution and higher purity is obtained, preferably, the concentration of the erythritol concentrate is 450-700 g / L, more preferably 560 g / L-680 g / L, and most preferably 650 g / L.

[0048] It is understandable that the "purity" and "concentration" mentioned are different concepts. Purity refers to the ratio of the weight of erythritol in the erythritol solution to the total weight of all sugar alcohols and sugars in the erythritol solution. Concentration, on the other hand, is the ratio of the total weight of all sugar alcohols and sugars in the erythritol solution to the volume of the erythritol solution. During the preparation process, due to actual operations such as reaction, fermentation or extraction, the erythritol solution obtained may also include other sugars or sugar alcohols in addition to erythritol. When calculating the concentration, the amount of these other sugars or sugar alcohols is also taken into account.

[0049] According to the present invention, the concentration method is not particularly limited and can be a conventional method in the art. Preferably, the concentration method comprises: performing reduced pressure concentration at a temperature not exceeding 80°C. It is understood that a temperature not exceeding 80°C can significantly reduce energy consumption while ensuring crystallization efficiency, and can also prevent impurities in the erythritol solution from caramelizing due to localized excessive temperatures during the concentration process, thereby causing the concentrate to brown, resulting in yellow crystals.

[0050] It is understood that in the reduced pressure concentration, the lower the concentration pressure is generally, the better. However, taking into account both cost and ease of operation, the concentration pressure is based on the principle of being able to achieve faster concentration of the purified erythritol solution at a lower temperature.

[0051] Among them, in order to facilitate operation during the industrial scale-up process and lower the threshold for process technology scale-up, the equipment used for concentration can be single-effect, double-effect, triple-effect, or quadruple-effect concentration equipment.

[0052] According to the present invention, preferably, the amount of ethanol used is 0.3-10 L, more preferably 0.5-5 L, relative to 1 L of erythritol concentrate. The inventors of the present invention have found in their research that impurities have a high solubility in an ethanol-water system. When the amount of ethanol used meets the above range, while reducing the amount and fully utilizing the ethanol, it can also further ensure a higher crystallization yield, further ensuring a more uniform particle size distribution and a higher purity crystalline product.

[0053] According to the present invention, although the purpose of the present invention can be achieved by using an intermittent ultrasonic wave, in order to further improve the crystallization yield and further ensure that a crystalline product with more uniform particle size distribution and higher purity is obtained, preferably, the method of providing ultrasonic wave is as follows: ultrasonic wave is applied for 10-60s (for example, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s) every 10-120s (for example, 10s, 20s, 30s, 40s, 50s, 60s), and this is continued for 1-10min (for example, 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min), then the ultrasonic wave is turned off and maintained for 20-60min (for example, 20min, 30min, 40min, 50min, 60min), and the ultrasonic wave is repeated and the ultrasonic wave is turned off until the pre-crystallization is completed. Preferably, ultrasonic method is provided: ultrasonic 15-30s every 15-30s, after so continuing 3-7min, turn off ultrasonic and maintain 25-40min, repeat ultrasonic and turn off ultrasonic to pre-crystallization and end. For example, ultrasonic 20s can be performed every 20s, after so continuing 5min, turn off ultrasonic and maintain 30min, repeat ultrasonic and turn off ultrasonic to pre-crystallization and end. It can be understood that if the time period of turning off ultrasonic and maintaining closure has reached the time of setting, then directly enter decrease temperature crystallization; if ultrasonic 10-60s every 10-120s, after so continuing 1-10min, the time of pre-crystallization has reached the time of setting, then after reaching the pre-crystallization time, no longer perform the operation of ultrasonic 10-60s every 10-120s, directly turn off ultrasonic, enter decrease temperature crystallization. In addition, the inventor of the present invention further finds that, using the scheme as described above, it is also possible to effectively save energy consumption, and in the operation of alternating ultrasonic and turning off ultrasonic, it is also helpful to better control temperature.

[0054] According to the present invention, in order to further improve the crystallization yield and further ensure that a crystalline product with more uniform particle size distribution and higher purity is obtained, preferably, the power of the ultrasound is 100-1000W / m 3 Mixed material, preferably 300-500W / m 3 Mixed material, most preferably 400W / m 3 Mixed materials.

[0055] According to the present invention, in order to further improve the crystallization yield and further ensure that a crystalline product with more uniform particle size distribution and higher purity is obtained, preferably, the conditions of the pre-crystallization include: a temperature of 30-80°C (for example, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C), a time of 1-2h (for example, 1h, 1.5h, 2h), and a stirring speed of 50-350rpm (for example, 50rpm, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm). The inventors of the present invention further found in the study that when the above range is met, local supersaturation can be avoided while avoiding crystal breakage, so that the crystals are uniformly precipitated.

[0056] According to the present invention, in order to further improve the crystallization yield and further ensure that a crystalline product with a more uniform particle size distribution and higher purity is obtained, preferably, the conditions for the cooling crystallization include: cooling at a cooling rate of 0.1-0.5°C / min, cooling to 0-15°C and maintaining the temperature at 0-15°C, and the stirring rate during the cooling crystallization process is 50-350rpm (for example, it can be 50rpm, 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm); wherein the cooling crystallization time is 4-13h (for example, it can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, which time includes the time required for cooling and maintenance). It can be understood that within the above range, especially within the cooling rate range, it is possible to avoid excessive changes in conditions, which may affect the purity and particle uniformity of the erythritol crystals. In the process of cooling, the cooling rate can vary slightly within the range of 0.1-0.5°C / min. For example, at the beginning, the cooling can be performed at a slightly faster rate, such as 0.5°C / min, to obtain a faster crystallization growth rate. After cooling to 22-27°C, the cooling can be performed at a slightly slower rate, such as 0.1°C / min, to 0-15°C, to ensure that the obtained crystals are larger and more uniform.

[0057] The inventors of the present invention have discovered that using the ultrasonic method described above, combined with the pre-crystallization and cooling crystallization conditions described above, can result in more uniform crystal precipitation at a more appropriate rate, avoiding agglomeration caused by rapid precipitation and uneven heating of the heat exchange surface. Furthermore, the ultrasonic method described above prevents excessive supersaturation of the solution on the container surface, reduces the forces acting on the crystals and the container wall, and avoids the formation of crystal scaling on the heat exchange surface, which can reduce heat transfer efficiency.

[0058] It can be understood that after entering the cooling crystallization, ultrasound is no longer applied to the mixture, and there is no operation of repeating ultrasound and turning off ultrasound.

[0059] According to the present invention, preferably, the solid-liquid separation is selected from at least one of centrifugal separation and filtration separation, and a combination of centrifugal separation and filtration separation may also be used.

[0060] After solid-liquid separation, the obtained erythritol crystals may be dried. The drying method may be conventional in the art, for example, at least one selected from fluidized bed drying and vacuum drying.

[0061] According to the present invention, in order to further improve the crystallization yield of erythritol, preferably, a portion of the mother liquor is taken and returned to be mixed with the purified erythritol solution and concentrated together;

[0062] The amount of the mother liquor is such that after the mother liquor is returned and mixed with the purified erythritol solution, the purity of the obtained material is not less than 88% by weight.

[0063] According to the present invention, preferably, the remaining part of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0064] According to a particularly preferred embodiment of the present invention, erythritol crystals are prepared according to the following method:

[0065] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of not less than 88% by weight.

[0066] The purified erythritol solution as described above is concentrated under reduced pressure at a temperature not higher than 80° C. to a concentration of 600-660 g / L to obtain an erythritol concentrate.

[0067] Take the above erythritol concentrate and mix it with erythritol seed crystals (relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 8-15g), then add the material to anhydrous ethanol (relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 2-3L) and stir evenly.

[0068] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 350-450W / m 3The mixture is then ultrasonicated for 18-22 seconds every 18-22 seconds for 4-6 minutes. The ultrasonication is then turned off and maintained for 28-33 minutes. This process is repeated until the pre-crystallization is complete. The pre-crystallization conditions include a stirring rate of 180-220 rpm, a temperature of 45-55°C, and a duration of 1.2-1.8 hours.

[0069] After the pre-crystallization is completed, the crystallization is carried out by cooling. The conditions of the cooling crystallization include: cooling at a cooling rate of 0.4-0.5°C / min to 23-26°C, then cooling at a cooling rate of 0.1-0.2°C / min to 3-7°C and maintaining the temperature at 3-7°C, stirring at a rate of 180-220 rpm during the cooling crystallization process, and continuing the cooling crystallization for 7-9 hours. After completion, a slurry is obtained.

[0070] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0071] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 88% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0072] The present invention will be described in detail below by way of examples.

[0073] Ultrasonic cycle extraction machine, model GCXZ-2B, was purchased from Beijing Hongxianglong Biotechnology Co., Ltd.;

[0074] Vacuum drying oven, model DZF-6050, purchased from Shanghai Bozheng Industrial Co., Ltd.;

[0075] The centrifugal filter, model SSC300, was purchased from Yongle Machinery Equipment Manufacturing Co., Ltd.

[0076] Erythritol standard was purchased from Inokane.

[0077] Example 1

[0078] Used to illustrate the method for preparing erythritol crystals provided by the present invention

[0079] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of 89% by weight.

[0080] The purified erythritol solution was concentrated under reduced pressure at 70° C. to a concentration of 650 g / L to obtain an erythritol concentrate.

[0081] Take 20L of the above-mentioned erythritol concentrate and mix it with 0.2kg of erythritol seed crystals (ie, relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 10g), and then add the material to 50L of anhydrous ethanol (ie, relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 2.5L) and stir evenly.

[0082] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 400W / m 3 The mixture was ultrasonicated for 20 seconds every 20 seconds for 5 minutes, then the ultrasonic wave was turned off and maintained for 30 minutes. The ultrasonic wave was repeated on and off until the pre-crystallization was completed. The pre-crystallization conditions included a stirring rate of 200 rpm, a temperature of 50°C, and a time of 1.5 hours.

[0083] After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling at a cooling rate of 0.4°C / min to 25°C, then cooling at a cooling rate of 0.1°C / min to 4°C and maintaining the temperature at 4°C, stirring at a rate of 200 rpm during the cooling crystallization process, and continuing the cooling crystallization for 8 hours. After completion, a slurry is obtained.

[0084] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0085] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 89% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0086] Example 2

[0087] Used to illustrate the method for preparing erythritol crystals provided by the present invention

[0088] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of 88.5% by weight.

[0089] The purified erythritol solution was concentrated under reduced pressure at 65° C. to a concentration of 680 g / L to obtain an erythritol concentrate.

[0090] Take 150L of the above-mentioned erythritol concentrate and mix it with 4.5kg of erythritol seed crystals (ie, relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 30g), and then add the material to 750L of anhydrous ethanol (ie, relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 5L) and stir evenly.

[0091] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 300W / m 3 The mixture was then ultrasonicated for 15 seconds every 15 seconds for 7 minutes. The ultrasonication was then turned off and maintained for 40 minutes. This process was repeated until the pre-crystallization was complete. The pre-crystallization conditions included a stirring rate of 50 rpm, a temperature of 30°C, and a duration of 1 hour.

[0092] After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling at a cooling rate of 0.4°C / min to 25°C, then cooling at a cooling rate of 0.1°C / min to 15°C and maintaining the temperature at 15°C, stirring at a rate of 50 rpm during the cooling crystallization process, and continuing the cooling crystallization for 4 hours. After completion, a slurry is obtained.

[0093] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0094] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after returning to be mixed with the purified erythritol solution is not less than 88.5% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0095] Example 3

[0096] Used to illustrate the method for preparing erythritol crystals provided by the present invention

[0097] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of 88% by weight.

[0098] The purified erythritol solution was concentrated under reduced pressure at 70° C. to a concentration of 560 g / L to obtain an erythritol concentrate.

[0099] Take 45L of the above-mentioned erythritol concentrate and mix it with 0.225kg of erythritol seed crystals (ie, relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 5g), and then add the material to 22.5L of anhydrous ethanol (ie, relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 0.5L) and stir evenly.

[0100] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 500W / m 3 The mixture was then ultrasonicated for 30 seconds every 30 seconds for 3 minutes. This process was then turned off and maintained for 25 minutes. This process was repeated until the pre-crystallization was complete. The pre-crystallization conditions included a stirring rate of 350 rpm, a temperature of 80°C, and a duration of 2 hours.

[0101] After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling at a cooling rate of 0.4°C / min to 25°C, then cooling at a cooling rate of 0.1°C / min to 0°C and maintaining the temperature at 0°C, stirring at a rate of 350 rpm during the cooling crystallization process, and continuing the cooling crystallization for 13 hours. After completion, a slurry is obtained.

[0102] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0103] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 88% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0104] Example 4

[0105] Used to illustrate the method for preparing erythritol crystals provided by the present invention

[0106] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of 88% by weight.

[0107] The purified erythritol solution was concentrated under reduced pressure at 75° C. to a concentration of 450 g / L to obtain an erythritol concentrate.

[0108] Take 20L of the above-mentioned erythritol concentrate and mix it with 0.02kg of erythritol seed crystals (ie, relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 1g), and then add the material to 6L of anhydrous ethanol (ie, relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 0.3L) and stir evenly.

[0109] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 100W / m 3 The mixture was ultrasonicated for 10 seconds every 10 seconds for 1 minute, then turned off and maintained for 20 minutes. This process was repeated until the pre-crystallization was complete. The pre-crystallization conditions included a stirring rate of 350 rpm, a temperature of 60°C, and a duration of 2 hours.

[0110] After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling at a cooling rate of 0.4°C / min to 25°C, then cooling at a cooling rate of 0.1°C / min to 0°C and maintaining the temperature at 0°C, stirring at a rate of 350 rpm during the cooling crystallization process, and continuing the cooling crystallization for 10 hours. After completion, a slurry is obtained.

[0111] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0112] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 88% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0113] Example 5

[0114] Used to illustrate the method for preparing erythritol crystals provided by the present invention

[0115] (1) The erythritol solution to be purified is purified by eluting with a cationic resin and an anionic resin in sequence to obtain a purified erythritol solution with a purity of 88% by weight.

[0116] The purified erythritol solution was concentrated under reduced pressure at 80° C. to a concentration of 700 g / L to obtain an erythritol concentrate.

[0117] Take 20L of the above-mentioned erythritol concentrate and mix it with 1kg of erythritol seed crystals (ie, relative to 1L of erythritol concentrate, the amount of erythritol seed crystals is 50g), and then add the material to 200L of anhydrous ethanol (ie, relative to 1L of erythritol concentrate, the amount of anhydrous ethanol is 10L) and stir evenly.

[0118] (2) Use an ultrasonic circulation extractor, insert the ultrasonic probe below the liquid surface of the mixture, and adjust the ultrasonic power to 1000W / m 3 The mixture was ultrasonicated for 120 seconds every 120 seconds for 10 minutes, then the ultrasonication was turned off and maintained for 60 minutes. This ultrasonication cycle was repeated until the pre-crystallization was complete. The pre-crystallization conditions included a stirring rate of 100 rpm, a temperature of 60°C, and a duration of 2 hours.

[0119] After the pre-crystallization is completed, the crystallization is carried out by cooling. The cooling crystallization conditions include: cooling at a cooling rate of 0.4°C / min to 25°C, then cooling at a cooling rate of 0.1°C / min to 7°C and maintaining the temperature at 7°C, stirring at a rate of 100 rpm during the cooling crystallization process, and continuing the cooling crystallization for 10 hours. After completion, a slurry is obtained.

[0120] (3) The slurry is centrifuged to obtain erythritol crystals and mother liquor, and the erythritol crystals are vacuum-dried and weighed.

[0121] A portion of the mother liquor is returned to be mixed with the purified erythritol solution and concentrated together; wherein the amount of the mother liquor is such that the purity of the resulting material after being returned to be mixed with the purified erythritol solution is not less than 88% by weight. The remaining mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

[0122] Example 6

[0123] Erythritol crystals were prepared according to the method of Example 1, except that, during the pre-crystallization process, ultrasound was continued for 20 seconds every 20 seconds, that is, the ultrasound was not turned off and maintained.

[0124] Comparative Example 1

[0125] D-psicose crystallization was performed according to the method of Example 1, except that ultrasonic wave was not provided in the pre-crystallization.

[0126] Comparative Example 2

[0127] 20 L of the purified erythritol solution obtained in Example 1 was taken and an organic solvent was added to perform crystallization using the method described in CN201210364267.X.

[0128] Test Case

[0129] The erythritol crystals obtained in Examples 1-6 and Comparative Examples 1-2 were tested for purity, crystallization rate, and particle uniformity. The presence of cavities or agglomerates in the crystals was observed, and the presence of obvious crystal scaling on the heat exchange surfaces of the equipment was observed. The crystals obtained are those obtained after solid-liquid separation of the slurry and drying of the erythritol crystals, i.e., before the mother liquor is returned.

[0130] The purity of erythritol was determined by preparing an erythritol standard solution (10.0 mg / mL) using an erythritol standard substance, followed by dilution to concentrations of 10.0 mg / mL, 8.0 mg / mL, 6.0 mg / mL, 4.0 mg / mL, 2.0 mg / mL, 1.0 mg / mL, 0.5 mg / mL, and 0.25 mg / mL. The peak area of ​​the erythritol standard solution was determined using a high performance liquid chromatography system. A standard curve was drawn using the peak area (average of 3 sets of parallel samples) as the ordinate and the solution concentration as the abscissa. The erythritol samples of Examples 1-6 and Comparative Examples 1-2 were quantitatively analyzed based on the standard curve.

[0131] The calculation method of the crystallization rate is: (mass of erythritol crystals) / (mass of erythritol in the erythritol concentrate+mass of seed crystals)×100%.

[0132] Crystal uniformity evaluation method: Use 40-mesh and 60-mesh sieves to determine the ratio of the weight of erythritol particles with a particle size in the range of 40-60 mesh to the total mass of erythritol crystals to evaluate the uniformity of the erythritol crystal particles.

[0133] Table 1

[0134]

[0135]

[0136] From the results in Table 1, it can be seen that the crystallization rate and purity of Examples 1-6 using the technical solution of the present invention are high, and the obtained crystal particle size distribution is relatively uniform, and the occurrence of cavities or agglomerations in the crystals is avoided, and there is no obvious crystal scale on the heat exchange surface, among which Examples 1-3 have better effects. Compared with Example 6, the method in Example 1 can save more energy and control the temperature more accurately. The crystallization rate and purity of Comparative Examples 1-2 are poor, the crystal particle size distribution is uneven, there are obvious agglomerations and cavities in the crystals, and there is obvious crystal scale on the heat exchange surface. Moreover, from the results of Example 1 and Comparative Example 1, it can be seen that the technical solution of the present invention can obtain a higher crystallization rate in a shorter time, thereby significantly shortening the time and improving efficiency.

[0137] In addition, the technical solution of the present invention has simple process, mild operating conditions, low equipment requirements, low cost, easy industrialization, and good industrialization prospects.

[0138] The following examples are used to illustrate the Yarrowia lipolytica used to prepare the erythritol solution to be purified and the method of preparing the erythritol solution to be purified by fermentation using the Yarrowia lipolytica.

[0139] In the following examples, the activation culture medium contained: 150 g / L glucose, 15 g / L yeast extract, and 0.5 g / L potassium dihydrogen phosphate.

[0140] Glycerol bacteria refers to Yarrowia lipolytica CGMCC No.22632 preserved in glycerol, with a viable cell count of 10 7 cfu / mL.

[0141] The concentration of glucose in the fermentation broth (supernatant) was detected using an SBA-40E biosensor with a D-glucose enzyme membrane and an injection volume of 25 μL;

[0142] The erythritol, mannitol, arabitol, and glycerol contents (all referring to the contents in the fermentation broth (supernatant)) were determined by liquid chromatography using an Agilent Technologies 1260 Infinity II chromatograph and a RID detector, an Aminex HPX-87H Column 300×7.8 mm, and a 0.005 M sulfuric acid mobile phase.

[0143] The sugar alcohol conversion rate is the ratio of the mass of erythritol produced by fermentation to the mass of glucose consumed.

[0144] Example 7

[0145] Yarrowia lipolytica CGMCC No. 22632 was inoculated into activation medium and cultured at 30°C, 200 rpm for 20 hours. A 10% (v / v) inoculum was then inoculated into 50 ml of fermentation medium (composition of the fermentation medium: 325 g / L glucose, 5 g / L yeast extract, 1 g / L potassium dihydrogen phosphate, 0.2 g / L magnesium sulfate, 5 g / L ammonium sulfate, pH 6). Culture was continued at 32°C, 250 rpm, with sampling and evaporation of water every 24 hours. After 96 hours of culture, erythritol production was significantly increased and byproducts were essentially undetectable. This strain produced 168.5 g / L of erythritol in 96 hours, with the byproduct mannitol content below 1 g / L, and arabitol and glycerol levels undetectable. This strain was named CoY1-M1.

[0146] CoY1-M1 glycerol culture was inoculated into an activation medium at a 3‰ (v / v) inoculum, incubated at 30°C, 200 rpm for 20 h, and then inoculated into a 5L fermentor containing fermentation medium at a 10% (v / v) inoculum. Samples were taken regularly for testing (glucose concentration was measured every 12 h during the initial fermentation period. The fermentation rate was estimated based on the glucose concentration. The fermentation endpoint, i.e., glucose depletion, was determined based on the glucose concentration and fermentation rate. Glucose concentration was measured every 0.5 h for 12 h before the fermentation endpoint). After inoculation, the fermentor was filled to 60% by volume. The fermentation medium consisted of 315 g / L glucose, 5 g / L yeast extract, 1 g / L potassium dihydrogen phosphate, 0.2 g / L magnesium sulfate, and 5 g / L ammonium sulfate, with a pH of 6. The fermentation temperature was controlled at 32°C, the rotation speed was 200-800 rpm, and the aeration rate was 0.5-1 vvm (L / min·L) to maintain a dissolved oxygen level of 20-25 vol%. CoY1-M1 consumed glucose within 92 hours. At the end of the CoY1-M1 fermentation (glucose depletion), the erythritol content was 189.3 g / L, the mannitol content was 0.39 g / L, and arabitol and glycerol were undetectable. After the fermentation broth was sealed and stored at room temperature for one day, samples were taken for testing. The erythritol content remained unchanged (increasing by no more than 0.5 g / L), while the mannitol content decreased to 0.05 g / L. Further sampling after seven days revealed no significant change in erythritol content, and mannitol was essentially undetectable. This strain has the advantages of producing few byproducts and not utilizing erythritol.

[0147] The CoY1-M1 fermentation broth was treated using a centrifugation-microfiltration-nanofiltration process. The fermentation broth was first centrifuged, and the supernatant was subsequently subjected to microfiltration and then nanofiltration. The treatment conditions were: centrifugation at 4000 rpm for 15 minutes at 25°C; microfiltration using a ceramic membrane at an operating pressure of 0.15 MPa and a temperature of 30°C; and nanofiltration with a molecular weight cutoff of 250-300 Da, an operating pressure of 1 MPa, and a temperature of 30°C. The CoY1-M1 fermentation broth had a microfiltration permeation volume ratio of 80% per unit time and a nanofiltration permeation volume ratio of 75% per unit time. The concentrated nanofiltration side of the CoY1-M1 fermentation broth produced less liquid and was free of white, viscous impurities, making it more suitable for subsequent crystallization separation.

[0148] Example 8

[0149] The composition ratio of the fermentation medium is: glucose 325g / L, yeast extract powder 5g / L, potassium dihydrogen phosphate 1g / L, magnesium sulfate 0.5g / L, ammonium citrate 5g / L, pH 5.8.

[0150] The preserved glycerol bacteria were inoculated into 300 mL activation medium at 3‰ (v / v), and cultured at 30℃ and 200rpm for 20h (OD 600=10), and inoculated into a 5L fermentor containing fermentation medium at a 10% (v / v) inoculum size. After inoculation, the fermentor was filled with 60% by volume, the fermentation temperature was controlled at 32°C, the rotation speed was 200-1000 rpm, the ventilation rate was 0.5-1 vvm (L / min·L), and the dissolved oxygen content was controlled at 25-32 vol%. Samples were taken every 12 h to detect the glucose concentration in the early stage of fermentation. The fermentation rate was estimated based on the glucose concentration. The fermentation endpoint (glucose exhaustion) was determined based on the glucose concentration and fermentation rate. Samples were taken every 0.5 h for 12 h before the fermentation endpoint to detect the glucose concentration.

[0151] The fermentation was completed when the glucose concentration in the fermentation broth was less than 1 g / L. After the fermentation was completed, the content of erythritol in the fermentation broth was determined, and the sugar alcohol conversion rate was calculated.

[0152] After 97 hours of fermentation, the erythritol content was 199.4 g / L and the sugar alcohol conversion rate was 61.3%.

[0153] Example 9

[0154] The composition ratio of the fermentation medium is: glucose 220g / L, yeast extract powder 1g / L, corn steep liquor 5g / L, potassium dihydrogen phosphate 1g / L, magnesium sulfate 0.2g / L, ammonium sulfate 5g / L, Tween 80 0.25g / L, pH 6.

[0155] The preserved glycerol bacteria were inoculated into 100 mL activation medium at 3‰ (v / v), cultured at 30℃ 200rpm overnight (16h), and then transferred to 600 mL fermentation medium at 10% (v / v) inoculation volume, cultured at 30℃ 240rpm for 16h to obtain seed solution (OD 600 =25).

[0156] The entire seed solution was inoculated into a 10L fermentor. After inoculation, the fermentor was filled to 60% by volume. The fermentation temperature was controlled at 32°C, the rotation speed was 200-900 rpm, the ventilation rate was 0.5-1 vvm (L / min·L), and the dissolved oxygen content was controlled at 20-25 vol%. During the initial fermentation, glucose concentration was measured every 12 hours. The fermentation rate was estimated based on the glucose concentration. The fermentation endpoint (glucose exhaustion) was determined based on the glucose concentration and fermentation rate. For 12 hours before the fermentation endpoint, glucose concentration was measured every 0.5 hours.

[0157] The fermentation was completed when the glucose concentration in the fermentation broth was less than 1 g / L. After the fermentation was completed, the content of erythritol in the fermentation broth was determined, and the sugar alcohol conversion rate was calculated.

[0158] After 61 hours of fermentation, the erythritol content was 122.7 g / L and the sugar alcohol conversion rate was 55.8%.

[0159] Example 10

[0160] In this embodiment, the fermentation medium has the following composition ratios: glucose 280 g / L, yeast extract 8 g / L, potassium dihydrogen phosphate 1 g / L, magnesium sulfate 1 g / L, ammonium citrate 5 g / L, pH 6.

[0161] The glycerol bacteria stored on the slant were inoculated into 350 mL of activation medium and cultured overnight at 30°C and 200 rpm for 16 h. The inoculation volume was then transferred to a 5 L fermentor containing fermentation medium at a rate of 10% (v / v). The volume of the fermentor after inoculation was 70% by volume. The fermentation was controlled at 30°C, a constant speed of 350 rpm, and a ventilation rate of 0.5 vvm (L / min·L). The seed solution (OD 600 =25).

[0162] The seed liquor is all accessed to a 70L fermentor tank. The liquid capacity of the fermentor tank after inoculation is 60% by volume. The fermentation temperature is controlled at 32°C, the rotating speed is 200-800rpm, and the ventilation rate is 0.3-0.8vvm (L / min·L), which controls the dissolved oxygen content at 20-25vol%. The glucose concentration is detected every 12h in the early fermentation stage. When the glucose concentration in the fermented liquid is lower than 100g / L, a 650g / L glucose solution is started to be fed. The flow rate of the glucose solution is controlled to maintain a sugar concentration in the fermented liquid at 100-120g / L. After 18L of feed, the fed solution is stopped (converting total sugar to be approximately 390g / L) and fermentation is continued. The glucose concentration is detected every 12h. The fermentation rate is estimated according to the glucose concentration. The fermentation endpoint (exhaustion of glucose) is judged according to the glucose concentration and the fermentation rate. The glucose concentration is detected every 0.5h 12h before the fermentation endpoint.

[0163] The fermentation was completed when the glucose concentration in the fermentation broth was less than 1 g / L. After the fermentation was completed, the content of erythritol in the fermentation broth was determined, and the sugar alcohol conversion rate was calculated.

[0164] After 98 h of fermentation, the erythritol content in the fermentation broth was 225.2 g / L, and the sugar alcohol conversion rate was 57.6%.

[0165] According to Examples 7-10, it can be seen that the production of erythritol by fermentation with Yarrowia lipolytica has high erythritol production and high yield, with few fermentation byproducts and impurities.

[0166] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing erythritol crystals, characterized in that: The method includes: (1) saccharifying and liquefying starch into glucose, and then converting it into an erythritol solution to be purified by yeast fermentation, wherein the yeast is Yarrowia lipolytica, and the preservation number of the Yarrowia lipolytica is CGMCC No. 22632; purifying the erythritol solution to be purified to obtain a purified erythritol solution, concentrating the purified erythritol solution to obtain an erythritol concentrate; mixing the erythritol concentrate and erythritol seed crystals, and then adding the materials into ethanol to obtain a mixed material; (2) pre-crystallizing the mixed material in the presence of intermittent ultrasonic waves, and then cooling and crystallizing the mixed material to obtain a slurry; The method of providing ultrasound is as follows: ultrasound is applied for 15-30 seconds every 15-30 seconds for 3-7 minutes, then ultrasound is turned off and maintained for 25-40 minutes, and ultrasound is repeatedly applied and turned off until the pre-crystallization is completed; The power of ultrasound is 300-500W / m 3 Mixing materials; (3) subjecting the slurry to solid-liquid separation to obtain erythritol crystals and mother liquor.

2. The method according to claim 1, wherein: The method for obtaining an erythritol concentrated solution comprises: purifying an erythritol solution to be purified to obtain a purified erythritol solution, and concentrating the purified erythritol solution to obtain an erythritol concentrated solution; Wherein, the purity of the purified erythritol solution is not less than 88% by weight.

3. The method according to claim 1, wherein: The concentration of the erythritol concentrated solution is 450-700 g / L.

4. The method according to claim 1, wherein: The concentration of the erythritol concentrated solution is 560 g / L-680 g / L.

5. The method according to claim 2, wherein: The concentration method comprises: performing reduced pressure concentration at a temperature not higher than 80°C.

6. The method according to any one of claims 1 to 3, wherein: Relative to 1L of erythritol concentrated solution, the amount of the erythritol seed crystals used is 1-50g.

7. The method according to claim 1, wherein: Relative to 1L of erythritol concentrated solution, the amount of ethanol used is 0.3-10L.

8. The method according to claim 1, wherein: Relative to 1L of erythritol concentrated solution, the amount of the erythritol seed crystals used is 5-30g; And / or, relative to 1L of erythritol concentrate, the amount of ethanol used is 0.5-5L.

9. The method according to claim 1, wherein: The pre-crystallization conditions include: temperature of 30-80° C., time of 1-2 h, and stirring speed of 50-350 rpm.

10. The method according to claim 1 or 8, wherein: The conditions for the cooling crystallization include: cooling at a cooling rate of 0.1-0.5°C / min, cooling to 0-15°C and maintaining the temperature at 0-15°C, and the stirring rate during the cooling crystallization process is 50-350rpm; Among them, the cooling crystallization time is 4-13h.

11. The method according to claim 1, wherein: The method further comprises: taking a portion of the mother liquor, returning it to mix with the purified erythritol solution, and concentrating them together; The amount of the part of the mother liquor is such that after it is returned and mixed with the purified erythritol solution, the purity of the obtained material is not less than 88% by weight.

12. The method according to claim 11, wherein: The remaining part of the mother liquor is returned to be mixed with the erythritol solution to be purified and purified together.

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