Method for purifying erythritol

Abstract

The invention belongs to the technical field of purification, and particularly relates to a purification method of erythritol. The method for purifying erythritol comprises the following steps: (1) filtering erythritol fermentation liquor by adopting a ceramic membrane and an organic membrane in sequence to obtain erythritol clear liquor; (2) performing electrodialysis on the erythritol clear liquid to obtain a primary material; and (3) concentrating and crystallizing the primary material to obtain erythritol. According to the purification method, a high-purity erythritol product can be prepared without adopting an anion and cation exchange process, and the purification method has the advantages of greenness, environmental protection, high efficiency and economy.

Description

Technical Field

[0001] The invention belongs to the technical field of purification, and particularly relates to a method for purifying erythritol. Background Art

[0002] Erythritol (scientific name: 1,2,3,4-butanetetrol) is a natural healthy sugar alcohol that is widely present in animal and plant tissues in nature. It has been widely used in many fields such as food, medicine, cosmetics, and chemicals due to its good thermal stability, low hygroscopicity, harmonious sweetness, low freezing point, anti-caries properties, no increase in blood sugar, and high tolerance. It is especially competitive in the sweetener market.

[0003] There are three main types of erythritol production methods: biological extraction, chemical synthesis, and fermentation. At present, the production of erythritol in my country is mainly based on fermentation.

[0004] The erythritol fermentation broth obtained by microbial fermentation usually needs to undergo solid-liquid separation, fine filtration, decolorization and desalination, concentration, crystallization, separation, and drying to obtain a commercialized erythritol product. For example, patents CN102249856B (a method for separating and purifying erythritol from yeast fermentation broth), CN 102249855B (a process for preparing erythritol) and CN112457166B (a method for separating and purifying erythritol fermentation broth) all involve ion exchange, that is, the clarified fermentation broth is passed through an anion and cation exchange column to achieve the purpose of desalting and decolorizing.

[0005] When using ion exchange resin for desalination and decolorization, since most of the pigments in sugar production are ionized and negatively charged, they can be exchanged with the hydroxide ions on the anion exchange resin. Therefore, after passing through the anion exchange resin, the pigment is adsorbed on the resin, and the hydroxide ions are desorbed and flow out, thereby achieving the purpose of removing the pigment. Similarly, since metal ions are positively charged, cation exchange resins can also effectively remove metal ions in liquids to achieve the purpose of desalination.

[0006] Although the erythritol products produced by the anion and cation exchange process have high purity, with the increasing popularity of green and environmental protection concepts in industrial production, the problem that the anion and cation exchange process requires a large amount of acid and alkali to continuously regenerate the resin has attracted more and more attention.

[0007] Therefore, the present invention hopes to provide an extraction method that can produce a high-purity erythritol product without using an anion-cation exchange process. Summary of the invention

[0008] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for purifying erythritol. The purification method can produce a high-purity erythritol product without using anion and cation exchange process, and has the advantages of being green, environmentally friendly, efficient and economical.

[0009] The present invention provides a method for purifying erythritol, comprising the following steps:

[0010] (1) filtering the erythritol fermentation broth using a ceramic membrane and an organic membrane in sequence to obtain an erythritol clear solution;

[0011] (2) subjecting the erythritol clear solution to electrodialysis to obtain a preliminary material;

[0012] (3) Concentrating and crystallizing the preliminary material to obtain erythritol.

[0013] In the above purification process, ceramic membrane and organic membrane are used for secondary filtration to remove impurities (remove bacteria, insoluble matter, and macromolecular impurities), and then the electrodialysis process is used to further desalinate and remove impurities, and finally the erythritol product is obtained by concentration and crystallization.

[0014] It should be noted that the erythritol fermentation liquid is obtained by microbial fermentation. Yarrowia lipolytica can be used as a fermentation microorganism, and the process of fermenting erythritol is mainly converted into erythritol through a series of metabolic pathways by using glucose as a carbon source. In this process, glucose is first converted into glucose-6-phosphate, then enters the pentose phosphate pathway (PPP), and finally generates erythritol precursor 4-phosphate erythrose through oxidation and non-oxidation stages, and then generates erythritol through dephosphorylation and reduction reactions.

[0015] Preferably, the pore size of the ceramic membrane in step (1) is 0.05-0.2 μm.

[0016] Preferably, the operating conditions for filtering using a ceramic membrane in step (1) are: temperature 1-40° C., pressure 0.2-0.35 MPa.

[0017] Preferably, before the electrodialysis in step (2), the sugar content of the erythritol clear solution is adjusted to 10-20° Bx.

[0018] Preferably, the polar water used in the electrodialysis in step (2) is 2%-3% (w / v) sodium chloride solution or 2%-3% (w / v) sodium sulfate solution.

[0019] Preferably, the operating voltage of the electrodialysis in step (2) is 10-18V.

[0020] Preferably, the concentration method in step (3) is: concentrating the preliminary material to a sugar content ≥ 50° Bx at 60-80°C.

[0021] Preferably, the crystallization method in step (3) is: at a cooling rate of 1-2.5°C / h and a stirring rate of 20-40rpm / min, the temperature of the concentrated material is reduced to below 10°C and maintained for not less than 6h.

[0022] Preferably, step (3) further comprises the steps of washing the crystals with pure water and drying after the crystallization.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The purification method of erythritol in the present invention does not require the use of anion and cation exchange processes, thereby eliminating environmental problems when the resin is discarded and reducing a large amount of acid and alkali consumption, making the process more environmentally friendly;

[0025] (2) The present invention uses electrodialysis desalting and decolorization to ensure that the purity of the crystalline product meets national standards;

[0026] (3) The present invention does not use organic solvents such as ethanol in the crystallization step, nor does it need to add activated carbon for decolorization, so the process is safe and clean. DETAILED DESCRIPTION

[0027] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0028] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0029] Example 1

[0030] This embodiment provides a method for purifying erythritol, comprising the following steps:

[0031] (1) Pumping the erythritol fermentation liquid to a microfiltration raw material tank, filtering through a ceramic membrane microfiltration system to remove most of the bacteria and insoluble matter, controlling the filtration pressure to ≤0.30 MPa, the filtration temperature to ≤40° C., and the ceramic membrane cutoff pore size to 0.05 μm, and adding clean water to wash the material in the equipment after the filtration to improve the yield, to obtain a microfiltration clear liquid;

[0032] (2) fine filtering the microfiltration clear liquid through an organic membrane nanofiltration system to remove cell lysates, proteins, polysaccharides and other macromolecular impurities, controlling the filtration pressure to ≤1.8 MPa, the filtration temperature to ≤40°C, and the molecular weight cutoff (MWCO) to 600 Da. After the filtration is completed, clean water is added to top wash the material in the equipment to increase the yield, thereby obtaining an erythritol clear liquid;

[0033] (3) The erythritol clear solution is put into the electrodialysis equipment, the sugar content of the material is adjusted to 15°Bx, and a 2% Na2SO4 aqueous solution with a pH adjusted to 3 is used as the polar water of the electrodialysis process. The initial voltage of the equipment is 10V, and the operating pressures of the material (i.e., the erythritol clear solution), concentrated water (pure water), and polar water are all 0.15MPa. As the electrodialysis proceeds, the current first increases and then decreases. When the current drops to 0.00A, the machine is stopped and the material is discharged to obtain a preliminary material;

[0034] (4) The preliminary material is concentrated under reduced pressure, the material temperature is ≤70°C, and it is concentrated to a sugar content of 60°Bx, and crystal nuclei are visibly generated. The material is pumped to a crystallization tank, and the crystallization tank is cooled to 8°C at a cooling rate of 1°C / h and a stirring rate of 20 rpm / min, and kept warm for 8 hours to obtain a crystal slurry;

[0035] (5) The obtained crystal slurry is separated into solid and liquid by a centrifuge, and the wet crystal part is washed for 4 seconds per time, for a total of 3 times. The obtained crystals are dried in a fluidized bed to obtain the erythritol product.

[0036] After calculation, the total yield of the obtained erythritol product is 86%. According to the method of "GB 26404-2011 National Food Safety Standard Food Additive Erythritol" (the physical and chemical indicators in Table 2 of the standard indicate that the purity index of erythritol is 99.5% to 100.5%), the obtained erythritol product has a 30-60 mesh product accounting for 80%, and the product purity is 100.1%.

[0037] Example 2

[0038] This embodiment provides a method for purifying erythritol, comprising the following steps:

[0039] (1) Pumping the erythritol fermentation liquid to a microfiltration raw material tank, filtering through a ceramic membrane microfiltration system to remove most of the bacteria and insoluble matter, controlling the filtration pressure to ≤0.30 MPa, the filtration temperature to ≤40° C., and the ceramic membrane cutoff pore size to 0.2 μm, and adding clean water to wash the material in the equipment after the filtration to improve the yield, to obtain a microfiltration clear liquid;

[0040] (2) fine filtering the microfiltration clear liquid through an organic membrane nanofiltration system to remove cell lysates, proteins, polysaccharides and other macromolecular impurities, controlling the filtration pressure to ≤1.8 MPa, the filtration temperature to ≤40°C, and the molecular weight cutoff (MWCO) to 600 Da. After the filtration is completed, clean water is added to top wash the material in the equipment to increase the yield, thereby obtaining an erythritol clear liquid;

[0041] (3) The erythritol clear solution is put into the electrodialysis equipment, the sugar content of the material is adjusted to 15°Bx, and a 2% Na2SO4 aqueous solution with a pH adjusted to 2 is used as the polar water of the electrodialysis process. The initial voltage of the equipment is 10V, and the operating pressures of the material (i.e., the erythritol clear solution), concentrated water (pure water), and polar water are all 0.1MPa. As the electrodialysis proceeds, the current first increases and then decreases. When the current drops to 0.03A, the machine is stopped and the material is discharged to obtain a preliminary material;

[0042] (4) The preliminary material was concentrated under reduced pressure until the material temperature was ≤70°C, and concentrated to a sugar content of 55°Bx. Crystal nuclei were observed to be generated, and the material was pumped to a crystallization tank. The crystallization tank was cooled to 10°C at a cooling rate of 1.5°C / h and a stirring rate of 20 rpm / min, and kept warm for 6 hours to obtain a crystal slurry;

[0043] (5) The obtained crystal slurry is separated into solid and liquid by a centrifuge, and the wet crystal part is washed for 4 seconds per time, for a total of 3 times. The obtained crystals are dried in a fluidized bed to obtain the erythritol product.

[0044] After calculation, the total yield of the obtained erythritol product is 88%. According to the method of "GB 26404-2011 National Food Safety Standard Food Additive Erythritol" (the physical and chemical indicators in Table 2 of the standard indicate that the purity index of erythritol is 99.5% to 100.5%), the obtained erythritol product has a 30-60 mesh product accounting for 90%, and the product purity is 99.8%.

[0045] Comparative Example 1

[0046] This comparative example provides a method for purifying erythritol, comprising the following steps:

[0047] (1) Pumping the erythritol fermentation liquid to a microfiltration raw material tank, filtering through a ceramic membrane microfiltration system to remove most of the bacteria and insoluble matter, controlling the filtration pressure to ≤0.30 MPa, the filtration temperature to ≤40° C., and the ceramic membrane cutoff pore size to 0.2 μm, and adding clean water to wash the material in the equipment after the filtration to improve the yield, to obtain a microfiltration clear liquid;

[0048] (2) fine filtering the microfiltration clear liquid through an organic membrane nanofiltration system to remove cell lysates, proteins, polysaccharides and other macromolecular impurities, controlling the filtration pressure to ≤1.8 MPa, the filtration temperature to ≤40°C, and the molecular weight cutoff (MWCO) to 600 Da. After the filtration is completed, clean water is added to top wash the material in the equipment to increase the yield, thereby obtaining an erythritol clear liquid;

[0049] (3) Desalting and decolorizing the erythritol clear solution through anion and cation exchange columns. Taking 900 kg of anion exchange resin and 1000 kg of cation exchange resin as an example, each time the resin is regenerated, about 3.5 T of food-grade 4% hydrochloric acid, about 4.0 T of food-grade 4% sodium hydroxide, and about 12 tons of pure water are required;

[0050] (4) Concentrating, crystallizing and drying the material after passing through the anion and cation exchange resin to obtain the erythritol product.

[0051] After calculation, the total yield of the obtained erythritol product was 86%. According to the method of "GB 26404-2011 National Food Safety Standard Food Additive Erythritol" (the physical and chemical indicators in Table 2 of the standard indicate that the purity index of erythritol is 99.5% to 100.5%), the purity of the obtained erythritol product was 99.9%.

[0052] By comparing Examples 1-2 with Comparative Example 1, it can be seen that although both can produce high-purity erythritol products, compared with Examples 1-2, the use of anion and cation exchange resins in Comparative Example 1 requires more resources (resins, acids and bases, etc.) and is not conducive to green environmental protection. Therefore, the erythritol purification method of Examples 1-2 has more practical application value.

[0053] The embodiments of the present application are described in detail above, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present application.

Claims

1. A method for purifying erythritol, characterized in that: The following steps are involved: (1) filtering the erythritol fermentation broth using a ceramic membrane and an organic membrane in sequence to obtain an erythritol clear solution; (2) subjecting the erythritol clear solution to electrodialysis to obtain a preliminary material; (3) Concentrating and crystallizing the preliminary material to obtain erythritol.

2. The purification method according to claim 1, characterized in that The pore size of the ceramic membrane in step (1) is 0.05-0.2 μm.

3. The purification method according to claim 1, characterized in that The operating conditions for filtering using a ceramic membrane in step (1) are: temperature 1-40° C., pressure 0.2-0.35 MPa.

4. The purification method according to claim 1, characterized in that Before performing the electrodialysis in step (2), the sugar content of the erythritol clear solution is adjusted to 10-20° Bx.

5. The purification method according to claim 1, characterized in that The polar water used in the electrodialysis in step (2) is 2%-3% sodium chloride solution or 2%-3% sodium sulfate solution.

6. The purification method according to claim 1, characterized in that The operating voltage of the electrodialysis in step (2) is 10-18V.

7. The purification method according to claim 1, characterized in that The concentration method in step (3) is: concentrating the preliminary material to a sugar content ≥ 50° Bx at 60-80°C.

8. The purification method according to claim 1, characterized in that The crystallization method in step (3) is: at a cooling rate of 1-2.5°C / h and a stirring rate of 20-40rpm / min, the temperature of the concentrated material is reduced to below 10°C and maintained for not less than 6h.

9. The purification method according to claim 1, characterized in that After the crystallization, step (3) also includes the steps of washing the crystals with pure water and drying.