A method for purifying D-psicose

Abstract

The present invention discloses a method for purifying a psicose reaction solution, which comprises the following steps: (1) filtering the psicose reaction solution generated by fructose catalyzed by D-psicose 3-epimerase through an ultrafiltration membrane to clarify and obtain an ultrafiltration clear liquid; (2) sending the ultrafiltration membrane clear liquid to a nanofiltration system for decolorization to obtain a nanofiltration clear liquid; (3) then sending the nanofiltration clear liquid to a resin system for desalination to obtain a desalted feed liquid; (4) then subjecting the desalted feed liquid to chromatographic separation and purification to obtain a pure psicose solution; (5) finally, concentrating, crystallizing or drying the psicose solution to obtain a psicose finished product. The present invention has the advantages that: using a "membrane + resin" method purification process, the process is short, production efficiency can be effectively improved, labor costs can be reduced, and the quality and yield of the product can also be improved. In addition, the system has a small footprint, a high degree of automation, a low operating cost, can reduce evaporation energy consumption, and can be cleaned in a CIP manner, has good regeneration performance, and has a long service life, thereby achieving green, environmentally friendly, and energy-saving production of D-psicose.

Description

Technical Field

[0001] The invention relates to a method for purifying a psicose reaction solution, and belongs to the field of food raw material processing. Background Art

[0002] D-psicose (D-ribo-2-hexolose; molecular weight, 180; molecular formula, C6H12O6) is a diastereomer of fructose and a monosaccharide that occurs naturally but in extremely small quantities. As a novel sweetener, D-psicose has approximately 70% of the sweetness of sucrose and only 0.3% of its calories. Compared to other natural sweeteners, D-psicose has a significantly lower caloric value. However, compared to sucrose, D-psicose can satisfy consumers' sweet taste needs to the same degree. Its sweetness is mild, and its sweetness does not change with temperature, making it an ideal sucrose substitute. Furthermore, allulose exhibits multiple physiological benefits, including neuroprotection, lowering blood sugar and lipids, and promoting weight loss. It can also improve food flavor and appearance, extending its shelf life. Consequently, the development and production of allulose has garnered increasing attention.

[0003] D-psicose is mainly prepared by biotransformation and chemical synthesis. The chemical synthesis of D-psicose mainly uses glucose as the raw material and molybdate as the catalyst, and produces crystalline D-psicose through chemical catalysis, chromatographic separation and purification, and concentration and crystallization. The chemical synthesis method has disadvantages such as high cost, operational risks, high process difficulty, complex purification, low yield, and easy environmental pollution, making it unsuitable for industrial production. Therefore, D-psicose is currently mainly produced by biotransformation. The biotransformation method uses glucose and fructose as substrates and produces psicose through an enzymatic reaction. The main methods for purifying the psicose reaction solution are plate and frame filtration or centrifugation, followed by activated carbon decolorization, desalination by ion exchange, chromatographic separation and purification, and then concentration and crystallization. The disadvantages of this purification method are the low degree of automation of plate and frame filtration, high labor costs, and the filtrate after plate and frame treatment still contains a large amount of impurities, resulting in low purity of the final product. In view of this, it is still necessary to find a new method for purifying psicose. Summary of the Invention

[0004] The present invention provides a green, efficient, and energy-saving method for purifying a psicose reaction solution. This method utilizes an integrated membrane and resin process to purify psicose, resulting in a short process, high production efficiency, a high degree of automation, and low operating costs. Furthermore, the membrane filtration process boasts high precision, effectively improving product quality and yield. Furthermore, the system has a small footprint, is CIP-cleanable, exhibits excellent regeneration performance, and has a long service life.

[0005] A method for purifying a psicose reaction solution comprises the following steps:

[0006] Step 1: filtering the D-psicose 3-epimerase-catalyzed psicose reaction solution into fructose through an ultrafiltration membrane to obtain an ultrafiltration membrane clear solution;

[0007] Step 2: sending the ultrafiltration membrane clear solution into the nanofiltration membrane for decolorization to obtain the nanofiltration membrane clear solution;

[0008] In the third step, the nanofiltration membrane clear liquid is sent to the resin system for desalination to obtain the desalted feed liquid;

[0009] In step 4, the desalted liquid is subjected to chromatographic separation and purification to obtain a pure psicose solution;

[0010] In step 5, the allulose solution is concentrated, crystallized, and dried to obtain the finished allulose product.

[0011] The D-psicose 3-epimerase is a mixed liquid prepared by fermenting Bacillus subtilis, centrifuging and breaking the cell wall.

[0012] The ultrafiltration membrane adopts an organic membrane or a ceramic membrane; the molecular weight cutoff of the organic membrane is 1.5KD-1000KD, preferably the membrane molecular weight cutoff is 5KD-500KD, the feed liquid temperature in the membrane filtration process is 5-45°C, the pressure is 0.1-1.0Mpa, the membrane surface flow rate is 2-5m / s, and the concentration multiple is 1 to 30 times; the pore size of the ceramic membrane is 1-1200nm, preferably the membrane pore size is 4-200nm, more preferably 4-10nm, the feed liquid temperature in the ceramic membrane filtration process is 5-80°C, the pressure is 0.1-0.5Mpa, the membrane surface flow rate is 2-5m / s, and the concentration multiple is 1 to 30 times.

[0013] During the filtration and clarification with ultrafiltration membrane, water needs to be added in the later stage to perform dialysis on the ultrafiltration concentrate. In the dialysis operation, the amount of water added is 0.1 to 1 times the amount of the original liquid.

[0014] The nanofiltration membrane is a nanofiltration membrane made of ceramic or organic material, with a molecular weight cut-off of 150-1500 Da and a filtration pressure of 0.4-4.0 MPa.

[0015] In the later stage of decolorization by the nanofiltration membrane, water needs to be added to dialyze the nanofiltration concentrate. In the dialysis operation, the amount of water added is 0.1 to 3 times the amount of the original solution.

[0016] In step 2, when the permeability of allulose through the nanofiltration membrane drops to a set threshold, decolorization is stopped.

[0017] The transmittance is predicted and calculated by the following steps:

[0018] Step 1: Obtain the value of the flux changing with time during the nanofiltration process, and take the derivative of the flux with respect to time, and use the derivative as the flux decay rate. When the flux decay rate drops to the initial threshold, the time node is defined as the turning point time of the first and second stage decolorization;

[0019] Step 2: For the first stage, the transmittance and filtration time are fitted using T1%=a×t+b to obtain the relationship between the transmittance and time of the first stage; where T1 refers to the transmittance of the first stage, t refers to time, and a / b is a parameter;

[0020] For the second stage, T2%=e (m+n×t2+p×t2^2) The transmittance and filtration time were fitted using the equation -q×P^1.5-s×L to obtain the time-dependent relationship between the transmittance in the second stage; where m / n / p / q / s are parameters, L is the transmittance of the ultrafiltration clear fluid, and P is the operating pressure;

[0021] Step 3: When filtering, calculate the transmittance based on the fitted curve.

[0022] The resin system uses anion exchange resin and / or anion exchange resin, controls the flow rate to be 3-5Bv / h, the temperature to be 30-60°C, and the light transmittance of the liquid after resin desalination is ≥99%.

[0023] The chromatographic separation steps are as follows: the chromatographic type adopted is calcium gel type cation exchange resin, the chromatographic operation pressure is 0.20-0.30 MPa, the temperature is 60-70° C., and the water consumption ratio is 1:(1.3-1.6).

[0024] In step 5, the sugar solution is first concentrated to 30% Brix by organic membrane and then concentrated to 70%-85% Brix by evaporation.

[0025] The crystallization reaction conditions are as follows: a temperature of 50-70°C, adding seed crystals accounting for 10-30% of the solute mass, stirring evenly, standing at 50-70°C for 8-16 hours, then slowly cooling at a rate of 1°C per 3-6 hours while slowly stirring until a large number of uniform and regular crystals are formed in the solution, and then separating to obtain D-psicose.

[0026] The drying is spray drying, and the steps are as follows: the concentrated sugar solution enters the drying tower, the air inlet temperature is 130-150°C, the atomizer is started, and the liquid is spray-dried into a powdery solid.

[0027] Beneficial effects

[0028] The present invention provides a method for purifying a D-psicose reaction liquid, which is produced through a membrane and resin integrated process. The process has short steps, compact equipment, and a small footprint. The membrane filtration has high precision and the resin separation effect is good, effectively improving product quality and yield. The equipment has a high degree of automation and low labor costs, which can reduce evaporation energy consumption, reduce operating costs, and effectively improve production efficiency. The equipment is also CIP cleanable, has good regeneration performance, and a long service life, thereby achieving green, environmentally friendly, and energy-saving production of D-psicose. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a process flow chart of the present invention.

[0030] Figure 2 This is a graph showing the process of predicting the permeability of D-psicose. DETAILED DESCRIPTION

[0031] Example 1

[0032] After the reaction, 200 L of the D-psicose reaction solution was filtered through an 8 nm ceramic membrane at a temperature of 25-55°C and a pressure of 0.25 MPa. After the solution was concentrated to 20 times, softened water was added for rinsing at a rate of 30 L, yielding an ultrafiltration solution and an ultrafiltration concentrate, respectively. The ultrafiltration permeate was then concentrated by nanofiltration using a ceramic nanofiltration membrane with a pore size of 4 nm and an operating pressure of 2.5 MPa. Decolorization was then performed. When the D-psicose transmittance through the nanofiltration membrane dropped to 80%, the decolorization process was stopped and the nanofiltration membrane was cleaned, yielding a nanofiltration permeate and a nanofiltration concentrate. The nanofiltration membrane clear liquid was desalted by LX-160 cation exchange resin and D-354 anion exchange resin at a flow rate of 3-5 Bv / h at 45°C. The desalted liquid was separated by chromatography (DOWEX310 Ca) at an operating pressure of 0.20 MPa, a temperature of 65°C, a water consumption ratio of 1:1.2, and a feed of 2 m3 / h. 3 , collecting the elution liquid during the 40-60 minute elution time to obtain high-purity allulose; concentrating the liquid to a concentration of 70%-85% using a four-effect falling film evaporator with a vacuum degree of 0.06 MPa and a liquid temperature of 85°C; the concentrated sugar liquid enters a drying tower with an inlet air temperature of 150°C, starting an atomizer, and spray drying the liquid to obtain the finished D-psicose.

[0033] Example 2

[0034] After the reaction, 200 L of the D-psicose reaction solution was filtered through a 10KD spiral membrane at a temperature of 25-45°C and a pressure of 5.0 MPa. After the solution was concentrated to 20 times, softened water was added for rinsing at a rate of 30 L, yielding an ultrafiltration permeate and an ultrafiltration concentrate, respectively. The ultrafiltration permeate was then concentrated by nanofiltration using a ceramic nanofiltration membrane with a pore size range of 4-5 nm and an operating pressure of 2.5 MPa. Decolorization was then performed. When the D-psicose permeability through the nanofiltration membrane dropped to 80%, the decolorization process was stopped and the nanofiltration membrane was cleaned, yielding a nanofiltration permeate and a nanofiltration concentrate. The nanofiltration membrane clear liquid was desalted by LX-160 cation exchange resin and D-354 anion exchange resin at a flow rate of 3-5 Bv / h at 45°C. The desalted liquid was separated by chromatography (DOWEX310 Ca) at an operating pressure of 0.20 MPa, a temperature of 65°C, a water consumption ratio of 1:1.2, and a feed of 2 m3 / h. 3 , collecting the elution liquid during the 40-60 minute elution time to obtain high-purity allulose; concentrating the liquid to a concentration of 70%-85% using a four-effect falling film evaporator with a vacuum degree of 0.06 MPa and a liquid temperature of 85°C; the concentrated sugar liquid enters a drying tower with an inlet air temperature of 150°C, starting an atomizer, and spray drying the liquid to obtain the finished D-psicose.

[0035] In the above process, the main test indicators and parameters of the materials are shown in the following table:

[0036]

[0037] During the above process, as D-fructose and D-psicose in the reaction solution permeate the nanofiltration membrane under high pressure, the colloid and pigment components in the raw liquid gradually form a gel deposition layer. This causes the permeability of D-psicose to gradually decrease in the presence of the gel layer, resulting in a decrease in yield and irreversible fouling of the nanofiltration membrane. By constructing a permeability curve, the nanofiltration decolorization time is controlled. During nanofiltration decolorization, the flux of the nanofiltration membrane initially decreases rapidly. During this process, an organic retention layer is initially formed on the membrane surface. When the flux decline slows, the organic layer is essentially formed. As decolorization continues, the organic layer gradually densifies under higher pressure, causing the D-psicose content to decrease. First, by determining the basic formation time of the organic layer, the flux curve is derivatized with respect to time (if the sampling interval is large, spline interpolation can be used to obtain intermediate data points). When the decline rate is 15% of the initial decline rate, it is considered that the organic layer has been formed. The transmittance in the first stage decreases relatively slowly, and is basically a linear relationship with time. T1% = a×t+b(t <T e ), where T1 refers to the transmittance of the first stage, t refers to the time, T eIt refers to the switching time node between the first and second stages, and a / b is a parameter. Next, the nanofiltration pressure and the transmittance of the initial feed solution are the main influencing factors. The lower the transmittance, the easier it is to form a gel layer, and the higher the pressure, the easier it is to form a gel layer. Take T2% = e (m+n×t2+p×t2^2) -q×P^1.5-s×L, where m / n / p / q / s are parameters, L refers to the transmittance of ultrafiltration liquid, and P is the operating pressure;

[0038] Based on the above method, the equation parameters for the first and second stages are obtained as follows: R2 is 0.99589 / 0.95742, respectively. a = -0.05193; b = 100.00117; m = 4.58076; n = -7.19512E-5; p = -1.20218E-6; q = 1.41785E-3; s = 4.29444E-3; The model curves and experimental values ​​for the first and second stages are shown in Figure 2. Figure 2 As shown on the left and right.

[0039] Nanofiltration treatment was performed under the conditions of L = 75 (percentage) and P = 2 MPa. The transmittance at different time periods was calculated according to the above formula. Five experimental values ​​(50 / 150 / 200 / 250 / 300 min) were taken and compared with the actual values, as follows:

[0040]

[0041] It can be seen that the method of this patent can effectively predict the transmittance of D-psicose during the decolorization process of the nanofiltration membrane, with an error within 5%. Therefore, the nanofiltration process can be experimentally monitored during the treatment process. When the transmittance drops to the set value, the decolorization can be stopped and the nanofiltration membrane cleaning process can be started.

Claims

1. A method for purifying a psicose reaction solution, characterized in that: The steps include: Step 1: filtering the D-psicose 3-epimerase-catalyzed psicose reaction solution into fructose through an ultrafiltration membrane to obtain an ultrafiltration membrane clear solution; Step 2: sending the ultrafiltration membrane clear solution into the nanofiltration membrane for decolorization to obtain the nanofiltration membrane clear solution; In the third step, the nanofiltration membrane clear liquid is sent to the resin system for desalination to obtain the desalted feed liquid; In step 4, the desalted liquid is subjected to chromatographic separation and purification to obtain a pure psicose solution; In step 5, the psicose solution is concentrated, crystallized, and dried to obtain the finished psicose product; In step 2, when the permeability of allulose through the nanofiltration membrane drops to a set threshold, decolorization is stopped; The transmittance is predicted and calculated by the following steps: Step 1: Obtain the value of the flux changing with time during the nanofiltration process, and take the derivative of the flux with respect to time, and use the derivative as the flux decay rate. When the flux decay rate drops to the initial threshold, the time node is defined as the turning point time of the first and second stage decolorization; Step 2: For the first stage, T1%=a×t+b is used to fit the transmittance and filtration time to obtain the relationship between the transmittance and time of the first stage; where T1 refers to the transmittance of the first stage, t refers to time, and a / b is a parameter; For the second stage, T2%=e (m+n×t2+p×t2^2) The transmittance and filtration time were fitted using the equation -q×P^1.5-s×L to obtain the time-dependent relationship between the transmittance in the second stage; where m / n / p / q / s are parameters, L is the transmittance of the ultrafiltration clear fluid, and P is the operating pressure; Step 3: When filtering, calculate the transmittance according to the fitted curve; The ultrafiltration membrane adopts an organic membrane or a ceramic membrane; the molecular weight cutoff of the organic membrane is 5KD-500KD, the feed liquid temperature in the membrane filtration process is 5-45°C, the pressure is 0.1-1.0Mpa, the membrane surface flow rate is 2-5m / s, and the concentration multiple is 1 to 30 times; the pore size of the ceramic membrane is 4-10nm, the feed liquid temperature in the ceramic membrane filtration process is 5-80°C, the pressure is 0.1-0.5Mpa, the membrane surface flow rate is 2-5m / s, and the concentration multiple is 1 to 30 times.

2. The method for purifying a psicose reaction solution according to claim 1, wherein: The D-psicose 3-epimerase is a mixed liquid prepared by fermenting Bacillus subtilis, centrifuging and breaking the cell wall.

3. The method for purifying a psicose reaction solution according to claim 1, wherein: During the filtration and clarification with ultrafiltration membrane, water needs to be added in the later stage to perform dialysis on the ultrafiltration concentrate. In the dialysis operation, the amount of water added is 0.1 to 1 times the amount of the original liquid.

4. The method for purifying a psicose reaction solution according to claim 1, wherein: The nanofiltration membrane is a nanofiltration membrane made of ceramic or organic material, with a molecular weight cut-off of 150-1500 Da and a filtration pressure of 0.4-4.0 MPa.

5. The method for purifying a psicose reaction solution according to claim 1, wherein: In the later stage of decolorization by the nanofiltration membrane, water needs to be added to dialyze the nanofiltration concentrate. In the dialysis operation, the amount of water added is 0.1 to 3 times the amount of the original solution.

6. The method for purifying a psicose reaction solution according to claim 1, wherein: The resin system uses anion exchange resin and / or anion exchange resin, controls the flow rate to be 3-5Bv / h, the temperature to be 30-60°C, and the transmittance of the feed liquid after resin desalination is ≥99%.

7. The method for purifying a psicose reaction solution according to claim 1, wherein: The chromatographic separation steps are as follows: the chromatographic type used is a calcium-based gel-type cation exchange resin, the chromatographic operating pressure is 0.20-0.30 MPa, the temperature is 60-70°C, and the water consumption ratio is 1:(1.3-1.6); In step 5, the sugar solution is first concentrated to 30% Brix by organic membrane, and then concentrated to 70%-85% Brix by evaporation; The crystallization reaction conditions are as follows: adding seed crystals at 10-30% of the solute mass at a temperature of 50-70°C, stirring evenly, standing at 50-70°C for 8-16 hours, then slowly cooling at a rate of 1°C every 3-6 hours while stirring slowly until a large number of uniform and regular crystals are formed in the solution, and then separating to obtain D-psicose. The drying is spray drying, and the steps are as follows: the concentrated sugar solution enters the drying tower, the air inlet temperature is 130-150°C, the atomizer is started, and the liquid is spray-dried into a powdery solid.

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