Method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor

Abstract

The invention discloses a method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor. Belongs to the technical field of erythritol production. The invention discloses and provides a method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor, which comprises the following steps: adding the trehalose mother liquor and the sodium gluconate mother liquor into a fermentation culture medium, fermenting by using candida lipolytica, enabling the conversion rate of the fermented erythritol to be 70%, and simultaneously filtering by using different nanofiltration membranes, according to the method, the erythritol finished product is obtained, the trehalose and sodium gluconate mixed solution is also obtained, and the trehalose and sodium gluconate mixed solution can be added into fermentation liquor again after being dissolved, so that cyclic utilization is realized; the production efficiency is improved, and the cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of erythritol production, and more particularly to a method for co-producing erythritol with trehalose mother liquor and sodium gluconate mother liquor. Background Art

[0002] Erythritol is a four-carbon polyol with a sweetness of about 60-70% of sucrose. Erythritol cannot be metabolized by the human body and is quickly excreted from the body with urine. It has no calories and has no effect on blood sugar. It has become the preferred sweetener for sugar-free beverages.

[0003] Sodium gluconate is a physiological alkaline salt. The consumption of sodium gluconate during the fermentation process will cause the pH to rise, which can offset the pH drop caused by glucose metabolism and provide compatible conditions for cell growth, thus playing a good role in stabilizing the pH value during the fermentation process. Sodium gluconate mother liquor is the liquid left after the liquid sodium gluconate is concentrated, crystallized, purified and separated during the production of sodium gluconate. The soluble solids content in the liquid is 45-55%, of which 30-40% is sodium gluconate and 12-14% is reducing sugar.

[0004] Trehalose and maltose are isomers of each other and are non-reducing disaccharides. Trehalose has good stability and stabilizes the bacterial structure. In addition, trehalose has the advantages of low caloric value, strong cooling feeling and anti-caries, and is used as a good substitute for sucrose in the production of candy, chocolate and other products. Trehalose is produced by enzymatic method, mainly using maltodextrin as substrate, and trehalose is generated by the two-step synergistic catalysis of malto-oligosaccharide trehalose synthase and malto-oligosaccharide trehalose hydrolase. The generated trehalose solution still contains a large amount of short-chain maltodextrin. Usually, saccharifying enzymes are added for saccharification to decompose short-chain maltodextrin into glucose, which leads to a large amount of glucose in the saccharified liquid. Since trehalose and glucose have similar physical and chemical properties, the trehalose mother liquor contains a large amount of glucose after chromatographic separation. And studies have shown that the addition of trehalose is conducive to the fermentation of erythritol by yeast.

[0005] Therefore, providing a method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0006] In view of this, the present invention provides a method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor, aiming to utilize trehalose mother liquor and sodium gluconate mother liquor for fermentation to produce erythritol, providing a new idea for erythritol production and maximizing the utilization of waste for conversion.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0009] (1) Preparation of fermentation broth: adding trehalose mother liquor and sodium gluconate mother liquor to glucose solution, wherein the total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.3-0.6% of the volume of the glucose solution, and the volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1; then adding 0.5% yeast extract by mass volume ratio, adjusting the soluble solid content to 26.0-28.0%; filling the fermentation tank according to 70% of the liquid filling volume, adjusting the pH to 6.0-6.5; sterilizing at 115°C for 30 minutes, then cooling to 28-30°C, inoculating Candida lipolytica, inoculating at 5%-8%, and the bacterial concentration OD 600 Control the temperature at 15-20, and control the fermentation conditions: 28-30℃, dissolved oxygen DO at 10-25%, tank pressure at 0.06-0.1MPa; after 70-75h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0010] (2) Ceramic membrane sterilization: The fermentation liquid is filtered through a ceramic membrane with a pore size of 0.1 μm to remove bacteria;

[0011] (3) Polysaccharide removal by nanofiltration membrane: After filtration by ceramic membrane, the solution is first passed through a nanofiltration membrane with a pore size of 350 Da to remove macromolecular impurities, thereby obtaining a mixed solution of trehalose solution and sodium gluconate; then, the solution is passed through a nanofiltration membrane with a pore size of 200 Da to obtain an erythritol solution;

[0012] (4) Ion exchange desalination: The obtained erythritol solution is first passed through a cation exchange resin and then through an anion exchange resin to remove salts;

[0013] (5) Concentration and crystallization separation; the obtained erythritol solution is concentrated to a soluble solid content of 50-55% by an evaporator, and then enters a crystallization tank for cooling and crystallization. The cooling rate is controlled at 6-7°C / h and the discharge temperature is 40°C. After separation by an overhead centrifuge, erythritol crystals are obtained.

[0014] Furthermore, the parameters of the trehalose mother solution in step (1) are: soluble solid content of 9-12%, pH = 6.2-6.8, reducing sugar 8-12%, trehalose 0.2-0.5%; the parameters of the sodium gluconate mother solution are: pH = 4.4-5.5, soluble solid content of 45-55%, reducing sugar content of 12-14%.

[0015] Furthermore, the concentration of the glucose solution in step (1) is 180-200 g / L.

[0016] Furthermore, the ceramic membrane filtration index of step (2) is: feed soluble solid content is 20-25%, temperature = 30-35°C, flow rate is 12-14m 3 / h.

[0017] Furthermore, the filtration index of the nanofiltration membrane in step (3) is: 350Da nanofiltration membrane temperature = 30-35°C, flow rate 12-14m 3 / h; 200Da nanofiltration membrane temperature = 30-35°C, flow rate 12-14m 3 / h.

[0018] Furthermore, the final conductivity of the ion exchange output in step (4) is controlled at 20-50 μs / cm.

[0019] Furthermore, the control conditions of the evaporator in step (5) are as follows: the evaporation temperature is 80-95° C., and the discharge specific gravity is controlled at 1.22-1.25.

[0020] Furthermore, the separation conditions of the overhead centrifuge in step (5) are as follows: the overhead centrifuge speed is 150 r / min, the feeding starts, and when the material is full, the speed is increased to 700 r / min, and the material is washed with pure water for 15-20 s, then the speed is increased to 1300 r / min, and the material is washed with pure water for 10 s, and then the speed is reduced to 60 r / min to separate the erythritol crystals.

[0021] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor, which has the following beneficial effects:

[0022] (1) The present invention realizes the reuse of trehalose mother liquor and sodium gluconate mother liquor, and provides a technical method for turning waste into treasure. Comparison shows that the conversion rate of glucose fermentation to erythritol is 64%, and the conversion rate of erythritol after adding trehalose mother liquor and sodium gluconate mother liquor for compound fermentation is 70%, which increases the conversion rate by 6%. Moreover, it is found in the fermentation process that the addition of sodium gluconate mother liquor is beneficial to stabilizing the pH value in the middle and late stages of fermentation and inhibiting the production of by-product acid substances by yeast.

[0023] (2) By using different nanofiltration membranes, both the erythritol product and the mixed solution of trehalose and sodium gluconate were obtained. This partially dissolved solution can be added to the fermentation liquid to achieve recycling, thereby improving production efficiency and saving costs. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Candida lipolytica was purchased from Shanghai Huzheng Biotechnology Co., Ltd.

[0026] Example 1

[0027] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0028] (1) Preparation of reaction system: Add trehalose mother liquor (soluble solid content of 9.2%, pH = 6.5, reducing sugar 8%, trehalose 0.2%) and sodium gluconate mother liquor (pH = 4.4, soluble solid content of 45%, reducing sugar content of 12%) to a glucose solution with a concentration of 180 g / L. The total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.3% of the volume of the glucose solution. The volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1.

[0029] Yeast extract was added at a mass volume ratio of 0.5% to adjust the soluble solid content to 26.0%; and the mixture was charged into the fermentation tank at a filling volume of 70%.

[0030] (2) Fermentation: Adjust pH = 6.0; sterilize at 115°C for 30 min, then cool to 28.5°C, inoculate Candida lipolytica, inoculate at 5%, and obtain a bacterial concentration of OD 600 Control the temperature at 15, control the fermentation conditions: 28-30℃, dissolved oxygen DO 10-25%, tank pressure 0.06-0.1MPa; after 75h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0031] (3) Ceramic membrane sterilization: The fermentation liquid with a soluble solid content of 20% was heated to 12 m 3 / h flow rate is filtered through a ceramic membrane with a pore size of 0.1μm to remove bacteria; the feed temperature is controlled at 30-35℃.

[0032] (4) Nanofiltration membrane filtration to remove impurities: The fermentation reaction liquid after the ceramic membrane filtration was heated to 12 m 3 / h flow rate first passes through a nanofiltration membrane with a pore size of 350Da to remove large molecular impurities to obtain a mixed solution of trehalose solution and sodium gluconate; then press 12m 3 / h flow rate passes through a nanofiltration membrane with a filter element pore size of 200Da to obtain an erythritol solution; and the feed temperature is controlled at 30-35°C.

[0033] (5) Ion exchange desalination: The obtained erythritol solution was first passed through a cation exchange resin of model SQD-67, and then passed through an anion exchange resin of model D301-F, and the output conductivity was 20 μs / cm.

[0034] (6) Concentration and crystallization separation; the obtained erythritol solution is treated in an evaporator at a temperature of 80-95° C. and concentrated to a soluble solid content of 50%. The specific gravity is controlled at 1.22, and then enters a crystallization tank for cooling and crystallization. The cooling rate is controlled at 6-7° C. / h, and the discharge temperature is 40° C. The solution is separated in an overhead centrifuge. The speed of the overhead centrifuge is controlled at 150 r / min. Feeding is started. After the feed is full, the speed is increased to 700 r / min. The feed is washed with pure water for 15-20 s, and then the speed is increased to 1300 r / min. The feed is washed with pure water for 10 s, and then the speed is reduced to 60 r / min. The erythritol crystals are separated and the purity is 99.7% as detected by high performance liquid chromatography.

[0035] The erythritol conversion rate was 69.8%. The erythritol conversion rate was calculated by high performance liquid chromatography, and the calculation method was: the erythritol content at the end of fermentation was divided by the initial glucose value.

[0036] Example 2

[0037] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0038] (1) Preparation of reaction system: Add trehalose mother liquor (soluble solid content of 10%, pH = 6.5, reducing sugar 10%, trehalose 0.3%) and sodium gluconate mother liquor (pH = 5, soluble solid content of 50%, reducing sugar content of 13%) to a glucose solution with a concentration of 190 g / L, the total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.4% of the volume of the glucose solution, and the volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1. Add 0.5% yeast extract in a mass volume ratio to adjust the soluble solid content to 27%; and load into the fermenter according to 70% of the liquid filling volume.

[0039] (2) Fermentation: Adjust pH = 6.2; sterilize at 115°C for 30 min, then cool to 28-30°C, inoculate Candida lipolytica, inoculate at 6%, and obtain a bacterial concentration of OD 600 Control the temperature at 18, control the fermentation conditions: 28-30°C, dissolved oxygen DO 10-25%, tank pressure 0.06-0.1MPa; after 73h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0040] (3) Ceramic membrane sterilization: The fermentation liquid with a soluble solid content of 23% was heated to 13 m 3 / h flow rate is filtered through a ceramic membrane with a pore size of 0.1μm to remove bacteria; the feed temperature is controlled at 30-35℃.

[0041] (4) Nanofiltration membrane filtration to remove impurities: The fermentation reaction liquid after the ceramic membrane filtration was heated to 13m 3 / h flow rate first passes through a nanofiltration membrane with a pore size of 350Da to remove large molecular impurities to obtain a mixed solution of trehalose solution and sodium gluconate; then press 13m 3 / h flow rate passes through a nanofiltration membrane with a filter element pore size of 200Da to obtain an erythritol solution; and the feed temperature is controlled at 30-35°C.

[0042] (5) Ion exchange desalination: The obtained erythritol solution was first passed through a cation exchange resin of model SQD-67, and then passed through an anion exchange resin of model D301-F, and the output conductivity was 30 μs / cm.

[0043] (6) Concentration, crystallization and separation; the obtained erythritol solution is treated in an evaporator at a temperature of 80-95°C and concentrated to a soluble solid content of 52%, the specific gravity is controlled at 1.23, and then enters a crystallization tank for cooling and crystallization, the cooling rate is controlled at 6-7°C / h, the discharge temperature is 40°C, and separated by an overhead centrifuge, the speed of the overhead centrifuge is controlled at 150r / min, and the feeding begins. After the material is full, the speed is increased to 700r / min, and the material is washed with pure water for 15-20s, then the speed is increased to 1300r / min, and the material is washed with pure water for 10s, and then the speed is reduced to 60r / min, and erythritol crystals are separated, with a purity of 99.8%. The erythritol conversion rate is 70.1%.

[0044] Example 3

[0045] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0046] (1) Preparation of reaction system: Add trehalose mother liquor (soluble solid content of 12%, pH = 6.8, reducing sugar 12%, trehalose 0.5%) and sodium gluconate mother liquor (pH = 5.5, soluble solid content of 55%, reducing sugar content of 14%) to a 200 g / L glucose solution, the total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.6% of the volume of the glucose solution, and the volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1. Add 0.5% yeast extract in a mass volume ratio to adjust the soluble solid content to 28.0%; and charge the fermenter according to 70% of the liquid filling volume.

[0047] (2) Fermentation: pH = 6.5; sterilize at 115°C for 30 min, then cool to 30°C, inoculate with Candida lipolytica, inoculation amount 8%, bacterial concentration OD 600Control the temperature at 20, control the fermentation conditions: 28-30℃, dissolved oxygen DO 10-25%, tank pressure 0.06-0.1MPa; after 70h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0048] (3) Ceramic membrane sterilization: The fermentation liquid with a soluble solid content of 25% was heated to 14 m 3 / h flow rate is filtered through a ceramic membrane with a pore size of 0.1μm to remove bacteria; the feed temperature is controlled at 30-35℃.

[0049] (4) Nanofiltration membrane filtration to remove impurities: The fermentation reaction liquid after the ceramic membrane filtration was heated to 14m 3 / h flow rate first passes through a nanofiltration membrane with a pore size of 350Da to remove large molecular impurities to obtain a mixed solution of trehalose solution and sodium gluconate; then press 14m 3 / h flow rate passes through a nanofiltration membrane with a filter element pore size of 200Da to obtain an erythritol solution; and the feed temperature is controlled at 30-35°C.

[0050] (5) Ion exchange desalination: The obtained erythritol solution is first passed through a cation exchange resin of model SQD-67, and then through an anion exchange resin of model D301-F, and the output conductivity is 50 μs / cm.

[0051] (6) Concentration, crystallization and separation; the obtained erythritol solution is treated in an evaporator at a temperature of 80-95°C and concentrated to a soluble solid content of 55%, the specific gravity is controlled at 1.25, and then enters a crystallization tank for cooling and crystallization, the cooling rate is controlled at 6-7°C / h, the discharge temperature is 40°C, and the solution is separated by an overhead centrifuge, the speed of the overhead centrifuge is controlled at 150r / min, and the feed is started. After the feed is full, the speed is increased to 700r / min, and the feed is washed with pure water for 15-20s, then the speed is increased to 1300r / min, and the feed is washed with pure water for 10s, and then the speed is reduced to 60r / min, and erythritol crystals are separated, with a purity of 99.6%. The erythritol conversion rate is 69.7%.

[0052] Example 4

[0053] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0054] (1) Preparation of reaction system: Add trehalose mother liquor (soluble solid content of 10%, pH = 6.5, reducing sugar 10%, trehalose 0.3%), sodium gluconate mother liquor (pH = 5, soluble solid content of 50%, reducing sugar content of 13%) and the mixed solution of trehalose and sodium gluconate filtered by nanofiltration membrane in Example 2 to a glucose solution with a concentration of 190 g / L, add 0.5% yeast extract by mass volume ratio, adjust the soluble solid content to 27%; and load into the fermentation tank according to the liquid filling volume of 70%. The total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.3% of the volume of the glucose solution, and the volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1; the amount of trehalose solution and sodium gluconate mixed solution filtered by nanofiltration membrane in Example 2 is 0.05% of the volume of the glucose solution.

[0055] (2) Fermentation: Adjust pH = 6.2; sterilize at 115°C for 30 min, then cool to 28-30°C, inoculate Candida lipolytica, inoculate at 6%, and obtain a bacterial concentration of OD 600 Control the temperature at 18, control the fermentation conditions: 28-30°C, dissolved oxygen DO 10-25%, tank pressure 0.06-0.1MPa; after 73h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0056] (3) Ceramic membrane sterilization: The fermentation liquid with a soluble solid content of 23% was heated to 13 m 3 / h flow rate is filtered through a ceramic membrane with a pore size of 0.1μm to remove bacteria; the feed temperature is controlled at 30-35℃.

[0057] (4) Nanofiltration membrane filtration to remove impurities: The fermentation reaction liquid after the ceramic membrane filtration was heated to 13m 3 / h flow rate first passes through a nanofiltration membrane with a pore size of 350Da to remove large molecular impurities to obtain a mixed solution of trehalose solution and sodium gluconate; then press 13m 3 / h flow rate passes through a nanofiltration membrane with a filter element pore size of 200Da to obtain an erythritol solution; and the feed temperature is controlled at 30-35°C.

[0058] (5) Ion exchange desalination: The obtained erythritol solution was first passed through a cation exchange resin of model SQD-67, and then passed through an anion exchange resin of model D301-F, and the output conductivity was 30 μs / cm.

[0059] (6) Concentration, crystallization and separation; the obtained erythritol solution is treated in an evaporator at a temperature of 80-95°C and concentrated to a soluble solid content of 50-55%, and the specific gravity is controlled at 1.23, and then enters a crystallization tank for cooling and crystallization, and the cooling rate is controlled at 6-7°C / h, and the discharge temperature is 40°C. After separation in an overhead centrifuge, the speed of the overhead centrifuge is controlled at 150r / min, and the feeding begins. After the material is full, the speed is increased to 700r / min, and the material is washed with pure water for 15-20s, and then the speed is increased to 1300r / min, and then the material is washed with pure water for 10s, and then the speed is reduced to 60r / min, and erythritol crystals are separated, and the purity is 99.7%. The erythritol conversion rate is 69.2%.

[0060] Comparative Example

[0061] A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor comprises the following steps:

[0062] (1) Preparation of reaction system: Add 0.5% yeast extract by mass volume ratio to a 300 g / L glucose solution to adjust the soluble solid content to 27%; and fill the fermentation tank at 70% of the liquid filling volume.

[0063] (2) Fermentation: Adjust pH = 6.2; sterilize at 115°C for 30 min, then cool to 28-30°C, inoculate Candida lipolytica, inoculate at 6%, and obtain a bacterial concentration of OD 600 Control the temperature at 18, control the fermentation conditions: 28-30°C, dissolved oxygen DO 10-25%, tank pressure 0.06-0.1MPa; after 73h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid;

[0064] (3) Ceramic membrane sterilization: The fermentation liquid with a soluble solid content of 23% was heated to 13 m 3 / h flow rate is filtered through a ceramic membrane with a pore size of 0.1μm to remove bacteria; the feed temperature is controlled at 30-35℃.

[0065] (4) Nanofiltration membrane filtration to remove impurities: The fermentation reaction liquid after the ceramic membrane filtration was heated to 13m 3 / h flow rate passes through a nanofiltration membrane with a filter element pore size of 200Da to obtain an erythritol solution; and the feed temperature is controlled at 30-35°C.

[0066] (5) Ion exchange desalination: The obtained erythritol solution was first passed through a cation exchange resin of model SQD-67, and then passed through an anion exchange resin of model D301-F, and the output conductivity was 25 μs / cm.

[0067] (6) Concentration, crystallization and separation; the obtained erythritol solution is treated in an evaporator at a temperature of 80-95°C and concentrated to a soluble solid content of 52%, the specific gravity is controlled at 1.23, and then enters a crystallization tank for cooling and crystallization, the cooling rate is controlled at 6-7°C / h, the discharge temperature is 40°C, and the solution is separated by an overhead centrifuge, the speed of the overhead centrifuge is controlled at 150r / min, and the feed is started. After the feed is full, the speed is increased to 700r / min, and the feed is washed with pure water for 15-20s, and then the speed is increased to 1300r / min, and then the feed is washed with pure water for 10s, and then the speed is reduced to 60r / min, and erythritol crystals are separated, with a purity of 99.7%. The erythritol conversion rate is 64.2%.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor, characterized in that: The following steps are involved: (1) Preparation of fermentation broth: adding trehalose mother liquor and sodium gluconate mother liquor to glucose solution, wherein the total amount of trehalose mother liquor and sodium gluconate mother liquor added is 0.3-0.6% of the volume of the glucose solution, and the volume ratio of trehalose mother liquor to sodium gluconate mother liquor is 5:1; then adding 0.5% yeast extract by mass volume ratio, adjusting the soluble solid content to 26.0-28.0%; filling the fermentation tank according to 70% of the liquid filling volume, adjusting the pH to 6.0-6.5; sterilizing at 115°C for 30 minutes, then cooling to 28-30°C, inoculating Candida lipolytica, inoculating at 5%-8%, and the bacterial concentration OD 600 Control the temperature at 15-20, and control the fermentation conditions: 28-30℃, dissolved oxygen DO at 10-25%, tank pressure at 0.06-0.1MPa; after 70-75h of fermentation, when the glucose content in the tank is ≤0.5g / L, the fermentation is terminated to obtain the fermentation liquid; (2) Ceramic membrane sterilization: The fermentation liquid is filtered through a ceramic membrane with a pore size of 0.1 μm; (3) Removal of polysaccharides by nanofiltration membrane: After filtration by ceramic membrane, the solution first passes through a nanofiltration membrane with a pore size of 350 Da to obtain a mixed solution of trehalose solution and sodium gluconate; then passes through a nanofiltration membrane with a pore size of 200 Da to obtain an erythritol solution; (4) Ion exchange desalination: the obtained erythritol solution is first passed through a cation exchange resin and then through an anion exchange resin; (5) Concentration and crystallization separation; the obtained erythritol solution is concentrated to a soluble solid content of 50-55% by an evaporator, and then enters a crystallization tank for cooling and crystallization. The cooling rate is controlled at 6-7°C / h and the discharge temperature is 40°C. After separation by an overhead centrifuge, erythritol crystals are obtained.

2. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The parameters of the trehalose mother liquor in step (1) are: soluble solid content of 9-12%, pH=6.2-6.8, reducing sugar 8-12%, trehalose 0.2-0.5%; the parameters of the sodium gluconate mother liquor are: pH=4.4-5.5, soluble solid content of 45-55%, reducing sugar content of 12-14%.

3. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The concentration of the glucose solution in step (1) is 180-200 g / L.

4. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The ceramic membrane filtration index of step (2) is: feed soluble solid content is 20-25%, temperature = 30-35°C, flow rate is 12-14m 3 / h.

5. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The filtration index of the nanofiltration membrane in step (3) is: 350Da nanofiltration membrane temperature = 30-35°C, flow rate 12-14m 3 / h; 200Da nanofiltration membrane temperature = 30-35°C, flow rate 12-14m 3 / h.

6. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The final conductivity of the ion exchange output in step (4) is controlled at 20-50 μs / cm.

7. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The control conditions of the evaporator in step (5) are as follows: the evaporation temperature is 80-95° C., and the discharge specific gravity is controlled at 1.22-1.

25.

8. The method for co-producing erythritol from trehalose mother liquor and sodium gluconate mother liquor according to claim 1, characterized in that: The separation conditions of the overhead centrifuge in step (5) are as follows: the overhead centrifuge speed is 150 r / min, the feeding starts, and the speed is increased to 700 r / min after the material is full, and the material is washed with pure water for 15-20 s, then the speed is increased to 1300 r / min, and the material is washed with pure water for 10 s, and then the speed is reduced to 60 r / min to separate the erythritol crystals.