A kind of preparation method of sodium gluconate

Abstract

The present invention belongs to the field of biochemical engineering technology, and specifically relates to a method for preparing sodium gluconate. The method for preparing sodium gluconate of the present invention comprises the following steps: providing a saccharification liquid of starch, wherein the glucose content in the saccharification liquid accounts for 85-90% of the dry matter; after mixing the saccharification liquid, glucose oxidase and catalase, introducing an oxygen-containing gas to carry out saccharification and oxidation co-reaction to obtain sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH value regulator is a sodium hydroxide solution. The present invention adds glucose oxidase and catalase to the partially saccharified saccharification liquid, introduces air or oxygen, and can realize the simultaneous saccharification process and oxidation process. The present invention can simplify the reaction process, shorten the reaction cycle, and save equipment investment.

Description

Technical Field

[0001] The invention belongs to the technical field of biochemical engineering, and particularly relates to a method for preparing sodium gluconate. Background Art

[0002] Sodium gluconate is widely used in food, medicine, construction, water treatment, printing and dyeing industry, steel surface treatment and other industries.

[0003] The earliest method of producing sodium gluconate was microbial fermentation. With the development of enzyme technology, enzymatic production emerged. The principle of both methods is that glucose oxidase and catalase catalyze the reaction of glucose and oxygen to produce gluconic acid. This process is accompanied by the synthesis and decomposition of hydrogen peroxide. Gluconic acid is neutralized with sodium hydroxide to produce sodium gluconate. Among them, enzymatic production of sodium gluconate has the advantages of not requiring strains, not being affected by the concentration of various auxiliary materials, good product purity, and easy extraction and refining compared to microbial fermentation. At present, the production of sodium gluconate in my country mostly adopts enzymatic production. The production process mainly includes liquefying and saccharifying starch to obtain glucose solution, then adding glucose oxidase and catalase for oxidation reaction to obtain gluconic acid, and finally neutralizing with sodium hydroxide to obtain sodium gluconate. The reaction process involves four main steps: liquefaction, saccharification, oxidation and neutralization. In the starch liquefaction process, high-temperature resistant amylase is generally used to hydrolyze starch into starch liquefied liquid. In the saccharification process, complex saccharifying enzymes are generally used to hydrolyze starch liquefied liquid, and the polysaccharides and oligosaccharides in the liquefied liquid are hydrolyzed into glucose. In the oxidation process, glucose oxidase and catalase are used to catalyze the reaction of glucose and oxygen to generate gluconic acid. In the neutralization process, sodium hydroxide is used for flow addition to produce sodium gluconate.

[0004] The existing enzymatic production of sodium gluconate uses the original production equipment of the microbial fermentation method. The saccharification reaction uses a large stainless steel stirring tank as a reactor, and the reaction cycle is more than 30 hours; the oxidation process uses an aerobic fermentation tank as a reactor, and the general reaction cycle is 18 to 24 hours. In the existing enzymatic production of sodium gluconate, there is a common problem of long production cycle. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing sodium gluconate. The method for preparing sodium gluconate of the present invention can realize simultaneous saccharification and oxidation processes, simplify the reaction steps, and shorten the reaction time.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing sodium gluconate, comprising the following steps:

[0008] Providing starch saccharification liquid, wherein the glucose content in the saccharification liquid accounts for 85-90% of the dry matter;

[0009] After the saccharification liquid, glucose oxidase and catalase are mixed, oxygen-containing gas is introduced to carry out saccharification and oxidation co-reaction to obtain sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH value regulator is sodium hydroxide solution.

[0010] Preferably, the method for preparing the starch saccharification liquid comprises: adjusting the pH value of the starch liquefied liquid and mixing it with a composite saccharifying enzyme to carry out a saccharification reaction to obtain the starch saccharification liquid, wherein the solid content of the starch liquefied liquid is 20-27%.

[0011] Preferably, the pH value of the starch liquefaction liquid after pH adjustment is 4.3-4.7.

[0012] Preferably, the enzyme activity of the composite saccharifying enzyme is 120,000 to 150,000 U / g; and the added amount of the composite saccharifying enzyme is 0.25 to 0.35 g per 1 kg of solids in the starch liquefaction liquid.

[0013] Preferably, the temperature of the saccharification reaction is 55-62° C.; the saccharification reaction is carried out under stirring conditions, and the stirring speed is 100-150 rpm.

[0014] Preferably, the saccharified liquid is cooled before being mixed with the glucose oxidase and catalase, and the temperature after cooling is 42-52°C.

[0015] Preferably, the enzymatic activity of the glucose oxidase is 15,000 to 25,000 U / g, and the enzymatic activity of the catalase is 600,000 to 750,000 U / g.

[0016] Preferably, the conditions for the saccharification and oxidation co-reaction include: the pressure of the oxygen-containing gas introduced is 0.25-0.35 MPa, the ventilation ratio is 0.3-0.8 vvm, the tank pressure is 0.05-0.15 MPa, and the stirring speed is 250-350 rpm.

[0017] Preferably, after the saccharification and oxidation co-reaction, the process further comprises: sequentially decolorizing, concentrating, solid-liquid separating and drying the obtained co-reaction liquid.

[0018] Preferably, the decolorization is activated carbon decolorization, and before the activated carbon decolorization, the pH value of the co-reaction liquid is adjusted to 6.8-7.2.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing sodium gluconate, comprising the following steps: providing a saccharification liquid of starch, wherein the percentage (DX) of glucose content in the saccharification liquid to dry matter is 85-90%; after mixing the saccharification liquid, glucose oxidase and catalase, introducing an oxygen-containing gas to carry out saccharification and oxidation co-reaction to obtain sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH value regulator is a sodium hydroxide solution. The present invention can achieve simultaneous saccharification and oxidation processes by adding glucose oxidase and catalase to the partially saccharified saccharification liquid and introducing air or oxygen, thereby simplifying the reaction steps and shortening the reaction time. Moreover, the saccharification reaction and the saccharification and oxidation co-reaction of the present invention can be carried out in the same reactor, thereby reducing equipment investment. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing sodium gluconate, comprising the following steps:

[0022] Providing starch saccharification liquid, wherein the glucose content in the saccharification liquid accounts for 85-90% of the dry matter;

[0023] After the saccharification liquid, glucose oxidase and catalase are mixed, oxygen-containing gas is introduced to carry out saccharification and oxidation co-reaction to obtain sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH value regulator is sodium hydroxide solution.

[0024] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0025] The invention provides starch saccharification liquid, wherein the percentage (DX) of glucose content in the saccharification liquid to dry matter is 85-90%.

[0026] In the present invention, the method for preparing the starch saccharification liquid preferably comprises: adjusting the pH value of the starch liquefied liquid and mixing it with a composite saccharifying enzyme to carry out a saccharification reaction to obtain the starch saccharification liquid.

[0027] In the present invention, the starch liquefaction liquid is obtained by liquefying starch. The present invention has no special requirements for the starch liquefaction process and can be prepared by methods commonly used by those skilled in the art, such as hydrolyzing starch by high temperature and liquefaction enzyme to obtain starch liquefaction liquid.

[0028] In the present invention, the solid content of the starch liquefaction is preferably 20-27%, more preferably 22-25%, and even more preferably 23%.

[0029] In the present invention, the pH value of the starch liquefaction liquid after the pH value adjustment is preferably 4.3-4.7, more preferably 4.5; the regulator used for adjusting the pH value preferably includes hydrochloric acid solution or sodium carbonate solution.

[0030] In the present invention, the enzyme activity of the composite saccharifying enzyme is preferably 120,000 to 150,000 U / g; based on the solid content in every 1 kg of starch liquefaction liquid, the added amount of the composite saccharifying enzyme is preferably 0.25 to 0.35 g, more preferably 0.28 to 0.33 g, and even more preferably 0.30 g.

[0031] In the present invention, the temperature of the saccharification reaction is preferably 55-62° C., more preferably 60° C.; the saccharification reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 100-150 rpm.

[0032] In the present invention, the saccharification reaction time is preferably 14 to 16 hours.

[0033] In the present invention, the saccharification reaction is preferably carried out in an aerobic fermentation tank, and the aerobic fermentation tank preferably has a stirring function, and a temperature and pH value detection and adjustment function.

[0034] After obtaining the saccharified liquid, the present invention mixes the saccharified liquid, glucose oxidase and catalase, introduces oxygen-containing gas, performs saccharification and oxidation co-reaction, and obtains sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH regulator is a sodium hydroxide solution.

[0035] In the present invention, the saccharified liquid is cooled before being mixed with the glucose oxidase and catalase. The temperature after cooling is preferably 42-52°C, more preferably 45-48°C.

[0036] In the present invention, the enzymatic activity of the glucose oxidase is preferably 15,000 to 25,000 U / g, more preferably 20,000 U / g.

[0037] In the present invention, the added amount of the glucose oxidase is preferably 0.2 to 0.35 g, more preferably 0.3 g, per 1 kg of solids in the saccharified liquid.

[0038] In the present invention, the enzymatic activity of the catalase is preferably 600,000 to 750,000 U / g, more preferably 700,000 U / g.

[0039] In the present invention, the amount of catalase added is preferably 0.2 to 0.35 g, more preferably 0.3 g, per 1 kg of solids in the saccharified liquid.

[0040] In the present invention, the saccharification and oxidation co-reaction is preferably carried out in an aerobic fermenter, and the conditions of the aerobic fermenter include: the pressure of the oxygen-containing gas introduced is preferably 0.25-0.35 MPa, more preferably 0.27 MPa; the ventilation ratio is preferably 0.3-0.8 vvm, more preferably 0.5 vvm; the tank pressure is preferably 0.05-0.15 MPa, more preferably 0.1-0.12 MPa; the stirring speed is preferably 250-350 rpm, more preferably 300 rpm. The oxygen-containing gas preferably includes oxygen or air.

[0041] In the present invention, the pH value of the reaction solution is preferably maintained at 5.0 to 5.2 during the saccharification and oxidation co-reaction process. In the present invention, the pH value of the reaction solution is adjusted by sodium hydroxide solution during the saccharification and oxidation co-reaction process, and gluconic acid can be converted into sodium gluconate.

[0042] In the present invention, during the saccharification and oxidation co-reaction, the total sugar and reducing sugar in the reaction system are preferably detected every 3 hours, and the reaction is stopped when the total sugar content in the reaction system is lower than 2% and the reducing sugar content is lower than 1.5%.

[0043] In the present invention, after the saccharification and oxidation co-reaction, the following steps are preferably further performed: decolorizing, concentrating, solid-liquid separation and drying the obtained co-reaction liquid in sequence to obtain the sodium gluconate.

[0044] In the present invention, the decolorization is preferably activated carbon decolorization, and the activated carbon decolorization preferably also includes adjusting the pH value of the co-reaction liquid with sodium hydroxide solution before the decolorization, and the adjusted pH value is preferably 6.8-7.2, more preferably 7.0.

[0045] In the present invention, the amount of activated carbon is preferably 0.8-1.5% of the mass of sodium gluconate in the feed liquid, and more preferably 1.2%; the decolorization is preferably carried out in a decolorization mixing tank, the stirring speed during the decolorization is preferably 100-150 rpm, the temperature is preferably 70-75°C, and the time is preferably 1.5-2 hours; the decolorization conditions described in the present invention can fully adsorb impurities in the reaction feed liquid.

[0046] In the present invention, after decolorization, it is preferred that filtration with a plate and frame filter is further performed to remove activated carbon in the feed liquid to obtain a clear liquid.

[0047] In the present invention, the solid-liquid separation method is preferably centrifugation, and the centrifugal rotation speed is preferably 2800 rpm.

[0048] In the present invention, the drying temperature is preferably 90° C. and the drying time is 5 min. The drying is preferably carried out in a fluidized bed.

[0049] In the preparation method of sodium gluconate provided by the invention, saccharification and oxidation reactions are carried out simultaneously in the same reactor, which can simplify the reaction process, shorten the reaction cycle and save equipment investment.

[0050] In order to further illustrate the present invention, the preparation method of sodium gluconate provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0051] The glucose content in the examples and comparative examples is the percentage of glucose content in the saccharified liquid to dry matter (DX).

[0052] Example 1

[0053] A method for preparing sodium gluconate by saccharification and oxidation co-reaction comprises the following steps:

[0054] (1) Starch liquefaction and saccharification process

[0055] A stainless steel aerobic fermentation tank was used as a reactor. The starch was liquefied to obtain a starch liquefaction with a solid content of 25%. The pH value of the starch liquefaction was adjusted to 4.5 using hydrochloric acid solution and sodium carbonate solution. A composite saccharifying enzyme with an enzyme activity of 120,000 U / g was added, and the enzyme addition amount was 0.33 g / kg solid. The temperature was maintained at 60°C, and the stirring was turned on at 150 rpm. The saccharification was performed until the glucose content reached 85%. At this time, the saccharification reaction time was 16 hours.

[0056] (2) Glycation and oxidation co-reaction process

[0057] The reaction solution obtained in step (1) is cooled to 48°C, and glucose oxidase with an enzyme activity of 20,000 U / g and catalase with an enzyme activity of 700,000 U / g are added (the optimal reaction temperature range and pH range of the two enzymes can cover 48°C and pH value 5.0), and the addition amount of the two enzymes is 0.3g / kg solid, so that saccharification and oxidation are carried out simultaneously; during this process, 0.25MPa of air needs to be introduced, the ventilation ratio is 0.50vvm, and the tank pressure is 0.10MPa; stirring is turned on, and the stirring speed is adjusted to 300 rpm; 32wt% sodium hydroxide solution is used to adjust the pH value, and the pH value is controlled at 5.0 in real time; total sugar and reducing sugar are detected every 3 hours during the reaction process, and the reaction is stopped when the total sugar content in the reaction system is less than 2% and the reducing sugar content is less than 1.5%. When stopped, the total time of saccharification reaction and oxidation reaction is 37h (including the saccharification process in step (1)).

[0058] (3) Activated carbon adsorption

[0059] The pH value of the reaction solution was adjusted to 7.0 using sodium hydroxide solution, the feed solution was transferred into a decolorization mixing tank, and 1.2% (based on the mass of sodium gluconate in the feed solution) of activated carbon was added, stirred at 100 rpm, the temperature was 75°C, and maintained for 2 hours to fully adsorb impurities in the reaction.

[0060] (4) Plate and frame filtration

[0061] Use a plate and frame filter to filter out the activated carbon in the liquid and obtain a clear liquid. When using a filter cloth plate and frame filter press, it should be fully circulated first to form an effective activated carbon filter layer on the filter cloth surface. When the plate and frame filtrate is cool and transparent, it can enter the clear liquid tank.

[0062] (5) Concentration and evaporation

[0063] The excess water in the clear liquid is removed by using a vacuum concentration evaporator, and the solid-liquid separation is performed by using a centrifuge at a speed of 2800 rpm. The solid after centrifugation is put into a fluidized bed and fluidized and dried at 90°C in the fluidized bed to obtain a finished sodium gluconate product with a purity of ≥99.6%.

[0064] Example 2

[0065] A method for preparing sodium gluconate by saccharification and oxidation co-reaction, using the same stainless steel aerobic fermentation tank as in Example 1 as a reactor, and the specific steps are as follows:

[0066] (1) Starch liquefaction and saccharification process

[0067] After the starch is liquefied, the solid content of the starch liquefied liquid is 23%; the pH value of the starch liquefied liquid is adjusted to 4.5 using hydrochloric acid solution and sodium carbonate solution; a composite saccharifying enzyme with an enzyme activity of 120,000 U / g is added, the enzyme addition amount is 0.3g / kg solid, the temperature is maintained at 60°C, and stirring is started at 150 rpm until the glucose content reaches 85%. At this time, the saccharification reaction time is 14h.

[0068] (2) Glycation and oxidation co-reaction process

[0069] The reaction solution obtained in step (1) is cooled to 48°C, and glucose oxidase with an enzyme activity of 20,000 U / g and catalase with an enzyme activity of 700,000 U / g are added (the optimal reaction temperature range and pH range of the two enzymes can cover 48°C and pH value 5.0), and the addition amount of the two enzymes is 0.3g / kg solid, so that saccharification and oxidation are carried out simultaneously; during this process, 0.27MPa of air needs to be introduced, the ventilation ratio is 0.50vvm, and the tank pressure is 0.12MPa; stirring is turned on, and the stirring speed is adjusted to 300 rpm; sodium hydroxide solution is used to adjust the pH value, and the pH value is controlled at 5.0 in real time; total sugar and reducing sugar are detected every 3 hours during the reaction process, and the reaction is stopped when the total sugar content in the reaction system is less than 2% and the reducing sugar content is less than 1.5%. When stopped, the total time of saccharification reaction and oxidation reaction is 35h (including the saccharification process in step (1)).

[0070] The subsequent operations were carried out according to steps (3), (4) and (5) in Example 1 to obtain a finished sodium gluconate product with a purity of ≥99.6%.

[0071] Example 3

[0072] A method for preparing sodium gluconate by saccharification and oxidation co-reaction, using the same stainless steel aerobic fermentation tank as in Example 1 as a reactor, and the specific steps are as follows:

[0073] (1) Starch liquefaction and saccharification process

[0074] After the starch is liquefied, the solid content of the starch liquefied liquid is 22%; the pH value of the starch liquefied liquid is adjusted to 4.5 using hydrochloric acid solution and sodium carbonate solution; a composite saccharifying enzyme with an enzyme activity of 120,000 U / g is added, the enzyme addition amount is 0.28g / kg solid, the temperature is maintained at 60°C, and stirring is started at 150 rpm until the glucose content reaches 85%. At this time, the saccharification reaction time is 16 hours.

[0075] (2) Glycation and oxidation co-reaction process

[0076] The reaction solution obtained in step (1) is cooled to 42°C, and glucose oxidase with an enzyme activity of 20,000 U / g and catalase with an enzyme activity of 700,000 U / g are added (the optimal reaction temperature range and pH range of the two enzymes can cover 45°C and pH value 5.5), and the addition amount of the two enzymes is 0.3g / kg solid, so that saccharification and oxidation are carried out simultaneously; during this process, 0.25MPa of air needs to be introduced, the ventilation ratio is 0.50vvm, and the tank pressure is 0.10MPa; stirring is turned on, and the stirring speed is adjusted to 300 rpm; sodium hydroxide solution is used to adjust the pH value, and the pH value is controlled at 5.5 in real time; total sugar and reducing sugar are detected every 3 hours during the reaction process, and the reaction is stopped when the total sugar content in the reaction system is less than 2% and the reducing sugar content is less than 1.5%. When stopped, the total time of saccharification reaction and oxidation reaction is 40h (including the saccharification process in step (1)).

[0077] The sodium gluconate product was obtained by performing subsequent operations according to steps (3), (4) and (5) in Example 1, with a purity of ≥99.6%.

[0078] Comparative Example 1

[0079] A method for preparing sodium gluconate in which the saccharification reaction of starch liquefaction and the glucose oxidation reaction are carried out separately, wherein step (1) is carried out in a saccharification tank, and step (2) uses the same aerobic fermentation tank as in Example 1 as a reactor, and the specific steps are as follows:

[0080] (1) Starch liquefaction and saccharification reaction

[0081] After the starch is liquefied, the solid content of the starch liquefied liquid is 25%; the pH value of the starch liquefied liquid is adjusted to 4.5 using hydrochloric acid solution and sodium carbonate solution; a composite saccharifying enzyme with an enzyme activity of 120,000 U / g is added, the enzyme addition amount is 0.3 g / kg solid, the temperature is maintained at 60°C, and stirring is started at 150 rpm until the glucose content reaches 97%. The saccharification time under this condition is 33.5 hours.

[0082] (2) Glucose oxidation reaction

[0083] The reaction solution obtained in step (1) is cooled to 42°C, and glucose oxidase with an enzyme activity of 20,000 U / g and catalase with an enzyme activity of 700,000 U / g are added (the optimal reaction temperature range and pH range of the two enzymes can cover 42°C and pH value 5.5), and the enzyme addition amount is 0.3 g / kg solid. During this process, 0.25 MPa of air needs to be introduced, the ventilation ratio is 0.50 vvm, and the tank pressure is 0.10 MPa; stirring is started, and the stirring speed is adjusted to 300 rpm; sodium hydroxide solution is used to adjust the pH value, and the pH value is controlled at 5.5 in real time; total sugar and reducing sugar are detected every 3 hours during the reaction process, and the reaction is stopped when the total sugar content in the reaction system is less than 2% and the reducing sugar content is less than 1.5%. The reaction time of the glucose oxidation stage is 20 hours, and the total time of the saccharification reaction and the oxidation reaction is 53.5 hours.

[0084] The sodium gluconate product was obtained by performing subsequent operations according to steps (3), (4) and (5) in Example 1, with a purity of ≥99.6%.

[0085] Comparative Example 2

[0086] A method for preparing sodium gluconate by saccharification and oxidation co-reaction, using the same stainless steel aerobic fermentation tank as in Example 1 as a reactor, and the specific steps are as follows:

[0087] (1) Starch liquefaction and saccharification process

[0088] After the starch is liquefied, the solid content of the starch liquefied liquid is 23%; the pH value of the starch liquefied liquid is adjusted to 4.5 using hydrochloric acid solution and sodium carbonate solution; a composite saccharifying enzyme with an enzyme activity of 120,000 U / g is added, the enzyme addition amount is 0.3g / kg solid, the temperature is maintained at 60°C, and the stirring is turned on at 150 rpm until the glucose content reaches 80%. At this time, the saccharification reaction time is 13h.

[0089] (2) Glycation and oxidation co-reaction process

[0090] The reaction solution obtained in step (1) is cooled to 48°C, and glucose oxidase with an enzyme activity of 20,000 U / g and catalase with an enzyme activity of 700,000 U / g are added (the optimal reaction temperature range and pH range of the two enzymes can cover 48°C and pH value 5.0), and the addition amount of the two enzymes is 0.3g / kg solid, so that saccharification and oxidation are carried out simultaneously; during this process, 0.27MPa of air needs to be introduced, the ventilation ratio is 0.50vvm, and the tank pressure is 0.12MPa; stirring is turned on, and the stirring speed is adjusted to 300 rpm; sodium hydroxide solution is used to adjust the pH value, and the pH value is controlled at 5.0 in real time; total sugar and reducing sugar are detected every 3 hours during the reaction process, and the reaction is stopped when the total sugar content in the reaction system is less than 2% and the reducing sugar content is less than 1.5%. When stopped, the total time of saccharification reaction and oxidation reaction is 39h (including the saccharification process in step (1)).

[0091] The subsequent operations were carried out according to steps (3), (4) and (5) in Example 1 to obtain a finished sodium gluconate product with a purity of ≥99.6%.

[0092] The total time of saccharification reaction and oxidation reaction in Comparative Example 1 is 53.5 h, while the total time of saccharification reaction and oxidation reaction in Examples 1 to 3 are 37 h, 35 h and 40 h, respectively. It can be seen that the reaction cycle in the examples is significantly shortened.

[0093] The difference between Comparative Example 2 and Example 2 is that the percentage of glucose content in the saccharified liquid to dry matter (DX) is different: 80% in Comparative Example 2 and 85% in Example 2; the total time of saccharification reaction and oxidation reaction in Comparative Example 2 is 39 hours, and that in Example 2 is 35 hours. It can be seen that Comparative Example 2 does not further shorten the reaction cycle, while the present invention achieves a shortening of the reaction cycle by controlling the percentage of glucose content in the saccharified liquid to dry matter.

[0094] It can be seen from the above examples and comparative data that in the examples of the present invention, glucose oxidase and catalase are added to the saccharified liquid that has been saccharified for a certain period of time, air or oxygen is supplied, and sodium hydroxide solution is added to adjust the pH value, so that the simultaneous reaction of the saccharification process and the oxidation process can be achieved, and the two reactions are carried out simultaneously in an aerobic fermentation tank with stirring, temperature and pH value detection and adjustment functions. In the comparative example, the slurry that has been fully saccharified in the saccharification tank is transferred to an aerobic fermentation tank with stirring, temperature and pH value detection and adjustment functions for oxidation reaction. The reaction cycle is obviously long, and more equipment is required, and the process is complicated. The present invention simplifies the reaction process, shortens the reaction cycle, and saves equipment investment by carrying out saccharification and oxidation reactions simultaneously in the same reactor.

[0095] Although the above-mentioned embodiments have made a detailed description of the present invention, they are only some embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on the embodiments of the present invention without creative work, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing sodium gluconate, characterized in that, The following steps are involved: Providing starch saccharification liquid, wherein the glucose content in the saccharification liquid accounts for 85% to 90% of the dry matter; After the saccharification liquid, glucose oxidase and catalase are mixed, oxygen-containing gas is introduced to carry out saccharification and oxidation co-reaction to obtain sodium gluconate; during the saccharification and oxidation co-reaction, the pH value of the reaction liquid is maintained at 4.8-5.5, and the pH value regulator is sodium hydroxide solution; The method for preparing the starch saccharification liquid comprises: adjusting the pH value of the starch liquefied liquid and mixing it with a composite saccharifying enzyme to carry out a saccharification reaction to obtain the starch saccharification liquid, wherein the solid content of the starch liquefied liquid is 20% to 27%; The pH value of the starch liquefied liquid after the pH value is adjusted is 4.3 to 4.7; The enzyme activity of the composite saccharifying enzyme is 120,000 to 150,000 U / g; based on the solid content in 1 kg of starch liquefaction liquid, the added amount of the composite saccharifying enzyme is 0.25 to 0.35 g.

2. The preparation method according to claim 1, characterized in that: The temperature of the saccharification reaction is 55-62° C.; the saccharification reaction is carried out under stirring conditions, and the stirring speed is 100-150 rpm.

3. The preparation method according to claim 1, characterized in that: The saccharification liquid is cooled before being mixed with the glucose oxidase and the catalase, and the temperature after the cooling is 42-52°C.

4. The preparation method according to claim 1, characterized in that: The enzymatic activity of the glucose oxidase is 15,000 to 25,000 U / g, and the enzymatic activity of the catalase is 600,000 to 750,000 U / g.

5. The preparation method according to claim 1, characterized in that: The conditions for the saccharification and oxidation co-reaction include: the pressure of the oxygen-containing gas introduced is 0.25-0.35 MPa, the ventilation ratio is 0.3-0.8 vvm, the tank pressure is 0.05-0.15 MPa, and the stirring speed is 250-350 rpm.

6. The preparation method according to claim 1, characterized in that: After the saccharification and oxidation co-reaction, the method further comprises: sequentially decolorizing, concentrating, solid-liquid separating and drying the obtained co-reaction liquid.

7. The preparation method according to claim 6, characterized in that: The decolorization is activated carbon decolorization, and before the activated carbon decolorization, the pH value of the co-reaction liquid is adjusted to 6.8-7.2.