Method for extracting citric acid from citric acid fermentation liquor

Abstract

The invention discloses a method for extracting citric acid from citric acid fermentation broth, and belongs to the technical field of chemical production, and the method for extracting citric acid from citric acid fermentation broth comprises the following steps: A1, carrying out low-temperature heat treatment on the citric acid fermentation broth to enable the citric acid fermentation broth to reach 55-65 DEG C, the citric acid fermentation liquor subjected to low-temperature heat treatment is obtained. And A2, filtering and sterilizing the citric acid fermentation liquid subjected to low-temperature heat treatment through an electric field cross-flow membrane filtering device to obtain the citric acid treatment liquid. According to the method disclosed by the invention, substances such as mycelia, proteins, colloids, pigments, inorganic zwitterions and the like in the citric acid fermentation liquor can be effectively intercepted, so that the final death rate of thalli reaches 99.9% or above, the acidity of the citric acid treatment liquor reaches 18.9% or above, the turbidity is lower than 5.6, the mass content of Ca < 2 + > is lower than 40ppm, and the mass content of SO4 < 2-> is lower than 160ppm.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and particularly relates to a method for extracting citric acid from citric acid fermentation broth. Background Art

[0002] Citric acid is the largest organic acid. Due to its physical properties, chemical properties, and the properties of its derivatives, it is widely used in food, medicine, daily chemicals and other industries. In industrial production, citric acid is mainly produced by deep fermentation using starchy substances such as corn and cassava as raw materials. After fermentation, a large amount of citric acid fermentation mash will be obtained, which contains many impurities such as mycelium, protein, colloid, pigment, inorganic anions and cations. The fermentation liquid containing citric acid needs to be further separated and purified before use.

[0003] At present, the domestic method of purifying and separating citric acid from citric acid fermentation broth by neutralization calcium salt method or continuous ion exchange method is mostly used, and finally the citric acid product is obtained by refining. The characteristics of the currently used process are that the neutralization calcium salt method consumes a lot of acid and alkali in production, and produces a lot of waste gas, waste liquid and waste residue; the continuous ion exchange method requires high quality of fermentation broth and less impurities, otherwise it will affect the stability and separation effect of continuous ion exchange.

[0004] The patent with patent announcement number CN105152912A discloses a citric acid fermentation liquid pretreatment method, which performs low-temperature heat treatment on the fermented citric acid fermentation liquid to make the citric acid fermentation liquid reach a predetermined temperature. Then the citric acid fermentation liquid reaching the predetermined temperature is filtered and sterilized by an electric field cross-flow membrane filter device, which is composed of a high-voltage pulse electric field and a ceramic membrane. The ceramic membrane microfiltration membrane is under the electric field strengthening effect of the high-voltage pulse unidirectional DC electric field. The filtration performance of the membrane is improved, the anti-pollution performance is increased, and the permeation flux is greatly increased. The mycelium of Aspergillus niger cells and suspended solid impurities and other macromolecular substances can be intercepted by the treatment, so that the final cell mortality rate reaches more than 99.5%, so that the acidity of the purified citric acid fermentation liquid is higher than 16%, and the turbidity is lower than 8NTU, which solves the problem of high energy consumption and large energy waste in the pretreatment process of citric acid fermentation liquid at this stage. However, there are still many impurities in the citric acid after the ceramic membrane filtration of the patent and the prior art, which is not conducive to subsequent treatment. Summary of the invention

[0005] In order to solve the problem in the prior art that there are still many impurities in citric acid after filtration through a ceramic membrane, which is not conducive to subsequent treatment, the purpose of the present invention is to provide a method for extracting citric acid from citric acid fermentation broth.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0008] Step A1: subjecting the citric acid fermentation broth to low-temperature heat treatment to make the citric acid fermentation broth reach 55-65° C., thereby obtaining the citric acid fermentation broth after low-temperature heat treatment.

[0009] Step A2: filtering and sterilizing the citric acid fermentation liquid after low-temperature heat treatment through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid; the electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field combined with a modified ceramic membrane, wherein the modified ceramic membrane is a composite membrane composed of modified graphene oxide and a ceramic membrane, and the modified graphene oxide is prepared by methacryloylethyl sulfobetaine grafted onto graphene oxide.

[0010] Ceramic membrane is a membrane made of powder materials such as aluminum oxide, zirconium oxide and titanium oxide through a special process. The wall of the ceramic membrane is densely covered with micropores. Under pressure, the raw material liquid flows outside the membrane in the membrane tube, small molecules (or liquids) pass through the membrane, and large molecules (or solid particles, liquid droplets) are intercepted by the membrane to achieve the purpose of separation, concentration and purification of different components of the liquid. Ceramic membrane materials have good high temperature resistance and chemical stability, can work in strong acid and alkali environments, and are suitable for various complex components that may exist in citric acid fermentation broth.

[0011] The modified ceramic membrane is a composite membrane composed of modified graphene oxide and ceramic membrane, wherein the modified graphene oxide is prepared by grafting graphene oxide with methacryloylethyl sulfobetaine, wherein methacryloylethyl sulfobetaine has quaternary ammonium salt groups and sulfonic acid groups, and the above groups can be present on the modified graphene oxide after methacryloylethyl sulfobetaine is grafted with graphene oxide. The quaternary ammonium salt groups and graphene oxide itself can inhibit microorganisms, and when the modified graphene oxide is coated on the surface of the ceramic membrane, the ability of the modified ceramic membrane to filter microorganisms can be significantly enhanced. The surface of the modified graphene oxide contains quaternary ammonium salt groups, sulfonic acid groups, hydroxyl groups and carboxyl groups, so that the modified ceramic membrane can filter both anions and cations, thereby improving the ability of the modified ceramic membrane to filter calcium ions and chloride ions. In addition, the composite membrane of the present invention is more closely combined, and has a better effect on the removal of impurities.

[0012] Furthermore, in step A1, the low-temperature heat treatment is achieved using a high-efficiency heat exchanger, which is any one of a spiral plate heat exchanger, a spiral flat tube heat exchanger or a two-phase jet heat exchanger.

[0013] Furthermore, in step A2, the high-voltage pulse electric field is a unidirectional direct current electric field, and its electric field strength is 80kv / cm-110kv / cm, the pulse frequency is 100Hz-130Hz, the pulse width is 6μs-18μs, and the processing time is 8s-55s.

[0014] Furthermore, in step A2, the structure of the modified ceramic membrane filtration is any one of plate and frame filtration, tubular filtration or multi-channel filtration.

[0015] Furthermore, the preparation method of the modified ceramic membrane is:

[0016] Step B1: adding graphene oxide and methacryloylethyl sulfobetaine to deionized water, ultrasonically mixing for 18-24 hours, centrifuging, and freeze-drying to obtain modified graphene oxide;

[0017] The usage ratio of graphene oxide, methacryloylethyl sulfobetaine and deionized water is 1 g: 2-4 g: 100 mL.

[0018] Methacryloylethyl sulfobetaine undergoes an oxa-M i chael addition reaction with graphene oxide, thereby grafting methacryloylethyl sulfobetaine onto graphene oxide to obtain modified graphene oxide.

[0019] Step B2: dissolving the modified graphene oxide in water to obtain a modified graphene oxide dispersion, applying a slurry coating on the ceramic membrane with the modified graphene oxide dispersion, drying, repeating the coating once, drying, and then heat treating at 150° C. to obtain a modified ceramic membrane.

[0020] Among them, the usage ratio of modified graphene oxide to water is 0.3-0.5g:1L.

[0021] Since the modified graphene oxide is obtained by treating with methacryloylethyl sulfobetaine, methacryloylethyl sulfobetaine can improve the agglomeration phenomenon of the modified graphene oxide and help to form a more compact and uniform composite film.

[0022] Furthermore, in step B2, the pore size of the ceramic membrane is 0.05-1 μm, and the type of the ceramic membrane is any one of an aluminum oxide ceramic membrane, a zirconium oxide ceramic membrane and a titanium oxide ceramic membrane.

[0023] Beneficial effects of the present invention:

[0024] 1. The method of the present invention can effectively intercept mycelium, protein, colloid, pigment, inorganic anion and cation and other substances in the citric acid fermentation liquid, so that the final bacterial mortality rate reaches more than 99.9%, the acidity of the citric acid treatment liquid reaches more than 18.9%, the turbidity is lower than 5.6, and the Ca 2+ The mass content is less than 40ppm, SO4 2- The mass content is less than 160ppm. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0026] The graphene oxide in the present invention has a C / O molar ratio of 6.9-7.1 and is purchased from Beijing Carbon Century Technology Co., Ltd.

[0027] Preparation Example 1

[0028] The preparation method of the modified ceramic membrane of this preparation example is:

[0029] Step B1: 1 g of graphene oxide and 2 g of methacryloylethyl sulfobetaine were added to 100 mL of deionized water, ultrasonically mixed for 18 h, centrifuged, and freeze-dried to obtain modified graphene oxide;

[0030] Step B2: Dissolve 0.3 g of modified graphene oxide in 1 L of water to obtain a modified graphene oxide dispersion, apply the modified graphene oxide dispersion on a 1 μm titanium oxide ceramic membrane for slurry coating, dry, repeat the coating once, dry, and then heat treat at 150°C to obtain a modified ceramic membrane.

[0031] Preparation Example 2

[0032] The preparation method of the modified ceramic membrane of this preparation example is:

[0033] Step B1: 1 g of graphene oxide and 3 g of methacryloylethyl sulfobetaine were added to 100 mL of deionized water, ultrasonically mixed for 24 h, centrifuged, and freeze-dried to obtain modified graphene oxide;

[0034] Step B2: Dissolve 0.4 g of modified graphene oxide in 1 L of water to obtain a modified graphene oxide dispersion, apply the modified graphene oxide dispersion on a 0.07 μm zirconia ceramic membrane for slurry coating, dry, repeat the coating once, dry, and then heat treat at 150°C to obtain a modified ceramic membrane.

[0035] Preparation Example 3

[0036] The preparation method of the modified ceramic membrane of this preparation example is:

[0037] Step B1: 1 g of graphene oxide and 4 g of methacryloylethyl sulfobetaine were added to 100 mL of deionized water, ultrasonically mixed for 22 h, centrifuged, and freeze-dried to obtain modified graphene oxide;

[0038] Step B2: Dissolve 0.5 g of modified graphene oxide in 1 L of water to obtain a modified graphene oxide dispersion, apply the modified graphene oxide dispersion on a 0.05 μm alumina ceramic membrane for slurry coating, dry, repeat the coating once, dry, and then heat treat at 150°C to obtain a modified ceramic membrane.

[0039] Preparation Example 4

[0040] The preparation method of the modified ceramic membrane of this preparation example is:

[0041] Step B1: adding 1 g of graphene oxide and 0.7 g of acryloyloxyethyltrimethylammonium chloride into 100 mL of deionized water, ultrasonically mixing for 18 h, centrifuging, and freeze-drying to obtain modified graphene oxide;

[0042] Step B2: Dissolve 0.3 g of modified graphene oxide in 1 L of water to obtain a modified graphene oxide dispersion, apply the modified graphene oxide dispersion on a 1 μm titanium oxide ceramic membrane for slurry coating, dry, repeat the coating once, dry, and then heat treat at 150°C to obtain a modified ceramic membrane.

[0043] Preparation Example 5

[0044] The preparation method of the modified ceramic membrane of this preparation example is:

[0045] 0.3 g of graphene oxide was dissolved in 1 L of water to obtain a graphene oxide dispersion, and the graphene oxide dispersion was slurried and coated on a 1 μm titanium oxide ceramic membrane. After drying, the coating was repeated once, dried, and then heat treated at 150° C. to obtain a modified ceramic membrane.

[0046] Preparation Example 6

[0047] This preparation example uses a 1 μm titanium oxide ceramic film.

[0048] Example 1

[0049] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0050] Step A1: using a spiral flat tube heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 55° C., and obtains the citric acid fermentation liquid after low-temperature heat treatment.

[0051] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 1. The unidirectional DC electric field strength is 80 kV / cm, the pulse frequency is 100 Hz, the pulse width is 6 μs, and the processing time is 8 s; the modified ceramic membrane is constructed as a multi-channel type.

[0052] Example 2

[0053] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0054] Step A1: using a two-phase jet heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 65° C., and obtaining the citric acid fermentation liquid after low-temperature heat treatment.

[0055] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 2. The unidirectional DC electric field strength is 110 kv / cm, the pulse frequency is 120 Hz, the pulse width is 18 μs, and the treatment time is 55 s; the modified ceramic membrane is tubular in structure.

[0056] Example 3

[0057] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0058] Step A1: using a spiral plate heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 60° C., and obtains the citric acid fermentation liquid after low-temperature heat treatment.

[0059] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 3. The unidirectional DC electric field strength is 100 kv / cm, the pulse frequency is 130 Hz, the pulse width is 12 μs, and the processing time is 39.5 s; the modified ceramic membrane is constructed as a plate-frame type.

[0060] Comparative Example 1

[0061] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0062] Step A1: using a spiral flat tube heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 55° C., and obtains the citric acid fermentation liquid after low-temperature heat treatment.

[0063] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 4. The unidirectional DC electric field strength is 80 kV / cm, the pulse frequency is 100 Hz, the pulse width is 6 μs, and the processing time is 8 s; the modified ceramic membrane is constructed as a multi-channel type.

[0064] Comparative Example 2

[0065] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0066] Step A1: using a spiral flat tube heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 55° C., and obtains the citric acid fermentation liquid after low-temperature heat treatment.

[0067] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 5. The unidirectional DC electric field strength is 80 kV / cm, the pulse frequency is 100 Hz, the pulse width is 6 μs, and the processing time is 8 s; the modified ceramic membrane is constructed as a multi-channel type.

[0068] Comparative Example 3

[0069] A method for extracting citric acid from citric acid fermentation broth comprises the following steps:

[0070] Step A1: using a spiral flat tube heat exchanger to perform low-temperature heat treatment on the citric acid fermentation liquid, so that the citric acid fermentation liquid reaches 55° C., and obtains the citric acid fermentation liquid after low-temperature heat treatment.

[0071] Step A2: The citric acid fermentation liquid after low-temperature heat treatment is filtered and sterilized through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid. The electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field and a modified ceramic membrane prepared in Preparation Example 6. The unidirectional DC electric field strength is 80 kV / cm, the pulse frequency is 100 Hz, the pulse width is 6 μs, and the processing time is 8 s; the modified ceramic membrane is constructed as a multi-channel type.

[0072] The citric acid treated liquids obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the test items were as follows: (1) microscopic examination of the bacteria to count the mortality rate in accordance with GB 478915-2010 National Food Safety Standard Food Microbiology Examination Mold and Yeast Count; (2) acidity was tested in accordance with GB / T 9736-2008 General Method for Determination of Acidity and Alkalinity of Chemical Reagents; (3) turbidity was tested in accordance with GB13200-91 Determination of Turbidity of Water Quality; (4) Ca 2+ Mass content: Take 1mL of the ion exchange liquid sample and add it to a colorimetric tube, add 2mL of 4wt% ammonium oxalate, add 1mL of 95wt% ethanol, and dilute to 10mL with water. Leave it for 10 minutes. Take another colorimetric tube and add calcium standard solution (1mL, 10ppm). Perform the same operation as the sample and compare the turbidity of the sample tube with that of the standard tube. (5) SO42- Mass content: Take 1mL of sample in a 50mL colorimetric tube, add 1mL, 24wt% hydrochloric acid solution, then add 3mL, 25wt% BaCl2 solution, shake well, add distilled water to 25mL, shake well, and leave for 10 minutes; take another colorimetric tube, add sulfate standard solution (1mL, 10ppm), perform the same operation as the sample, and compare the turbidity of the sample tube and the standard tube. The test results are shown in Table 1.

[0073] Table 1

[0074]

[0075] It can be seen from Table 1 that the contents of bacteria and other impurities in the citric acid-treated liquid obtained by the methods of Examples 1 to 3 are lower than those in the citric acid-treated liquid obtained by the methods of Comparative Examples 1 to 3; the citric acid acidity of the citric acid-treated liquid obtained by the methods of Examples 1 to 3 is higher than that of the citric acid-treated liquid obtained by the methods of Comparative Examples 1 to 3.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for extracting citric acid from citric acid fermentation broth, characterized in that: The following steps are involved: Step A1: subjecting the citric acid fermentation broth to low-temperature heat treatment to make the citric acid fermentation broth reach 55-65° C., thereby obtaining the citric acid fermentation broth after low-temperature heat treatment; Step A2: filtering and sterilizing the citric acid fermentation liquid after low-temperature heat treatment through an electric field cross-flow membrane filtration device to obtain a citric acid treated liquid; the electric field cross-flow membrane filtration device is composed of a high-voltage pulse electric field combined with a modified ceramic membrane, wherein the modified ceramic membrane is a composite membrane composed of modified graphene oxide and a ceramic membrane, and the modified graphene oxide is prepared by methacryloylethyl sulfobetaine grafted onto graphene oxide.

2. A method for extracting citric acid from citric acid fermentation broth according to claim 1, characterized in that: In step A1, the low-temperature heat treatment is achieved using a high-efficiency heat exchanger, which is any one of a spiral plate heat exchanger, a spiral flat tube heat exchanger or a two-phase jet heat exchanger.

3. A method for extracting citric acid from citric acid fermentation broth according to claim 1, characterized in that: In step A2, the high-voltage pulse electric field is a unidirectional direct current electric field, the electric field strength of which is 80 kv / cm-110 kv / cm, the pulse frequency is 100 Hz-130 Hz, the pulse width is 6 μs-18 μs, and the processing time is 8s-55s.

4. A method for extracting citric acid from citric acid fermentation broth according to claim 1, characterized in that: In step A2, the structure of the modified ceramic membrane filtration is any one of plate and frame filtration, tubular filtration or multi-channel filtration.

5. The method for extracting citric acid from citric acid fermentation broth according to claim 1, characterized in that: The preparation method of the modified ceramic membrane is as follows: Step B1: adding graphene oxide and methacryloylethyl sulfobetaine to deionized water, ultrasonically mixing for 18-24 hours, centrifuging, and freeze-drying to obtain modified graphene oxide; Step B2: dissolving the modified graphene oxide in water to obtain a modified graphene oxide dispersion, applying a slurry coating on the ceramic membrane with the modified graphene oxide dispersion, drying, repeating the coating once, drying, and then heat treating at 150° C. to obtain a modified ceramic membrane.

6. A method for extracting citric acid from citric acid fermentation broth according to claim 5, characterized in that: In step B1, the usage ratio of graphene oxide, methacryloylethyl sulfobetaine, and deionized water is 1 g: 2-4 g: 100 mL.

7. The method for extracting citric acid from citric acid fermentation broth according to claim 5, characterized in that: In step B2, the usage ratio of modified graphene oxide to water is 0.3-0.5 g:1 L.

8. The method for extracting citric acid from citric acid fermentation broth according to claim 5, characterized in that: In step B2, the pore size of the ceramic membrane is 0.05-1 μm, and the type of the ceramic membrane is any one of an aluminum oxide ceramic membrane, a zirconium oxide ceramic membrane and a titanium oxide ceramic membrane.

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