Method for purifying polyglutamic acid

Abstract

The invention relates to a polyglutamic acid purification method, and belongs to the technical field of polyglutamic acid purification, the polyglutamic acid purification method comprises the following steps: S1, dilution, heating, centrifugation and reflux of a polyglutamic acid-rich fermentation broth; and S2, concentrating the ultrafiltrate. The method is simple to operate, and the obtained polyglutamic acid purified liquid is high in polyglutamic acid content and molecular weight, so that the polyglutamic acid purified liquid has the characteristics of good application feeling and strong effect. In addition, fermentation liquor rich in polyglutamic acid is synchronously diluted by water and heated and then centrifuged, and centrifugate after centrifugation is directly collected in a buffer tank and is subjected to ultrafiltration concentration through a hollow fiber ultrafiltration column; and the ultrafiltration concentration work of the buffer tank and the hollow fiber ultrafiltration column is kept while the dilution tank and the tubular centrifuge are cleaned, so that the efficiency of the whole process is improved. And a plurality of devices in the system are tightly matched to form a closed-loop high-efficiency concentration circulating continuous operation, so that the loss of the polyglutamic acid in the purification process is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polyglutamic acid purification, and in particular relates to a polyglutamic acid purification method. Background Art

[0002] Polyglutamic acid (PGA) is generally produced by Bacillus subtilis during fermentation by utilizing glutamic acid to biosynthesize macromolecular polyglutamic acid, with a molecular weight of 1-5 million Da. The content of polyglutamic acid in the fermentation broth generally reaches 10.0 g / L or above. With such a high molecular weight and high polyglutamic acid content, the fermentation broth is often very viscous in the later stage of fermentation. Such a viscous fermentation broth separates the bacterial cells and fermentation medium residues and impurities from the polyglutamic acid, which has become a technical difficulty in purifying polyglutamic acid. The commonly used polyglutamic acid purification technology on the market generally uses hydrochloric acid to adjust the pH of the fermentation filter to 3.0, which is about the isoelectric point of polyglutamic acid, so that the viscosity of polyglutamic acid is reduced, and then the bacteria are removed by microfiltration, and then polyglutamic acid is precipitated by 3-4 times the volume of ethanol, and finally the precipitate is washed with water to finally obtain the polyglutamic acid cost, but this technology requires the consumption of hydrochloric acid, and the operation of hydrochloric acid is dangerous. At the same time, a large amount of ethanol is required. If the process needs to be scaled up, a large container is required to store ethanol. At the same time, the ethanol after use needs to be distilled and regenerated again. Operating such a large amount of ethanol has a very large safety hazard. Although there is such a technology to purify PGA, the molecular weight of the most PGA finished product on the market is about 700,000, and there are few or no manufacturers of PGA with a larger molecular weight. This shows that modern technology has great difficulties in producing large molecular weight PGA, such as it is more difficult to reduce the viscosity of large molecular weight PGA, and it is difficult to microfilter and sterilize after viscosity reduction, which is easy to cause clogging of microfiltration membranes, etc., resulting in very few or no large molecular weight PGA finished products. As a biological moisturizing macromolecular material, if the molecular weight of PGA is restricted, then its functions will be greatly restricted, such as moisturizing function, film-forming function, application feeling, etc.

[0003] Therefore, it is of great practical significance to provide a method for purifying PGA with high content and large molecular weight. Summary of the invention

[0004] The purpose of the present invention is to provide a polyglutamic acid purification method, which solves the problems in the prior art that the polyglutamic acid purified solution has low polyglutamic acid content and molecular weight, and the polyglutamic acid purification method has complicated operation steps.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A polyglutamic acid purification method specifically comprises the following steps:

[0007] S1, dilution, heating, centrifugation, and reflux of polyglutamic acid-rich fermentation broth: add polyglutamic acid-rich fermentation broth to the dilution tank, add water to dilute, and heat to obtain diluted fermentation broth, start the tubular centrifuge for centrifugal sterilization, obtain the centrifuge and collect it in the buffer tank for stirring, and at the same time open the valve to introduce the centrifuge into the hollow fiber ultrafiltration column for ultrafiltration and concentration to obtain waste liquid and concentrated liquid, discharge the waste liquid, reflux the concentrated liquid into the buffer tank to mix with the centrifuge, and repeat the ultrafiltration and concentration process until the polyglutamic acid-rich fermentation broth in the dilution tank is completely centrifuged, and stop the tubular centrifuge;

[0008] S2. Ultrafiltrate concentration: Clean the dilution tank and tubular centrifuge, while maintaining the ultrafiltration concentration work of the buffer tank and hollow fiber ultrafiltration column. After the dilution tank and tubular centrifuge are cleaned, the concentrated liquid after ultrafiltration concentration is returned to the dilution tank, and the water adding and heating processes are repeated. Then, the concentrated liquid is circulated and centrifuged and ultrafiltered and concentrated through the tubular centrifuge and hollow fiber ultrafiltration column until the conductivity count value meets the standard. The concentrated liquid after the conductivity count value meets the standard is returned to the buffer tank. At the same time, the liquid in the dilution tank is also collected in the buffer tank after centrifugation and mixed with the concentrated liquid and then continues to be concentrated. Participate in ultrafiltration and concentration until all the liquid in the dilution tank has been centrifuged, then turn off the tubular centrifuge, focus on the ultrafiltration and concentration work in the buffer tank, read the conductivity count value and determine whether to measure the polyglutamic acid content of the concentrate. If not, inject water to dilute the concentrate. If it is determined, continue to determine whether the polyglutamic acid content meets the standard. If the polyglutamic acid content does not meet the standard, continue the ultrafiltration and concentration work. If the polyglutamic acid content meets the standard, stop the ultrafiltration and concentration work, release the concentrate, control the temperature and sterilize under high pressure, and complete the purification operation of polyglutamic acid to obtain a purified polyglutamic acid solution.

[0009] As a preferred technical solution of the present invention, the temperature increase in step S1 is to increase the temperature to 50.2-50.6°C.

[0010] As a preferred technical solution of the present invention, the speed of the tubular centrifuge in step S1 is 10000-10500 rpm.

[0011] As a preferred technical solution of the present invention, the standard value of the conductivity counting value in step S2 is ≤100μs / cm.

[0012] As a preferred technical solution of the present invention, step S2 of reading the conductivity count value and determining whether to determine the polyglutamic acid content of the concentrated solution is specifically as follows: reading the conductivity count value, when the values ​​in the 1# conductivity meter and the 2# conductivity meter are greater than 100 μs / cm, slightly opening the 22# valve to inject a small amount of water to dilute the concentrated solution to reduce the conductivity, and after the values ​​in the 2# conductivity meter and the 1# conductivity meter are both less than 100 μs / cm, determining the polyglutamic acid content of the concentrated solution in the cache tank.

[0013] As a preferred technical solution of the present invention, the standard value for judging whether the polyglutamic acid content meets the standard in step S2 is that the polyglutamic acid content is ≥20 g / L.

[0014] As a preferred technical solution of the present invention, the temperature of the temperature-controlled high-pressure sterilization in step S2 is 121° C. and the time is 30 minutes.

[0015] As a preferred technical solution of the present invention, the present invention also provides a cleaning operation of the device after the polyglutamic acid is purified, comprising the following steps:

[0016] Cleaning water is introduced from each valve to clean the dilution tank, liquid pump, tubular centrifuge, buffer tank and hollow fiber ultrafiltration column respectively, and the cleaning wastewater is discharged after the cleaning is completed.

[0017] Furthermore, the cleaning operation of the device more specifically includes the following steps:

[0018] After the cleaning water is introduced from the 6# valve to clean the dilution tank, the cleaning wastewater is discharged from the 2# valve to the waste liquid pipeline. After the 1# liquid pump and tubular centrifuge are cleaned, the wastewater is discharged from the 7# valve through the waste liquid pipeline. The cleaning water of the buffer tank is discharged into the buffer tank from the 22# valve and the 9# valve. After cleaning, the wastewater is discharged from the 12# valve through the waste liquid pipeline; after cleaning the 2# liquid pump and its pipeline, it is discharged from the 14# valve through the waste liquid pipeline; the hollow fiber ultrafiltration column is based on Figure 3 The membrane is cleaned inside and outside as shown in routes 1, 2, and 3. Specifically, route 1 introduces cleaning water from valve 18# to clean the outer surface of the membrane and then discharges it from valve 16# through the waste liquid pipeline. Route 2 is to directly flush pipeline 4#. Route 3 introduces cleaning water from valve 19# to clean the inner surface of the membrane of the hollow fiber ultrafiltration column and then discharges it from valves 15# and 14# through the waste liquid pipeline.

[0019] Beneficial effects of the present invention:

[0020] (1) The method of the present invention is simple to operate, and the obtained polyglutamic acid purified liquid has a high polyglutamic acid content and molecular weight, which makes it have the characteristics of good application feeling and strong efficacy. In cosmetics, only about 5% of the polyglutamic acid purified liquid purified by the purification method of the present invention needs to be added to make the polyglutamic acid content in skin care products reach a level of >1.0g / L, which greatly improves the application feeling and efficacy of cosmetics and has very good application prospects.

[0021] (2) The present invention dilutes the polyglutamic acid-rich fermentation broth with water and temperature synchronously and then centrifuges it. The centrifuge liquid after centrifugation is directly collected in a buffer tank and ultrafiltered and concentrated through a hollow fiber ultrafiltration column. In the ultrafiltrate concentration stage, the ultrafiltration and concentration work of the buffer tank and the hollow fiber ultrafiltration column is maintained while the dilution tank and the tubular centrifuge are cleaned, making full use of the time difference between the equipment and improving the efficiency of the entire process. In addition, the multiple devices in the system work closely together to form a closed-loop high-efficiency concentration cycle continuous operation. This cycle continuous operation can maximize the recovery of polyglutamic acid, reduce the loss of polyglutamic acid during the purification process, improve the yield of the product, and ensure that the polyglutamic acid can be fully concentrated to a level that meets the quality requirements;

[0022] In addition, the centrifugation process can effectively remove most of the bacteria and larger particle impurities in the fermentation broth, providing easier-to-handle materials for ultrafiltration concentration; and ultrafiltration concentration can further separate polyglutamic acid and small molecule impurities. This relay operation process synergistically improves the efficiency of the entire purification process, allowing polyglutamic acid to be quickly concentrated and purified. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a schematic diagram of a device for purifying polyglutamic acid according to the present invention;

[0025] Figure 2 This is a schematic diagram of the work of purifying polyglutamic acid in the present invention;

[0026] Figure 3 This is a schematic diagram of cleaning the device for purifying polyglutamic acid according to the present invention.

[0027] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0028] 1. Dilution tank; 2. Manhole; 3. 1# sight glass; 4. 1# stirring blade; 5. 1# valve; 6. Jacket; 7. Thermometer; 8. 2# valve; 9. 3# valve; 10. 4# valve; 11. 5# valve; 12. 1# motor; 13. 6# valve; 14. Production water pipeline; 15. Reflux pipeline; 16. 2# motor; 17. Tubular centrifuge; 18. 1# liquid pump; 19. Waste liquid pipeline; 20. 1# pipeline; 21. 7# valve; 22. 2# pipeline; 23. 8# valve; 24. 9# valve; 25. 3# pipeline; 26. 3# motor; 27. 10 # valve; 28, buffer tank; 29, 2# sight glass; 30, 2# stirring blade; 31, 1# conductivity meter; 32, 11# valve; 33, 12# valve; 34, 2# liquid pump; 35, 13# valve; 36, 14# valve; 37, 15# valve; 38, 16# valve; 39, 4# pipeline; 40, 17# valve; 41, hollow fiber ultrafiltration column; 42, 18# valve; 43, 19# valve; 44, 20# valve; 45, 5# pipeline; 46, 21# valve; 47, 22# valve; 48, 23# valve; 49, 2# conductivity meter; 50, 24# valve. DETAILED DESCRIPTION

[0029] 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.

[0030] Example 1

[0031] A polyglutamic acid purification method specifically comprises the following steps:

[0032] S1. Dilution, heating, centrifugation and reflux of polyglutamic acid-rich fermentation liquid: add polyglutamic acid-rich fermentation liquid to dilution tank 1 from 23# valve 48, introduce water into production water pipeline 14 and add water into dilution tank 1 through 6# valve 13 to dilute polyglutamic acid-rich fermentation liquid, start 1# stirring blade 4 to stir, so that polyglutamic acid-rich fermentation liquid in dilution tank 1 becomes thinner and viscosity decreases, introduce hot water into jacket 6 through 1# valve 5 to heat dilution tank 1, and read the temperature of polyglutamic acid-rich fermentation liquid in dilution tank 1 from thermometer 7, after polyglutamic acid-rich fermentation liquid is heated to 50.4°C, discharge hot water from 4# valve 10, and viscosity of polyglutamic acid-rich fermentation liquid in dilution tank 1 diluted by water further decreases under the action of temperature increase, to obtain To the diluted fermentation liquid, start the 1# liquid pump 18 and the tubular centrifuge 17, open the 3# valve 9, and allow the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10250rpm to remove the bacteria to obtain the centrifuge liquid, collect the centrifuge liquid in the buffer tank 28 through the 2# pipeline 22 and the 8# valve 23, start the 2# stirring blade 30 of the buffer tank 28 to stir the centrifuge liquid, and at the same time start the 2# liquid pump 34 to open the 11# valve 32, the 13# valve 35, the 15# valve 37, the 19# valve 43, and the 20# valve 44, so that the centrifuge liquid passes through the hollow fiber ultrafiltration column 41 for ultrafiltration and concentration, and the waste liquid generated by the ultrafiltration and concentration is discharged from the 18# valve 42 and the 16# valve 38, and discharged through the waste liquid pipeline 19, and the ultrafiltration The concentrated liquid obtained is refluxed to the buffer tank 28 through the 3# pipeline 25 to mix with the centrifuge, and the ultrafiltration concentration process is repeated until the polyglutamic acid-rich fermentation liquid in the dilution tank 1 is completely centrifuged, so that all the fermentation liquids are ensured to have been centrifuged and concentrated to the buffer tank 28 through ultrafiltration, and the tubular centrifuge 17 is stopped, and the 8# valve 23 is closed. The dilution tank 1 and the tubular centrifuge 17 are cleaned of any residual bacteria, and the ultrafiltration concentration work in the buffer tank 28 and the hollow fiber ultrafiltration column 41 is continued. Because the ultrafiltration concentration is being carried out all the time, the volume of the liquid in the system may gradually decrease, but the conductivity of the polyglutamic acid-rich fermentation liquid has not yet dropped to a value that meets the corresponding quality standard, and the polyglutamic acid-rich fermentation liquid is ultrafiltered. Concentration to a corresponding purity requires relatively more water. Therefore, the opening degree of valve 22# 47 can be determined according to the flow rate of waste liquid discharged from the waste liquid generated by ultrafiltration concentration, so that the flow rate of water added is less than or equal to the flow rate of waste liquid discharged from the waste liquid generated by ultrafiltration concentration. Therefore, it can be ensured that when cleaning the dilution tank 1 and the buffer tank 28, the polyglutamic acid-rich fermentation liquid will not be concentrated to a very high concentration, resulting in a large viscosity that affects the ultrafiltration speed. At the same time, the buffer tank 28 will not overflow due to the large amount of added production water. If the volume becomes smaller after ultrafiltration concentration, but the value in the 1# conductivity meter 31 does not drop below ≤100μs / cm, the 22# valve 47 can be slightly opened to dilute the concentrate, and ultrafiltration concentration can be continued;

[0033] S2, ultrafiltrate concentration: clean the dilution tank 1 and the tubular centrifuge 17, open the 5# valve 11 after cleaning, close the 9# valve 24, let the concentrate enter the dilution tank 1, open the 6# valve 13 to repeat the water adding and temperature raising process to dilute the concentrate to the scale of the first dilution level, and start the tubular centrifuge 17 again to centrifuge the bacteria that may remain in the concentrate. After the liquid level in the dilution tank 1 drops due to the volume of diluted fermentation liquid consumed by centrifugation, water can be continuously added for dilution; Figure 2 As shown by the arrow, the refluxed concentrated ultrafiltration liquid returns to the dilution tank 1 and mixes with the liquid in the tank, and enters the next dilution, heating, centrifugation and ultrafiltration concentration cycle until the value in the 1# conductivity meter 31 is ≤100μs / cm, close the 5# valve 11, open the valve 9#24, and allow the concentrated ultrafiltration liquid to return to the buffer tank 28. At the same time, the liquid in the dilution tank 1 is also collected in the buffer tank 28 after centrifugation and mixed with the concentrated liquid to continue to participate in ultrafiltration concentration. After all the liquid in the dilution tank 1 has been centrifuged, close the tubular centrifuge 17, focus on the ultrafiltration concentration work in the buffer tank 28, read the conductivity count value, and when the 1# conductivity meter 31 is ≤100μs / cm, close the 5# valve 11, open the valve 9#24, and allow the concentrated ultrafiltration liquid to return to the buffer tank 28. When the values ​​in the conductivity meter 31 and the 2# conductivity meter 49 are greater than 100 μs / cm, slightly open the 22# valve 47 to inject a small amount of water to dilute the concentrate to reduce the conductivity. After the values ​​in the 2# conductivity meter 49 and the 1# conductivity meter 31 are both less than 100 μs / cm, measure the polyglutamic acid content of the concentrate in the buffer tank 28. If the polyglutamic acid content does not meet the standard, continue the ultrafiltration concentration work. If the polyglutamic acid content meets the standard, stop the ultrafiltration concentration work, release the concentrate from the 24# valve 50, control the temperature at 121°C and sterilize under high pressure for 30 minutes to kill the remaining microorganisms, thus completing the purification operation of polyglutamic acid and obtaining a polyglutamic acid purified solution.

[0034] Example 2

[0035] A polyglutamic acid purification method specifically comprises the following steps:

[0036] S1, dilution, heating, centrifugation and reflux of polyglutamic acid-rich fermentation liquid: add polyglutamic acid-rich fermentation liquid to dilution tank 1 from 23# valve 48, introduce water into production water pipeline 14 and add water 3 times the volume of polyglutamic acid-rich fermentation liquid into dilution tank 1 through 6# valve 13 to dilute the polyglutamic acid-rich fermentation liquid, start 1# stirring blade 4 to stir, so that the polyglutamic acid-rich fermentation liquid in dilution tank 1 becomes thinner and the viscosity decreases, introduce high-temperature steam into jacket 6 through 1# valve 5 to heat dilution tank 1, and read the temperature of polyglutamic acid-rich fermentation liquid in dilution tank 1 from thermometer 7, and wait until the polyglutamic acid-rich fermentation liquid is heated to 50.After the temperature reaches 6°C, the high-temperature steam is discharged from the 4# valve 10. The viscosity of the polyglutamic acid-rich fermentation liquid diluted with water in the dilution tank 1 is further reduced under the effect of temperature increase to obtain the diluted fermentation liquid. The 1# liquid pump 18 and the tubular centrifuge 17 are started, and the 3# valve 9 is opened to allow the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10000rpm to remove the bacteria to obtain the centrifuge liquid. The centrifuge liquid is collected in the buffer tank 28 through the 2# pipeline 22 and the 8# valve 23, and the 2# stirring blade 30 of the buffer tank 28 is started to stir the centrifuge liquid. At the same time, the 2# liquid Pump 34 opens 11# valve 32, 13# valve 35, 15# valve 37, 19# valve 43, 20# valve 44, so that the centrifuge liquid passes through hollow fiber ultrafiltration column 41 for ultrafiltration concentration, and the waste liquid generated by ultrafiltration concentration is discharged from 18# valve 42 and 16# valve 38, and discharged through waste liquid pipeline 19, and the concentrated liquid obtained after ultrafiltration continues to flow back to buffer tank 28 through 3# pipeline 25 to mix with the centrifuge liquid, and the ultrafiltration concentration process is repeated until the polyglutamic acid-rich fermentation liquid in dilution tank 1 is completely centrifuged, so that all the fermentation liquid can be ensured to be centrifuged and concentrated to buffer tank 28 through ultrafiltration. In the embodiment of the present invention, the tubular centrifuge 17 is stopped, the 8# valve 23 is closed, and the possible residual bacteria are cleaned in the dilution tank 1 and the tubular centrifuge 17. Meanwhile, the ultrafiltration and concentration work in the buffer tank 28 and the hollow fiber ultrafiltration column 41 is continued. Because the ultrafiltration and concentration is being carried out all the time, the volume of the liquid in the system may gradually decrease, but the conductivity of the polyglutamic acid-rich fermentation broth has not dropped to a value that meets the corresponding quality standard, and the ultrafiltration and concentration of the polyglutamic acid-rich fermentation broth to the corresponding purity itself requires relatively more water consumption. Therefore, the flow rate of the waste liquid discharged from the waste liquid generated by the ultrafiltration and concentration can be used to determine the amount of waste liquid discharged. Open the 22# valve 47 to make the flow rate of the water added in less than or equal to the flow rate of the waste liquid discharged from the ultrafiltration concentration. Therefore, it can be ensured that when cleaning the dilution tank 1 and the buffer tank 28, the polyglutamic acid-rich fermentation liquid will not be concentrated to a very high viscosity, which will affect the ultrafiltration speed. At the same time, the buffer tank 28 will not overflow due to the large amount of added production water. If the volume becomes smaller after ultrafiltration concentration, but the value in the 1# conductivity meter 31 does not drop to ≤100μs / cm, the 22# valve 47 can be slightly opened to dilute the concentrate and continue ultrafiltration concentration;.

[0037] S2, ultrafiltrate concentration: clean the dilution tank 1 and the tubular centrifuge 17, open the 5# valve 11 after cleaning, close the 9# valve 24, let the concentrate enter the dilution tank 1, open the 6# valve 13 to repeat the water adding and temperature raising process to dilute the concentrate to the scale of the first dilution level, and start the tubular centrifuge 17 again to centrifuge the bacteria that may remain in the concentrate. After the liquid level in the dilution tank 1 drops due to the volume of diluted fermentation liquid consumed by centrifugation, water can be continuously added for dilution; Figure 2 As shown by the arrow, the refluxed concentrated ultrafiltration liquid returns to the dilution tank 1 and mixes with the liquid in the tank, and enters the next dilution, heating, centrifugation and ultrafiltration concentration cycle until the value in the 1# conductivity meter 31 is ≤100μs / cm, close the 5# valve 11, open the valve 9#24, and allow the concentrated ultrafiltration liquid to return to the buffer tank 28. At the same time, the liquid in the dilution tank 1 is also collected in the buffer tank 28 after centrifugation and mixed with the concentrated liquid to continue to participate in ultrafiltration concentration. After all the liquid in the dilution tank 1 has been centrifuged, close the tubular centrifuge 17, focus on the ultrafiltration concentration work in the buffer tank 28, read the conductivity count value, and when the 1# conductivity meter 31 and the 2# conductivity meter 31 are When the value in the conductivity meter 49 is greater than 100 μs / cm, the 22# valve 47 is slightly opened to inject a small amount of water to dilute the concentrate to reduce the conductivity. After the values ​​in the 2# conductivity meter 49 and the 1# conductivity meter 31 are both less than 100 μs / cm, the polyglutamic acid content of the concentrate in the buffer tank 28 is determined to be up to standard. The standard value is that the polyglutamic acid content is ≥20 g / L. If the polyglutamic acid content does not meet the standard, the ultrafiltration concentration work is continued. If the polyglutamic acid content meets the standard, the ultrafiltration concentration work is stopped, and the concentrate is discharged from the 24# valve 50. The temperature is controlled at 121° C. and autoclaved for 30 minutes to kill the remaining microorganisms. The purification operation of polyglutamic acid is completed to obtain a polyglutamic acid purified solution.

[0038] S3, device cleaning: Figure 3 As shown by the arrow, after the cleaning water is introduced from the 6# valve 13 to clean the dilution tank 1, the cleaning wastewater is discharged from the 2# valve 8 to the waste liquid pipeline 19, and the wastewater after cleaning of the 1# liquid pump 18 and the tubular centrifuge 17 is discharged from the 7# valve 21 through the waste liquid pipeline 19, and the cleaning water of the buffer tank 28 is discharged into the buffer tank 28 from the 22# valve 47 and the 9# valve 24, and the cleaned wastewater is discharged from the 12# valve 33 through the waste liquid pipeline 19; the 2# liquid pump 34 and its pipeline are cleaned and discharged from the 14# valve 36 through the waste liquid pipeline 19; the hollow fiber ultrafiltration column 41 is discharged from the 14# valve 36 through the waste liquid pipeline 19 according to the hollow fiber ultrafiltration column 41. Figure 3 As shown in routes 1, 2, and 3, cleaning is performed inside and outside the membrane. Specifically, route 1 introduces cleaning water from 18# valve 42, cleans the outer surface of the membrane, and then discharges it from 16# valve 38 through waste liquid pipeline 19. Route 2 directly flushes 4# pipeline 39. Route 3 introduces cleaning water from 19# valve 43 to clean the inner surface of the membrane of the hollow fiber ultrafiltration column 41, and then discharges it from 15# valve 37 and 14# valve 36 through waste liquid pipeline 19.

[0039] After testing, the polyglutamic acid-rich fermentation liquid added to the dilution tank 1 from the 23# valve 48 in step S1 of this embodiment has a viscosity of 373.8cp and a mass of 100.35kg. At this time, the polyglutamic acid content in the polyglutamic acid-rich fermentation liquid is 15.39g / L, and the molecular weight is 320,000 Da; the viscosity of the fermentation liquid after dilution in step S1 is 0.0cp (Note: the actual viscosity generally cannot reach 0.0cp, but will only approach 0.0cp, but because it is measured by the equipment, when it approaches 0.0cp, the equipment will measure it as 0.0cp); the polyglutamic acid purified liquid obtained in step S2 has a mass of 58.75kg, the polyglutamic acid content in the polyglutamic acid purified liquid is 24.32g / L, and the molecular weight is 2.5 million Da.

[0040] Example 3

[0041] Compared with Example 2, the only difference is that in Example 3, the "after the temperature of the polyglutamic acid-rich fermentation liquid is raised to 50.6°C" in step S1 of Example 2 is replaced by "after the temperature of the polyglutamic acid-rich fermentation liquid is raised to 50.2°C" and the "allowing the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10000 rpm to remove the bacteria" in step S1 is replaced by "allowing the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10250 rpm to remove the bacteria", and the other operating steps and parameters remain unchanged.

[0042] After testing, the polyglutamic acid-rich fermentation liquid added to the dilution tank 1 from the 23# valve 48 in step S1 of this embodiment has a viscosity of 811.25cp and a mass of 100.48kg. At this time, the polyglutamic acid content in the polyglutamic acid-rich fermentation liquid is 15.67g / L, and the molecular weight is 300,000 Da; the viscosity of the fermentation liquid after dilution in step S1 is 0.0cp (Note: the actual viscosity generally cannot reach 0.0cp, but will only approach 0.0cp, but because it is measured by the equipment, when it approaches 0.0cp, the equipment will measure it as 0.0cp); the polyglutamic acid purified liquid obtained in step S2 has a mass of 98.87kg, a polyglutamic acid content of 23.78g / L, and a molecular weight of 2.4 million Da.

[0043] Example 4

[0044] Compared with Example 2, the only difference is that in Example 4, the "after the temperature of the polyglutamic acid-rich fermentation liquid is raised to 50.6°C" in step S1 of Example 2 is replaced by "after the temperature of the polyglutamic acid-rich fermentation liquid is raised to 50.4°C", the "allowing the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10000 rpm to remove the bacteria" in step S1 is replaced by "allowing the diluted fermentation liquid to be pumped by the 1# liquid pump 18 through the tubular centrifuge 17 at a speed of 10500 rpm to remove the bacteria", and "high-temperature steam" is replaced by "hot water", and the other operating steps and parameters remain unchanged.

[0045] After testing, the polyglutamic acid-rich fermentation liquid added to the dilution tank 1 from the 23# valve 48 in step S1 of this embodiment has a viscosity of 648.34cp and a mass of 100.62kg. At this time, the polyglutamic acid content in the polyglutamic acid-rich fermentation liquid is 15.35g / L, and the molecular weight is 310,000 Da; the viscosity of the fermentation liquid after dilution in step S1 is 0.0cp (Note: the actual viscosity generally cannot reach 0.0cp, but will only approach 0.0cp, but because it is measured by the equipment, when it approaches 0.0cp, the equipment will measure it as 0.0cp); the polyglutamic acid purified liquid obtained in step S2 has a mass of 79.84kg, a polyglutamic acid content of 23.67g / L, and a molecular weight of 2.43 million Da.

[0046] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0047] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for purifying polyglutamic acid, characterized in that: The specific steps include: S1, dilution, heating, centrifugation, and reflux of polyglutamic acid-rich fermentation broth: add polyglutamic acid-rich fermentation broth to the dilution tank, add water to dilute, and heat to obtain diluted fermentation broth, start the tubular centrifuge for centrifugal sterilization, obtain the centrifuge and collect it in the buffer tank for stirring, and at the same time open the valve to introduce the centrifuge into the hollow fiber ultrafiltration column for ultrafiltration and concentration to obtain waste liquid and concentrated liquid, discharge the waste liquid, reflux the concentrated liquid into the buffer tank to mix with the centrifuge, and repeat the ultrafiltration and concentration process until the polyglutamic acid-rich fermentation broth in the dilution tank is completely centrifuged, and stop the tubular centrifuge; S2. Ultrafiltrate concentration: Clean the dilution tank and tubular centrifuge, while maintaining the ultrafiltration concentration work of the buffer tank and hollow fiber ultrafiltration column. After the dilution tank and tubular centrifuge are cleaned, the concentrated liquid after ultrafiltration concentration is returned to the dilution tank, and the water adding and heating processes are repeated. Then, the concentrated liquid is circulated and centrifuged and ultrafiltered and concentrated through the tubular centrifuge and hollow fiber ultrafiltration column until the conductivity count value meets the standard. The concentrated liquid after the conductivity count value meets the standard is returned to the buffer tank. At the same time, the liquid in the dilution tank is also collected in the buffer tank after centrifugation and mixed with the concentrated liquid and then continues to be concentrated. Participate in ultrafiltration and concentration until all the liquid in the dilution tank has been centrifuged, then turn off the tubular centrifuge, focus on the ultrafiltration and concentration work in the buffer tank, read the conductivity count value and determine whether to measure the polyglutamic acid content of the concentrate. If not, inject water to dilute the concentrate. If it is determined, continue to determine whether the polyglutamic acid content meets the standard. If the polyglutamic acid content does not meet the standard, continue the ultrafiltration and concentration work. If the polyglutamic acid content meets the standard, stop the ultrafiltration and concentration work, release the concentrate, control the temperature and sterilize under high pressure, and complete the purification operation of polyglutamic acid to obtain a purified polyglutamic acid solution.

2. The polyglutamic acid purification method according to claim 1, characterized in that The temperature increase in step S1 is to increase the temperature to 50.2-50.6°C.

3. The polyglutamic acid purification method according to claim 1, characterized in that The speed of the tubular centrifuge in step S1 is 10000-10500 rpm.

4. The polyglutamic acid purification method according to claim 1, characterized in that: The conductivity counting value in step S2 meets the standard and the standard value is ≤100 μs / cm.

5. The polyglutamic acid purification method according to claim 1, characterized in that: Step S2 is to read the conductivity count value and determine whether to measure the polyglutamic acid content of the concentrated solution, specifically: read the conductivity count value, when the values ​​in the 1# conductivity meter and the 2# conductivity meter are greater than 100μs / cm, slightly open the 22# valve to inject a small amount of water to dilute the concentrated solution to reduce the conductivity, and after the values ​​in the 2# conductivity meter and the 1# conductivity meter are both less than 100μs / cm, measure the polyglutamic acid content of the concentrated solution in the cache tank.

6. The polyglutamic acid purification method according to claim 1, characterized in that: The standard value for judging whether the polyglutamic acid content meets the standard in step S2 is that the polyglutamic acid content is ≥ 20 g / L.

7. The polyglutamic acid purification method according to claim 1, characterized in that: The temperature of the temperature-controlled high-pressure sterilization in step S2 is 121° C. and the time is 30 minutes.

8. The polyglutamic acid purification method according to claim 1, characterized in that: After the polyglutamic acid is purified, the device is also cleaned, including the following steps: washing water is introduced from each valve to respectively wash the dilution tank, liquid pump, tubular centrifuge, buffer tank and hollow fiber ultrafiltration column, and the washing wastewater is discharged after the washing is completed.

9. The polyglutamic acid purification method according to claim 8, characterized in that: The cleaning operation of the device more specifically includes the following steps: After the cleaning water is introduced from the 6# valve to clean the dilution tank, the cleaning wastewater is discharged from the 2# valve to the waste liquid pipeline. After the 1# liquid pump and tubular centrifuge are cleaned, the wastewater is discharged from the 7# valve through the waste liquid pipeline. The cleaning water of the buffer tank is discharged into the buffer tank from the 22# valve and the 9# valve, and the cleaning wastewater is discharged from the 12# valve through the waste liquid pipeline; after the 2# liquid pump and its pipeline are cleaned, they are discharged from the 14# valve through the waste liquid pipeline; the hollow fiber ultrafiltration column is cleaned inside and outside the membrane. Specifically, route 1 introduces cleaning water from the 18# valve, cleans the outer surface of the membrane, and then discharges it from the 16# valve through the waste liquid pipeline. Route 2 is for directly flushing the 4# pipeline; route 3 introduces cleaning water from the 19# valve to clean the inner surface of the membrane of the hollow fiber ultrafiltration column, and then discharges it from the 15# valve and the 14# valve through the waste liquid pipeline.

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