LU500313B1 - Process for clean extraction of l-aspartic acid - Google Patents

Abstract

The disclosure relates a process for clean extraction of L-aspartic acid. In the process for clean extraction of L-aspartic acid, an Escherichia coli culture solution producing aspartase and fumaric acid-containing substrate solution are used as raw materials and converted into L-aspartic acid by ammonification to obtain a conversion solution. The process for clean extraction of L-aspartic acid is characterized in that subsequent to decoloration of the conversion solution via activated carbon, L-aspartic acid is crystallized and extracted by using a method of adjusting pH with fumaric acid; a mother solution is recovered, and supplemented with fumaric acid to be prepared into a substrate solution again for second enzyme reaction, as such, the above steps are repeated and cycled for 5 times; after the sixth decolorization of conversion solution, L-aspartic acid is crystallized and precipitated by adjusting pH to an isoelectric point of L-aspartic acid with sulfuric acid after heating.

Description

DESCRIPTION PROCESS FOR CLEAN EXTRACTION OF L-ASPARTIC ACID TECHNICAL FIELD

[0001] The disclosure relates to the technical field of amino acid production, and particularly to a process for clean extraction of L-aspartic acid.

BACKGROUND

[0002] L-aspartic acid (L-Asp) is an important acidic amino acid, and is widely applied to food, medicines, chemical industry and other fields. In the aspect of food industry, L-aspartic acid is a nutritional supplement for many kinds of food, and is also used to synthesize aspartame; in the aspect of medicines, it can be used as a liver function promoter, an ammonia antidote, a fatigue recovery agent and the like, and is also a main raw material for synthesis of L-alanine and a variety of medical intermediates; in the aspect of chemical industry, it can be used to synthesize high polymer material polyaspartic acid.

[0003] At present, L-aspartic acid is obtained by catalyzing addition reaction of fumaric acid and ammonia utilizing L-aspartase. The process mainly adopts a free cell method which has the advantages of high enzyme activity, simple process and less equipment investment. In this process, extraction of L-aspartic acid is performed by adjusting a enzyme conversion solution with pH of about 8.5 to its isoelectric point of 2.8 with sulfuric acid, crystallizing, precipitating, filtering and drying to obtain a finished product. According to statistics, production of 1t of L-aspartic acid needs to consume 0.7t of concentrated sulfuric acid so as to produce 6-7 m° acid wastewater in which about 500 kg of ammonium sulfate is also contained. In general, acidic wastewater is discharged after industrially adopting neutralization and biochemical treatment. Some enterprises also use a single effect evaporation concentration method to recover high-concentration ammonium sulfate in wastewater, which has long process, high steam energy consumption and low yield, and reduces the economic benefits of enterprises to a certain extent. In addition, it is reported that L-aspartic acid is extracted by adding fumaric acid into enzyme conversion solution. The crystal obtained by this method has high purity and low extraction rate. Therefore, a process for clean extraction of L-aspartic acid is obtained through study on extraction conditions of L-aspartic acid.

SUMMARY

[0004] In order to make up for the deficiency of the prior art, the disclosure provides a process for clean extraction of L-aspartic acid, which has good crystallization quality, high product yield and clean environmental protection.

[0005] The disclosure is realized by the following technical solution:

[0006] Provide is a process for clean extraction of L-aspartic acid, an Escherichia coli culture solution producing aspartase and a fumaric acid-containing substrate solution being used as raw materials and being converted into L-aspartic acid by ammonification to obtain a conversion solution, wherein subsequent to decoloration of the conversion solution via activated carbon, L-aspartic acid is crystallized and extracted by using a method of adjusting pH with fumaric acid, filtered at reduced pressure and dried to obtain L-aspartic acid crystals; a mother solution is recovered, and supplemented with fumaric acid to be prepared into a substrate solution again for second enzyme reaction, as such, the above steps are repeated and cycled for 5 times; after the sixth decolorization of conversion solution, the conversion solution is heated to 80-95, and L-aspartic acid is crystallized and precipitated by adjusting pH to an isoelectric point of L-aspartic acid with sulfuric acid; and finally, a byproduct is recovered by using a triple effect evaporation process, crystallized and dried to obtain ammonium sulfate crystals.

[0007] According to the disclosure, a method for adjusting pH with fumaric acid and sulfuric acid is used to extract L-aspartic acid, which reduces discharge of wastewater, relives pollution on environment and improves product crystallization quality and product yield. By using this method, extraction rate reaches 75% or more, the purity reaches 90% or more, light transmittance reaches 98% or more, and specific rotation [a]” is between +24.5° and +25.5°; in addition, the three effect evaporation crystallization process is used to recover ammonium sulfate from wastewater and has obvious energy saving and emission reduction effect, with a recovery rate of 96% or more, water content of 1% or less and steam consumption of 2.5t or less per t product.

[0008] The above process for clean extraction specifically comprises the following steps:

[0009] (1) inoculating activated Escherichia coli thalli into a shake flask for culture to obtain a primary seed solution, and converting the primary seed solution into a fermentation medium for culture to obtain a secondary culture solution;

[0010] (2) mixing and evenly shaking the secondary culture solution with the substrate solution for conversion reaction to obtain a converted solution;

[0011] (3) heating the converted solution and then adding activated carbon for decoloration, and filtering to collect filtrate;

[0012] (4) heating the filtrate and then adding fumaric acid, rapidly stirring and dissolving, continuing to slowly stir under the state of heat preservation so that a large amount of L-aspartic acid crystals are precipitated out, then slowing cooling, continuing to stir, precipitating, filtering and drying to obtain L-aspartic acid crystals;

[0013] (5) recovering the filtered mother solution and supplementing with fumaric acid to be prepared again into a substrate solution for second enzyme reaction, as such repeating and cycling the above steps for 5 times, after the sixth decolorization of conversion solution, heating the conversion solution to 80-95°C, stirring and dropwise adding sulfuric acid until the pH of solution is 2.8, cooling to room temperature, filtering to extract crystals, and drying to obtain L-aspartic acid crystals; and

[0014] (6) treating the filtered solution with a triple effect fair current forced circulation heating pump evaporation process, crystallizing and drying to obtain ammonium sulfate.

[0015] Preferably, in step (1), a ring of activated slant thalli are inoculated into a shake flask (500mL, the amount of solution in the shake flask is SOML) and cultured for 8 h under 200 rpm at 35-37 °C to obtain a primary seed solution; the primary seed solution is transferred to a fermentation medium according to an inoculation amount of 1% by volume, and cultured for 10 h under 200 rpm to obtain a secondary culture solution.

[0016] Preferably, in step (1), the slant medium comprises the following components: 3 g/L of corn pulp dry powder, 3 g/L of yeast powder, 1 g/L of peptone, 5 g/L of sodium chloride, 0.05 g/L. of manganese sulfate, 20 g/L of agar, pH 7.0-7.2; the fermentation medium comprises the following components: 10 g/L of fumaric acid, 8 g/L of corn pulp dry powder, 2 g/L of yeast powder, 7 g/L. of peptone, 5 g/L. of sodium chloride, 1 g/L. of potassium dihydrogen phosphate,

0.2 g/L of magnesium sulfate, pH 6.0.

[0017] Preferably, in step (2), the secondary culture solution and the substrate solution are mixed and evenly shaken in a volume ratio of 1:7 and then subjected to conversion reaction at 45°C, and the reaction is ended when the mass concentration of fumaric acid in the substrate solution is reduced to less than 0.2%; wherein, the substrate solution comprises the following components: 200 g/L of fumaric acid, 0.2 g/L of magnesium sulfate, pH 9.0.

[0018] Preferably, in step (3), the conversion solution is heated to 50-70°C, and then decolored for 1-2 h by adding activated carbon with a mass fraction of 0.1-0.3%; the filtrate is collected by filtration, the light transmittance reaches 95% or more.

[0019] Preferably, in step (4), the filtrate is heated to 70-90°C and added with fumaric acid to be rapidly stirred and dissolved, followed by precipitating out L-aspartic acid crystals; the above solution 1s continued to be slowly stirred for 30 min under the state of heat preservation so that a large amount of L-aspartic acid crystals are precipitated out; the solution is slowly cooed to 25-50 °C when continued to be stirred for 30 min so that precipitation of L-aspartic acid crystals is completed, and the precipitated L-aspartic acid crystals are filtered and dried for 2-3 h to obtain L-aspartic acid crystals, with the extraction rate being 65% or more.

[0020] Preferably, the mother solution in step (4) still contains a large amount of L-aspartic acid which is not crystallized and precipitated out, so the mother solution is recovered and supplemented with fumaric acid to be prepared into a substrate solution again for second enzyme reaction, as such, the above steps are repeated and cycled for 5 times;

[0021] in step (5), after the sixth decolorization of the conversion solution, the decolored conversion solution is heated to 90°C, sulfuric acid is dropwise added at the rate of 10-30MI/h under the condition of stirring until the pH of the solution is 2.8; the solution is cooled to room temperature 5-25 min, filtered to extract crystals, the crystals are dried for 2-3h to obtain L-aspartic acid crystals; extraction rate reaches 75% or more, and the purity reaches 90% or more.

[0022] Analysis on L-aspartic acid product: light transmittance reaches 98% or more, and specific rotation [a]? is between +24.5° and +25.5°.

[0023] The determination of the above light transmittance: spectrophotometry, pure water is used as reference, c = 8g/mL, the optical range is 10 mm, and the wavelength is 640nm.

[0024] The determination of the above fumaric acid content: UV visible spectrophotometry and its absorbance was determined at 240nm.

[0025] The extraction rate of the above L-aspartic acid (%) = dry mass of crystal (mass of fumaric acid in substrate solution x relative molecular weight of aspartic acid x conversion rate) x 100%.

[0026] The determination of the purity of the above L-aspartic acid: U3000 high performance liquid chromatography, SinoChrom ODS BP C18 5 um ® 4.6 mm x 250 mm analysis column; mobile phase: 0.03mol/L KH2PO4-H3PO4 buffer (pH2.5); detection of wavelength: 210 nm; flow rate: 0.8 mL/min; sample injection volume: 20 pL.

[0027] The determination of the above optical rotation: JASCO p-1020 polarimeter, c =

0.08g/mL, 6mol/L HCI.

[0028] Preferably, in step (6), the filtered solution is fed to a heating chamber of a primary effect evaporator to be evaporated at the temperature of 109°C under the pressure of 20 KPa (gage pressure); the heat source of the heating chamber of the first effect evaporator adopts

1.0MPa saturated steam for heating, the generated secondary steam is indirectly condensed via a condenser, the condensed water is used for second-level heating of raw materials, and uncondensed gas is directly discharged to the outside;

[0029] the obtained solution is subjected to gas-liquid separation in a separation chamber of the primary effect evaporator, wherein a liquid phase enters into the heating chamber of the secondary effect evaporator under the action of pressure difference, and a gas phase is used as a heat source of the heating chamber of the secondary effect evaporator, with a temperature of 93°C and a pressure of 40 KPa (vacuum degree); the condensed water from the heating chamber of the secondary effect evaporator enters into the triple effect evaporator through a pipeline to enter into a condensed water pipe together with the condensed water from the triple effect heating chamber and be discharged out by a condensed water pump;

[0030] the obtained solution is subjected to gas-liquid separation of the secondary effect evaporator, wherein the liquid phase enters into the heating chamber of the triple effect evaporator under the action of pressure difference to be further evaporated and concentrated, and the gas phase is used as a heat source of the heating chamber of the triple effect evaporator, with a temperature of 66.5°C and a pressure of 80 KPa (vacuum degree); the resulting solution is continued to be concentrated until the solid content reaches 25% and then discharged.

[0031] The concentrated solution in the three effect evaporator is fed into a hydrocyclone for thickening via a discharging pump, and a thickened ammonium sulfate solution with 45% solid content enters into a thickener for crystallization, wherein the crystallization temperature is 50-70°C, the pressure is an atmospheric pressure, and the solid content reaches 50% after crystallization is completed, and then the solid is spin-dried by a centrifuge and then enters into a mother solution pool, and then the solution returns back to the three effect evaporator via a submerged pump to be further evaporated,

[0032] When the content of oil in the system is high, the hydrocyclone is closed, the system directly returns back to a valve of a triple effect separation chamber, a valve of a layering device at the back of the hydrocyclone is turned on, ammonium sulfate solution enters into the layering device, the oil component on the upper part of the layering device 1s extracted via a pressure balancer, and the separated solution returns back to the triple effect separator;

[0033] the obtained ammonium sulfate crystals enter into a disc type dryer, and is heated indirectly by steam, wherein the drying temperature is 65-78°C, so that the ammonium sulfate product is obtained, water is extracted out from the top of the dryer through a fan, and tail gas is rinsed via a bath tower to be discharged into atmosphere.

[0034] The recovery rate of the ammonium sulfate product reaches 96% or more, water content is less than 1% and steam consumption is 2.5t/t or less.

[0035] The disclosure has the advantages of good crystallization quality, high product yield, clean and environmental protection, not only reduces the consumption of sulfuric acid, the generation amount of ammonium salt and the discharge amount of wastewater, but also solves the problem of low extraction rate of L-aspartic acid with fumaric acid alone while realizing the resource utilization of a byproduct (ammonium sulfate) and has significant economic and environmental benefits. The product meets the USP quality standard and is worthy of popularization and application.

DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solution of the disclosure will be described in detail in combination with specific examples so as to facilitate the understanding of the disclosure, but not limiting the disclosure.

[0037] Example 1: a process for clean extraction of L-aspartic acid

[0038] (1) Preparation of conversion culture solution

[0039] A ring of activated slant thualli were taken and inoculated into a 500 mL (50 mL loading solution amount) shake flask and cultured for 8 h under 200 rpm at 35-37 °C to obtain a primary seed solution; and the primary seed solution was transferred to a fermentation medium according to an inoculation amount of 1% (v/v) and cultured for 10 h under 200 rpm to obtain a secondary culture solution. Where, the components of the slant medium were as follows: 3 g/L. of corn pulp dry powder, 3 g/L. of yeast powder, 1 g/L. of peptone, 5 g/L of sodium chloride, 0.05 g/L of manganese sulfate, 20 g/L of agar, pH 7.0-7.2; the components of the fermentation medium were as follows: 10 g/L of fumaric acid, 8 g/L of corn pulp dry powder, 2 g/L of yeast powder, 7 g/L of peptone, 5 g/L of sodium chloride, 1 g/L of potassium dihydrogen phosphate, 0.2 g/L of magnesium sulfate, pH 6.0.

[0040] (2) Conversion reaction via enzymatic method

[0041] The E. coli culture solution and substrate solution were mixed in a volume ratio of 1:7 and evenly shaken, and subjected to conversion reaction at 45°C. When the mass concentration of fumaric acid in the substrate solution was decreased to 0.2% or less, the reaction was ended. Where, the components of the substrate solution were as follows: 200 g/L of fumaric acid, 0.2 g/L of magnesium sulfate, and pH 9.0.

[0042] (3) Decolorization and filtration

[0043] The conversion solution obtained in step (2) was heated to 55°C, decolorized for 1-2 h by adding 0.15% by mass activated carbon, and then filtered to collect the filtrate. The light transmittance reached 99.6%.

[0044] (4) Crystallization of fumaric acid

[0045] The filtrate was heated to 80 °C, and the amount of fumaric acid was 0.65 times of the initial amount of fumaric acid in the substrate solution. After rapid stirring and dissolution, L-aspartic acid crystals begun to precipitate out, the solution was continued to slowly stirred for min at this temperature so that a large number of L-aspartic acid crystals were precipitated out, and then slowly cooled to 40°C, and then continued to slowly stirred for 30 min at this temperature, so as to complete the precipitation of L-aspartic acid crystals, the precipitated L-aspartic acid crystals were filtered and dried for 2-3 h to obtain L-aspartic acid crystal with the extraction rate of 65.6% and the purity of 96.2%.

[0046] (5) Crystallization of sulfuric acid

[0047] The mother liquor in step (4) was recovered and supplemented with fumaric acid to be prepared into the substrate solution again for second enzyme reaction, as such the above steps were repeated and cycled for 5 times. After the sixth decoloration of conversion solution was ended, 600 mL of filtrate was heated to 87°C. Under the stirring condition, 60 mL of sulfuric acid was added at the dripping rate of 20 mL/h until the pH of the solution reached 2.8, and then the solution was cooled to room temperature for 14 min. The solution was filtered, crystallized and dried for 2-3h to obtain L-aspartic acid crystals, with an extraction rate being 76.1% and purity being 93.8%.

[0048] Analysis of the L-aspartic acid product obtained in this example: the light transmittance reaches 98%, and the specific rotation [a]? is + 24.8°.

[0049] (6) Recovery of byproducts from acidolysis of sulfuric acid

[0050] The ammonium sulfate solution produced in step (5) entered into the heating chamber of the primary effect evaporator to be evaporated and concentrated, and its temperature was controlled at 109 °C, and its pressure was 20 Kpa (gauge pressure). After vapor-liquid separation in the separation chamber of the primary effect evaporator, the liquid phase entered into the secondary effect evaporator to be further evaporated and concentrated; the gas phase was used as the heat source of the heating chamber of the secondary effect evaporator. The heat source of the primary effect heating chamber was heated by using 1.0 MPa saturated steam. The generated secondary steam was condensed by an indirect condenser. The condensed water was used for secondary preheating of raw materials, and the uncondensed gas was directly discharged to the outside.

[0051] Under the effect of pressure difference, the first effect concentrated solution entered into the heating chamber of the secondary effect evaporator to be further concentrated, the temperature was controlled at 93 °C and the pressure was 40 Kpa (vacuum degree). The above concentrated solution was subjected to gas-liquid separation in the secondary separation chamber, wherein the liquid phase entered into the triple effect evaporator to be further evaporated and concentrated, and the gas phase was used as the heat source of the heating chamber of the triple effect evaporator. The condensed water from the secondary effect heating chamber entered into the triple effect heating chamber through a pipeline and then entered into a condensed water tank together with the condensed water from the triple effect heating chamber, and was discharged out by a condensed water pump.

[0052] Under the effect of pressure difference, the secondary effect concentrated solution entered into the heating chamber of the triple effect evaporator, the temperature was controlled at 66.5°C and the pressure was 80 KPa (vacuum degree). The above concentrated solution continued to be concentrated until the solid content reached 25%, and then entered into the hydrocyclone via a discharging pump for thickening, a thickened ammonium sulfate solution with 45% solid content entered into a thickener for crystallization, wherein the crystallization temperature was 50-70°C, the pressure was an atmospheric pressure, and the solid content reached 50% after crystallization was completed, and then the solid was spin-dried by a centrifuge and then entered into a mother solution pool, and then the solution returned back to the three effect evaporator via a submerged pump to be further evaporated.

[0053] The obtained ammonium sulfate crystals entered into a disc type dryer, and was heated indirectly by steam, wherein the drying temperature was 75°C, the water was extracted from the top of the dryer through the fan and the tail gas was discharged into the atmosphere through the bath tower. The recovery rate of ammonium sulfate product was 96.5%, the water content was

0.5%, and the steam consumption in product per ton was 2.2t/t.

[0054] Example 2: a process for clean extraction of L-aspartic acid

[0055] (1) Preparation of conversion culture solution

[0056] A ring of activated slant thualli were taken and inoculated into a 500 mL (50 mL loading solution amount) shake flask and cultured for 8 h under 200 rpm at 35-37 °C to obtain a primary seed solution; and the primary seed solution was transferred to a fermentation medium according to an inoculation amount of 1% (v/v) and cultured for 10 h under 200 rpm to obtain a secondary culture solution. Where, the components of the slant medium were as follows: 3 g/L of corn pulp dry powder, 3 g/L of yeast powder, 1 g/L of peptone, 5 g/L of sodium chloride, 0.05 g/L of manganese sulfate, 20 g/L of agar, pH 7.0-7.2; the components of the fermentation medium were as follows: 10 g/L of fumaric acid, 8 g/L of corn pulp dry powder, 2 g/L of yeast powder, 7 g/L of peptone, 5 g/L of sodium chloride, 1 g/L of potassium dihydrogen phosphate, 0.2 g/L of magnesium sulfate, pH 6.0.

[0057] (2) Conversion reaction via enzymatic method

[0058] The E. coli culture solution and substrate solution were mixed in a volume ratio of 1:7 and evenly shaken, and subjected to conversion reaction at 45°C. When the mass concentration of fumaric acid in the substrate solution was decreased to 0.2% or less, the reaction was ended. Where, the components of the substrate solution were as follows: 200 g/L of fumaric acid, 0.2 g/L of magnesium sulfate, and pH 9.0.

[0059] (3) Decolorization and filtration

[0060] The conversion solution obtained in step (2) was heated to 50°C, decolorized for 1-2 h by adding 0.2% by mass activated carbon, and then filtered to collect the filtrate. The light transmittance reached 99%.

[0061] (4) Crystallization of fumaric acid

[0062] The filtrate was heated to 90 °C, and the amount of fumaric acid was 0.65 times of the initial amount of fumaric acid in the substrate solution. After rapid stirring and dissolution, L-aspartic acid crystals begun to precipitate out, the solution was continued to slowly stirred for min at this temperature so that a large number of L-aspartic acid crystals were precipitated out, and then slowly cooled to 37°C, and then continued to slowly stirred for 30 min at this temperature, so as to complete the precipitation of L-aspartic acid crystals, the precipitated L-aspartic acid crystals were filtered and dried for 2-3 h to obtain L-aspartic acid crystal with the extraction rate of 71.6% and the purity of 99.0%.

[0063] (5) Crystallization of sulfuric acid

[0064] The mother liquor in step (4) was recovered and supplemented with fumaric acid to be prepared into the substrate solution again for second enzyme reaction, as such the above steps were repeated and cycled for 5 times. After the sixth decoloration of conversion solution was ended, 600 mL of filtrate was heated to 91°C. Under the stirring condition, 60 mL of sulfuric acid was added at the dripping rate of 23 mL/h until the pH of the solution reached 2.8, and then the solution was cooled to room temperature for 12 min. The solution was filtered, crystallized and dried for 2-3h to obtain L-aspartic acid crystals, with an extraction rate being 78.4% and purity being 98.2%.

[0065] Analysis of the L-aspartic acid product obtained in this example: the light transmittance reaches 98.9%, and the specific rotation [a]? is + 25.2°.

[0066] (6) Recovery of byproducts from acidolysis of sulfuric acid

[0067] The ammonium sulfate solution produced in step (5) entered into the heating chamber of the primary effect evaporator to be evaporated and concentrated, and its temperature was controlled at 109 °C, and its pressure was 20 Kpa (gauge pressure). After vapor-liquid separation in the separation chamber of the primary effect evaporator, the liquid phase entered into the secondary effect evaporator to be further evaporated and concentrated; the gas phase was used as the heat source of the heating chamber of the secondary effect evaporator. The heat source of the primary effect heating chamber was heated by using 1.0 MPa saturated steam. The generated secondary steam was condensed by an indirect condenser. The condensed water was used for secondary preheating of raw materials, and the uncondensed gas was directly discharged to the outside.

[0068] Under the effect of pressure difference, the first effect concentrated solution entered into the heating chamber of the secondary effect evaporator to be further concentrated, the temperature was controlled at 93 °C and the pressure was 40 Kpa (vacuum degree). The above concentrated solution was subjected to gas-liquid separation in the secondary separation chamber, wherein the liquid phase entered into the triple effect evaporator to be further evaporated and concentrated, and the gas phase was used as the heat source of the heating chamber of the triple effect evaporator. The condensed water from the secondary effect heating chamber entered into the triple effect heating chamber through a pipeline and then entered into a condensed water tank together with the condensed water from the triple effect heating chamber, and was discharged out by a condensed water pump.

[0069] Under the effect of pressure difference, the secondary effect concentrated solution entered into the heating chamber of the triple effect evaporator, the temperature was controlled at 66.5°C and the pressure was 80 KPa (vacuum degree). The above concentrated solution continued to be concentrated until the solid content reached 25%, and then entered into the hydrocyclone via a discharging pump for thickening, a thickened ammonium sulfate solution with 45% solid content entered into a thickener for crystallization, wherein the crystallization temperature was 55 °C, the pressure was an atmospheric pressure, and the solid content reached 50% after crystallization was completed, and then the solid was spin-dried by a centrifuge and then entered into a mother solution pool, and then the solution returned back to the three effect evaporator via a submerged pump to be further evaporated.

[0070] The obtained ammonium sulfate crystals entered into a disc type dryer, and was heated indirectly by steam, wherein the drying temperature was 70°C, the water was extracted from the top of the dryer through the fan and the tail gas was discharged into the atmosphere through the bath tower. The recovery rate of ammonium sulfate product was 97.2%, the water content was

0.4%, and the steam consumption in product per ton was 1.8t/t.

[0071] In the above examples, the preferred embodiments of the disclosure are described. Obviously, many changes can still be made under the inventive concept of the disclosure. Here, it should be explained that any changes made under the inventive concept of the disclosure will fall into the protective scope of the disclosure.

Claims (10)

Claims

1. À process for clean extraction of L-aspartic acid, an Escherichia coli culture solution producing aspartase and a fumaric acid-containing substrate solution being used as raw materials and being converted into L-aspartic acid by ammonification to obtain a conversion solution, wherein subsequent to decoloration of the conversion solution via activated carbon, L-aspartic acid is crystallized and extracted by using a method of adjusting pH with fumaric acid, filtered at reduced pressure and dried to obtain L-aspartic acid crystals; a mother solution is recovered, and supplemented with fumaric acid to be prepared into a substrate solution again for second enzyme reaction, as such, the above steps are repeated and cycled for 5 times; after the sixth decolorization of conversion solution, the conversion solution is heated to 80-95, and L-aspartic acid is crystallized and precipitated by adjusting pH to an isoelectric point of L-aspartic acid with sulfuric acid; and finally, a byproduct is recovered by using a triple effect evaporation process, crystallized and dried to obtain ammonium sulfate crystals.

2. The process for clean extraction of L-aspartic acid according to claim 1, specifically comprising the following steps: (1) inoculating activated Escherichia coli thalli into a shake flask for culture to obtain a primary seed solution, and converting the primary seed solution into a fermentation medium for culture to obtain a secondary culture solution; (2) mixing and evenly shaking the secondary culture solution with the substrate solution for conversion reaction to obtain a converted solution; (3) heating the converted solution and then adding activated carbon for decoloration, and filtering to collect filtrate; (4) heating the filtrate and then adding fumaric acid, rapidly stirring and dissolving, continuing to slowly stir under the state of heat preservation so that a large amount of L-aspartic acid crystals are precipitated out, then slowing cooling, continuing to stir, precipitating, filtering and drying to obtain L-aspartic acid crystals; (5) recovering the filtered mother solution and supplementing with fumaric acid to be prepared again into a substrate solution for second enzyme reaction, as such repeating and cycling the above steps for 5 times, after the sixth decolorization of conversion solution, heating the conversion solution to 80-95°C, stirring, dropwise adding sulfuric acid until the pH of solution is 2.8, cooling to room temperature, filtering to extract crystals, and drying to obtain L-aspartic acid crystals; and (6) treating the filtered solution with a triple effect fair current forced circulation heating pump evaporation process, crystallizing and drying to obtain ammonium sulfate.

3. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (1), a ring of activated slant thalli are inoculated into a shake flask and cultured for 8 h under 200 rpm at 35-37°C to obtain a primary seed solution; the primary seed solution is transferred to a fermentation medium according to an inoculation amount of 1% by volume, and cultured for 10 h under 200 rpm to obtain a secondary culture solution.

4. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (1), the slant medium comprises the following components: 3 g/L of corn pulp dry powder, 3 g/L of yeast powder, 1 g/L of peptone, 5 g/L of sodium chloride, 0.05 g/L of manganese sulfate, 20 g/L of agar, pH 7.0-7.2; the fermentation medium comprises the following components: 10 g/L of fumaric acid, 8 g/L of corn pulp dry powder, 2 g/L of yeast powder, 7 g/L of peptone, 5 g/L. of sodium chloride, 1 g/L of potassium dihydrogen phosphate, 0.2 g/L of magnesium sulfate, pH 6.0.

5. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (2), the secondary culture solution and the substrate solution are mixed and evenly shaken in a volume ratio of 1:7 and then subjected to conversion reaction at 45°C, and the reaction is ended when the mass concentration of fumaric acid in the substrate solution is reduced to less than 0.2%; wherein, the substrate solution comprises the following components: 200 g/L. of fumaric acid, 0.2 g/L. of magnesium sulfate, pH 9.0.

6. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (3), the conversion solution is heated to 50-70°C, and then decolored for 1-2 h by adding activated carbon with a mass fraction of 0.1-0.3%.

7. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (4), the filtrate is heated to 70-90°C and added with fumaric acid to be rapidly stirred and dissolved, followed by precipitating out L-aspartic acid crystals; the above solution is continued to be slowly stirred for 30 min under the state of heat preservation so that a large amount of L-aspartic acid crystals are precipitated out; the solution is slowly cooed to 25-50°C when continued to be stirred for 30 min so that precipitation of L-aspartic acid crystals is completed, and the precipitated L-aspartic acid crystals are filtered and dried for 2-3h to obtain L-aspartic acid crystals.

8. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (5), after the sixth decolorization of the conversion solution, the decolored conversion solution is heated to 90°C, sulfuric acid is dropwise added at the rate of 10-30 mL/h under the condition of stirring until the pH of the solution is 2.8; the solution is cooled to room temperature 5-25 min and filtered to extract crystals, the crystals are dried for 2-3 h to obtain L-aspartic acid crystals.

9. The process for clean extraction of L-aspartic acid according to claim 2, wherein in step (6), the filtered solution is fed to a heating chamber of a primary effect evaporator to be evaporated at the temperature of 109°C under the pressure of 20 KPa; the obtained solution is subjected to gas-liquid separation in a separation chamber of the primary effect evaporator, wherein a liquid phase enters into the heating chamber of the secondary effect evaporator, and a gas phase is used as a heat source of the heating chamber of the secondary effect evaporator, with a temperature of 93°C and a pressure of 40 KPa; the obtained solution is subjected to gas-liquid separation of the secondary effect evaporator, wherein the liquid phase enters into the heating chamber of the triple effect evaporator to be further evaporated and concentrated, and the gas phase is used as a heat source of the heating chamber of the triple effect evaporator, with a temperature of 66.5°C and a pressure of 80 KPa; the resulting solution is continued to be concentrated until the solid content reaches 25%, and then discharged.

10. The process for clean extraction of L-aspartic acid according to claim 9, wherein the concentrated solution in the three effect evaporator is fed to a hydrocyclone for thickening via a discharging pump, and a thickened ammonium sulfate solution with 45% solid content enters into a thickener for crystallization, wherein the crystallization temperature is 50-70 C, the pressure is an atmospheric pressure, and the solid content reaches 50% after crystallization is completed, and then the solid is spin-dried by a centrifuge and then enters into a mother solution pool, and then the solution returns back to the three effect evaporator via a submerged pump to be further evaporated; the obtained ammonium sulfate crystals enter into a disc type dryer, and is heated indirectly by steam, wherein the drying temperature is 65-78 °C, so that the ammonium sulfate product is obtained.