A method for improving lactic acid purity and yield in large-scale fermentation
The purification process, which involves alkalization flocculation, rotary evaporation concentration, granular activated carbon decolorization, and continuous ion exchange, solves the problem of removing impurities from lactic acid fermentation broth, thereby improving the purity and yield of lactic acid. It is suitable for large-scale fermentation systems using second-generation raw materials, reducing production costs and increasing product purity and yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HENAN JINDAN LACTIC ACID TECH CO LTD
- Filing Date
- 2026-04-17
- Publication Date
- 2026-07-10
AI Technical Summary
In the large-scale fermentation of lactic acid, impurities are difficult to remove effectively, resulting in low purity and yield of lactic acid. In particular, when using second-generation raw materials such as corn stalks and corn cobs, which are lignocellulose, traditional activated carbon has limited adsorption efficiency and poor selectivity, affecting the purity and yield of lactic acid products.
The purification process employs alkalization flocculation, rotary evaporation concentration, granular activated carbon decolorization, and continuous ion exchange. By combining modified activated carbon and functional solutions, the process achieves efficient removal of impurities and improves the purity and yield of lactic acid through flocculation solid removal, acid hydrolysis concentration, granular activated carbon decolorization, and continuous ion exchange purification.
It significantly improved the purity and yield of lactic acid, reduced production costs, achieved resource recycling, reduced regenerant consumption and wastewater discharge, and improved processing efficiency and product purity.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lactic acid purification technology, specifically a method for improving the purity and yield of lactic acid in large-scale fermentation. Background Technology
[0002] In large-scale lactic acid fermentation, the physical properties such as mixing, mass transfer, and heat transfer are difficult to maintain in the same way as in small laboratory reactors, leading to changes in cell metabolism. The fermentation broth contains a large number of cells, proteins, and unconverted substrates such as residual sugars (glucose, xylose, etc.). It also contains pigments and colloids produced by Maillard reactions during fermentation, as well as neutralizing agents from the culture medium or used to adjust pH (such as calcium salts). This results in a large number of ions such as calcium, magnesium, and sodium in the fermentation broth. These impurities seriously affect the composition of the final fermentation broth and bring great difficulty to the downstream purification process.
[0003] In existing technologies, activated carbon possesses strong adsorption properties, capable of adsorbing pigments and impurities in fermentation broths, and is often used for decolorization and preliminary purification of fermentation broths. However, traditional activated carbon adsorption processes suffer from limited adsorption efficiency and poor selectivity. While removing target impurities, they inevitably result in the loss of lactic acid, affecting the final purity and yield of lactic acid. This is especially true when using second-generation raw materials (such as corn stalks, corn cobs, and other lignocellulose), whose composition is more complex, with higher pigment and inorganic salt content. The large amount of activated carbon required during purification further reduces the purity and yield of the subsequent lactic acid product. In large-scale production, these limitations of traditional processes are amplified, leading to poor lactic acid purification efficiency and difficulty in consistently achieving high purity, severely restricting the large-scale production and application of lactic acid.
[0004] Therefore, developing an efficient method for removing impurities from large-scale fermentation broths to effectively improve the purity and yield of lactic acid has become a key issue that the lactic acid industry urgently needs to address. Summary of the Invention
[0005] Therefore, this invention provides a method for improving the purity and yield of lactic acid in large-scale fermentation, which solves the problem of low purity and yield of lactic acid obtained in the large-scale fermentation broth of second-generation raw materials, and achieves efficient removal of impurity components in the fermentation broth, thereby effectively improving the purity and yield of lactic acid.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0008] S1. The lactic acid fermentation broth is alkalized and flocculated, filtered, and sulfuric acid is added to the obtained liquid phase to adjust the pH to 1-2. Then it is filtered again and concentrated by rotary evaporation to obtain the acid hydrolysis concentrate.
[0009] S2. The acid hydrolysis concentrate is purified and decolorized with granular activated carbon to obtain a clear lactic acid solution;
[0010] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid.
[0011] In the above scheme, the purification process of "flocculation and solid removal → acid hydrolysis and concentration → granular activated carbon decolorization → continuous ion exchange purification" can effectively remove impurities and achieve a high lactic acid yield. Among these processes, alkalization flocculation is a pretreatment step for removing mycelia and proteins. Using cationic polyacrylamide for flocculation results in a lower lactic acid loss rate. Simultaneously, flocculation not only improves filtration, but the resulting flocs (containing mycelia and proteins) can be returned to the fermentation system for reuse, increasing raw material utilization. After filtration, sulfuric acid is added to adjust the pH to 1-2, converting calcium lactate into lactic acid and calcium sulfate precipitates. Rotary evaporation then concentrates the precipitate to remove most of the water, significantly increasing the concentration and processing efficiency of subsequent processes. Decolorization and solvent purification effectively adsorb and remove impurities such as pigments, residual sugars, and some organic acids. Compared to powdered activated carbon, granular activated carbon is suitable for large-scale continuous operation, enabling dynamic adsorption and regeneration, reducing losses and operational intensity, and achieving good decolorization and adsorption effects. Compared to traditional fixed-bed ion exchange, continuous ion exchange systems can automatically switch and continuously operate adsorption, desorption, and regeneration processes, improving resin utilization, processing efficiency, and product purity, while reducing regenerant consumption and wastewater discharge.
[0012] Further, in step S1: the fermentation strain of lactic acid fermentation broth is Pediococcus lactis, the fermentation carbon source is lignocellulose hydrolysate, the raw material source of lignocellulose is one or a mixture of two of corn cobs and corn stalks, calcium carbonate is used as a pH adjuster, and the final lactic acid content in the fermentation broth is 50-80 g / L.
[0013] In the above scheme, using agricultural waste corn cobs and corn stalks as raw materials can reduce the production cost of lactic acid and realize resource utilization. Using Pediococcus lactis as a fermentation strain can efficiently utilize lignocellulose hydrolysate to produce lactic acid and improve the utilization rate of raw materials. Adding calcium carbonate to react with lactic acid to produce calcium lactate can neutralize the acidity and maintain the pH within a suitable range, which helps to form saturated calcium lactate and further purify lactic acid in subsequent processing.
[0014] Furthermore, in step S1: during the alkalization process, the alkalizing substance is calcium hydroxide, and the pH of the liquid phase system is adjusted to 11-12.
[0015] In the above scheme, alkalization treatment can inactivate microorganisms in fermentation broth and promote the flocculation and precipitation of impurities such as cells and proteins. Under strongly alkaline conditions (pH 11-12), soluble proteins will denature and coagulate, ensuring the flocculation effect.
[0016] Furthermore, in step S1: during the flocculation process, the flocculant is polyacrylamide, and the amount of polyacrylamide added is 10 to 30 ppm of the mass of the lactic acid fermentation broth.
[0017] In the above scheme, the amount of polyacrylamide added balances the dissolution efficiency, solution viscosity and dispersion performance. Too much addition will result in excessive load and difficulty in sufficient dispersion, while too little addition will affect the flocculation effect.
[0018] Further, in step S2: the amount of granular activated carbon added is 0.2 to 0.5 g / L, based on the volume of the acid hydrolysis concentrate.
[0019] In the above scheme, most of the bacteria, proteins and other macromolecular impurities have been removed before decolorization, which creates conditions for low-dose and high-efficiency decolorization, and can reduce the amount of activated carbon used (0.2-0.5 g / L), which helps to reduce the loss of the target product (lactic acid) caused by adsorption.
[0020] Furthermore, in step S2: during the impurity removal and decolorization process, the processing temperature is 40-50℃ and the processing time is 30-60min.
[0021] In the above scheme, appropriately increasing the temperature (40-50℃) can reduce the viscosity of the feed solution, increase the diffusion rate of pigment molecules and impurities in the solution, and make them more likely to reach the internal pores of activated carbon, thereby accelerating the adsorption rate and reaching adsorption equilibrium in a shorter time, which can further improve the purification efficiency.
[0022] Furthermore, the preparation process of granular activated carbon includes the following:
[0023] A1. Place activated carbon in a chitosan solution, soak for 0.5-2 hours, filter and dry, then pyrolyze at 700-900℃ for 2-3 hours, cool to room temperature, and sieve to obtain pretreated activated carbon;
[0024] A2. Mix the pretreated activated carbon and the functional solution evenly, granulate them, and dry them to obtain granular activated carbon.
[0025] In the above scheme, chitosan has a high carbon content and its molecular chain is rich in active functional groups such as amino (-NH2) and hydroxyl (-OH). Incomplete carbonization of chitosan not only retains the active groups but also allows it to physically modify the surface of activated carbon, resulting in an ultraporous carbon material. The incomplete carbonization of chitosan creates a carbon layer with unique surface chemical activity in situ on the inner wall of the activated carbon pores, introducing a large number of oxygen- and nitrogen-containing functional groups, which become active sites for subsequent adsorption processes. This significantly improves the surface activity and adsorption capacity of the material. At the same time, under the acidic conditions of the acid hydrolysis concentrate, the amino groups in the chitosan molecules can be protonated, making them positively charged cationic electrolytes. These cationic electrolytes adsorb negatively charged impurities through electrostatic interactions, further improving the purification effect.
[0026] Furthermore, the mass fraction of chitosan in the chitosan solution is 0.2% to 0.5%.
[0027] In the above scheme, the 0.2-0.5% chitosan solution has a suitable viscosity, which can ensure that the chitosan molecular chains are fully extended and effectively adsorbed onto the pore surface and between particles of activated carbon, and will not affect the uniformity of mixing due to excessive viscosity. This concentration can ensure the formation of a thin and uniform chitosan-derived carbon precursor coating on the surface of activated carbon.
[0028] Furthermore, the functional solution is a mixed aqueous solution of sophorolipid and disodium EDTA.
[0029] In the above scheme, disodium ethylenediaminetetraacetate can form stable chelates with various ions and can be used as an auxiliary functional material to remove impurity ions in the liquid phase and enhance the adsorption performance of the material. Sophorolipids are glycolipid biosurfactants produced through fermentation processes. Their molecular structure consists of hydrophilic sophorose and hydrophobic hydroxy fatty acids, which can effectively bind to impurity particles while reducing surface tension. This effectively improves the wettability and penetration of activated carbon by the acid hydrolysis concentrate, ultimately resulting in a composite material in which activated carbon possesses adsorption, chelation capabilities, and good surface activity.
[0030] Furthermore, the mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.08–0.12:0.01–0.03:10.
[0031] In the above scheme, controlling the amount of sophorolipid and disodium EDTA can ensure the stability and activity of both in the aqueous acid hydrolysis concentrate, so that the two work together to effectively improve the adsorption performance of activated carbon materials.
[0032] The technical solution of the present invention achieves the following beneficial technical effects:
[0033] 1. This invention significantly improves the purity and yield of lactic acid in large-scale fermentation through process optimization and material modification. The purification process of "flocculation and solid removal → acid hydrolysis and concentration → granular activated carbon decolorization → continuous ion exchange purification" is applicable to second-generation lactic acid fermentation systems using lignocellulose such as corn stalks and corn cobs as raw materials. It specifically solves the problems of high impurity removal difficulty and low yield in large-scale fermentation broth, and can significantly improve the purity and yield of lactic acid products while reducing production costs and realizing resource recycling. This provides strong technical support for the large-scale industrial production and high-value-added application of lactic acid.
[0034] 2. Alkaline flocculation pretreatment can efficiently remove large molecular impurities such as bacteria and proteins, and the flocculants can be returned to the fermentation system, improving raw material utilization and reducing production costs; the acidification and concentration step not only realizes the conversion of calcium lactate to lactic acid, but also improves the efficiency of subsequent treatment by removing a large amount of water, reducing the energy consumption of subsequent processes; the continuous ion exchange system can achieve efficient and continuous ion removal, improving resin utilization and product purity, and reducing regenerant consumption and wastewater discharge.
[0035] 3. Innovative modification of activated carbon was carried out through incomplete carbonization of chitosan and the combination of sophorolipid and disodium EDTA functional solution, which endowed the activated carbon with richer surface functional groups, higher adsorption activity and selectivity, effectively reducing the loss of lactic acid during the decolorization process. At the same time, sophorolipid can improve the wettability of the feed solution, and disodium EDTA enhances the chelation ability of metal ions, further improving the impurity removal effect of activated carbon. Detailed Implementation
[0036] Example 1
[0037] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0038] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 63.9 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution at a mass fraction of 20 ppm of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 60% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0039] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.35 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 45℃ and the treatment time was 45 min. After filtration, the lactic acid solution was obtained.
[0040] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0041] The preparation process of granular activated carbon includes the following:
[0042] A1. Prepare 99.65 kg of an acidic solution with pH 3 using lactic acid, then add 0.35 kg of chitosan and dissolve it completely to obtain a chitosan solution. Soak 10 kg of activated carbon in the chitosan solution for 1 hour, filter and dry it, then pyrolyze it at 800℃ for 2.5 hours, cool it to room temperature, and pass it through a 100-mesh sieve to obtain pretreated activated carbon.
[0043] A2. The pretreated activated carbon and functional solution are mixed evenly at a mass ratio of 100:5. The mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.10:0.02:10. The mixture is then granulated, with the particle size controlled to be 0.5-2 mm. After drying, granular activated carbon is obtained.
[0044] Example 2
[0045] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0046] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 52.4 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution, with the amount of polyacrylamide added being 10 ppm of the mass of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 50% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0047] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.2 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 40℃ and the treatment time was 60 min. After filtration, the lactic acid solution was obtained.
[0048] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0049] The preparation process of granular activated carbon includes the following:
[0050] A1. Prepare 99.8 kg of an acidic solution with pH 3 using lactic acid, then add 0.2 kg of chitosan to dissolve it, and obtain a chitosan solution. Soak activated carbon in the chitosan solution for 0.5 h, filter and dry it, then pyrolyze it at 700 °C for 3 h, cool it to room temperature, and pass it through a 100-mesh sieve to obtain pretreated activated carbon.
[0051] A2. The pretreated activated carbon and functional solution are mixed evenly at a mass ratio of 100:5. The mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.10:0.02:10. The mixture is then granulated, with the particle size controlled to be 0.5-2 mm. After drying, granular activated carbon is obtained.
[0052] Example 3
[0053] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0054] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 76.1 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution at a mass fraction of 30 ppm of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 70% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0055] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.5 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 50℃ and the treatment time was 30 min. After filtration, the lactic acid solution was obtained.
[0056] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0057] The preparation process of granular activated carbon includes the following:
[0058] A1. Prepare 99.5 kg of an acidic solution with pH 3 using lactic acid, then add 0.5 kg of chitosan and dissolve it completely to obtain a chitosan solution. Soak activated carbon in the chitosan solution for 2 hours, filter and dry it, then pyrolyze it at 900℃ for 2 hours, cool it to room temperature, and pass it through a 100-mesh sieve to obtain pretreated activated carbon.
[0059] A2. The pretreated activated carbon and functional solution are mixed evenly at a mass ratio of 100:5. The mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.10:0.02:10. The mixture is then granulated, with the particle size controlled to be 0.5-2 mm. After drying, granular activated carbon is obtained.
[0060] Example 4
[0061] The only difference between this embodiment and Embodiment 1 is that the granular activated carbon is obtained by granulating ordinary activated carbon.
[0062] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0063] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 63.9 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution at a mass fraction of 20 ppm of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 60% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0064] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.35 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 45℃ and the treatment time was 45 min. After filtration, the lactic acid solution was obtained.
[0065] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0066] The preparation process of granular activated carbon includes the following:
[0067] A1. Prepare 99.65 kg of an acidic solution with pH 3 using lactic acid, then add 0.35 kg of chitosan and dissolve it completely to obtain a chitosan solution. Soak activated carbon in the chitosan solution for 1 hour, filter, dry, and pass through a 100-mesh sieve to obtain pretreated activated carbon.
[0068] A2. Mix pretreated activated carbon and water at a mass ratio of 100:5 until uniform, then granulate the mixture, controlling the particle size to be 0.5-2 mm, and dry to obtain granular activated carbon.
[0069] Example 5
[0070] The only difference between this embodiment and Embodiment 1 is that chitosan was not subjected to pyrolysis in the preparation of the granular activated carbon.
[0071] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0072] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 63.9 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution at a mass fraction of 20 ppm of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 60% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0073] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.35 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 45℃ and the treatment time was 45 min. After filtration, the lactic acid solution was obtained.
[0074] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0075] The preparation process of granular activated carbon includes the following:
[0076] A1. Prepare 99.65 kg of an acidic solution with pH 3 using lactic acid, then add 0.35 kg of chitosan and dissolve it completely to obtain a chitosan solution. Soak activated carbon in the chitosan solution for 1 hour, filter, dry, and pass through a 100-mesh sieve to obtain pretreated activated carbon.
[0077] A2. The pretreated activated carbon and functional solution are mixed evenly at a mass ratio of 100:5. The mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.10:0.02:10. The mixture is then granulated, with the particle size controlled to be 0.5-2 mm. After drying, granular activated carbon is obtained.
[0078] Example 6
[0079] The only difference between this embodiment and Embodiment 1 is that no functional solution was added during the preparation of the granular activated carbon; that is, the functional solution was replaced with water.
[0080] A method for improving lactic acid purity and yield in large-scale fermentation includes the following steps:
[0081] S1. Add calcium hydroxide to a lactic acid fermentation broth with a lactic acid content of 63.9 g / L to adjust the pH of the system to 11-12. Add a 0.2% polyacrylamide solution at a mass fraction of 20 ppm of the lactic acid fermentation broth. Then filter the broth. Add sulfuric acid to the filtered liquid phase to adjust the pH to 1-2. Filter again and concentrate by rotary evaporation to remove 60% of the water, obtaining an acid hydrolysis concentrate. The fermentation strain of the lactic acid fermentation broth is Pediococcus lactis, and the fermentation carbon source is lignocellulose hydrolysate. The raw material source of lignocellulose is a mixture of corn cob and corn stalk in a mass ratio of 1:3.
[0082] S2. The acid hydrolysis concentrate was treated with granular activated carbon to remove impurities and decolorize it. The amount of granular activated carbon added was 0.35 g / L based on the volume of the acid hydrolysis concentrate. The treatment temperature was 45℃ and the treatment time was 45 min. After filtration, the lactic acid solution was obtained.
[0083] S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid;
[0084] The preparation process of granular activated carbon includes the following:
[0085] A1. Prepare 99.65 kg of an acidic solution with pH 3 using lactic acid, then add 0.35 kg of chitosan and dissolve it completely to obtain a chitosan solution. Soak activated carbon in the chitosan solution for 1 hour, filter and dry it, then pyrolyze it at 800℃ for 2.5 hours, cool it to room temperature, and pass it through a 100-mesh sieve to obtain pretreated activated carbon.
[0086] A2. Mix pretreated activated carbon and water at a mass ratio of 100:5 until uniform, then granulate the mixture, controlling the particle size to be 0.5-2 mm, and dry to obtain granular activated carbon.
[0087] Proof of effectiveness
[0088] After treating the lactic acid fermentation broth using the methods described in Examples 1-6, the chemical purity and yield of the obtained lactic acid product were tested. The yield was defined as the percentage of the total lactic acid after purification to the total lactic acid equivalent to calcium lactate in the lactic acid fermentation broth before purification. Specific test results are shown in Table 1.
[0089] Table 1
[0090]
[0091] As can be seen from Examples 1-6 and the data in Table 1, after treating the lactic acid fermentation broth with the methods described in Examples 1-6, the chemical purity of the obtained lactic acid product reaches over 86.2%, and the yield reaches over 80.8%, achieving high chemical purity and lactic acid yield. This indicates that the method provided by the present invention has a good impurity removal and purification effect. Furthermore, in the preferred embodiments of the present invention (Examples 1-3), the chemical purity of the obtained lactic acid product reaches over 92.7%, and the yield reaches over 81.2%, demonstrating excellent impurity removal and purification effects.
[0092] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.
Claims
1. A method for improving the purity and yield of lactic acid in large-scale fermentation, characterized in that, Includes the following steps: S1. The lactic acid fermentation broth is alkalized and flocculated, filtered, and sulfuric acid is added to the obtained liquid phase to adjust the pH to 1-2. Then it is filtered again and concentrated by rotary evaporation to obtain the acid hydrolysis concentrate. S2. The acid hydrolysis concentrate is purified and decolorized with granular activated carbon to obtain a clear lactic acid solution; S3. The lactic acid solution is subjected to continuous ion exchange, concentration and dehydration to obtain the finished lactic acid.
2. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 1, characterized in that, In step S1: the fermentation strain of lactic acid fermentation broth is Pediococcus lactis, the fermentation carbon source is lignocellulose hydrolysate, the raw material source of lignocellulose is one or a mixture of two of corn cobs and corn stalks, calcium carbonate is used as pH adjuster, and the final lactic acid content in the fermentation broth is 50-80 g / L.
3. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 2, characterized in that, In step S1: During the alkalization process, the alkalizing substance is calcium hydroxide, and the pH of the liquid phase system is adjusted to 11-12.
4. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 3, characterized in that, In step S1: During the flocculation process, the flocculant is polyacrylamide, and the amount of polyacrylamide added is 10 to 30 ppm of the mass of the lactic acid fermentation broth.
5. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 1, characterized in that, In step S2: the amount of granular activated carbon added is 0.2 to 0.5 g / L based on the volume of the acid hydrolysis concentrate.
6. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 5, characterized in that, In step S2: During the impurity removal and decolorization process, the processing temperature is 40-50℃ and the processing time is 30-60min.
7. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 5, characterized in that, The preparation process of granular activated carbon includes the following: A1. Place activated carbon in a chitosan solution, soak for 0.5-2 hours, filter and dry, then pyrolyze at 700-900℃ for 2-3 hours, cool to room temperature, and sieve to obtain pretreated activated carbon; A2. Mix the pretreated activated carbon and the functional solution evenly, granulate them, and dry them to obtain granular activated carbon.
8. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 7, characterized in that, The chitosan solution contains 0.2% to 0.5% chitosan by mass.
9. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 7, characterized in that, The functional solution is a mixed aqueous solution of sophorolipid and disodium EDTA.
10. The method for improving lactic acid purity and yield in large-scale fermentation according to claim 9, characterized in that, The mass ratio of sophorolipid, disodium EDTA, and water in the functional solution is 0.08–0.12:0.01–0.03:10.