Synthetic method of lauroyl glycine

Abstract

The invention belongs to the field of surfactants, discloses a synthesis method of lauroyl glycine, and aims to solve the problems that a reaction system is free of flowability, thick, difficult to purify, low in production amount of lauroyl glycine, incapable of meeting green and environment-friendly requirements and the like under the condition of no organic solvent. According to the method, lauric acid and glycine are used as raw materials, novozymes 435 lipase is used as a catalyst, lauroyl glycine is synthesized through a reaction, lauric acid is added in batches, the appropriate pH value is adjusted, the addition amount of lauric acid is increased, the problem that a reaction system is thick is solved, the production amount of lauroyl glycine is greatly increased, and the method is suitable for industrial production. The conditions of green industrial production of the lauroyl glycine are met.

Description

Technical Field

[0001] The invention relates to the field of surfactants, and in particular to a method for synthesizing lauroylglycine. Background Art

[0002] Amino acid surfactants are a type of renewable, green and environmentally friendly surfactant based on biomass. N-acyl amino acid surfactants not only have a wide range of raw material sources, low toxicity and side effects, mild performance, low irritation, good biodegradability, and green production process, but also have good emulsification, wetting, solubilization, dispersion, foaming and other properties that have attracted much attention and are gradually being used in many fields such as washing, personal care and food industry.

[0003] At present, the synthesis of N-acyl amino acids has the disadvantages of being difficult, having low yields, and being non-green. The main reason is that the synthesis of N-acyl amino acids that can be used for commercialization is mainly chemical, and the most commonly used method is the Schotten-Bowman reaction, which is a type of reaction between fatty acyl chlorides and amino acids in an organic solvent-water mixture as a reaction medium and a strong base as a catalyst. The byproducts and environmental pollution problems of this reaction are difficult to solve.

[0004] In 1989, Nagao of Novo-Nordisk proposed the enzyme-catalyzed synthesis of N-acyl amino acids. Compared with the chemical method, the enzymatic synthesis of N-acyl amino acids has milder reaction conditions and fewer toxic byproducts, so it has attracted widespread attention. However, there are many problems with the enzymatic synthesis of N-acyl amino acids. For example, the types of N-acyl amino acids synthesized by the enzymatic method are relatively small; in organic solvents, most enzymes cannot maintain high activity, but the substrate solubility in the aqueous phase is relatively poor. Therefore, the yield of N-acyl amino acids synthesized by the enzymatic method is low. Using lipase and protease as catalysts, lauroyl glycine was synthesized in an acetone-water solvent system with a conversion rate of 40% (Claudia Bernal ab, Fanny Guzman c, Andres Illanes d, Lorena Wilson d. Selective and eco-friendly synthesis of lipoaminoacid-based surfactants for food, using immobilized lipase and protease biocatalysts. Food chemistry 2018 (239): 189-195.). Therefore, the enzymatic synthesis of N-acyl amino acids has not yet achieved large-scale industrial production.

[0005] Based on this, the applicant has discovered a new green and environmentally friendly synthesis process of lauroyl glycine through preliminary exploration. In the absence of organic solvents, lauric acid and amino acid aqueous solution are mixed and reacted at 45°C. Although lauroyl glycine can be obtained, the system will become a viscous paste at the end of the reaction. HPLC detection shows that the amount of lauroyl glycine produced is extremely low. Summary of the invention

[0006] In order to better solve the problems that, under the condition of no organic solvent, the reaction system has no fluidity, the system is viscous, it is difficult to purify, the amount of lauroyl glycine generated is low, and it fails to meet the requirements of green environmental protection, the present invention improves the synthesis method of lauroyl glycine, and adjusts the appropriate pH value by adding lauric acid in batches, thereby solving the problem of viscosity of the reaction system while increasing the amount of lauric acid added, the reaction system has good fluidity, the amount of lauroyl glycine generated is greatly increased, and the conditions for green industrial production of lauroyl glycine are met.

[0007] The invention provides a method for synthesizing lauroyl glycine. Lauric acid and glycine are used as raw materials, Novozymes 435 lipase is used as a catalyst, lauric acid is added in batches during the reaction, a suitable pH value is adjusted, and lauroyl glycine is directly synthesized in a one-step method.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A method for synthesizing lauroyl glycine comprises taking lauric acid and glycine as raw materials, using Novozymes 435 lipase as a catalyst, and reacting to synthesize lauroyl glycine, wherein the lauric acid is added in batches.

[0010] Preferably, Novozymes 435 lipase is added to the aqueous solution of glycine, and after stirring evenly, lauric acid is added in batches, with a fixed amount of lauric acid added to each batch, and each batch is added in the form of a solid at one time, the pH value is adjusted, and the reaction is continued until a uniform, transparent, and fluid liquid is obtained.

[0011] As for the selection of the number of times to add lauric acid in batches, preliminary experiments have found that when lauric acid is added all at once without the use of an organic solvent, lauric acid, glycine aqueous solution and Novozymes 435 lipase are mixed and reacted at 45°C. After the reaction is completed, the enzyme-catalyzed reaction in the reaction system in the aqueous phase has a low substrate conversion rate, the reaction system is viscous, and the system is difficult to separate, resulting in difficulties in industrial production.

[0012] Through experiments, it was found that the above problems can be greatly improved by continuously adding the substrate lauric acid to the reaction system in batches. Since lauric acid is added in batches, the reaction substrate is gradually consumed during the reaction, and there is no large amount of substrate accumulation in the reaction system. Finally, the viscosity of the reaction system is greatly alleviated, which is conducive to the purification of the product, so that large-scale industrial production can be carried out.

[0013] Preferably, lauric acid is added in batches 3-10 times, and further, 4-6 times. Experiments have found that when the number of additions exceeds 10 times, there is no obvious effect on the reaction, and the operation will be more complicated, while if the number of additions is too small (less than 3 times), a large amount of lauric acid needs to be added each time, which will make the reaction system viscous and the reaction conversion rate very low.

[0014] Preferably, the total added concentration of lauric acid is 100-600 mmol / L, preferably 500 mmol / L.

[0015] Preferably, the concentration of glycine is 1.5 mol / L-3 mol / L, preferably 3 mol / L. This is because when the concentration of glycine is low (<1.5 mol / L), the reaction rate is slow, while when the concentration is high (>3 mol / L), the glycine cannot be completely dissolved, and solids will exist, which is not conducive to the reaction.

[0016] The experiment found that the pH value of the reaction system also has a great influence on the yield of the product. Novozymes 435 lipase is more conducive to alkaline conditions, and when the pH is less than 6 under acidic conditions, lauric acid cannot be dissolved in the reaction system and the reaction cannot proceed. Too high alkalinity will cause enzyme inactivation, and the reaction cannot proceed. The reaction system is maintained at an appropriate pH value of 5-9 (preferably, the pH value of the system is adjusted to 7.5) through sodium hydroxide aqueous solution, so that the substrate lauric acid and the product gradually dissolve in the aqueous phase as the reaction proceeds, so that the reaction system is finally a uniform and transparent reaction system.

[0017] Preferably, the added amount of Novozymes 435 lipase is 1 mg / mL-10 mg / mL; preferably 3 mg / mL-6 mg / mL.

[0018] Preferably, the reaction temperature is 25-65°C; further, the reaction temperature is selected to be 40-50°C; further, the reaction temperature is selected to be 45°C.

[0019] Preferably, the reaction time is 12-24 hours; further, the reaction time is selected to be 16-18 hours. This is because the reaction is relatively slow in 18-24 hours, and the reaction is basically unchanged after 24 hours. It is meaningless to continue to extend the reaction. The reaction conversion rate is relatively low before 12 hours, and the amount of product generated is small.

[0020] Beneficial effects of the present invention:

[0021] The synthesis method of lauroyl glycine of the present invention uses lauric acid and glycine as raw materials, Novozymes 435 lipase as a catalyst, adds lauric acid in batches during the reaction, and adds a fixed amount of lauric acid in each batch, each batch is added in a solid form at one time, and a suitable pH value is adjusted, and lauroyl glycine is directly synthesized in a one-step method. Compared with the prior art, no organic solvent is added during the reaction of the present invention, and the problem of viscosity of the reaction system is solved, the amount of the product lauroyl glycine is greatly increased, and the method increases the conversion rate of lauric acid by more than 5 times under the original condition of no organic solvent, and meets the conditions for green industrial production of lauroyl glycine. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below. However, the following contents are only used to explain the present invention and are not used to limit the protection scope of the present invention.

[0023] Embodiment 1:

[0024] In a 50mL reaction bottle, add 36ml of 3mol / L glycine aqueous solution and 4mg of Novozymes 435 lipase, stir evenly, heat to 45°C, add 0.8g of lauric acid (each 0.8g of lauric acid corresponds to 100mmol / L), after reacting for 1h, the reaction system is in a uniform and transparent state, and the pH of the reaction system is maintained at 7.5 by sodium hydroxide aqueous solution during the reaction, and continue to add 0.8g of lauric acid, and continue to react for 1h. Add lauric acid once every 1h of reaction, and add a total of 4.0g of lauric acid (i.e., add 5 times, a total of 500mmol / L). After all the lauric acid is added, continue to react for 12h. After the reaction is completed, the reaction system is a uniform, transparent liquid with good fluidity, and the concentration of lauroyl glycine is detected by HPLC external standard.

[0025] Example 2

[0026] The above operation is the same as that in Example 1, except that lauric acid (0.8 g) is added once every 1 h of reaction, the total amount of lauric acid added is 3.2 g (i.e., added 4 times, a total of 400 mmol / L), and the concentration of lauroylglycine is detected by HPLC external standard.

[0027] Example 3

[0028] The above operation is exactly the same as that in Example 1, except that lauric acid (0.8 g) was added once every 1 h of reaction, the total amount of lauric acid added was 4.8 g (i.e., added 6 times, a total of 600 mmol / L), and the concentration of lauroylglycine was detected by HPLC external standard.

[0029] Example 4

[0030] The above operation is completely consistent with Example 1, except that the pH of the reaction system is maintained at 6.5 during the reaction, and the concentration of lauroylglycine is detected by HPLC external standard.

[0031] Example 5

[0032] The above operation is completely consistent with Example 1, except that the pH of the reaction system is maintained at 8.3 during the reaction, and the concentration of lauroylglycine is detected by HPLC external standard.

[0033] Comparative Example 1:

[0034] In a 50 mL reaction bottle, add 36 ml of 3 mol / L glycine aqueous solution and 4 mg of Novozymes 435 lipase, stir evenly, heat to 45°C, add 0.8 g of lauric acid (i.e., 100 mmol / L), react for 12 h, and detect the amount of lauroyl glycine produced by HPLC.

[0035] Comparative Example 2:

[0036] The experimental operation was exactly the same as that of Comparative Example 1, except that only 1.6 g (ie, 200 mmol / L) of lauric acid was added, and the amount of lauroylglycine produced was detected by HPLC.

[0037] Comparative Example 3:

[0038] The experimental operation was exactly the same as that of Comparative Example 1, except that only 3.2 g (ie, 400 mmol / L) of lauric acid was added, and the amount of lauroylglycine produced was detected by HPLC.

[0039] Comparative Example 4:

[0040] The experimental operation was exactly the same as that of Comparative Example 1, except that only 4.0 g (ie, 500 mmol / L) of lauric acid was added, and the amount of lauroylglycine produced was detected by HPLC.

[0041] The product detection method involved in the above embodiments and comparative examples is as follows: the product is detected by high performance liquid chromatography, and the test parameters are: chromatographic column: C18, 250mm; mobile phase: 85% acetonitrile and 15% 0.05% trifluoroacetic acid aqueous solution; detection wavelength: 220nm; column temperature: 30°C; flow rate: 1mL / min; detection time: 15min. The relative value of the amount of lauroyl glycine generated in each embodiment and comparative example relative to comparative example 1 is recorded, and the specific results are shown in Table 1:

[0042] Table 1. Relative value of the amount of lauroyl glycine produced relative to Comparative Example 1

[0043]

[0044]

[0045] The experimental results of Comparative Examples 1-4 show that in a pure water environment (without organic solvent), the amount of lauroylglycine produced by Novozymes 435 lipase-catalyzed synthesis decreases with the increase in the amount of substrate lauric acid added; and the experiment found that as the amount of lauric acid added increases, the viscosity of the reaction system increases. Finally, when the concentration of lauric acid added reaches 500mmol / L, the reaction system is finally in a paste state without any fluidity, so only a small amount of lauroylglycine is produced in the end of the reaction.

[0046] The results of Examples 1, 2, and 3 show that in a pure water environment (without organic solvent), when the number of times lauric acid is added in batches and the total amount added are different, it can have a greater impact on the product lauroylglycine. The addition concentration of lauric acid in Example 2 is 400mmol / l, and the addition concentration of lauric acid in Example 1 is 500mmol / l. The amount of lauroylglycine generated in Example 2 is significantly lower than that in Example 1. When the amount is continued to be added to 600mmol / l (i.e., the amount added in Example 3), the amount of lauroylglycine generated increases, but it is not significantly increased compared with Example 1, indicating that the remaining amount of lauric acid is also increasing. Considering the cost and the difficulty of subsequent purification, it is believed that the addition amount of 500mmol / l is better.

[0047] The results of Examples 1, 4, and 5 show that, under a pure water environment (without an organic solvent), when the number of batch additions and the amount of addition of lauric acid are fixed, the pH value is changed, wherein the pH values ​​of Examples 1, 4, and 5 are 7.5, 6.5, and 8.3, respectively. When comparing the amount of production of the product lauroyl glycine, the amount of production of lauroyl glycine is higher when pH=7.5. The reason is that: the solubility of lauric acid is low when pH=6.5, and the most suitable condition for the enzyme is alkalinity, so the amount of production of lauroyl glycine is low, and when pH=8.3, the activity of the enzyme under this condition is affected to a certain extent, and because the alkalinity is too strong, more sodium laurate is produced, and sodium laurate cannot react with glycine, so the amount of production of lauroyl glycine is also low.

[0048] Therefore, it can be seen that the concentration of lauric acid added is more suitable at 500mmol / l, and pH=7.5 is the most suitable pH value.

[0049] The above embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope of the claims. Those skilled in the art may think of other alternative means, which are all within the scope of the claims of the present invention.

Claims

1. A method for synthesizing lauroylglycine, characterized in that: Lauroylglycine was synthesized by reaction using lauric acid and glycine as raw materials and Novozymes 435 lipase as catalyst, wherein lauric acid was added in batches.

2. The method for synthesizing lauroylglycine according to claim 1, wherein: Add Novozymes 435 lipase to the aqueous solution of glycine, stir evenly, then add lauric acid in batches, add a fixed amount of lauric acid each time, add each batch in the form of solid at one time, adjust the pH value, and continue to react until a uniform, transparent liquid with good fluidity is obtained.

3. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: Lauric acid is added in 3-10 batches, preferably 4-6 batches.

4. The method for synthesizing lauroylglycine according to claim 2, wherein: The pH value of the reaction system is adjusted with sodium hydroxide aqueous solution to maintain the pH value at 5-9, preferably at 7.

5.

5. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The concentration of glycine added to the reaction system is 1.5-3.0 mol / L, preferably 3 mol / L.

6. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The amount of Novozymes 435 lipase added to the reaction system is 1 mg / mL-10 mg / mL, preferably 3 mg / mL-6 mg / mL.

7. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The total concentration of lauric acid added to the reaction system is 100-600 mmol / L.

8. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The total concentration of lauric acid added to the reaction system was 500 mmol / L.

9. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The reaction temperature is 25-65°C; preferably, the reaction temperature is 40-50°C; further, the reaction temperature is selected to be 45°C.

10. The method for synthesizing lauroylglycine according to claim 1 or 2, characterized in that: The reaction time is 12-24h; preferably the reaction time is 16-18h.

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