METHOD FOR RECOVERING ACETIC ACID FROM FERMENTATION BROTH OR RESIDUAL FERMENTATION LIQUOR AND REUSING IT

Abstract

The present application relates to: a method for recovering acetic acid in the form of an acetic acid solution from a fermentation broth or a waste liquor thereof; and / or a method for reusing the recovered acetic acid in a fermentation process.

Description

1 / 28 METHOD FOR RECOVERING ACETIC ACID FROM FERMENTATION BROTH OR RESIDUAL FERMENTATION LIQUOR AND REUSING THE SAME Technical Field

[001] The present invention relates to a method for recovering acetic acid in the form of an acetic acid solution from a fermentation broth or residual liquor thereof and / or a method for reusing the recovered acetic acid in a fermentation process. Previous Technique

[002] In some cases, the production of a target substance through fermentation produces acetic acid. For example, US patent 9029105 B2 describes a method for producing L-methionine from O-acetyl-L-homoserine using a conversion enzyme, from which acetic acid is produced as a byproduct. However, when such acetic acid is treated as wastewater, it must be diluted to at least 10% by weight or less and then neutralized before being drained, which causes a problem due to the energy and cost required for wastewater treatment. Consequently, a method for recovering residual acetic acid from a fermentation broth comprising a large amount of acetic acid or a residual liquor thereof and reusing it is Petition 870250070806, dated 12 / 08 / 2025, p. 50 / 83 2 / 28 contemplated.

[003] However, US patent 9752167 B2 mentions a method for recovering acetic acid from a fermentation broth or residual liquor thereof and a process for reusing the acetic acid recovered in fermentation. However, since the acetic acid is recovered in a form dissolved in an organic acid, a separate process for separating the acetic acid by an organic solvent extraction process is required. The organic solvent extraction process is complicated because it incurs costs due to solvent use and requires an additional solvent recovery process, which reduces economic viability. Furthermore, even a trace amount of the available organic solvent can act as a toxin in the fermentation process, making it difficult to apply in the fermentation process. Description Technical Problem

[004] One objective of the present description is to provide a method for recovering acetic acid in the form of an acetic acid solution from a fermentation broth or residual fermentation liquor comprising acetic acid.

[005] Another objective of the present description is to provide a method for reusing acetic acid by separation. Petition 870250070806, dated 12 / 08 / 2025, p. 51 / 83 3 / 28 of acetic acid in the form of an acetic acid solution from a fermentation broth or residual fermentation liquor comprising acetic acid. Technical Solution

[006] The present description will be described in detail as follows. However, each description and embodiment described in this description may also be applied to other descriptions and embodiments. That is, all combinations of various elements described in this description fall within the scope of the present description. Additionally, the scope of the present description is not limited by the specific description described below. Furthermore, several patent papers and documents are referenced and cited throughout this descriptive report. The descriptions of the cited patent papers and documents are incorporated herein by reference in their entirety to further clarify the level and scope of the subject matter to which the present description pertains.

[007] To achieve the above objectives, one aspect of the present description provides a method for recovering acetic acid from a fermentation broth or residual fermentation liquor, the method comprising the steps of:

[008] (a) addition of a basic substance to the fermentation broth or residual fermentation liquor comprising Petition 870250070806, dated 12 / 08 / 2025, pp. 52 / 83 4 / 28 acetic acid to adjust the pH to 4.6 to 6.0; and

[009] (b) Concentration of the fermentation broth with pH adjustment or residual fermentation liquor by a reverse osmosis process to obtain an acetic acid solution.

[0010] Unlike the existing method for recovering acetic acid in dissolved form in an organic acid (US 9752167 B2), the method for recovering acetic acid from a fermentation broth in the form of an acetic acid solution and reusing it described herein can recover acetic acid in the form of an acetic acid solution without a separate extraction process, thus recovering acetic acid with a high yield in the form of an acetic acid solution from a fermentation broth or residual fermentation liquor without using an organic solvent. Consequently, the method is advantageous because the process is simplified, thus increasing economic efficiency, and no organic solvent remains, and thus it can be applied to a fermentation process, and the acetic acid obtained can be used immediately without a redissolution process.Therefore, when the acetic acid recovered, according to the method of the present description, is reused in a fermentation process with a long fermentation time, for example. Petition 870250070806, dated 12 / 08 / 2025, pp. 53 / 83 5 / 28 in a fermentation process for the production of amino acids such as L-methionine, etc., there are advantages in increasing productivity and decreasing culture time, and thus the method can be applied very usefully.

[0011] As used herein, the term “fermentation broth” may refer broadly to a medium comprising acetic acid, which is obtained by carrying out the culture of a microorganism that produces a fermentation product, a culture comprising the microorganism subjected to carrying out the culture together with the medium or an enzymatic conversion solution thereof, etc.

[0012] Specifically, the fermentation broth may comprise (1) a fermentation broth of a target substance, a precursor thereof or a derivative thereof, comprising acetic acid, (2) a fermentation broth comprising a target substance or a derivative thereof produced by a strain that produces a precursor of the target substance, a substrate and a converting enzyme; and acetic acid or (3) a fermentation broth comprising a target substance or a derivative thereof produced by adding a converting enzyme or a microorganism that expresses the converting enzyme; and a substrate to a fermentation broth precursor of the target substance; and acetic acid, but is not limited to these.

[0013] More specifically, the fermentation broth Petition 870250070806, dated 12 / 08 / 2025, p. 54 / 83 6 / 28 may comprise an amino acid or a derivative thereof prepared by the addition of (i) O-acyl-homoserine; and (ii) O-acyl-homoserine converting enzyme or a microorganism expressing it.

[0014] As used herein, the term “O-acyl-homoserine” includes, but is not limited to, O-acetyl-L-homoserine, O-succinyl-L-homoserine, propionyl-homoserine, acetoacetylhomoserine, coumaroyl-homoserine, malonyl-homoserine, hydroxymethylglutaryl-homoserine, pimelyl-homoserine.

[0015] More specifically, the fermentation broth may be a fermentation broth comprising an amino acid or a derivative thereof prepared by adding a converting enzyme or a microorganism expressing it to a fermentation broth of O-acetyl-L-homoserine and acetic acid. In addition, the fermentation broth may specifically be a fermentation broth comprising L-homocysteine, L-methionine or a derivative thereof prepared by adding O-acetyl-homoserine sulfhydrylase or a microorganism expressing it and methyl mercaptan (CH3SH) to a fermentation broth of O-acetyl-L-homoserine and acetic acid (US 8426171 B2).

[0016] The type of “fermentation product” is not limited as long as the fermentation broth comprises acetic acid. However, it can be specifically a Petition 870250070806, dated 12 / 08 / 2025, pp. 55 / 83 7 / 28 target substance produced by fermentation, a derivative or precursor thereof. Furthermore, the target substance can be an amino acid, for example, L-homocysteine ​​or L-methionine, but is not limited to this. Additionally, the derivative of the target substance can be a derivative of an amino acid, specifically, a derivative of L-homocysteine ​​or a derivative of L-methionine. Furthermore, the precursor of the target substance can be a precursor of an amino acid, specifically, a precursor of L-homocysteine ​​or a precursor of L-methionine. More specifically, it can be O-acetyl-L-homoserine, but is not limited to this.

[0017] As used herein, the term “residual fermentation liquor” may be a liquid obtained by separating and removing part or all of the fermentation product from the fermentation broth, but is not limited to this. Specifically, residual fermentation liquor may be a liquid obtained by separating and removing part or all of an amino acid, a derivative or precursor thereof, from a fermentation broth comprising the amino acid, the derivative or precursor thereof, and acetic acid, but is not limited to this. For example, residual fermentation liquor may be a liquid obtained by separating and removing part or all of an amino acid or a derivative thereof from a fermentation broth comprising the amino acid, the derivative thereof, and acetic acid or a Petition 870250070806, dated 12 / 08 / 2025, pp. 56 / 83 8 / 28 liquid obtained by separating and removing part or all of an amino acid or a derivative thereof from a fermentation broth comprising the amino acid or its derivative, which is produced by a substrate and a converting enzyme or a microorganism that produces the same in a precursor amino acid fermentation broth and acetic acid. More specifically, residual fermentation liquor may be, for example, a liquid obtained by separating and removing part or all of L-homocysteine, L-methionine or a derivative thereof from a fermentation broth comprising L-homocysteine, L-methionine or its derivative, which is produced by adding O-acetyl-homoserine sulfhydrylase or a microorganism that expresses it; and methyl mercaptan (CH3SH) to a fermentation broth of O-acetyl-L-homoserine; and acetic acid, but is not limited to this.

[0018] In the present description, step (a) (pH adjustment step) is a pH adjustment step for the fermentation broth or fermentation residue liquor comprising acetic acid. The pH of the fermentation broth or fermentation residue liquor comprising acetic acid, which is obtained in the pH adjustment step, can be adjusted to 4.6 to 6.0, specifically, 4.8 to 6.0 and, more specifically, 5.0 to 6.0.

[0019] When the pH of the fermentation broth or liquor Petition 870250070806, dated 12 / 08 / 2025, pp. 57 / 83 9 / 28 of the residual fermentation, which includes acetic acid obtained in the pH adjustment step, is less than 4.6. This presents a problem because the final acetic acid recovery rate is less than 50%.

[0020] However, the reverse osmosis process is based on a principle of separation, from a solution, of a solvent that passes through a semipermeable membrane and a solute that does not pass through the semipermeable membrane by applying a pressure greater than the osmotic pressure. In this respect, the ammonium acetate generated in the neutralization reaction of ammonia and acetic acid cannot pass through the semipermeable membrane and is thus separated. However, when ammonium acetate is produced excessively during this process, a problem occurs in which the semipermeable membrane is blocked and the solvent is not separated.

[0021] In other words, when the pH of the fermentation broth or residual fermentation liquor containing acetic acid, which is obtained in the pH adjustment step, exceeds 6.0, there is a problem because the reverse osmosis process will experience equipment limitations. Furthermore, the pH adjustment step in this description can be performed by adding a basic substance to the fermentation broth or residual fermentation liquor containing acetic acid. Petition 870250070806, dated 12 / 08 / 2025, pp. 58 / 83 10 / 28

[0022] In one particular embodiment, the basic substance may be ammonia or sodium hydroxide, but is not limited to these. Specifically, the pH adjustment step may be performed by adding ammonia gas (NH3 (g)) or water with ammonia (NH4OH(liq)).

[0023] In a particular embodiment, the method may further comprise, prior to step (a), (i) a step of preparing a fermentation broth comprising L-homocysteine, L-methionine or a derivative thereof by using microorganisms in a fermentation medium comprising O-acyl-homoserine and (ii) a step of obtaining the fermentation broth or residual fermentation liquor comprising the acetic acid of step (a) from the fermentation broth; or the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or a derivative thereof from the fermentation broth, but is not limited to these.

[0024] In a specific embodiment, step (ii) may additionally comprise a step of evaporation and cooling of the fermentation broth; or of the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or a derivative thereof from the fermentation broth to obtain condensate comprising water and acetic acid, but is not limited to that.

[0025] In a specific embodiment, condensed water Petition 870250070806, dated 12 / 08 / 2025, pp. 59 / 83 11 / 28 may contain acetic acid at a concentration of 5 g / L to 15 g / L, but is not limited to this.

[0026] In the present description, step (b) is a step of concentrating the fermentation broth with pH adjustment or residual fermentation liquor by a reverse osmosis process to obtain an acetic acid solution.

[0027] As used herein, the term “concentration” is not limited to one method, provided that it is capable of increasing the concentration of acetic acid ions contained in the fermentation broth or residual fermentation liquor and can be carried out by a method known in the art. Specifically, concentration can be carried out by evaporation, heating, depressurization, ventilation, freezing, etc., but is not limited to these.

[0028] In a specific example, step (b) may comprise a step of reconcentrating the acetic acid solution obtained, but is not limited to that.

[0029] By carrying out the reverse osmosis process, the acetic acid recovery rate can be increased and a retentate from which various suspended substances have been removed by filtration can be obtained.

[0030] As used herein, the term “retentate” may refer to a solution with an increased solute concentration as a result of the reverse osmosis process.

[0031] In any of the modalities Petition 870250070806, dated 12 / 08 / 2025, pp. 60 / 83 12 / 28 as described above, the resulting acetic acid solution may comprise acetic acid at a concentration of 25 g / L to 45 g / L, but is not limited to this.

[0032] In any embodiment of the embodiments described above, the reconcentrated solution prepared in the reconcentration step may comprise acetic acid at a concentration of 200 g / L to 400 g / L, but is not limited to this.

[0033] The method for recovering acetic acid in the form of an acetic acid solution from fermentation broth and reusing the same described herein can recover acetic acid with a high yield in the form of an acetic acid solution from fermentation broth or residual fermentation liquor without using an organic solvent through a simple process consisting only of adjusting the pH and concentration of the fermentation broth or residual fermentation liquor containing the acetic acid without a separate extraction process. Consequently, the method is advantageous in that the process is simplified, thus increasing economic efficiency and no organic solvent remains, and thus it can be applied to a fermentation process, and the acetic acid obtained in the form of an acetic acid solution can be used immediately without a redissolution process. Petition 870250070806, dated 12 / 08 / 2025, pp. 61 / 83 13 / 28

[0034] In a specific embodiment, the acetic acid recovered by the method of the present description may comprise acetic acid and / or an acetic acid salt and / or an acetic acid ester.

[0035] In a specific embodiment, the acetic acid solution recovered by the method of the present description may be, but is not limited to, an aqueous solution of acetic acid.

[0036] Another aspect of the present description provides a method for reusing acetic acid from a fermentation broth or residual fermentation liquor, the method comprising the steps of:

[0037] (a) addition of a basic substance to a fermentation broth or residual fermentation liquor comprising acetic acid to adjust the pH to 4.6 to 6.0;

[0038] (b) concentration of the fermentation broth with pH adjustment or residual fermentation liquor by a reverse osmosis process to obtain an acetic acid solution; and

[0039] (c) introduction of acetic acid solution into a medium.

[0040] In the present description, step (c) is a step of reusing the acetic acid solution obtained in step (b) in the fermentation process.

[0041] In the present description, the reuse step Petition 870250070806, dated 12 / 08 / 2025, pp. 62 / 83 14 / 28 is a step in utilizing acetic acid in the form of an acetic acid solution, which is recovered by the method described herein, as an acetic acid and / or carbon source in various fermentation media that require acetic acid and / or a carbon source. The fermentation media described herein are not limited, provided they are media used in fermentation that require acetic acid and / or a carbon source with respect to the objectives of this description.

[0042] Yet another aspect of the present description provides a method for recovering acetic acid from a fermentation broth or residual fermentation liquor, the method comprising the steps of:

[0043] (a') production of O-acetyl-L-homoserine by a fermentation process using a microorganism that produces O-acetyl-L-homoserine;

[0044] (b') reaction of O-acetyl-L-homoserine produced in step (a') with methyl mercaptan (CH3SH) in the presence of O-acetyl-homoserine sulfhydrylase or a microorganism expressing it to produce a fermentation broth of L-homocysteine, L-methionine or a derivative thereof;

[0045] (c') obtaining the fermentation broth; or the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or a derivative thereof from the fermentation broth; Petition 870250070806, dated 12 / 08 / 2025, pages 63 / 83 15 / 28

[0046] (d') addition of a basic substance to the fermentation broth from step (a') or to the residual fermentation liquor from step (b') to adjust the pH to 4.6 to 6.0; and

[0047] (e') Concentration of fermentation broth with pH adjustment or residual fermentation liquor by a reverse osmosis process to obtain an acetic acid solution.

[0048] Yet another aspect of the present description provides a method for reusing acetic acid from a fermentation broth or residual fermentation liquor, the method comprising the steps of:

[0049] (a') production of O-acetyl-L-homoserine by a fermentation process using a microorganism that produces O-acetyl-L-homoserine;

[0050] (b') production of a fermentation broth of L-homocysteine, L-methionine or a derivative thereof by reacting O-acetyl-L-homoserine produced in step (a') with methyl mercaptan (CH3SH) in the presence of O-acetylhomoserine sulfhydrylase or a microorganism expressing it;

[0051] (c') obtaining the fermentation broth; or the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or a derivative thereof from the fermentation broth;

[0052] (d') addition of a basic substance to the broth Petition 870250070806, dated 12 / 08 / 2025, pp. 64 / 83 16 / 28 of fermentation from step (a') or residual fermentation liquor from step (b') to adjust the pH to 4.6 to 6.0;

[0053] (e') concentration of the fermentation broth with pH adjustment or residual fermentation liquor by a reverse osmosis process to obtain an acetic acid solution; and

[0054] (f') introduction of acetic acid solution into a medium.

[0055] In the present description, step (a') is a step for the production of O-acetyl-L-homoserine through a fermentation process using a microorganism that produces O-acetyl-L-homoserine. The microorganism that produces O-acetyl-L-homoserine can be any known microorganism capable of producing O-acetyl-L-homoserine and, as a non-limiting example, a microorganism with enhanced O-acetyl-L-homoserine production capacity (US 9029105 B2) can be used.

[0056] In the present description, step (b') is a conversion step of O-acetyl-L-homoserine to L-homocysteine, L-methionine or a derivative thereof by reaction with methyl mercaptan (CH3SH) under the catalytic action of the enzyme O-acetyl-homoserine sulfhydrylase.

[0057] Furthermore, in the present description, the conversion reaction can be carried out using not only the enzyme O-acetyl-homoserine sulfhydrilase, but also a Petition 870250070806, dated 12 / 08 / 2025, pages 65 / 83 17 / 28 microorganism expressing the enzyme. The enzyme and the microorganism expressing the enzyme can be obtained through means and methods known to those skilled in the art. Specifically, the enzyme O-acetylmoserine sulfhydrylase, an enzyme described in US patent 9029105 B2, etc., can be used, but is not limited to this.

[0058] In addition, in the present description, methyl mercaptan (CH3SH) may be added in various forms.

[0059] In the present description, a step of evaporation and cooling of the fermentation broth from step (b') or of the residual fermentation liquor from step (c'), to obtain condensate comprising water and acetic acid, may be further comprised between steps (c') and (d'), but is not limited to them.

[0060] In one particular embodiment, the condensed water may comprise acetic acid at a concentration of 5 g / L to 15 g / L, but is not limited to this.

[0061] In the present description, steps (d') to (f') are the same as the method for recovering and reusing acetic acid in the form of an acetic acid solution from the fermentation medium as described in the present description.

[0062] One embodiment of the method described herein may additionally comprise a reuse step. Petition 870250070806, dated 12 / 08 / 2025, pp. 66 / 83 18 / 28 of the acetic acid solution from step (f') as an acetic acid and / or carbon source in a fermentation medium.

[0063] In the present description, the reuse step is a step that utilizes acetic acid in the form of an acetic acid solution recovered by the method of the present description as an acetic acid and / or carbon source in various fermentation media that require acetic acid and / or a carbon source. With respect to the objectives of the present description, the fermentation medium of the present description is not limited as long as it is a medium used in fermentation that requires acetic acid and / or a carbon source. Advantageous Effects

[0064] Unlike the existing method for recovering acetic acid in dissolved form in an organic acid (US 9260732 B2), the present description investigated for the first time a method for recovering acetic acid in the form of an acetic acid solution without a separate extraction process, thereby recovering acetic acid in the form of an acetic acid solution from a fermentation broth or residual fermentation liquor without using an organic solvent and reusing the same in a fermentation process.

[0065] The method for recovering acetic acid in the form of an acetic acid solution from a broth Petition 870250070806, dated 12 / 08 / 2025, pp. 67 / 83 The fermentation and reuse method described herein can recover acetic acid in the form of an acetic acid solution from fermentation broth or residual fermentation liquor without using an organic solvent and can reuse it in the fermentation process. Therefore, there are no problems associated with organic solvents, such as the possibility of acting as a toxin in the fermentation process, additional costs incurred due to the use of solvents, and the complexity of the process due to the addition of a solvent recovery process, etc. Furthermore, since the acetic acid obtained can be used immediately without a redissolution process, it can be very usefully applied to the fermentation process. Brief Description of the Drawing

[0066] FIG. 1 is a graph showing the results of examining an acetic acid recovery rate, according to the acetic acid concentration of a reconcentrated solution when the pH of the condensed water comprising the acetic acid is less than 4.6. Detailed Description of Preferred Options

[0067] Next, the present description will be described in detail with reference to the following exemplary embodiments. However, the following exemplary embodiments are only for illustrative purposes of the present description and the scope of the Petition 870250070806, dated 12 / 08 / 2025, pp. 68 / 83 20 / 28 present description is not intended to be limited by the following exemplary modalities. Example 1. Preparation of Fermentation Broth or Residual Fermentation Liquor comprising Acetic Acid (Condensed Water comprising Acetic Acid)

[0068] A microorganism that produces O-acetyl-L-homoserine was cultured to obtain an O-acetyl-L-homoserine fermentation broth, and then the fermentation broth was reacted with methyl mercaptan (CH3SH) which utilizes O-acetyl-homoserine sulfhydrylase to obtain a fermentation broth comprising L-homocysteine, L-methionine or a derivative thereof (US 9029105 B2). Subsequently, a residual fermentation liquor obtained by separating and removing some or all of the L-homocysteine, L-methionine or a derivative thereof from the fermentation broth was evaporated and cooled to obtain condensate comprising water and acetic acid.

[0069] In detail, in the process for producing L-methionine using O-acetyl-L-homoserine produced through fermentation as a precursor for the enzymatic reaction, three types of crystallization tubes (crystallization tube A, crystallization tube B, crystallization tube C) and two types of concentration tubes (concentration tube A, concentration tube B) were Petition 870250070806, dated 12 / 08 / 2025, pp. 69 / 83 21 / 28 used. The condensed water generated from crystallization tube A was 882.5 kl and comprised acetic acid at a concentration of 7.2 g / L. The condensed water generated from crystallization tube B was 1105 kl and comprised acetic acid at a concentration of 9.6 g / L. They were mixed in a storage tank to obtain 1987.5 kl of a solution comprising 8.56 g / L of acetic acid as condensed water. In this way, the condensed water discharged from the crystallization tubes and the concentration tubes was mixed in a predetermined ratio to prepare condensed water comprising 5 g / L to 15 g / L of acetic acid. Example 2. Adjusting the pH of Condensate Water using Acetic Acid

[0070] To 1 L of 5 g / L to 15 g / L of the 25°C acetic acid solution prepared in Example 1, ammonia gas at the same temperature was introduced to adjust the pH.

[0071] For example, 4.3 g of ammonia gas were introduced into 1 L of 15 g / L acetic acid solution at 25°C to adjust its pH to 5.

[0072] On the other hand, when the pH of the pH-adjusted condensate water, which comprises the acetic acid prepared in Example 2, exceeds 6.0, equipment limitations occur in a reverse osmosis process and, thus, the maximum pH of the condensate water that can be separated by the process is exceeded. Petition 870250070806, dated 12 / 08 / 2025, pp. 70 / 83 The reverse osmosis of Example 3, 22 / 28, is 6.0. Example 3. Preparation of the Retentate

[0073] The pH-adjusted condensate water comprising 5 g / L to 15 g / L of acetic acid, prepared in Example 2, was concentrated by a reverse osmosis process to obtain a retentate comprising 25 g / L to 45 g / L of acetic acid.

[0074] In detail, the equipment (Alfa Laval, type RO 99) used in the reverse osmosis process consisted of two membranes in series, each having a membrane area of ​​811 m2 and 1217 m2, and a pressure of 3500 kPa (35 bar) was applied. Condensed water with pH adjustment comprising 5 g / L to 15 g / L of acetic acid, prepared in Example 2, was fed into the reverse osmosis process equipment at 35°C and 60 kl / h. The maximum flow rate of a pump used at this time was 65 kl / h. Example 4. Recovery of Acetic Acid using Fermentation Broth or Residual Fermentation Liquor comprising Acetic Acid

[0075] The retentate prepared in Example 3 was reconcentrated by evaporation to obtain a reconcentrated solution comprising 200 g / L to 400 g / L of acetic acid.

[0076] In detail, the concentration process through evaporation employed a method that uses steam as a Petition 870250070806, dated 12 / 08 / 2025, pp. 71 / 83 23 / 28 heat source to achieve a temperature higher than the boiling point of the solution under the internal pressure conditions of a concentration tube (Hantec, Multiple Effect Falling Film Evaporator (6 effects)). Experimental Example 1. Recovery of Acetic Acid and Ammonia, according to the Acetic Acid Concentration and pH of the Retentate.

[0077] The recovery rates of acetic acid and ammonia, according to the acetic acid concentration and pH of the retentate prepared by the reverse osmosis process in Example 3, were measured.

[0078] The acetic acid recovery rate (%) of the retentate is determined by a ratio of the acetic acid recovered (g) in the retentate after the reverse osmosis process of Example 3 to the initial acetic acid (g) of the initial condensate water of Example 1.

[0079] The results are shown in Table 1 below. Table 1 Concentration of acetic acid in condensed water (g / L) pH of condensed water Amount of ammonia added in 1 L of condensed water (g) Acetic acid recovery rate from retentate (%) 10.0 4.5 0.95 50.88 15.0 4.5 1.45 53.98 10.2 5.5 2.42 77.44 15.2 5.5 3.6 72.70 10.0 6.0 3.6 79.61 15.0 6.0 5.1 79.71 5.4 4.5 0.52 41.33 5.4 5.5 1.28 70.23 5.3 5.5 1.2 75.79 Petition 870250070806, dated 12 / 08 / 2025, pp. 72 / 83 24 / 28

[0080] As a result, as shown in Table 1, it was confirmed that when the pH of the condensate water comprising the acetic acid of Example 2 was 4.6 to 6.0 and the initial concentration of acetic acid in the residual condensate water liquor of Example 1 was 5 g / L to 15 g / L, the retentate showed an excellent acetic acid recovery rate.

[0081] It was also confirmed that when the pH of the condensed water increases, the retentate showed a more excellent acetic acid recovery rate.

[0082] On the other hand, when the pH of the pH-adjusted condensate water, which comprises the acetic acid prepared in Example 2, exceeds 6.0, equipment limitations occur in the reverse osmosis process and, therefore, the maximum pH of the condensate water that can be separated by the reverse osmosis process of Example 3 is 6.0. Experimental Example 2. Recovery of Acetic Acid using Fermentation Broth or Residual Fermentation Liquor comprising Acetic Acid

[0083] The acetic acid recovery rates were compared according to the concentration of the condensed water containing acetic acid from Example 1, the adjusted pH of the condensed water containing acetic acid from Example 2, the acetic acid concentration of the retentate from Example 3, and the acetic acid concentration of the solution. Petition 870250070806, dated 12 / 08 / 2025, pp. 73 / 83 25 / 28 re-concentrated from Example 4.

[0084] The final acetic acid recovery rate (%) is determined by a ratio of the acetic acid recovered (g) from the reconcentrated solution of Example 4 to the acetic acid (g) from the initial condensed water of Example 1.

[0085] The results are shown in Table 2 below. Table 2 Concentration of acetic acid in residual liquor condensed water (g / L) pH of condensed water Amount of ammonia added in 1L of condensed water (g) Concentration of acetic acid in retentate (g / L) Concentration of acetic acid in reconcentrated solution (g / L) Final acetic acid recovery rate (%) 1 5 5 2.2 25 200 62.78 2 5 5 2.2 30 200 58.65 3 5 5 2.2 45 200 61.01 4 5 5 2.2 45 300 51.21 5 5 6 2.9 25 200 83.01 6 5 6 2.9 25 300 59.08 7 5 6 2.9 30 200 75.16 8 5 6 2.9 30 300 60.87 9 5 6 2.9 45 200 85.25 10 5 6 2.9 45 300 69.94 11 5 6 2.9 45 400 54.63 12 10 5 3 25 200 56.51 13 10 5 3 30 200 54.17 14 10 5 3 45 200 62.01 15 10 6 3.6 25 200 74.64 16 10 6 3.6 30 200 69.59 17 10 6 3.6 30 300 52.52 18 10 6 3.6 45 200 81.90 19 10 6 3.6 45 300 64.35 20 15 4.6 3.59 24 200 52.00 21 15 5 4.3 25 200 58.98 22 15 5 4.3 30 200 55.30 23 15 5 4.3 45 200 62.87 24 15 6 5.1 25 200 74.63 25 15 6 5.1 30 200 71.63 26 15 6 5.1 30 300 55.05 27 15 6 5.1 45 200 78.55 28 15 6 5.1 45 300 67.10 29 15 6 5.1 45 400 55.66

[0086] As shown in Table 2, for example, in the case of No. 23, specifically, an acetic acid solution in Petition 870250070806, dated 12 / 08 / 2025, pp. 74 / 83 26 / 28 a concentration of 15 g / L, 35°C and pH 5 was fed to the reverse osmosis process equipment and the final recovery rate of acetic acid after reconcentration through the reverse osmosis process was 62.87%.

[0087] Through this, it was confirmed that, when the pH of the condensed water comprising the acetic acid of Example 2 was from 4.6 to 6.0 and the initial concentration of acetic acid of the condensed water of Example 1 was from 5 g / L to 15 g / L, the final recovery rate was 50% or more. Comparative Example 1. Recovery of Acetic Acid using Fermentation Broth or Residual Fermentation Liquor comprising Acetic Acid

[0088] With regard to the concentration of the condensed water comprising acetic acid from Example 1, the adjusted pH of the condensed water comprising acetic acid from Example 2, the acetic acid concentration of the retentate from Example 3, and the acetic acid concentration of the reconcentrated solution from Example 4, the acetic acid recovery rate was intended to be examined under conditions different from the optimum conditions confirmed in Experimental Example 2.

[0089] The final acetic acid recovery rate (%) is determined by a ratio of the acetic acid recovered (g) from the reconcentrated solution of Example 4 to the acetic acid (g) from the initial condensed water of Example 1.

[0090] The results are shown in Table 3 below. Petition 870250070806, dated 12 / 08 / 2025, pp. 75 / 83 27 / 28 and in FIG. 1. Table 3 No. Concentration of acetic acid in residual condensed water liquor (g / L) pH of condensed water Amount of ammonia added in 1 L of condensed water (g) Concentration of acetic acid in retentate (g / L) Concentration of acetic acid in reconcentrated solution (g / L) Final acetic acid recovery rate (%) 1 15 4.5 1.45 45 194.5 32.62 2 211.2 32.30 3 230.6 31.84 4 253.3 31.18 5 279.9 30.20 6 311.0 28.72 7 346.8 26.44 8 386.9 22.95 9 429.6 17.69 1 472.5 10.15

[0091] As shown in Table 3 and FIG. 1, it was confirmed that when the pH of the condensed water comprising the acetic acid of Example 2 was less than 4.6, the final recovery rate was less than 50%, regardless of the degree of reconcentration.

[0092] On the other hand, when the pH of the condensed water with pH adjustment comprising the acetic acid prepared in Example 2 exceeds 6.0, limitations of the equipment occur in the reverse osmosis process and, therefore, the maximum pH of the condensed water that can be separated by the reverse osmosis process of Example 3 is 6.0.

[0093] In other words, it was confirmed that the final recovery rate was 50% or more only under optimal conditions where the pH of the condensed water that Petition 870250070806, dated 12 / 08 / 2025, pp. 76 / 83 28 / 28 comprises the acetic acid concentration of Example 2, which was 4.6 to 6.0, and an initial acetic acid concentration of the condensed water from Example 1 was 5 g / L to 15 g / L.

[0094] Based on the above description, it will be understood by those skilled in the art that the present description can be implemented in a different specific form without changing the technical spirit or essential characteristics thereof. In this respect, it should be understood that the above embodiment is not limiting but illustrative in all respects. The scope of the description is defined by the appended claims rather than by the description preceding them, and therefore all changes and modifications that fall within the limits of the claims or the equivalents of such limits are therefore intended to be covered by the claims. Petition 870250070806, dated 12 / 08 / 2025, pp. 77 / 83

Claims

1 / 3 CLAIMS 1. Method for recovering acetic acid from a fermentation broth or residual fermentation liquor, the method characterized in that it comprises the steps of: (a) adding a basic substance to the fermentation broth or residual fermentation liquor comprising acetic acid to adjust the pH to 4.6 to 6.0; and (b) concentrating the fermentation broth or residual fermentation liquor with adjusted pH by a reverse osmosis process to obtain an acetic acid solution.

2. Method for reusing acetic acid from a fermentation broth or residual fermentation liquor, the method characterized in that it comprises the steps of: (a) adding a basic substance to a fermentation broth or residual fermentation liquor comprising acetic acid to adjust the pH to 4.6 to 6.0; (b) concentrating the fermentation broth or residual fermentation liquor with adjusted pH by a reverse osmosis process to obtain an acetic acid solution; and (c) introducing the acetic acid solution into a medium.

3. Method according to claim 1 or 2, characterized in that the fermentation broth comprises an amino acid or a derivative thereof prepared Petition 870250072260, dated 08 / 15 / 2025, page 9 / 14 2 / 3 by the addition of (i) O-acyl-homoserine; and (ii) O-acyl-homoserine converting enzyme or a microorganism expressing it.

4. Method according to claim 1 or 2, characterized in that it further comprises, before step (a), (i) a step for preparing a fermentation broth comprising L-homocysteine, L-methionine or a derivative thereof by using microorganisms in a fermentation medium comprising O-acyl-homoserine and (ii) a step for obtaining the fermentation broth or residual fermentation liquor comprising acetic acid from step (a) from the fermentation broth; or the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or a derivative thereof from the fermentation broth.

5. Method according to claim 4, characterized in that step (ii) further comprises a step of evaporation and cooling of the fermentation broth; or of the residual fermentation liquor obtained by removing L-homocysteine, L-methionine or derivatives thereof from the fermentation broth to obtain a condensed water comprising acetic acid.

6. Method according to claim 1 or 2, characterized in that the basic substance is ammonia or sodium hydroxide. Petition 870250072260, dated 08 / 15 / 2025, page 10 / 14 3 / 3 7. Method according to claim 1, characterized in that the fermentation broth or residual fermentation liquor comprising acetic acid comprises acetic acid in a concentration of 5 g / L to 15 g / L.

8. Method according to claim 1 or 2, characterized in that an acetic acid solution obtained in step (b) comprises acetic acid at a concentration of 25 g / L to 45 g / L.

9. Method according to claim 1 or 2, characterized in that step (b) comprises a step of reconcentrating the acetic acid solution obtained.

10. Method according to claim 9, characterized in that a reconcentrated solution prepared in the reconcentration step comprises acetic acid at a concentration of 200 g / L to 400 g / L. Petition 870250072260, dated 15 / 08 / 2025, page 11 / 14

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