Method for producing carboxylic acid

Abstract

Carboxylic acids can be efficiently produced by a method for producing carboxylic acids comprising the following steps (A) and (B): (A) filtering a fermentation broth containing carboxylic acids through a nanofiltration membrane to obtain a filtrate containing carboxylic acids from the permeate side; and (B) extracting carboxylic acids from the filtrate containing carboxylic acids obtained in step (A) using an extraction solvent that is phase-separable from the filtrate, and recovering the carboxylic acid extract that has been phase-separated from an aqueous phase.

Description

Technical Field

[0001] The present invention relates to a method for producing carboxylic acids from a fermentation broth containing the carboxylic acid. Background Art

[0002] In the past, as the means of reclaiming carboxylic acid from the fermentation liquid containing carboxylic acid, with the adsorption separation, electrodialysis, crystallization etc. of adopting anion exchange resin, often use extraction separation.In extracting carboxylic acid from the fermentation liquid containing carboxylic acid, it is known that the phase interface of fermentation liquid (aqueous phase) and extraction solvent (organic phase) generates the such phenomenon of the mesophase comprising solid component that neither dissolves in aqueous phase nor dissolves in organic phase, and it is known that because this phenomenon hinders the phase separation when extracting, there is the problem that needs to add the defectives such as solid matter removal process.As the means for solving this problem, the method using membrane filtration has been proposed.For example, in patent documentation 1, record in the case of reclaiming amino acid by extraction from amino acid fermentation liquid, by making amino acid fermentation liquid remove cytoplasm, other solid matter by the ultrafiltration membrane (UF membrane) that the molecule below molecular weight 1000 can see through in the front stage of extraction, amino acid fermentation liquid and extraction solvent are separated faster. Furthermore, Patent Document 2 describes that when recovering aliphatic dicarboxylic acids from an aliphatic dicarboxylic acid fermentation broth by extraction, microorganisms are removed by passing the broth through a microfiltration membrane (MF membrane), accelerating the phase separation between the aliphatic dicarboxylic acid fermentation broth and the extraction solvent. Furthermore, microfiltration membranes are more suitable as filtration membranes than ultrafiltration membranes. Furthermore, Patent Document 3 describes that impurities are removed by passing a monocarboxylic acid fermentation broth through a nanofiltration membrane, thereby improving the purity of the recovered monocarboxylic acid.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 62-277349

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-119738

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2010-095450 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Patent Documents 1 and 2 describe that passage through an ultrafiltration membrane and a microfiltration membrane, respectively, accelerates phase separation during extraction. However, the present inventors' research revealed that even when a fermentation broth containing carboxylic acid is passed through either a microfiltration membrane or an ultrafiltration membrane, sufficient phase separation between the aqueous phase and the organic phase during extraction remains problematic (Comparative Example 1 of the present application).

[0010] Therefore, the present invention aims to find a method for improving the phase separation between the aqueous phase and the organic phase when extracting carboxylic acid from a fermentation liquid containing the carboxylic acid.

[0011] Methods for solving problems

[0012] As described above, prior art methods for increasing the purity of monocarboxylic acids by passing a fermentation broth containing monocarboxylic acids through a nanofiltration membrane are known. However, there is no information regarding the effects of nanofiltration membrane treatment on the carboxylic acid extraction process. Instead, it is suggested that nanofiltration membranes, which have smaller mesh sizes than ultrafiltration membranes, are less suitable than ultrafiltration membranes. However, the present inventors conducted intensive research to address the aforementioned issues and discovered that by passing a carboxylic acid fermentation broth through a nanofiltration membrane before subjecting it to the carboxylic acid extraction process, the phase separation between the aqueous phase and the organic phase after extraction is promoted, leading to the completion of the present invention.

[0013] That is, the present invention is composed of the following (1) to (5).

[0014] (1) A method for producing a carboxylic acid, comprising the following steps (A) and (B):

[0015] Step (A): filtering the fermentation liquid containing carboxylic acid through a nanofiltration membrane, and obtaining a filtrate containing carboxylic acid from the permeate side.

[0016] Step (B): Carboxylic acid is extracted from the filtrate containing carboxylic acid obtained in step (A) using an extraction solvent that is phase-separable from the filtrate, and the carboxylic acid extract phase-separated from the aqueous phase is recovered.

[0017] (2) The method according to (1), wherein the pH of the fermentation liquid containing the carboxylic acid and / or the filtrate containing the carboxylic acid is adjusted to 4.5 or less.

[0018] (3) The method according to (1) or (2), wherein step (A) includes removing insoluble matter before passing the fermentation liquid containing the carboxylic acid through a nanofiltration membrane.

[0019] (4) The method according to (3), wherein the step of removing insoluble matter is a step of passing the fermentation liquid containing the carboxylic acid through a microfiltration membrane.

[0020] (5) The method according to any one of (1) to (4), wherein the molecular weight of the carboxylic acid is 200 or less.

[0021] Effects of the Invention

[0022] According to the present invention, when recovering carboxylic acid by extraction from a fermentation liquid containing carboxylic acid, phase separation between the aqueous phase and the organic phase after extraction can be promoted, thereby efficiently producing the carboxylic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a photograph of the carboxylic acid-containing filtrate obtained by passing through a nanofiltration membrane, immediately after the filtrate containing the carboxylic acid was brought into contact with the extraction solvent, in a carboxylic acid extraction test.

[0024] Figure 2 These are photographs taken immediately after (a) and 12 hours after (b) contacting the fermentation liquid containing carboxylic acids with the extraction solvent in a carboxylic acid extraction test of the fermentation liquid containing carboxylic acids that did not pass through the nanofiltration membrane. DETAILED DESCRIPTION

[0025] Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following embodiments.

[0026] In the present invention, carboxylic acid is a general term for compounds having one or more carboxyl groups (COOH groups) in the molecule. The carboxylic acid in the present invention is not particularly limited, but carboxylic acids with a molecular weight of about 200 or less are preferred because they have high permeability to the nanofiltration membrane described below. Specific examples of preferred carboxylic acids include formic acid, acetic acid, propionic acid, oxalic acid, glycolic acid, gluconic acid, acrylic acid, butyric acid, isobutyric acid, γ-aminobutyric acid, valeric acid, isovaleric acid, pyruvic acid, lactic acid, hydroxybutyric acid, succinic acid, fumaric acid, maleic acid, itaconic acid, malic acid, tartaric acid, oxaloacetic acid, glutaric acid, 2-oxoglutaric acid, adipic acid, adipic acid semialdehyde, 3-oxoadipate, 3-hydroxyadipate, 3-hydroxyadipate-3,6-lactone, α-hydromuconic acid, β-hydromuconic acid, muconic acid, muconolactone, 2-keto-L-gulonic acid, 6-aminohexanoic acid, aconitic acid, benzoic acid, 4-hydroxybenzoic acid, phenylacetic acid, terephthalic acid, isophthalic acid, shikimic acid, phenylalanine, tyrosine, and histidine.

[0027] In the present invention, the fermentation broth containing carboxylic acids includes not only a culture broth in which carboxylic acids are produced by the action of microorganisms in a liquid culture medium containing fermentation raw materials such as a carbon source, a nitrogen source, inorganic salts, amino acids, and vitamins, but also a culture broth in which microorganisms are cultured in a liquid culture medium containing fermentation raw materials and to which chemically or biologically synthesized carboxylic acids are added.

[0028] The carbon source used for the cultivation of microorganisms includes monosaccharides such as glucose, sucrose, fructose, galactose, mannose, xylose, arabinose, disaccharides formed by the combination of these monosaccharides, polysaccharides, molasses containing these sugars, beet molasses, cane molasses, waste molasses, starch saccharification liquid, biomass saccharification liquid containing cellulose, etc. As nitrogen source, ammonia, ammonia water, ammonium salts, urea, nitrates, other auxiliary organic nitrogen sources such as oil cakes, soybean hydrolyzate, casein decomposition products, other amino acids, vitamins, corn steep liquor, yeast or yeast extract, meat extract, peptone and other peptides. As inorganic salts, phosphates, magnesium salts, calcium salts, iron salts, manganese salts, etc. can be appropriately added. In addition, as the fermentation raw materials comprising these carbon sources, nitrogen sources, inorganic salts, amino acids, vitamins, etc., waste biomass can also be used. Examples of waste-based biomass include food waste, livestock manure, sewage sludge, agricultural residues, and wood-based waste.

[0029] The microorganisms used to prepare the fermentation liquid containing carboxylic acid are not particularly limited, and examples thereof include yeasts such as baker's yeast, bacteria such as Escherichia coli and coryneform bacteria, filamentous fungi, actinomycetes, etc. The microorganisms used may be those isolated from the natural environment, or those whose properties have been partially modified by mutation or genetic recombination.

[0030] [Step (A)]

[0031] In the present invention, first, as step (A), a fermentation liquid containing carboxylic acid is passed through a nanofiltration membrane to obtain a filtrate containing carboxylic acid.

[0032] In the present invention, "passing through a nanofiltration membrane" means passing a fermentation broth containing carboxylic acids through the nanofiltration membrane and recovering a permeate containing carboxylic acids from the permeate side. Furthermore, in this specification, the permeate containing carboxylic acids through the nanofiltration membrane is referred to as a filtrate containing carboxylic acids.

[0033] By passing the fermentation liquid containing carboxylic acid through a nanofiltration membrane, the formation of an intermediate phase containing solid components that are insoluble in neither the aqueous phase nor the organic phase is suppressed after the carboxylic acid is extracted in the subsequent step (B), thereby promoting phase separation between the aqueous phase and the organic phase.

[0034] The carboxylic acid in the fermentation liquid containing the carboxylic acid can be dissolved in water as the carboxylic acid or a salt of the carboxylic acid. Examples of the carboxylic acid salt include lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, and ammonium salts. Mixtures of these different salts may also be used.

[0035] The carboxylic acid concentration in the fermentation broth containing carboxylic acids filtered through a nanofiltration membrane is not particularly limited. A high concentration results in a high carboxylic acid concentration in the filtrate containing carboxylic acids, which is suitable for energy reduction when performing concentration. Methods for increasing the concentration of carboxylic acids, i.e., for concentration, include evaporation concentration to remove water, reverse osmosis membrane concentration to remove water through a reverse osmosis membrane, or a combination of these methods.

[0036] Among the raw materials of the nanofiltration membrane used in the present invention, polymer raw materials such as cellulose acetate polymers, polyamides, polyesters, polyimides, and vinyl polymers can be used, but it is not limited to the membrane composed of one of the above raw materials, and can be a membrane comprising multiple membrane raw materials. In addition, the membrane structure can be an asymmetric membrane having a dense layer on at least one side of the membrane and having micropores whose diameter gradually increases from the dense layer toward the inside of the membrane or the other side, or a composite membrane having a very thin functional layer formed by other raw materials on the dense layer of the asymmetric membrane. As a composite membrane, for example, a composite membrane of a nanofiltration membrane formed by a functional layer of polyamide on a support membrane using polysulfone as a membrane raw material, as described in Japanese Patent Application Laid-Open No. 62-201606, can be used.

[0037] Among these, the present invention preferably uses a composite membrane with polyamide as a functional layer, which has both high pressure resistance and high water permeability and high solute removal performance, and has excellent potential. Furthermore, in order to maintain durability against operating pressure, high water permeability, and barrier performance, it is preferred to use polyamide as a functional layer, and to use a structure in which the functional layer is supported by a support composed of a porous membrane or a non-woven fabric. In a nanofiltration membrane with polyamide as a functional layer, preferred carboxylic acid components as monomers constituting the polyamide include, for example, aromatic carboxylic acids such as trimesic acid, benzophenonetetracarboxylic acid, trimellitic acid, 1,2,4,5-benzenetetracarboxylic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, biphenylcarboxylic acid, and picolinic acid. However, if solubility in the membrane-forming solvent is considered, trimesic acid, isophthalic acid, terephthalic acid, or a mixture thereof is more preferred.

[0038] Preferred amine components of the monomers constituting the polyamide include m-phenylenediamine, p-phenylenediamine, benzidine, methylenebis(diphenylamine), 4,4'-diaminodiphenyl ether, dianisidine, 3,3',4-triaminodiphenyl ether, 3,3',4,4'-tetraaminodiphenyl ether, 3,3'-dioxybenzidine, 1,8-naphthalenediamine, m-(p)-monomethylphenylenediamine, 3,3'-monomethylamino-4,4'-diaminodiphenyl ether, 4,N,N'-(4-aminobenzoyl)-p-(m)-phenylenediamine-2,2'-bis(4-aminophenylbenzimidazole), 2,2'-bis(4-aminophenylbenzoyl)- A nanofiltration membrane having a functional layer made of a cross-linked polyamide containing piperazine or piperidine as a monomer is preferably used because it has heat resistance and chemical resistance in addition to pressure resistance and durability. More preferred is a nanofiltration membrane having the above-mentioned cross-linked piperazine polyamide or cross-linked piperidine polyamide as a main component. Examples of nanofiltration membranes having a functional layer made of a polyamide containing piperazine polyamide include those described in Japanese Patent Application Laid-Open No. 62-201606. Specific examples include UTC-60 and UTC-63, cross-linked piperazine polyamide-based semipermeable membranes manufactured by Toray Industries, Inc.

[0039] As spiral nanofiltration membrane elements used in the present invention, for example, nanofiltration modules SU-210, SU-220, SU-600, and SU-610 manufactured by Toray Co., Ltd., which include UTC-60 and UTC-63 with cross-linked piperazine polyamide as functional layers, can also be used. Furthermore, nanofiltration membranes NF-45, NF-90, NF-200, and NF-400 manufactured by FilmTech Co., Ltd., which have cross-linked piperazine polyamide as functional layers, nanofiltration membranes NF99, NF97, and NF99HF manufactured by Alphaval Co., Ltd., which have polyamide as functional layers, and GEsepa manufactured by GE Osmonics Co., Ltd., which are cellulose acetate-based nanofiltration membranes, can also be used.

[0040] In the present invention, filtration of the fermentation broth containing carboxylic acid using a nanofiltration membrane can be performed by applying pressure. The filtration pressure is not particularly limited, but if it is less than 0.1 MPa, the membrane permeation rate decreases, and if it is greater than 8 MPa, it affects membrane damage. Therefore, it is preferably used in the range of 0.1 MPa to 8 MPa. However, if it is used in the range of 0.5 MPa to 7 MPa, the membrane permeation flux is high, thereby allowing the carboxylic acid to permeate efficiently, which is more preferable.

[0041] In the present invention, the filtration of the fermentation broth containing carboxylic acid using a nanofiltration membrane can be repeated by returning the non-permeated liquid to the raw water to improve the recovery rate of the carboxylic acid.

[0042] Nanofiltration membranes have the property that unionized (non-dissociated) substances in solution are easier to pass through than ionized (dissociated) substances. Therefore, by making the pH of the fermentation liquid containing carboxylic acids acidic, the carboxylic acids in the carboxylic acid state that are not carboxylate salts increase and are easier to pass through the nanofiltration membrane. On the other hand, if the pH is too low, there is a concern about corrosion of the device, which is industrially disadvantageous. From these viewpoints, the pH of the fermentation liquid containing carboxylic acids passing through the nanofiltration membrane is preferably adjusted to pH 4.5 or less, more preferably adjusted to pH 1.5 or more and 4.5 or less, and further preferably adjusted to pH 2.0 or more and 4.0 or less.

[0043] The acid used for pH adjustment of the fermentation liquid containing carboxylic acid passing through the nanofiltration membrane is not particularly limited as long as it can make the pH acidic, and inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and boric acid can be preferably used.

[0044] The fermentation broth containing carboxylic acids contains insoluble substances derived from the microorganisms, unassimilated fermentation raw materials, and biomass such as proteins secreted by the microorganisms. From the perspective of suppressing clogging of the nanofiltration membrane, it is preferable to remove the insoluble substances from the fermentation broth containing carboxylic acids before the nanofiltration membrane treatment. It is more preferable to remove biomass such as proteins from the fermentation broth containing carboxylic acids simultaneously with the removal of the insoluble substances.

[0045] As a method for removing insoluble matter from a fermentation broth containing carboxylic acids, for example, by passing the fermentation broth containing carboxylic acids through a microfiltration membrane (MF membrane), a fermentation broth containing carboxylic acids from which insoluble matter has been removed can be obtained from the permeate side. Alternatively, by centrifuging the fermentation broth containing carboxylic acids to precipitate insoluble matter and recovering the supernatant, a fermentation broth containing carboxylic acids from which insoluble matter has been removed can be obtained. In the present invention, a step of removing insoluble matter by passing the fermentation broth through a microfiltration membrane is preferably employed.

[0046] There is no particular limitation on the microfiltration membrane as long as it has the function of separating insoluble substances derived from bacteria, unassimilated fermentation raw materials, etc. As materials, for example, porous ceramic membranes, porous glass membranes, porous organic polymer membranes, metal fiber braids, non-woven fabrics, etc. can be used, but among them, porous organic polymer membranes or ceramic membranes are particularly suitable.

[0047] As a structure of the microfiltration membrane, for example, from the viewpoint of anti-fouling properties, it is preferable to include a porous resin layer as a functional layer.

[0048] The microfiltration membrane including a porous resin layer preferably has a porous resin layer functioning as a functional layer on the surface of a porous base material.

[0049] The porous substrate is made of an organic material and / or an inorganic material, and preferably, organic fibers are used. Preferred porous substrates are woven or nonwoven fabrics made of organic fibers such as cellulose fibers, cellulose triacetate fibers, polyester fibers, polypropylene fibers, and polyethylene fibers. More preferably, nonwoven fabrics are used because they are easy to control in density, easy to manufacture, and inexpensive.

[0050] The porous resin layer can be suitably made of an organic polymer film. As the material of the organic polymer film, for example, polyethylene resins, polypropylene resins, polyvinyl chloride resins, polyvinyl fluoride resins, polysulfone resins, polyethersulfone resins, polyacrylonitrile resins, cellulose resins and cellulose triacetate resins can be cited. The organic polymer film can be a mixture of resins with these resins as the main component. The so-called main component here means that the component contains 50 weight% or more, preferably 60 weight% or more. The material of the organic polymer film is preferably polyvinyl chloride resins, polyvinyl fluoride resins, polysulfone resins, polyethersulfone resins and polyacrylonitrile resins, which are easy to form films using a solution and have excellent physical durability and chemical resistance. It is most preferred to use polyvinyl fluoride resins or resins with them as the main component.

[0051] Here, as the polyvinylidene fluoride resin, a homopolymer of vinylidene fluoride is preferably used. Furthermore, a copolymer of the polyvinylidene fluoride resin and a vinyl-based monomer copolymerizable with vinylidene fluoride is also preferably used. Examples of the vinyl-based monomer copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, and trichlorofluoroethylene.

[0052] As a method for removing biomass such as protein from a fermentation liquid containing carboxylic acid, for example, the fermentation liquid containing carboxylic acid is passed through an ultrafiltration membrane (UF membrane), thereby obtaining a fermentation liquid containing carboxylic acid from which biomass such as protein has been removed from the permeate side.

[0053] The molecular weight cutoff of the ultrafiltration membrane is not particularly limited as long as it is in the range of 2,000 to 100,000, but is preferably in the range of 5,000 to 100,000, and more preferably in the range of 5,000 to 30,000.

[0054] As the raw material of the ultrafiltration membrane, polyethersulfone, polysulfone, polyacrylonitrile, polyvinylidene fluoride, regenerated cellulose, cellulose, cellulose ester, sulfonated polysulfone, sulfonated polyethersulfone, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polytetrafluoroethylene, etc. can be used.

[0055] Specific examples of the ultrafiltration membrane used in the present invention include the M series and P series of the DESAL trademark manufactured by GE W&PT, the GH (G-10) type, GK (G-20) type, and GM (G-50) type of the G series, the HWS UF type and STD UF type of the "DURATHERM" (registered trademark) series, VT, MT, ST, SM, MK, MW, LY, BN, and BY manufactured by Synder, the "Microza" (registered trademark) UF series manufactured by Asahi Kasei Corporation, and NTR-7410 and NTR-7450 manufactured by Nitto Denko Corporation.

[0056] The order of removing insoluble substances derived from bacteria, fermentation raw materials, etc., and biological substances such as proteins is not particularly limited, but it is preferred to remove large insoluble substances derived from bacteria, fermentation raw materials, etc. first because clogging of the ultrafiltration membrane can be suppressed.

[0057] [Process (B)]

[0058] In the present invention, as step (B), carboxylic acid is extracted from the filtrate containing carboxylic acid obtained in step (A) using an extraction solvent that can phase-separate from the filtrate, and the carboxylic acid extract phase-separated from the aqueous phase is recovered.

[0059] The extraction solvent used in step (B) is not particularly limited as long as it can be separated from the filtrate containing carboxylic acid obtained in step (A) to extract the carboxylic acid. Examples thereof include aliphatic hydrocarbon extraction solvents such as pentane, hexane, and heptane; aromatic hydrocarbon extraction solvents such as benzene, toluene, and xylene; chlorine extraction solvents such as carbon tetrachloride, chloroform, dichloromethane, and trichloroethylene; ester extraction solvents such as ethyl acetate and butyl acetate; ketone extraction solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; Extraction solvents, ether-based extraction solvents such as dimethyl ether, diethyl ether, diisopropyl ether, and dibutyl ether, butanol, hexanol, octanol, decanol, oleyl alcohol, and other alcohol-based extraction solvents with more than 4 carbon atoms, chloroform / isopropanol mixed solutions, dichloromethane / isopropanol mixed solutions, ethyl acetate / isopropanol mixed solutions, and other isopropanol mixed solutions, long-chain amine-based extraction solvents such as trioctylamine, trinonylamine, and tridecylamine, alkylphosphine oxide-based extraction solvents such as tributylphosphine oxide and trioctylphosphine oxide, ammonium-based, imidazole Tie, Pyridine Pyrrolidine These extraction solvents may be used alone or as a mixture of two or more.

[0060] When using a chloroform / isopropanol mixed solution, a dichloromethane / isopropanol mixed solution, or an ethyl acetate / isopropanol mixed solution as the extraction solvent, the proportion of isopropanol mixed is preferably 40% by volume or less. If the proportion of isopropanol mixed is too high, the phase separation property with the filtrate containing the carboxylic acid tends to decrease.

[0061] The extraction temperature in step (B) is not particularly limited, but is preferably within a temperature range in which the filtrate containing the carboxylic acid and the extraction solvent do not solidify or boil. The temperature is more preferably 5°C to 100°C, further preferably 10°C to 90°C, and particularly preferably 20°C to 80°C.

[0062] The pH of the filtrate containing carboxylic acid in step (B) is not particularly limited as long as it is less than pH 7, which is an acidic condition. However, carboxylic acid that is not in the form of a carboxylate tends to be easily extracted into the extraction solvent, so a low pH is preferred. On the other hand, if the pH is too low, there is a concern about corrosion of the equipment, which is industrially disadvantageous. From these viewpoints, the pH of the filtrate containing carboxylic acid in step (B) is preferably adjusted to pH 4.5 or less, more preferably to pH 1.5 or more and pH 4.5 or less, and even more preferably to pH 2.0 or more and pH 4.0 or less.

[0063] The acid used for pH adjustment of the carboxylic acid-containing filtrate in step (B) is not particularly limited as long as it can make the pH acidic. However, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and boric acid, which are preferably used for pH adjustment in step (A), can be preferably used.

[0064] The carboxylic acid concentration in the filtrate containing carboxylic acid supplied to step (B) is not particularly limited, but the high concentration has a tendency that the carboxylic acid is easy to move to the extraction solvent. Specifically, it is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, further preferably 1% by weight or more, and particularly preferably 20% by weight or more. As a method for increasing the concentration of carboxylic acid, that is, a method for concentrating, an evaporation concentration method in which water is evaporated and removed, a reverse osmosis membrane concentration method in which water is removed by a reverse osmosis membrane, or a method combining them can be used. In addition, by appropriately adjusting the concentration of the fermentation liquid containing carboxylic acid supplied to step (A), the concentration pH of the filtrate containing carboxylic acid can be adjusted to a desired concentration.

[0065] By contacting the residual extract, which is the aqueous phase after the carboxylic acids have been extracted with the extraction solvent, with fresh extraction solvent, the carboxylic acids remaining in the residual extract can be further recovered, thereby improving the recovery rate of the carboxylic acids. The residual extract, with a sufficiently reduced carboxylic acid concentration, can be used as water to adjust the pH of the fermentation broth containing the carboxylic acids, or can be discharged from the system.

[0066] The extraction can be performed by batch extraction, parallel-current multiple extraction, countercurrent multi-stage extraction, etc. When the extraction is performed continuously on an industrial scale, a tower-type extraction apparatus such as a mixer-settler type extraction apparatus, a porous plate extraction tower, a pulse tower, or a mixer-settler tower can be used.

[0067] [Subsequent Process]

[0068] The recovery of carboxylic acid from the carboxylic acid extract can be carried out by conventional methods such as a method of simply distilling off the extraction solvent, a method of distilling the carboxylic acid, a method of precipitating the carboxylic acid and then performing solid-liquid separation, a method of extracting the carboxylic acid into water and then separating it from the water by distillation, concentration, or precipitation.

[0069] The extraction solvent removed from the extract may be directly reused as the extraction solvent in step (B), or may be purified by distillation and reused as the extraction solvent in step (B). When purification is performed by distillation, the amount of carboxylic acid recovered can be increased by recovering a trace amount of carboxylic acid contained in the extraction solvent.

[0070] [Other processes]

[0071] In the present invention, carboxylic acids can be concentrated by passing the fermentation broth containing carboxylic acids supplied to step (A), the filtrate containing carboxylic acids supplied to step (B), or an aqueous solution containing carboxylic acids that may be produced in a step subsequent to step (B), through a reverse osmosis membrane (RO membrane). "Passing through a reverse osmosis membrane" herein means filtering through the reverse osmosis membrane, removing water from the permeate side, and recovering an aqueous solution containing carboxylic acids having an increased carboxylic acid concentration from the retentate side.

[0072] As the membrane material of the reverse osmosis membrane used in the present invention, generally commercially available polymer materials such as cellulose acetate polymers, polyamides, polyesters, polyimides, and vinyl polymers can be used. However, the membrane is not limited to being composed of a single material and can be composed of multiple membrane materials. As the membrane form, a suitable membrane form such as a flat membrane type, a spiral type, or a hollow fiber type can be used.

[0073] Specific examples of the reverse osmosis membrane used in the present invention include polyamide reverse osmosis membranes (UTC) SU-710, SU-720, SU-720F, SU-710L, SU-720L, SU-720LF, SU-720R, SU-710P, SU-720P, SU-810, SU-820, SU-820L, and SU-820FA manufactured by Toray Industries, Inc.; and cellulose acetate reverse osmosis membranes SC-L100R, SC-L200R, SC-1100, SC-1200, SC-2100, SC-2200, SC-3100, and SC-3200 manufactured by Toray Industries, Inc. 00, SC-8100, SC-8200, NTR-759HR, NTR-729HF, NTR-70SWC, ES10-D, ES20-D, ES20-U, ES15-D, ES15-U, LF10-D made by Nitto Denko Corporation, RO98pHt, RO99, HR98PP, CE4040C-30D made by Alphaval, GESepa made by GE, BW30-4040, TW30-4040, XLE-4040, LP-4040, LE-4040, SW30-4040, SW30HRLE-4040 made by Filmtec, etc.

[0074] Filtration using a reverse osmosis membrane is performed by applying pressure. However, if the filtration pressure is less than 1 MPa, the membrane permeation rate decreases, and if it is greater than 8 MPa, it affects membrane damage. Therefore, the filtration pressure is preferably in the range of 1 MPa to 8 MPa. In addition, the filtration pressure is more preferably in the range of 1 MPa to 7 MPa, and even more preferably in the range of 2 MPa to 6 MPa.

[0075] Example

[0076] Hereinafter, the present invention will be described in more detail using reference examples, examples, and comparative examples, but the present invention is not limited to the following results.

[0077] [HPLC analysis conditions]

[0078] HPLC analysis was performed under the following analysis conditions.

[0079] Column 1: Synergi Polar-RP (manufactured by Phenomenex)

[0080] Column 2: Synergi Hydro-RP (manufactured by Phenomenex)

[0081] Column temperature: 45°C

[0082] Mobile phase 1: 5 mM formic acid aqueous solution / acetonitrile = 98 / 2 (vol / vol), 1 mL / min

[0083] Mobile phase 2: (5 mM formic acid, 20 mM Bis-Tris, 0.1 mM EDTA-2Na) aqueous solution / acetonitrile = 98 / 2 (vol / vol), 1 mL / min

[0084] Detection: Conductivity.

[0085] [pH analysis method]

[0086] A Horiba pH meter F-52 (manufactured by Horiba, Ltd.) was used. pH calibration was performed using a pH 4.01 standard solution (manufactured by Fuji Phyllum Wako Pure Chemical Co., Ltd.), a pH 6.86 standard solution (manufactured by Fuji Phyllum Wako Pure Chemical Co., Ltd.), and a pH 9.18 standard solution (manufactured by Fuji Phyllum Wako Pure Chemical Co., Ltd.).

[0087] (Reference Example 1) Preparation of fermentation broth containing carboxylic acids (acetic acid, succinic acid)

[0088] A fermentation broth containing carboxylic acids (model fermentation broth) was prepared by the following steps. The Escherichia coli NBRC3301 strain was inoculated into 5 mL of LB medium in a test tube and shake-cultured overnight (pre-culture). The pre-culture broth was inoculated into 1 L of the medium with the composition shown below and shake-cultured in a Sakaguchi flask (2 L capacity) for 24 hours. Acetic acid (manufactured by Fuji Filmu Wako Junyao Co., Ltd.) and succinic acid (manufactured by Fuji Filmu Wako Junyao Co., Ltd.) were added to the culture broth to a concentration of 10 g / L, respectively, to prepare a fermentation broth containing carboxylic acids.

[0089] [Culture medium composition]

[0090] Glucose 10g / L

[0091] Ammonium sulfate 0.5g / L

[0092] Potassium phosphate 50 mM

[0093] Magnesium sulfate 0.013g / L

[0094] Ferrous sulfate 0.032 mg / L

[0095] Manganese sulfate 1.35 mg / L

[0096] Calcium chloride 0.17 mg / L

[0097] Sodium chloride 1.25g / L

[0098] Bacto Tryptone 2.50g / L

[0099] Yeast extract 1.25g / L

[0100] pH6.5.

[0101] (Reference Examples 2 to 5)

[0102] The fermentation broth containing carboxylic acids prepared in Reference Example 1 was passed through a microfiltration membrane (a porous membrane with a pore size of 0.01 μm or more and less than 1 μm; manufactured by Toray Industries, Inc.) and then through an ultrafiltration membrane (molecular weight cutoff 10,000; manufactured by Toray Industries, Inc.). 1 L of the fermentation broth containing carboxylic acids was transferred to a raw water tank and passed through the nanofiltration membrane once under the following nanofiltration membrane treatment condition 1. The resulting filtrate containing carboxylic acids lost its color tone and became a clear aqueous solution. The carboxylic acid concentration was analyzed by HPLC, and the transmittance was calculated according to the following formula. The transmittance calculation results are shown in Table 1.

[0103] Permeability (%) = (compound concentration in permeate) / (compound concentration in raw water)×100.

[0104] (Reference Examples 6 to 9)

[0105] The experiments were conducted in the same manner as in Reference Examples 2 to 5, except that concentrated sulfuric acid (manufactured by Sigma-Aldrich Co., Ltd.) was added to the fermentation broth containing carboxylic acid after passing through the ultrafiltration membrane to adjust the pH to 4.0. The resulting filtrate containing carboxylic acid lost its hue, resulting in a clear aqueous solution. The calculated transmittance results are shown in Table 1.

[0106] (Reference Examples 10 to 13)

[0107] The experiment was conducted in the same manner as in Reference Examples 6 to 9 except that the pH was adjusted to 2.0. The color tone of the obtained filtrate containing carboxylic acid disappeared, and a clear aqueous solution was obtained. The calculated results of the transmittance are shown in Table 1.

[0108] [Nanofiltration membrane treatment conditions 1]

[0109] Separation membrane: UTC-63 (manufactured by Toray Industries, Inc.)

[0110] Membrane separation device: "SEPA" (registered trademark) CF-II (manufactured by GE W&PT)

[0111] Operating temperature: 25℃

[0112] Filtration pressure: 0.21~2.03MPa.

[0113] Reference Examples 2 to 13 demonstrate that passing a fermentation broth containing carboxylic acid through a nanofiltration membrane yields a filtrate containing carboxylic acid as a permeate containing carboxylic acid. Furthermore, adding an acid before passage through the nanofiltration membrane improves the permeability of carboxylic acid.

[0114] Table 1 Nanofiltration membrane permeation test of fermentation broth containing carboxylic acid

[0115]

[0116] (Reference Example 14)

[0117] One liter of the fermentation broth containing carboxylic acids prepared in Reference Example 1 was passed through a microfiltration membrane (porous membrane with a pore size of 0.01 μm or more and less than 1 μm; manufactured by Toray Industries, Inc.), followed by an ultrafiltration membrane (molecular weight cutoff 10,000; manufactured by Toray Industries, Inc.). Concentrated sulfuric acid (manufactured by Sigma-Aldrich Co., Ltd.) was then added to adjust the pH to 4.0. The fermentation broth containing carboxylic acids was transferred to a raw water tank and passed through the nanofiltration membrane under the following nanofiltration membrane treatment conditions 2.

[0118] [Nanofiltration membrane treatment conditions 2]

[0119] Separation membrane: UTC-63 (manufactured by Toray Industries, Inc.)

[0120] Membrane separation device: "SEPA" (registered trademark) CF-II (manufactured by GE W&PT)

[0121] Operating temperature: 25℃

[0122] Filtration pressure: 0.5MPa.

[0123] The filtrate containing carboxylic acid was concentrated using a rotary evaporator (manufactured by Tokyo Rikagaki Co., Ltd.) until it became 100 mL. The pH of the concentrated aqueous solution was 4.6. 0.5 mL of the aqueous solution and 0.5 mL of dichloromethane (manufactured by Fujifilm and Koujun Pharmaceutical Co., Ltd.) were added to a 2 mL Eppendorf tube and shaken at 1500 rpm for 1 hour at room temperature using a Keyuto Microscope CM-1000 (manufactured by Tokyo Rikagaki Co., Ltd.). After shaking, the carboxylic acid concentration in the aqueous phase was measured by HPLC and the extraction yield was calculated according to the following formula. The results are shown in Table 2.

[0124] Extraction rate (%)=(1-(concentration of the compound to be extracted in the residual extract) / (concentration of the compound to be extracted before extraction))×100.

[0125] (Reference Example 15)

[0126] The results are shown in Table 2.

[0127] (Reference Example 16)

[0128] The results are shown in Table 2.

[0129] (Reference Example 17)

[0130] The experiment was conducted in the same manner as in Reference Example 14 except that concentrated sulfuric acid (manufactured by Sigma-Aldrich Co., Ltd.) was added to the concentrated solution of the filtrate containing the carboxylic acid to adjust the pH to 4.0. The results are shown in Table 2.

[0131] (Reference Example 18)

[0132] The results are shown in Table 2.

[0133] (Reference Example 19)

[0134] The experiment was conducted in the same manner as in Reference Example 17, except that methyl isobutyl ketone (manufactured by Fujifilm Wako Junyao Co., Ltd.) was used instead of dichloromethane. The results are shown in Table 2.

[0135] Table 2 Extraction of carboxylic acids from filtrates containing carboxylic acids

[0136]

[0137] Reference Examples 14 to 19 show that carboxylic acid can be extracted from the filtrate containing carboxylic acid into the extraction solvent. In addition, it is shown that the extraction rate tends to increase when the pH of the filtrate containing carboxylic acid is 4.5 or less.

[0138] (Example 1)

[0139] One liter of the fermentation broth containing carboxylic acids prepared in Reference Example 1 was passed through a microfiltration membrane (a porous membrane with a pore size of 0.01 μm or more and less than 1 μm; manufactured by Toray Industries, Inc.), followed by an ultrafiltration membrane (molecular weight cutoff 10,000; manufactured by Toray Industries, Inc.). Concentrated sulfuric acid (manufactured by Sigma-Aldrich Co., Ltd.) was then added to adjust the pH to 4.0. The fermentation broth containing carboxylic acids was transferred to a raw water tank and passed through the nanofiltration membrane under the aforementioned nanofiltration membrane treatment condition 2. The retentate was returned to the raw water tank. If the retentate volume was insufficient, pure water was added to the raw water tank and the nanofiltration membrane treatment continued, yielding a filtrate containing carboxylic acids in which all the carboxylic acids were recovered as permeate. The filtrate containing carboxylic acid was concentrated using a rotary evaporator (manufactured by Tokyo Rika Instruments Co., Ltd.) until it became 100 mL, and concentrated sulfuric acid (manufactured by Shigma-Aldrich Co., Ltd.) was added to adjust the pH to 4.0. 10 mL of the aqueous solution was transferred to a glass separatory funnel (capacity 50 mL), 10 mL of ethyl acetate (manufactured by Fujifilm Wako Junyao Co., Ltd.) was added and shaken 30 times. The ethyl acetate phase was recovered, and 10 mL of ethyl acetate was further added to the extract residue and shaken 30 times to recover the ethyl acetate phase. The same operation was repeated, and a total of 100 mL of ethyl acetate was used to extract the carboxylic acid to obtain a carboxylic acid extract (acetic acid extraction rate 95%, succinic acid extraction rate 73%). In this extraction, the formation of an intermediate phase containing solid components was almost not observed between the aqueous phase and the ethyl acetate phase, and phase separation occurred extremely quickly within ten seconds ( Figure 1 ).

[0140] (Comparative Example 1)

[0141] A carboxylic acid extract (acetic acid extraction rate 70%, succinic acid extraction rate 55%) was obtained in the same manner as in Example 1, except that the fermentation liquid containing carboxylic acids was not passed through the nanofiltration membrane. In this extraction, an intermediate phase containing solid components was generated between the aqueous phase and the ethyl acetate phase, and no phase separation was observed immediately after shaking ( Figure 2 Even after further standing for 12 hours, the interface between the aqueous phase and the ethyl acetate phase was discernible but not clear ( Figure 2 Since the ethyl acetate phase needs to be recovered without involving the intermediate phase, the amount of the recovered carboxylic acid extract is reduced compared to Example 1.

[0142] (Example 2)

[0143] A carboxylic acid extract (acetic acid extraction yield 85%, succinic acid extraction yield 60%) was obtained in the same manner as in Example 1, except that methyl isobutyl ketone was used as the extraction solvent instead of ethyl acetate. During this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the methyl isobutyl ketone phase was hardly observed, and phase separation occurred extremely rapidly within ten seconds.

[0144] (Comparative Example 2)

[0145] A carboxylic acid extract (acetic acid extraction rate 63%, succinic acid extraction rate 41%) was obtained in the same manner as in Example 2, except that the fermentation liquid containing carboxylic acids was not passed through the nanofiltration membrane. In this extraction, an intermediate phase containing solid components was generated between the aqueous phase and the methyl isobutyl ketone phase, and no phase separation was observed immediately after shaking. Even after further standing for more than 12 hours, the interface between the aqueous phase and the methyl isobutyl ketone phase was recognizable but not clear. Because it was necessary to recover the methyl isobutyl ketone phase without involving the intermediate phase, the amount of carboxylic acid extract recovered was reduced compared to Example 2.

[0146] Examples 1 and 2 and Comparative Examples 1 and 2 showed that the phase separation during extraction through the nanofiltration membrane was clear and rapid, and the carboxylic acid extract separated from the aqueous phase could be recovered.

[0147] (Example 3)

[0148] After passing 1 L of the fermentation broth containing carboxylic acids prepared in Reference Example 1 through a microfiltration membrane (a porous membrane with a pore size of 0.01 μm or more and less than 1 μm; manufactured by Toray Industries, Inc.), concentrated sulfuric acid (manufactured by Sigma-Aldrich Co., Ltd.) was added to adjust the pH to 4.0. The broth was then passed through an ultrafiltration membrane (molecular weight cutoff 10,000; manufactured by Toray Industries, Inc.). Nanofiltration and extraction were then performed in the same manner as in Example 1 to obtain a carboxylic acid extract (acetic acid extraction yield 99%, succinic acid extraction yield 90%). During this extraction, no solid-containing interphase was observed between the aqueous phase and the ethyl acetate phase, and phase separation occurred extremely rapidly within ten seconds.

[0149] (Comparative Example 3)

[0150] A carboxylic acid extract (acetic acid extraction yield 90%, succinic acid extraction yield 65%) was obtained in the same manner as in Example 3, except that the nanofiltration membrane treatment was omitted. During this extraction, an intermediate phase containing solid components formed between the aqueous phase and the ethyl acetate phase. Furthermore, clear phase separation was observed after 10 minutes.

[0151] From Example 3 and Comparative Example 3, it was shown that the effect of the nanofiltration membrane was significant even when the pH of the fermentation liquid containing carboxylic acid was adjusted before the fermentation liquid passed through the ultrafiltration membrane.

[0152] 3-Hydroxyadipate-3,6-lactone and α-hydromuconic acid used in Reference Example 20 shown below were produced by the method described in International Publication No. 2016 / 068108.

[0153] (Reference Example 20) Preparation of various fermentation broths containing carboxylic acids

[0154] In Reference Example 1, instead of adding acetic acid and succinic acid, itaconic acid (manufactured by Fuji Feilumu Wako Jun Pharmaceutical Co., Ltd.), adipic acid (manufactured by Fuji Feilumu Wako Jun Pharmaceutical Co., Ltd.), 3-hydroxyadipate-3,6-lactone, α-hydromuconic acid, cis-cis-muconic acid (manufactured by Shigma-Aldrich Co., Ltd.), 4-hydroxybenzoic acid (manufactured by Fuji Feilumu Wako Jun Pharmaceutical Co., Ltd.), and L-phenylalanine (manufactured by Fuji Feilumu Wako Jun Pharmaceutical Co., Ltd.) were added to prepare a fermentation broth containing carboxylic acids. The concentrations of itaconic acid, adipic acid, 3-hydroxyadipate-3,6-lactone, and L-phenylalanine were each set to 10 g / L. The concentrations of α-hydromuconic acid and cis-cis-muconic acid were set at 0.2 g / L, respectively, and the concentration of 4-hydroxybenzoic acid was set at 2 g / L.

[0155] (Reference Examples 21 to 41)

[0156] The fermentation broth containing carboxylic acids prepared in Reference Example 20 was passed through a microfiltration membrane (a porous membrane with a pore size of 0.01 μm or more and less than 1 μm; manufactured by Toray Industries, Inc.) and then through an ultrafiltration membrane (molecular weight cutoff 10,000; manufactured by Toray Industries, Inc.). 1 L of the fermentation broth containing carboxylic acids was transferred to a raw water tank and passed through the nanofiltration membrane once under the above-mentioned nanofiltration membrane treatment condition 1. The resulting filtrate containing carboxylic acids lost its color tone and became a clear aqueous solution. The carboxylic acid concentration was analyzed by HPLC, and the transmittance was calculated according to the following formula. The transmittance calculation results are shown in Table 3.

[0157] Permeability (%) = (compound concentration in permeate) / (compound concentration in raw water)×100.

[0158] Table 3 Nanofiltration membrane permeation test of various fermentation broths containing carboxylic acids

[0159] carboxylic acid pH Filtration pressure (MPa) Transmittance (%) Reference Example 21 Itaconic acid 4.0 0.5 55 Reference Example 22 Itaconic acid 4.0 1.0 41 Reference Example 23 Itaconic acid 4.0 1.5 36 Reference Example 24 Adipic acid 4.0 0.5 61 Reference Example 25 Adipic acid 4.0 1.0 50 Reference Example 26 Adipic acid 4.0 1.5 45 Reference Example 27 3-Hydroxyadipic acid-3,6-lactone 4.0 0.5 89 Reference Example 28 3-Hydroxyadipic acid-3,6-lactone 4.0 1.0 76 Reference Example 29 3-Hydroxyadipic acid-3,6-lactone 4.0 1.3 71 Reference Example 30 α-hydromuconic acid 4.0 0.5 92 Reference Example 31 α-hydromuconic acid 4.0 1.0 86 Reference Example 32 α-hydromuconic acid 4.0 1.3 84 Reference Example 33 cis, cis-muconic acid 4.0 0.5 38 Reference Example 34 cis, cis-muconic acid 4.0 1.0 26 Reference Example 35 cis, cis-muconic acid 4.0 1.5 23 Reference Example 36 4-Hydroxybenzoic acid 4.0 0.5 70 Reference Example 37 4-Hydroxybenzoic acid 4.0 1.0 64 Reference Example 38 4-Hydroxybenzoic acid 4.0 1.5 62 Reference Example 39 L-Phenylalanine 4.0 0.5 21 Reference Example 40 L-Phenylalanine 4.0 1.0 9 Reference Example 41 L-Phenylalanine 4.0 1.5 6

[0160] (Reference Examples 42 to 48)

[0161] 20 mL of the filtrate containing carboxylic acid prepared in Reference Examples 22, 25, 28, 31, 34, 37, and 40 was transferred to a glass separatory funnel (100 mL capacity), 20 mL of ethyl acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and the mixture was shaken 30 times. After shaking, the carboxylic acid concentration in the aqueous phase was measured by HPLC, and the extraction yield was calculated according to the following formula. The results are shown in Table 4.

[0162] Extraction rate (%)=(1-(concentration of the compound to be extracted in the residual extract) / (concentration of the compound to be extracted before extraction))×100.

[0163] Table 4: Carboxylic acid extraction test from carboxylic acid-containing filtrate

[0164] carboxylic acid pH Extraction solvent Extraction rate (%) Reference Example 42 Itaconic acid 4.0 Ethyl acetate 14 Reference Example 43 Adipic acid 4.0 Ethyl acetate 43 Reference Example 44 3-Hydroxyadipic acid-3,6-lactone 4.0 Ethyl acetate 64 Reference Example 45 α-hydromuconic acid 4.0 Ethyl acetate 87 Reference Example 46 cis, cis-muconic acid 4.0 Ethyl acetate 44 Reference Example 47 4-Hydroxybenzoic acid 4.0 Ethyl acetate 93 Reference Example 48 L-Phenylalanine 4.0 Ethyl acetate 76

[0165] (Example 4)

[0166] An itaconic acid extract (extraction yield 45%) was obtained in the same manner as in Example 1, except that the itaconic acid-containing fermentation broth prepared in Reference Example 20 was used. In this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was hardly observed, and phase separation occurred extremely rapidly within ten seconds.

[0167] (Example 5)

[0168] An adipic acid extract (90% extraction yield) was obtained in the same manner as in Example 1, except that the adipic acid-containing fermentation broth prepared in Reference Example 20 was used. In this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was almost unobservable, and phase separation occurred extremely rapidly within ten seconds.

[0169] (Example 6)

[0170] A 3-hydroxyadipate-3,6-lactone extract (99% extraction yield) was obtained in the same manner as in Example 1, except that the fermentation broth containing 3-hydroxyadipate-3,6-lactone prepared in Reference Example 20 was used. During this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was almost unobservable, and phase separation occurred extremely rapidly within ten seconds.

[0171] (Example 7)

[0172] An α-hydromuconic acid extract (99% extraction yield) was obtained in the same manner as in Example 1, except that the α-hydromuconic acid-containing fermentation broth prepared in Reference Example 20 was used. During this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was hardly observed, and phase separation occurred extremely rapidly within ten seconds.

[0173] (Example 8)

[0174] A cis,cis-muconic acid extract (85% extraction yield) was obtained in the same manner as in Example 1, except that the fermentation broth containing cis,cis-muconic acid prepared in Reference Example 20 was used. In this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was hardly observed, and phase separation occurred extremely rapidly within ten seconds.

[0175] (Example 9)

[0176] A 4-hydroxybenzoic acid extract (99% extraction yield) was obtained in the same manner as in Example 1, except that the fermentation broth containing 4-hydroxybenzoic acid prepared in Reference Example 20 was used. In this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was almost unobservable, and phase separation occurred extremely rapidly within ten seconds.

[0177] (Example 10)

[0178] An L-phenylalanine extract (99% extraction yield) was obtained in the same manner as in Example 1, except that the L-phenylalanine-containing fermentation broth prepared in Reference Example 20 was used. In this extraction, formation of an intermediate phase containing solid components between the aqueous phase and the ethyl acetate phase was almost unobservable, and phase separation occurred extremely rapidly within ten seconds.

[0179] Examples 1 to 10 show that the present invention can be used for the recovery of various carboxylic acids.

Claims

1. A method for producing a carboxylic acid, comprising the following steps (A), (B), and (C): Step (A): filtering the fermentation liquid containing the carboxylic acid through a nanofiltration membrane, and obtaining a filtrate containing the carboxylic acid from the permeate side. Step (B): extracting the carboxylic acid from the filtrate containing the carboxylic acid obtained in step (A) using an extraction solvent that can be phase-separated from the filtrate, and recovering the extract of the carboxylic acid that has been phase-separated from the aqueous phase. Step (C): recovering the carboxylic acid from the extract of the carboxylic acid obtained in step (B), The carboxylic acid is acetic acid, succinic acid, itaconic acid, adipic acid, 3-hydroxyadipate-3,6-lactone, α-hydromuconic acid, cis,cis-muconic acid, 4-hydroxybenzoic acid or L-phenylalanine, The extraction solvent is one or two selected from ethyl acetate and methyl isobutyl ketone.

2. The method according to claim 1, wherein the pH of the fermentation liquid containing the carboxylic acid and / or the filtrate containing the carboxylic acid is adjusted to 4.5 or less.

3. The method according to claim 1 or 2, comprising, in step (A), a step of removing insoluble matter before passing the fermentation liquid containing the carboxylic acid through a nanofiltration membrane.

4. The method according to claim 3, wherein the step of removing insoluble matter is a step of passing the fermentation liquid containing the carboxylic acid through a microfiltration membrane.

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