Method for producing hydroxybenzoic acid crystals

Abstract

A method for producing hydroxybenzoic acid crystals with suppressed discoloration is provided. [Solution] A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 1.0 to 6.5; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.5.

Description

Technical Field

[0001] The present invention relates to a method for producing hydroxybenzoic acid crystals.

Background Art

[0002] Hydroxybenzoic acid is a kind of aromatic hydroxycarboxylic acid, and is a compound in which a hydroxy group and a carboxy group are each bonded to a benzene ring. There are three isomers of hydroxybenzoic acid due to the difference in the relative positions of the hydroxy group and the carboxy group. Hydroxybenzoic acid is used as a raw material for food preservatives, preservatives, pharmaceuticals, and the like.

[0003] Hydroxybenzoic acid has been industrially produced for many years by an organic chemical synthesis method known as the Kolbe-Schmitt reaction. On the other hand, due to problems such as environmental load and safety, recently, the development of a hydroxybenzoic acid production process by a fermentation method using microorganisms has been carried out. For example, in Patent Document 1, it has been reported that after obtaining a culture solution containing hydroxybenzoic acid by a bioprocess using plant-derived saccharides and microorganisms, the culture solution is concentrated, and then hydroxybenzoic acid crystals are recovered from the concentrated solution by a crystallization method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when hydroxybenzoic acid is produced and crystallized by a fermentation method using microorganisms, a problem has been found that the hydroxybenzoic acid crystals are colored. Therefore, the present invention relates to providing a method for producing hydroxybenzoic acid crystals with suppressed coloring. [Means for solving the problem]

[0006] The inventors have discovered that by adjusting an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to a predetermined pH, contacting it with an adsorbent, and then crystallizing it under predetermined pH conditions, hydroxybenzoic acid crystals with minimal discoloration and good color can be obtained.

[0007] In other words, the present invention provides a method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 1.0 to 6.5; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.5. [Effects of the Invention]

[0008] According to the present invention, hydroxybenzoic acid crystals with suppressed discoloration can be provided. [Modes for carrying out the invention]

[0009] [Method for producing hydroxybenzoic acid crystals] The present invention provides a method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 1.0 to 6.5; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.5. The present invention provides hydroxybenzoic acid crystals with suppressed discoloration. The reason why the discoloration of the hydroxybenzoic acid crystals is suppressed by the present invention is not clear, but it is presumed that one of the factors is that the separation of the crystallization mother liquor and the crystals is improved during filtration after crystallization, as larger particle size and fewer defects are obtained at higher pH levels.

[0010] (Hydroxybenzoic acid) Hydroxybenzoic acid exists in three isomers: o-, m-, and p-. These can be denoted as 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid, respectively. In this invention, hydroxybenzoic acid may be any of these isomers, or a mixture of any two or three of the isomers. This invention is more preferably used for the crystallization of p-4-hydroxybenzoic acid.

[0011] In the present invention, the aqueous solution containing hydroxybenzoic acid is an aqueous solution derived from a microbial culture medium. Fermentation production methods for hydroxybenzoic acid using microorganisms are well known and can be achieved by combining known biosynthesis techniques from carbon sources such as glucose, and the starting materials may not be sugars. For example, International Publication No. 2012 / 081084 describes a method for producing salicylic acid (2-hydroxybenzoic acid) from phthalic acid, Japanese Patent Publication No. Hei 7-184671 describes a method for producing 3-hydroxybenzoic acid from isophthalic acid, and Japanese Patent Publication No. 2004-215586 describes a method for producing 4-hydroxybenzoic acid from toluene or benzoic acid. The microorganism may be a wild-type strain, a mutant strain, or a mutant strain in which mutations such as insertion, substitution, or deletion of the base sequence have occurred through various genetic manipulations. It may also be a microorganism to which the ability to produce hydroxybenzoic acid has been conferred by known artificial modifications. For example, microorganisms capable of producing hydroxybenzoic acid include the genera Escherichia, Rhodococcus, Acinetobacter, Bradyrhizobium, Corynebacterium, Pseudomonas, Rhodopseudomonas, Sinorhizobium, and Brevibacterium. Examples of microorganisms include those belonging to the genera *m*, *Novosphingobium*, *Ralstonia*, *Nocardioidaceae*, *Microbacterium*, *Streptomyces*, *Amycolatopsis*, *Kineococcus*, *Pantoea*, *Klebsiella*, and *Arthrobacter*.

[0012] The culture medium used for culturing microorganisms capable of producing hydroxybenzoic acid preferably contains, as culture materials, a carbon source, an inorganic nitrogen source, or an organic nitrogen source, as well as other necessary organic trace nutrients that the microorganisms can utilize. Examples of carbon sources include sugars (glucose, sucrose, maltose, etc.), organic acids, dextran, soluble starch, methanol, and the like. Examples of inorganic or organic nitrogen sources include ammonium salts, nitrates, various amino acids, corn steep liquor, tryptone, peptone, casein, yeast extract, meat extract, soybean meal, potato extract, and the like. It may also contain inorganic salts (such as sodium chloride, calcium chloride, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, magnesium chloride, magnesium sulfate, and manganese sulfate), vitamins, and antibiotics (such as tetracycline, neomycin, kanamycin, spectinomycin, and erythromycin).

[0013] The cultivation of microorganisms can be carried out using general methods, provided that the conditions allow the microorganisms to grow and produce hydroxybenzoic acid. The culture temperature is preferably 20°C or higher, more preferably 30°C or higher, and also preferably 40°C or lower, more preferably 37°C or lower. The pH of the culture medium during cultivation is preferably pH 4 or higher, more preferably pH 5 or higher, and also preferably pH 9 or lower, more preferably pH 8 or lower. The inoculation amount of microorganisms into the culture medium is preferably 0.01% (v / v) or more, more preferably 0.1% (v / v) or more, even more preferably 0.5% (v / v) or more, and also preferably 40% (v / v) or less, more preferably 30% (v / v) or less, and even more preferably 20% (v / v) or less. The culture period for microorganisms can be set appropriately according to the growth of the microorganisms, but is preferably 0.1 days or more, more preferably 0.2 days or more, even more preferably 0.3 days or more, and also preferably 20 days or less, more preferably 10 days or less, and even more preferably 8 days or less, based on a 24-hour day. Conventional culture vessels can be used for cultivation as appropriate. For example, aerated and agitated culture vessels, bubble tower culture vessels, and fluidized bed culture vessels can be used, and the process can be carried out in batch, semi-batch, or continuous configurations.

[0014] Such cultivation yields a microbial culture medium containing hydroxybenzoic acid. Since this culture medium contains impurities, microbial cells, and unused culture raw materials in addition to hydroxybenzoic acid, it is preferable to perform a separation operation such as centrifugation, membrane separation, or adsorption separation to obtain an aqueous solution containing hydroxybenzoic acid. In the present invention, the aqueous solution containing hydroxybenzoic acid is obtained by removing mainly microbial cells from the microbial culture medium containing hydroxybenzoic acid through the above separation operation. In this specification, "aqueous solution containing hydroxybenzoic acid" is also referred to as "the aqueous solution."

[0015] (Hydroxybenzoic acid content in aqueous solution) The hydroxybenzoic acid content in the aqueous solution containing hydroxybenzoic acid should be less than or equal to the saturation solubility of hydroxybenzoic acid. From the viewpoint of productivity, it is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. Furthermore, from the viewpoint of improving the yield during the bacterial cell isolation operation, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less. The hydroxybenzoic acid content in the aqueous solution is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2.5 to 12% by mass.

[0016] (pH adjustment of aqueous solutions containing hydroxybenzoic acid) In this invention, from the viewpoint of suppressing discoloration of the crystals, a step is performed to adjust the pH of an aqueous solution containing hydroxybenzoic acid to 1.0 to 6.5 prior to the treatment of contacting the adsorbent. Within this range, the pH of the aqueous solution containing hydroxybenzoic acid into which the adsorbent is brought into contact is not limited, but from the viewpoint of adsorption of color components and corrosion of equipment, it is 1.0 or higher, more preferably 2.0 or higher, even more preferably 2.5 or higher, even more preferably 3.0 or higher, even more preferably 4.0 or higher, and also 6.5 or lower, even more preferably 6.0 or lower. The pH of the aqueous solution containing hydroxybenzoic acid into which the adsorbent is brought into contact is 1.0 to 6.5, more preferably 2.0 to 6.5, more preferably 2.0 to 6.0, even more preferably 2.5 to 6.0, even more preferably 3.0 to 6.0, and even more preferably 4.0 to 6.0. Acids described later can be used to adjust the pH. In this specification, the pH was measured using the pH measuring device described in the examples, calibrated at 25°C using three pH standard solutions (pH 1.68, 6.86, 9.18). If the sample temperature was other than 25°C, the pH was calculated using the automatic temperature compensation function of the pH meter.

[0017] (Process of bringing the adsorbent into contact with the material) As the adsorbent, a porous adsorbent is preferred, and examples thereof include activated carbon, silicon dioxide, and solid acid adsorbents. Examples of the solid acid adsorbent include acid clay, activated clay, activated alumina, silica gel, silica-alumina, aluminum silicate, and the like. These can be used alone or in combination of two or more. Among them, activated carbon is preferred from the viewpoint of suppressing crystal coloring. The raw material from which the activated carbon is derived is not particularly limited, and examples thereof include sawdust, coal, coconut shells, and the like. Further, activated carbon activated by a gas such as water vapor or a chemical is preferably used. The shape of the activated carbon is not particularly limited, and examples thereof include powder form, granular form, and fibrous form. As the activated carbon, commercially available products such as Egret P (Osaka Gas Chemical Co., Ltd.) and Kuraray Coal GW (Kuraray Co., Ltd.) can be used.

[0018] In this treatment, from the viewpoint of high filtration speed and good productivity, perlite, silicon dioxide, diatomaceous earth, etc. may be appropriately added as a filter aid.

[0019] The amount of the adsorbent used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, based on the aqueous solution containing hydroxybenzoic acid, from the viewpoint of suppressing crystal coloring. Also, from the viewpoint of industrial productivity, it is preferably 10% by mass or less, more preferably 6% by mass or less, still more preferably 3% by mass or less. The amount of the adsorbent used is preferably 0.1 to 10% by mass, more preferably 0.3 to 6% by mass, still more preferably 0.5 to 3% by mass, based on the aqueous solution containing hydroxybenzoic acid.

[0020] Examples of the method of contacting the aqueous solution containing hydroxybenzoic acid with the adsorbent include a batch method, a continuous method, and the like. In the case of the batch method, for example, an adsorbent may be added to the aqueous solution containing hydroxybenzoic acid, stirred for adsorption, and then the adsorbent may be recovered by a filtration operation. The atmosphere during the treatment may be under air or under an inert gas (nitrogen gas, argon gas, helium gas, carbon dioxide). In the case of a continuous process, for example, contact can be maintained by continuously processing using a column packed with an adsorbent. The liquid flow conditions can be set as appropriate.

[0021] The contact temperature between the aqueous solution containing hydroxybenzoic acid and the adsorbent is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher, from the viewpoint of the solubility of hydroxybenzoic acid so that hydroxybenzoic acid does not precipitate and adsorb onto the adsorbent. Furthermore, from the viewpoint of industrial productivity, it is preferably 150°C or lower, more preferably 135°C or lower, even more preferably 120°C or lower, and even more preferably 95°C or lower. The contact temperature is preferably 40 to 150°C, more preferably 50 to 135°C, even more preferably 60 to 120°C, and even more preferably 60 to 95°C.

[0022] The contact time can be appropriately selected depending on the contact means and scale, but from the viewpoint of adsorption equilibrium of the coloring component to the adsorbent, it is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 20 minutes or more. Also, from the viewpoint of industrial productivity, it is preferably within 10 hours, more preferably within 5 hours, and even more preferably within 3 hours. The contact time is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours, and even more preferably 20 minutes to 3 hours. The pressure can be atmospheric pressure, pressurized pressure, or reduced pressure.

[0023] After contacting the adsorbent with an aqueous solution containing hydroxybenzoic acid, the adsorbent is separated. Filtration is preferred as the separation method, and any of the following filtration methods are possible: suction filtration, pressure filtration, centrifugal filtration, etc.

[0024] Although it varies depending on the absorbance at the end of cultivation before the treatment in which the adsorbent is brought into contact with the water, the absorbance at a wavelength of 470 nm of the aqueous solution containing hydroxybenzoic acid after the operation to separate the adsorbent is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.4 or less.

[0025] In the present invention, a step of concentrating the aqueous solution containing hydroxybenzoic acid may be performed prior to crystallization, but it is preferable to perform crystallization without performing the concentration step. The hydroxybenzoic acid content in the aqueous solution containing hydroxybenzoic acid before crystallization is preferably less than 15% by mass, and more preferably less than 10% by mass. The lower limit is not particularly limited, but is preferably 1% by mass or more.

[0026] (Crystallization) In this invention, crystallization refers to generally known crystallization methods or processes, which involve precipitating a solute as crystals by reducing its solubility or decreasing the amount of solvent. Examples of crystallization methods include cooling, pH adjustment, evaporation, addition of a poor solvent, or chemical reactions (for example, the formation of a less solubility salt by neutralization). Crystallization may be carried out by a single method or by a combination of multiple methods. Among these, in this invention, crystallization by cooling (sometimes called cooling crystallization) is preferred from the viewpoint of crystal quality and industrial productivity. In the present invention, crystallization of hydroxybenzoic acid is carried out under conditions of pH 3.0 to 6.5. The pH at the time of crystallization should be between 3.0 and 6.5, and preferably the pH at the start of crystallization. Furthermore, it is more preferable that the pH remains within this range during crystallization. From the viewpoint of suppressing discoloration of the crystals, the pH is preferably 3.5 or higher, more preferably 4.0 or higher, and even more preferably 4.5 or higher. From the viewpoint of crystallization yield, the pH is preferably 6.0 or lower. The pH at the time of crystallization, preferably the pH at the start of crystallization, and more preferably the pH during crystallization is 3.0 to 6.0, more preferably 3.5 to 6.0, even more preferably 4.0 to 6.0, and even more preferably 4.5 to 6.0. Furthermore, since the pH may fluctuate between the start and end of crystallization, the pH may be adjusted during crystallization in this invention. Regardless of whether the pH is adjusted during crystallization or not, the pH at the end of crystallization is preferably 3.5 or higher, more preferably 4.5 or higher, even more preferably greater than 4.5, and 6.0 or lower. Alternatively, it is preferably 3.5 to 6.0, more preferably 4.5 to 6.0, and even more preferably greater than 4.5 to 6.0. It is even more preferable that the pH exceeds 4.5 by the end of crystallization, for example, 4.6 or higher. The acid used for pH adjustment can be any acid with a pKa lower than hydroxybenzoic acid, and inorganic acids are particularly preferred. Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid. Sulfuric acid and hydrochloric acid are preferred. When the adsorbent treatment is performed at a low pH, or to achieve a preferred pH range, an alkaline agent may be used for pH adjustment, and aqueous solutions of ammonia and sodium or potassium hydroxide can be used.

[0027] (Crystallization due to cooling) In the present invention, from the viewpoint of crystal formation, it is preferable to crystallize by cooling the aqueous solution containing hydroxybenzoic acid after adsorbent treatment. Preferably, the temperature of the aqueous solution containing hydroxybenzoic acid after the adsorbent treatment before cooling (the temperature at which cooling begins) is the same as the contact temperature between the aqueous solution and the adsorbent. The temperature at which cooling begins is, for example, preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, from the viewpoint of industrial productivity, it is preferably 150°C or lower, more preferably 135°C or lower, even more preferably 120°C or lower, and even more preferably 95°C or lower. Preferably 40-150°C, more preferably 50-135°C, even more preferably 60-120°C, and even more preferably 60-95°C. The cooling completion temperature is preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower, and also preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 8°C or higher, from the viewpoint of crystallization yield. The cooling temperature is preferably 0 to 50°C, more preferably 5 to 40°C, and even more preferably 8 to 30°C.

[0028] When cooling an aqueous solution containing hydroxybenzoic acid during crystallization, it is preferable to cool it at a rate of 1°C / min or less, more preferably 0.8°C / min or less, and even more preferably 0.5°C / min or less, from the viewpoint of suppressing discoloration of the crystals. Depending on the discoloration of the crystallization and the state of the crystals, the above cooling rate may be applied to one period of the cooling process or to the entire process. Furthermore, in this specification, the average cooling rate is defined by dividing the difference (°C) between the cooling start temperature and the cooling end temperature by the time (min) required to reach the cooling end temperature from the cooling start temperature. After starting cooling, it is also possible to temporarily stop cooling to maintain a constant temperature, i.e., to provide a period with a cooling rate of 0°C / min, but care should be taken to avoid the precipitation of impurities other than hydroxybenzoic acid. The average cooling rate is preferably 1°C / min or less, more preferably 0.5°C / min or less, and even more preferably 0.3°C / min or less, from the viewpoint of suppressing discoloration of the crystals, and is preferably 0.03°C / min or more, from the viewpoint of productivity. The average cooling rate is preferably 0.03 to 1°C / min, more preferably 0.03 to 0.5°C / min, and even more preferably 0.03 to 0.3°C / min.

[0029] Crystallization may be carried out under static conditions, or it may be carried out while stirring using a reaction vessel equipped with a stirring blade. The stirring blades can be of any shape, but paddle blades, turbine blades, propeller blades, anchor blades, large-diameter paddle blades, and Maxblend blades are preferred in order to ensure good crystal mixing. The peripheral speed of stirring is preferably 0.2 m / s or more, more preferably 0.3 m / s or more, and even more preferably 0.5 m / s or more, from the viewpoint of preventing the slurry from solidifying, and preferably 10 m / s or less, more preferably 5 m / s or less, and even more preferably 3 m / s or less, from the viewpoint of suppressing the crushing of hydroxybenzoic acid crystals. By adding nonionic surfactants or acid anhydrides during crystallization, more purified hydroxybenzoic acid crystals can be obtained.

[0030] (Separation and washing of hydroxybenzoic acid crystals) Hydroxybenzoic acid crystals can be separated by solid-liquid separation operations such as centrifugation, filtration, and decantation. The hydroxybenzoic acid crystals may be washed if necessary. Examples of solvents that can be used for washing include water, ethanol, acetone, and toluene.

[0031] (Drying of hydroxybenzoic acid crystals) The drying method for hydroxybenzoic acid crystals is not particularly limited as long as moisture can be removed. For example, conventional dryers such as shelf dryers, conical dryers, paddle dryers, Nauter mixers, fluidized bed dryers, vacuum agitation dryers, and disc dryers can be used. It is preferable to use a drying method that does not apply high shear to maintain the hydroxybenzoic acid crystal structure. The drying temperature is preferably -50°C or higher, more preferably -30°C or higher, even more preferably -20°C or higher, and also preferably 110°C or lower, more preferably 90°C or lower, and even more preferably 70°C or lower. Vacuum drying may also be performed. The dried hydroxybenzoic acid crystals may be subjected to further treatment, such as sieving, if necessary.

[0032] [Hydroxybenzoic acid crystals] Thus, hydroxybenzoic acid crystals are obtained. The hydroxybenzoic acid crystals obtained by the manufacturing method of the present invention have suppressed discoloration and good color. The absorbance at a wavelength of 400 nm, measured by the method described in the examples below, is preferably 0.60 or less, and more preferably 0.30 or less.

[0033] The hydroxybenzoic acid crystals of the present invention are useful not only for their own use but also as an intermediate raw material for producing various derivatives.

[0034] With regard to the embodiments described above, the present invention further discloses the following method for producing hydroxybenzoic acid crystals.

[0035] <1> A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 1.0 to 6.5; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.5.

[0036] <2> The pH of the aqueous solution containing hydroxybenzoic acid derived from the culture medium of microorganisms is adjusted to preferably 2.0 to 6.5, more preferably 2.5 to 6.0, even more preferably 3.0 to 6.0, and especially preferably 4.0 to 6.0. <1> A method for producing hydroxybenzoic acid crystals as described above. <3> The aforementioned microorganisms include the genera Escherichia, Rhodococcus, Acinetobacter, Bradyrhizobium, Corynebacterium, Pseudomonas, Rhodopseudomonas, Sinorhizobium, Brevibacterium, and Novosphingobium. It is at least one species selected from the genera Novosphingobium, Ralstonia, Nocardioidaceae, Microbacterium, Streptomyces, Amycolatopsis, Kineococcus, Pantoea, Klebsiella, and Arthrobacter. <1> or <2> A method for producing hydroxybenzoic acid crystals as described above. <4> The hydroxybenzoic acid content in the aqueous solution containing the hydroxybenzoic acid is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 2.5% by mass or more, and also preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 12% by mass or less, preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2.5 to 12% by mass. <1> ~ <3> A method for producing hydroxybenzoic acid crystals as described in any of the above. <5> The adsorbent is preferably at least one selected from activated carbon, silicon dioxide, acid clay, activated clay, activated alumina, silica gel, silica-alumina, and aluminum silicate. <1> ~ <4> A method for producing hydroxybenzoic acid crystals as described in any of the above. <6> The amount of adsorbent used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 6% by mass or less, even more preferably 3% by mass or less, preferably 0.1 to 10% by mass, more preferably 0.3 to 6% by mass, and even more preferably 0.5 to 3% by mass, relative to the aqueous solution containing hydroxybenzoic acid. <1> ~ <5> A method for producing hydroxybenzoic acid crystals as described in any of the above. <7> The contact temperature between the aqueous solution containing hydroxybenzoic acid and the adsorbent is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and also preferably 150°C or lower, more preferably 135°C or lower, even more preferably 120°C or lower, even more preferably 95°C or lower, preferably 40-150°C, more preferably 50-135°C, even more preferably 60-120°C, and even more preferably 60-95°C. <1> ~ <6> A method for producing hydroxybenzoic acid crystals as described in any of the above. <8> The contact time between the aqueous solution containing hydroxybenzoic acid and the adsorbent is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 20 minutes or more, and also preferably within 10 hours, more preferably within 5 hours, even more preferably within 3 hours, preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours, and even more preferably 20 minutes to 3 hours. <1> ~ <7> A method for producing hydroxybenzoic acid crystals as described in any of the above.

[0037] <9> The hydroxybenzoic acid content in the aqueous solution containing hydroxybenzoic acid before crystallization is preferably less than 15% by mass, more preferably less than 10% by mass, and preferably 1% by mass or more. <1> ~ <8> A method for producing hydroxybenzoic acid crystals as described in any of the above. <10> The pH at the time of crystallization is preferably 3.0 or higher, more preferably 3.5 or higher, even more preferably 4.0 or higher, and especially preferably 4.5 or higher, and also preferably 6.0 or lower, preferably 3.0 to 6.0, more preferably 3.5 to 6.0, even more preferably 4.0 to 6.0, and even more preferably 4.5 to 6.0. <1> ~ <9> A method for producing hydroxybenzoic acid crystals as described in any of the above. <11> Preferably, the pH during crystallization is the pH at the start of crystallization. <1> ~ <10> A method for producing hydroxybenzoic acid crystals as described in any of the above. <12> The pH at the end of crystallization is preferably 3.5 or higher, more preferably 4.5 or higher, even more preferably greater than 4.5, and also preferably 6.0 or lower, preferably between 3.5 and 6.0, more preferably between 4.5 and 6.0. <1> ~ <11> A method for producing hydroxybenzoic acid crystals as described in any of the above. <13> The pH fluctuation from the start to the end of crystallization is preferably 3.0 to 6.5, more preferably 3.0 to 6.0, more preferably 3.5 to 6.0, even more preferably 4.0 to 6.0, and even more preferably 4.5 to 6.0. <1> ~ <12> A method for producing hydroxybenzoic acid crystals as described in any of the above.

[0038] <14> The aqueous solution containing the hydroxybenzoic acid is crystallized by cooling it at a rate of 1°C / min or less. <1> ~ <13> A method for producing hydroxybenzoic acid crystals as described in any of the above. <15> The temperature at which cooling begins is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and also preferably 150°C or lower, more preferably 135°C or lower, even more preferably 120°C or lower, even more preferably 95°C or lower, preferably 40-150°C, more preferably 50-135°C, even more preferably 60-120°C, and even more preferably 60-95°C. <14> A method for producing hydroxybenzoic acid crystals as described above. <16> The cooling completion temperature is preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower, and also preferably 0°C or higher, more preferably 5°C or higher, even more preferably 8°C or higher, preferably 0 to 50°C, more preferably 5 to 40°C, and even more preferably 8 to 30°C. <14> or <15> A method for producing hydroxybenzoic acid crystals as described above. <17> The average cooling rate is preferably 1°C / min or less, more preferably 0.5°C / min or less, even more preferably 0.3°C / min or less, and also preferably 0.03°C / min or more, preferably 0.03 to 1°C / min, more preferably 0.03 to 0.5°C / min, and even more preferably 0.03 to 0.3°C / min. <14> ~ <16> A method for producing hydroxybenzoic acid crystals as described in any of the above.

[0039] <18> A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 3.0 to 6.0; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.0. <19> A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 4.0 to 6.0; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 4.0 to 6.0, wherein the pH at the end of crystallization is 4.5 or higher. <20> A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 3.0 to 6.0; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.0, wherein the crystallization is performed by cooling the aqueous solution at 1°C / min or less. [Examples]

[0040] [Method for measuring pH] The pH of the aqueous solution (stock solution) at 70°C was measured using a Horiba F-52 analyzer.

[0041] [Evaluation of the color of 4-hydroxybenzoic acid after crystallization] After crystallization, the obtained 4-hydroxybenzoic acid was dissolved in ethanol to prepare a 100 g / L solution. The solution was passed through a 0.20 μm pore size membrane filter, and the absorbance at a wavelength of 400 nm was measured using a Shimadzu UV-1800 ultraviolet-visible spectrophotometer with a 1 cm path length cell. A lower absorbance value indicates better color.

[0042] [Test Example 1] (Preparation of fermentation liquid) A culture solution containing 4-hydroxybenzoic acid was obtained by fermentation using transformants of the genus Corynebacterium. The pH of the culture solution containing 4-hydroxybenzoic acid was adjusted to 5.5 with sulfuric acid, and after sterilization at 70°C for 1 hour, the bacterial cells and solution were separated using a pressure filter, and the aqueous solution containing 4-hydroxybenzoic acid was recovered. The concentration of 4-hydroxybenzoic acid in the obtained aqueous solution was 40 g / L (4 mass%), and the absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured at 0.415 using a Shimadzu UV-1800 ultraviolet-visible spectrophotometer with a 1 cm path length cell.

[0043] (Activated carbon treatment [treatment involving contact with an adsorbent]) Next, the pH of the aqueous solution containing 4-hydroxybenzoic acid was adjusted to 7.0 with a 50% NaOH aqueous solution, and 1.0% (g / g solution) of activated carbon (Osaka Gas Chemical Co., Ltd.) was added as an adsorbent. The solution was then stirred at 70°C for 1 hour to perform activated carbon treatment. After that, the activated carbon was removed by passing the solution through a membrane filter with a pore size of 0.2 μm. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.138.

[0044] [Test Example 2] The procedure was carried out in the same manner as in Test Example 1, except that the pH before activated carbon adsorption was set to 6.5. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.129.

[0045] [Test Example 3] (Activated carbon treatment [treatment involving contact with an adsorbent]) An aqueous fermentation solution containing 4-hydroxybenzoic acid with a pH of 5.5, prepared in Test Example 1, was used. Activated carbon was added at a concentration of 1.0% (g / g solution) as an adsorbent, and the mixture was stirred at 70°C for 1 hour to perform activated carbon treatment. The solution was then passed through a 0.2 μm membrane filter to remove the activated carbon. The absorbance of the resulting aqueous solution at a wavelength of 470 nm was measured to be 0.124.

[0046] [Test Example 4] (Activated carbon treatment [treatment involving contact with an adsorbent]) An aqueous fermentation solution containing 4-hydroxybenzoic acid with a pH of 5.5, prepared in Test Example 1, was used. Subsequently, the pH of the aqueous solution containing 4-hydroxybenzoic acid was adjusted to 5.0 with sulfuric acid, and 1.0% (g / g solution) of activated carbon was added as an adsorbent. The solution was stirred at 70°C for 1 hour to perform activated carbon treatment. After that, the activated carbon was removed by passing the solution through a 0.2 μm membrane filter. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.114.

[0047] [Test Example 5] The procedure was carried out in the same manner as in Test Example 4, except that the pH before activated carbon adsorption was set to 4.0. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.073.

[0048] [Test Example 6] The procedure was carried out in the same manner as in Test Example 4, except that the pH before activated carbon adsorption was set to 3.0. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.043.

[0049] [Test Example 7] The procedure was carried out in the same manner as in Test Example 4, except that the pH before activated carbon adsorption was set to 2.0. The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured to be 0.031.

[0050] Table 1 shows the absorbance of the aqueous solutions at a wavelength of 470 nm for each test example.

[0051] [Table 1]

[0052] [Comparative Example 1] (Preparation of fermentation liquid) A culture solution containing 4-hydroxybenzoic acid was obtained by fermentation using transformants of the genus Corynebacterium. After sterilization at 70°C for 1 hour, the bacterial cells and solution were separated using a pressure filter, and the aqueous solution containing 4-hydroxybenzoic acid was recovered. The concentration of 4-hydroxybenzoic acid in the obtained aqueous solution was 87 g / L (8.7 mass%). The absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured using a Shimadzu UV-1800 ultraviolet-visible spectrophotometer with a 1 cm path length cell and was found to be 0.919.

[0053] (Activated carbon treatment [treatment involving contact with an adsorbent]) Next, the pH of the aqueous solution containing 4-hydroxybenzoic acid was adjusted to 5.5 with sulfuric acid, and 1.0% (g / g solution) of activated carbon (Osaka Gas Chemical Co., Ltd.) was added as an adsorbent. The solution was then stirred at 70°C for 1 hour to perform activated carbon treatment. After that, the activated carbon was removed by passing the solution through a membrane filter with a pore size of 0.20 μm. The concentration of 4-hydroxybenzoic acid in the resulting aqueous solution before crystallization was 90 g / L (9 mass%). Furthermore, the absorbance of the obtained aqueous solution at a wavelength of 470 nm was measured using a Shimadzu UV-1800 ultraviolet-visible spectrophotometer and a cell with a path length of 1 cm, and was found to be 0.37.

[0054] (Crystallization of 4-hydroxybenzoic acid) The aqueous solution containing 4-hydroxybenzoic acid after activated carbon treatment was adjusted to pH 2.6 with sulfuric acid. 30 mL of the aqueous solution was placed in a 50 mL screw-top bottle and sealed. The solution was cooled from 70°C to 10°C at a cooling rate of 0.1°C / min (the average cooling rate was also the same) while reciprocating shaking at 180 rpm to precipitate crystals. The precipitated crystals were then collected by passing them through a membrane filter with a pore size of 0.45 μm. The pH of the filtrate after crystal collection was 1.9. The recovered crystals were dispersed in 30 g of deionized water at 8°C, and then washed again by passing them through a membrane filter with a pore size of 0.45 μm. This crystal washing procedure was performed a total of two times. After washing, the crystals were collected in aluminum cups and dried at 105°C for more than 3 hours to obtain 4-hydroxybenzoic acid crystals.

[0055] [Example 1] The procedure was carried out in the same manner as in Comparative Example 1, except that the pH before crystallization was set to 3.0. The pH of the filtrate after crystal recovery was 2.5.

[0056] [Example 2] The procedure was carried out in the same manner as in Comparative Example 1, except that the pH before crystallization was set to 4.0. The pH of the filtrate after crystal recovery was 4.8.

[0057] [Example 3] The procedure was carried out in the same manner as in Comparative Example 1, except that the pH before crystallization was set to 5.0. The pH of the filtrate after crystal recovery was 6.0.

[0058] Table 2 shows the absorbance of hydroxybenzoic acid at a wavelength of 400 nm in each example and comparative example.

[0059] [Table 2]

[0060] As shown in Table 2, the hydroxybenzoic acid crystals obtained by the manufacturing method of the present invention were found to have little discoloration and good color.

Claims

1. A method for producing hydroxybenzoic acid crystals, comprising the steps of: adjusting the pH of an aqueous solution containing hydroxybenzoic acid derived from a microbial culture medium to 1.0 to 6.5; contacting the aqueous solution with an adsorbent; and crystallizing the hydroxybenzoic acid under conditions of pH 3.0 to 6.

5.

2. A method for producing hydroxybenzoic acid crystals according to claim 1, wherein an aqueous solution containing hydroxybenzoic acid is crystallized by cooling it at 1°C / min or less.

3. A method for producing hydroxybenzoic acid crystals according to claim 1 or 2, wherein the amount of adsorbent used is 0.1 to 10% by mass relative to the aqueous solution containing hydroxybenzoic acid.

4. A method for producing hydroxybenzoic acid crystals according to claim 1 or 2, wherein the content of hydroxybenzoic acid in the aqueous solution containing hydroxybenzoic acid before crystallization is less than 15% by mass.

5. A method for producing hydroxybenzoic acid crystals according to claim 1 or 2, wherein the adsorbent is activated carbon.

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