JP5080771B2 - Method for producing useful substance using immobilized enzyme - Google Patents

Description

  The present invention relates to a method for producing a useful substance by a reaction using a fixed bed type reaction column packed with an immobilized enzyme.

  As a reaction performed by passing the liquid through a fixed bed type reaction tower, a reaction using an immobilized enzyme used for L-aspartic acid production, transesterified oil production, lactose hydrolysis, fats hydrolysis, etc. Are known. Since these reactions have a relatively small calorific value, the simplest drum reactor is usually used.

  Among the reactions using immobilized enzymes, when two or more kinds of liquids are circulated through the reactor as in the hydrolysis of fats and oils, the reaction liquids are allowed to pass in a uniformly mixed state from the viewpoint of improving reaction efficiency. It is preferable to liquefy. In this case, since the oil phase substrate and the water phase substrate used for the hydrolysis do not become a single phase even if they are originally mixed, it is generally used as an emulsion. On the other hand, since emulsion particles are unlikely to reach the enzyme adsorbed in the pores of the carrier, there is a technique in which the liquid passing speed is within a range where the reaction liquid is not emulsified (see Patent Document 1).

In addition, as a method of circulating the oil phase substrate and the aqueous phase substrate through the fixed bed, there are a method of circulating countercurrent (see Patent Literatures 1 and 2) and a method of circulating in parallel flow (see Patent Literature 3). Since the former requires a special mechanism and operation method, generally, a method of circulating in parallel is adopted.
JP-A-61-85195 JP-A-1-98494 JP 2000-160188 A

  In the method of carrying out the reaction by flowing a liquid mixture that forms a two-liquid phase in the fixed bed type reaction tower packed with the immobilized enzyme, particularly when the liquid mixture is passed without emulsification, the diameter of the reaction tower It has been found that the flow of the reaction liquid in the column becomes non-uniform as the value increases, and there is a portion where the reaction does not proceed efficiently, resulting in a decrease in reactivity. In this case, in order to increase the reactivity, simply increasing the contact time between the immobilized enzyme and the reaction solution has a problem that the productivity (flow rate) decreases.

  Accordingly, the present invention provides a method for producing a useful substance in which a reaction is carried out by circulating a liquid mixture that forms a two-liquid phase through a fixed bed type reaction column packed with an immobilized enzyme. It is intended to provide a method for producing a useful substance more efficiently by enhancing and improving productivity.

  Therefore, as a result of analyzing the characteristics of the flow of the reaction liquid in the fixed bed type reaction column packed with the immobilized enzyme, the present inventor found that the smaller the cross-sectional area of the flow path, the more uniform the reaction liquid flow and the higher the reactivity. I found out. Therefore, the interior or piping is loaded so that a tubular structure having a circular or polygonal shape with a small cross section of one pipe is formed inside the fixed bed type reaction tower having a large cross section filled with the immobilized enzyme. It has been found that productivity can be improved while maintaining high reactivity by causing the enzyme reaction to occur in each tubular structure having a small cross-sectional area.

  The present invention relates to a method for producing a useful substance in which a liquid mixture that forms a two-liquid phase is supplied to a fixed bed type reaction column packed with an immobilized enzyme, and the reaction is carried out in parallel in the same direction. Using a fixed bed type reaction column loaded with interiors or piping so that a plurality of tubular structures having a circular shape with a diameter of 100 mm or less or a polygon with a diagonal length of 100 mm or less are formed, and the immobilized enzyme is contained in the tubular structure. The present invention provides a method for producing a useful substance that is filled and supplied with the liquid mixture in the tubular structure.

  According to the present invention, in a reaction performed by supplying a liquid mixture that forms a two-liquid phase to a fixed bed type reaction column filled with an immobilized enzyme, the flow of the entire reaction liquid in the column can be made uniform, As a result, the reactivity and productivity can be improved. In particular, in the hydrolysis of fats and oils, enzyme activity can be effectively expressed and fatty acids can be produced efficiently.

  In the present invention, it is necessary to supply a liquid mixture that forms two liquid phases to a fixed bed type reaction column packed with an immobilized enzyme. The fixed bed type reaction tower (hereinafter also referred to as “enzyme tower”) is a column in which immobilized enzyme is packed so that the reaction solution can be circulated through the space between the immobilized carriers and the pores of the immobilized carriers. Say things. The two-liquid phase means a state in which two types of liquids do not become one phase even after mixing, and includes those in which they are in an emulsified state even if they are uniform from those that are phase-separated.

  As an aspect of the present invention, an immobilized enzyme using an oil-degrading enzyme adsorbed on an immobilized carrier is used, and an oil phase substrate and an aqueous phase substrate are circulated as a two-liquid phase in a reaction tower packed with the enzyme. A method of producing fatty acids as useful substances by a hydrolysis reaction of fats and oils is preferable.

  In the present invention, it is necessary to cause two liquid phases to flow in the same direction. In this case, the two liquid phases may be mixed in advance and supplied as an emulsified state, or may be supplied while being separated. Further, the two liquid phases may be alternately supplied at regular intervals. Each substrate may be supplied to the enzyme tower in a downward flow from the tower top to the tower bottom or in an upward flow from the tower bottom to the tower top.

  The immobilized enzyme used in the present invention is one in which an enzyme is supported on an immobilized carrier by adsorption or the like. Immobilization carriers include celite, diatomaceous earth, kaolinite, silica gel, molecular sieves, porous glass, activated carbon, calcium carbonate, ceramics and other inorganic carriers, ceramic powder, polyvinyl alcohol, polypropylene, chitosan, ion exchange resin, hydrophobic adsorption Examples thereof include organic polymers such as resins, chelate resins, and synthetic adsorption resins, and ion exchange resins are particularly preferable from the viewpoint of high water retention. Of the ion exchange resins, a porous material is preferable because it has a large surface area and can increase the amount of adsorbed enzyme.

  The particle diameter of the resin used as the immobilization carrier is preferably 100 to 1000 μm, more preferably 250 to 750 μm. The pore diameter is preferably 10 to 150 nm, more preferably 10 to 100 nm. Examples of the material include phenol formaldehyde, polystyrene, acrylamide, divinylbenzene, and the like, and phenol formaldehyde resin (for example, Dulite A-568 manufactured by Rohm and Hass) is particularly preferable from the viewpoint of improving the enzyme adsorptivity.

  The enzyme used for the immobilized enzyme of the present invention is not particularly limited, but lipase is preferred as an enzyme for decomposing oils and fats from the viewpoint of a large productivity improvement effect. As the lipase, not only those derived from animals and plants but also commercially available lipases derived from microorganisms can be used. Examples of microorganism-derived lipases include the genus Risopus, the genus Aspergillus, the genus Mucor, the genus Pseudomonas, the genus Geotrichum and the genus Penicillium and the genus Penicillium The thing of origin is mentioned.

  The temperature at which the enzyme is immobilized can be determined depending on the properties of the enzyme, but is preferably 0 to 60 ° C., particularly 5 to 40 ° C. at which the enzyme is not deactivated. Moreover, the pH of the enzyme solution used at the time of immobilization may be in a range where no denaturation of the enzyme occurs, and can be determined by the characteristics of the enzyme as well as the temperature. In order to maintain this pH, a buffer solution is used. Examples of the buffer solution include an acetate buffer solution, a phosphate buffer solution, and a Tris-HCl buffer solution. The enzyme concentration in the enzyme solution is preferably not more than the saturation solubility of the enzyme and sufficient from the viewpoint of immobilization efficiency. Moreover, the enzyme solution can also use what was refine | purified by the supernatant obtained by removing the insoluble part by centrifugation, ultrafiltration, etc. as needed. Moreover, although the enzyme mass to be used varies depending on the enzyme activity, it is preferably 5 to 1000 mass%, particularly preferably 10 to 500 mass%, based on the mass of the carrier.

  When the enzyme is immobilized, the carrier and the enzyme may be directly adsorbed. However, in order to obtain an adsorption state that expresses high activity, the carrier may be treated with a fat-soluble fatty acid or a derivative thereof in advance before the enzyme adsorption. preferable. As a method for contacting the fat-soluble fatty acid or derivative thereof with the carrier, these may be added directly to water or an organic solvent, but in order to improve dispersibility, the fat-soluble fatty acid or derivative thereof is once dispersed and dissolved in the organic solvent. And then added to a carrier dispersed in water. Examples of the organic solvent include chloroform, hexane, ethanol, and the like. The used mass of the fat-soluble fatty acid or derivative thereof is preferably 1 to 500 mass%, particularly preferably 10 to 200 mass%, based on the mass of the carrier. The contact temperature is preferably 0 to 100 ° C, particularly preferably 20 to 60 ° C, and the contact time is preferably about 5 minutes to 5 hours. The carrier after this treatment is collected by filtration, but may be dried. The drying temperature is preferably room temperature to 100 ° C., and drying under reduced pressure may be performed.

  Among the fat-soluble fatty acids or derivatives thereof for treating the carrier in advance, the fat-soluble fatty acid has a saturated or unsaturated, linear or branched, hydroxy group having 4 to 24 carbon atoms, preferably 8 to 18 carbon atoms. Fatty acids that may be used are listed. Specific examples include capric acid, lauric acid, myristic acid, oleic acid, linoleic acid, α-linolenic acid, ricinoleic acid, isostearic acid and the like. Examples of the fat-soluble fatty acid derivatives include esters of these fat-soluble fatty acids with mono- or polyhydric alcohols or saccharides, phospholipids, and those obtained by adding ethylene oxide to these esters. Specific examples include methyl esters, ethyl esters, monoglycerides, diglycerides, ethylene oxide adducts thereof, polyglycerin esters, sorbitan esters, and sucrose esters of the above fatty acids. These fat-soluble fatty acids and derivatives thereof are preferably liquid at room temperature in terms of immobilizing the enzyme on the carrier. As these fat-soluble fatty acids or derivatives thereof, two or more of the above may be used in combination, and naturally derived fatty acids such as rapeseed fatty acids and soybean fatty acids may be used.

  The hydrolysis activity of the immobilized enzyme is preferably 20 U / g or more, more preferably 100 to 10,000 U / g, and particularly preferably 500 to 5000 U / g. Here, 1 U of enzyme produces 1 μmol of free fatty acid per minute when hydrolyzed at 40 ° C. for 30 minutes while stirring and mixing a mixture of fats and oils: water = 100: 25 (mass ratio). The resolution of the enzyme is shown.

  The hydrolysis activity (U / g-oil) of the immobilized enzyme imparted per unit mass of fats and oils and the time required to reach a certain hydrolysis rate are in a substantially inverse relationship. When hydrolysis is carried out using a packed bed (enzyme tower) packed with immobilized enzyme, the hydrolysis rate varies depending on the liquid feeding conditions (flow rate, temperature, etc.), but the time required for hydrolysis (retention time in the packed bed) ) And the weight (g-oil) of the fats and oils present in the packed bed and the packed weight (g) of the immobilized enzyme, the apparent activity (expression activity) (U / g) of the immobilized enzyme is determined.

  The oil phase substrate used in the present invention mainly refers to fats and oils. The fats and oils may contain diacylglycerol, monoacylglycerol, or fatty acids in addition to triacylglycerol, and are obtained as a result of hydrolysis. May contain fatty acids. Specific examples of the oil phase substrate include vegetable oils such as rapeseed oil, soybean oil, sunflower oil, palm oil and linseed oil, animal oils such as beef tallow, pork tallow and fish oil, or a combination of these. These fats and oils can be deodorized oil and non-deodorized fats and oils that have not been deodorized beforehand. However, the use of non-deodorized fats and oils for a part or all of these fats and oils may be trans Saturated fatty acids are preferred, and the plant sterols, plant sterol fatty acid esters, and tocopherols derived from raw oils and fats are preferred. In the oil phase substrate, oil-soluble components such as fatty acids may be mixed in addition to the oils and fats. Fatty acids refer to fatty acids obtained as a result of hydrolysis, as well as those containing one or more of the above glycerides.

  The aqueous phase substrate used in the present invention is water, but other water-soluble components such as glycerin obtained as a result of hydrolysis may be mixed.

  The fixed bed type reaction column (enzyme column) used in the present invention may have any shape as long as it can withstand the pushing pressure of the pump used. Moreover, it is preferable that a jacket be provided around the enzyme tower so that the reaction liquid flowing in the enzyme tower can be adjusted to a temperature suitable for the enzyme reaction. The temperature in the enzyme tower is preferably 0 to 60 ° C., more preferably 20 to 40 ° C., in order to extract the activity of the immobilized enzyme more effectively. The length of the enzyme column may be a length necessary for obtaining a desired decomposition rate, but it is in the range of 0.01 to 10 m, preferably 0.1 to 5 m from the viewpoint of reactivity, pressure loss in the column, etc. It is preferable that

  In the present invention, the inner column or the piping is loaded in the enzyme tower so that a plurality of tubular structures having a circular cross section with a diameter of 100 mm or less or a polygon with a diagonal length of 100 mm or less are formed in the enzyme tower. The structure is filled with an immobilized enzyme, and the liquid mixture is supplied into the tubular structure to carry out the reaction. By carrying out the reaction in a plurality of tubular structures having such a small cross-sectional area, the cross-sectional area of the flow path in the enzyme tower is reduced, and the flow of the reaction liquid in two liquid phases is made uniform. Can do. At this time, if there is a gap between the interior structure or piping in which the tubular structure is formed and the inner wall of the enzyme tower, filling the gap with the immobilized enzyme also makes the flow of the reaction solution uniform. It is preferable from the point of making. The interior or piping only needs to be able to form a plurality of tubular structures having the above-mentioned cross-sectional area in the enzyme tower. Examples of the interior are columns (FIG. 1), prisms (FIG. 2), plates (Partition plate) (FIG. 3). That is, the interior or piping is loaded in the vertical direction, preferably in a columnar shape. More specifically, a method of loading a pipe into a multi-tube type, a method of loading a vertical partition plate (a flat plate, a corrugated plate, etc.) inside an enzyme tower, an interior having a circular or polygonal cross section The method of loading etc. is mentioned. Among these, in the case of loading the interior, the shape of the cross section is preferably a regular triangle, a square, or a regular hexagon from the viewpoint of the efficiency of loading the interior. As an interior thing, the thing of the form which bundled the square pipe, for example can be used.

  The diameter or diagonal length of the cross section of one pipe (one flow path) formed of pipes or interiors is required to be 100 mm or less, but preferably 75 mm or less from the viewpoint of improving reactivity. Further, it is preferably 50 mm or less, particularly 35 mm or less.

A plurality of tubular structures formed by loading pipes or interiors into the enzyme tower are filled with the immobilized enzyme, and a two-liquid phase liquid mixture (reaction liquid) is supplied into the tubular structures (see FIG. 4).
By doing so, the flow in the enzyme tower of the two-liquid phase liquid mixture (reaction liquid) becomes uniform.

  When the immobilized enzyme is filled, there is a gap between the pipe or interior and the inner wall of the enzyme tower. If the gap is extremely narrow, it is difficult to fill the immobilized enzyme. Insufficient filling of the gaps may result in non-uniform filling of the enzyme tower as a whole and a decrease in bulk density. In this case, the flow of the reaction liquid becomes uneven, which may cause a reduction in reaction efficiency. Therefore, it is preferable that the gap between the pipe or interior and the inner wall of the enzyme tower be a certain level or more. Depending on the type and particle size of the packing such as the immobilized enzyme and the size of the pipe or interior, the narrowest part of the gap between the pipe or interior and the inner wall of the enzyme tower is preferably 1 mm or more. Further, it is preferable that the thickness is 5 mm or more from the viewpoint of uniformly filling the immobilized enzyme. The upper limit of the interval is preferably equal to or less than the diameter or diagonal length of the cross section of one pipe of the tubular structure of the pipe or the interior, from the point of making the flow of the reaction liquid uniform, and further 70 mm or less, particularly 50 mm or less. It is preferable to do.

  The length of the pipe or the interior in the enzyme tower is preferably equal to or greater than the packed thickness of the immobilized enzyme from the viewpoint of uniformizing the flow of the entire reaction liquid in the tower, but the packed thickness is shorter than the packed thickness. The same effect can be obtained if the content is in the range of 50% or more and 75% or more.

  In addition, the pipe or the interior may not be continuous over its entire length, but is divided into a plurality of stages in the vertical direction from the viewpoint of workability such as easy replacement of the packed immobilized enzyme. Is preferred. The number of stages depends on the total length of the enzyme tower, but is preferably 2 to 30 divisions, and more preferably 2 to 10 divisions. Furthermore, the pipes or interiors of each stage may be divided into a plurality of parts in the lateral direction from the viewpoint of ease of loading into the enzyme tower.

The flow rate of the reaction liquid is preferably 1 to 400 mm / min, more preferably 5 to 200 mm / min. The liquid flow rate (mm / min) is the amount of liquid fed per minute (mm ³ / min) (or liquid feed speed (10 ⁻³ mL / min)) as the packed layer cross-sectional area (mm ² ). The value expressed by the quotient divided by. As the pressure in the packed column increases by increasing the liquid flow rate, liquid passing becomes difficult and an enzyme packed column with high pressure resistance is required. In addition, the immobilized enzyme is crushed by the increased pressure in the column. Since a case may arise, it is preferable that the liquid passing velocity is 400 mm / min or less. Further, from the viewpoint of productivity, it is preferable that the liquid flow rate is 1 mm / min or more. Since the expression activity of the immobilized enzyme changes depending on the flow rate, the reaction can be performed according to the desired production capacity and manufacturing cost by selecting the optimal flow rate and determining the reaction conditions. it can.

  The residence time of the reaction liquid in the enzyme tower is 30 seconds to 60 minutes, and further 1 minute to 40 minutes from the viewpoint of avoiding the equilibrium state of the hydrolysis reaction, more effectively drawing out the activity of the immobilized enzyme, and improving productivity. Minutes are preferred. The residence time (minute) is represented by a value obtained by multiplying the thickness (mm) of the packed bed by the porosity and dividing this by the liquid linear velocity (mm / minute).

  In the present invention, the reaction solution that has passed through the enzyme tower may be used as it is as a reaction-finished product in consideration of reactivity, productivity, and the like. May be added again to the same enzyme tower in the same manner as described above, and may be repeatedly passed until a desired reaction rate is obtained. Alternatively, the reaction solution may be once separated into oil and water, and after separating the oil phase, fresh water may be added and supplied again to another enzyme tower by the same method as described above to perform a continuous reaction. In addition, by separating the reaction liquid into water using multiple enzyme towers, the oil phase is supplied to the next enzyme tower and the aqueous phase is supplied to the previous enzyme tower, so that the oil phase with a higher decomposition rate is fresh. You may carry out by the pseudo countercurrent method made to react with an aqueous phase. As an oil-water separation method of the reaction liquid, an oil-water separator such as a natural sedimentation type or a centrifugal separation type is generally used, but is not particularly limited.

(Preparation of immobilized lipase)
1 part by weight of Duolite A-568 (manufactured by Diamond Shamrock, particle size distribution: 100 to 1000 μm) was stirred for 1 hour in 10 parts by weight of NaOH solution of N / 10. After filtration, it was washed with 10 parts by mass of ion exchange water, and the pH was equilibrated with 10 parts by mass of 500 mM acetate buffer (pH 7). Thereafter, the pH was equilibrated twice with 10 parts by mass of 50 mM acetate buffer (pH 7) every 2 hours. Thereafter, filtration was performed and the carrier was recovered, and then ethanol substitution with 5 parts by mass of ethanol was performed for 30 minutes. After filtration, 5 parts by mass of ethanol containing 1 part by mass of ricinoleic acid was added and ricinoleic acid was adsorbed on the carrier for 30 minutes. After recovering the carrier by filtration, it was washed with 5 parts by mass of 50 mM acetate buffer (pH 7) four times for 30 minutes, ethanol was removed, and the carrier was recovered by filtration. Thereafter, 1 part by mass of commercially available lipase (Lipase AY, Amano Amano Pharmaceutical Co., Ltd.) was contacted with an enzyme solution dissolved in 9 parts by mass of 50 mM acetate buffer (pH 7) for 5 hours for immobilization. By filtration, the immobilized enzyme was recovered and washed with 10 parts by mass of 50 mM acetate buffer (pH 7) to remove unimmobilized enzyme and protein. Thereafter, 4 parts by mass of soybean oil to be actually decomposed was added and stirred for 12 hours. All the above operations were performed at 20 ° C. Then, it filtered and isolate | separated from fats and oils, and was set as the immobilized enzyme. As a result, an immobilized lipase having a hydrolysis activity (activity to be expressed) of 2700 U / g (dry weight) was obtained. The average particle diameter based on the weight of the immobilized enzyme was 451 μm.

<Example 1>
Stainless steel column with jacket (inner diameter 200 mm) loaded with interiors (5 stages, total height 1500 mm) with a square (wall thickness 1.5 mm) with a cross section of 24 mm × 24 mm and bundled 40 square pipes with a height of 300 mm And 10.5 kg (dry weight) of the above immobilized lipase (filling height 1500 mm), and kept at 35 ° C. with a jacket. A liquid in which rapeseed oil and distilled water were mixed at a weight ratio of 10: 6 was fed from the top of the column at 30 kg / Hr to conduct a hydrolysis reaction. The results are shown in Table 1. The decomposition rate in the table was calculated by dividing the acid value obtained by analysis by the saponification value. In addition, an acid value is American Oil Chemist. According to the method described in Society Official Method Ca 5a-40, the saponification value was determined by American Oil Chemists. It was measured by the method described in Society Official Method Cd 3a-94.

<Example 2>
Stainless steel column with jacket (inner diameter 200 mm) loaded with interior (5 stages, total height 1500 mm) with a square of 35 mm x 35 mm (wall thickness 1.5 mm) and bundled 16 square pipes 300 mm high The hydrolytic reaction was carried out in the same procedure as in Example 1 except that 11.4 kg of the above immobilized lipase was filled in a dry base at a height of 1600 mm (filling height of 1500 mm). The results are shown in Table 1.

<Example 3>
Stainless steel column with jacket (inner diameter 200 mm) loaded with interior (5 stages, total height 1500 mm) with a square section (wall thickness 1.5 mm) with a cross section of 52 mm x 52 mm and 7 square pipes 300 mm high. The hydrolytic reaction was carried out in the same procedure as in Example 1, except that 11.9 kg of the above immobilized lipase was filled in a dry base (height of filling: 1500 mm). The results are shown in Table 1.

<Example 4>
Stainless steel column with jacket (inner diameter 200 mm) loaded with an interior (5 steps, total height 1500 mm) with a square of 70 mm x 70 mm square (wall thickness 1.5 mm) and bundled 4 square pipes 300 mm high The hydrolytic reaction was carried out in the same procedure as in Example 1 except that 12.1 kg of the above immobilized lipase was filled in a dry base at a height of 1600 mm (filling height of 1500 mm). The results are shown in Table 1.

<Example 5>
A stainless steel column with a jacket (inner diameter 200 mm) loaded with an interior (5 stages, total height 1500 mm) with 16 square pipes with a cross section of 37 mm x 37 mm (thickness 1.5 mm) and 300 mm height. The hydrolytic reaction was carried out in the same procedure as in Example 1 except that 10.7 kg of the above immobilized lipase was filled in a dry base at a height of 1600 mm (filling height of 1500 mm). At this time, the gap between the interior and the inner wall of the column was 0.35 mm at the narrowest portion. The results are shown in Table 1.

<Comparative Example 1>
The hydrolysis reaction was carried out in the same procedure as in Example 1 except that a stainless steel column was not loaded with a square pipe, and 12.7 kg of the immobilized lipase was packed on a dry basis (packing height 1500 mm). The results are shown in Table 1.

  From the results shown in Table 1, by supplying the rapeseed oil and distilled water and hydrolyzing the interior of the fixed bed type reaction tower with the interiors so as to form a plurality of tubular structures having a constant cross section. It was revealed that the degradation rate was improved and the (apparent) activity of the immobilized enzyme was effectively expressed. In addition, when there is a narrow portion in the gap between the inner wall of the fixed bed type reaction tower and the interior, the porosity at the time of filling the immobilized enzyme slightly increases and the decomposition rate tends to decrease, but the gap is 1 mm. It became clear that it was solved by the above.

It is a figure which shows the cross section of the enzyme tower loaded with the cylindrical interior. It is a figure which shows the cross section of the enzyme tower with which the prismatic interior was loaded. It is a figure which shows the cross section of the enzyme tower loaded with plate-shaped (partition plate) interior. It is a conceptual diagram which shows the flow of the reaction liquid in an enzyme tower.

Claims (5)

In a method for producing fatty acids in which a liquid mixture comprising an oil phase substrate and an aqueous phase substrate is supplied to a fixed bed type reaction column packed with an immobilized lipase and subjected to a hydrolysis reaction in the same direction, a fixed bed type reaction is performed. The column is loaded with interiors or pipes so that a plurality of tubular structures having a circular cross section with a diameter of 100 mm or less or a polygon with a diagonal length of 100 mm or less are formed in the tower, and then inside the fixed bed reactor A method for producing fatty acids, in which an immobilized lipase is filled in a tubular structure formed in (1) and the liquid mixture is supplied into the tubular structure. The method for producing fatty acids according to claim 1, wherein the oil phase substrate is vegetable oil, animal oil, or a combination of these. The method for producing fatty acids according to claim 1 or 2 , wherein the interior or piping is divided into a plurality of stages in the vertical direction. The method for producing fatty acids according to any one of claims 1 to 3 , wherein the interior or the pipe is divided into a plurality of parts in the lateral direction. The method for producing fatty acids according to any one of claims 1 to 4 , wherein the narrowest portion of the gap between the interior or pipe and the inner wall of the fixed bed type reaction tower is 1 mm or more.

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