AU2019279165A1

AU2019279165A1 - Method for producing polyphenol composition from bagasse

Info

Publication number: AU2019279165A1
Application number: AU2019279165A
Authority: AU
Inventors: Shigeyuki Funada; Toma FURUTA; Satoru Itou; Hiroyuki Kurihara; Hisanori Nakajima; Katsushige Yamada
Original assignee: Mitsui Sugar Co Ltd
Current assignee: Mitsui DM Sugar Co Ltd
Priority date: 2018-05-29
Filing date: 2019-05-29
Publication date: 2020-10-22
Anticipated expiration: 2039-05-29
Also published as: AU2019279165B2; WO2019230803A1; CN111655663B; CN111655663A; JP2019206489A; JP6703562B2

Abstract

One aspect of the present invention is a method for producing a polyphenol composition from bagasse, which comprises: a step wherein bagasse is pre-treated with use of at least one alkaline solution that is selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution and an aqueous ammonia solution, thereby obtaining a pretreatment liquid; a step wherein after the pH of the pretreatment liquid is adjusted to an acidic value with use of hydrochloric acid, the pretreatment liquid is filtered and the filtrate is subsequently recovered; and a step wherein the filtrate is passed through a column that is filled with an aromatic synthetic adsorbent and the component adsorbed on the aromatic synthetic adsorbent is subsequently eluted by means of a mixed solvent of ethanol and water, thereby obtaining the eluted fraction as a polyphenol composition.

Description

DESCRIPTION

Title of Invention METHOD FOR PRODUCING POLYPHENOL COMPOSITION FROM BAGASSE Technical Field

[0001] The present invention relates to a method for producing a polyphenol composition from bagasse. Background Art

[0002] In recent years, utilization of biomass has been studied from the viewpoint of reducing an environmental load. One example thereof is a method for obtaining a polyphenol composition from a plant material. A method for subjecting a plant material, particularly waste corn, to alkaline extraction through boiling and/or an enzymatic treatment, recovering an aqueous liquid phase containing ferulic acid and polysaccharides, and subsequently recovering ferulic acid is disclosed in Patent Literature 1.

[0003] A method for obtaining polyphenols by treating bagasse or the like with an alkaline solution is disclosed in Non-Patent Literature 1 to 3. Non-Patent Literature 1 discloses that, when an alkali treatment is applied to a sugar cane husk, ester bonds with polysaccharides undergo hydrolysis to release ferulic acid or p-coumaric acid. Non Patent Literature 2 and Non Patent Literature 3 disclose that coumaric acid is released by treating bagasse with an aqueous sodium hydroxide solution as an alkali treatment for extracting coumaric acid and ferulic acid.

[0004] On the other hand, as another example relating to utilization of biomass, recovery of sugar, as a main product, from a plant material is performed due to its high absolute amount and high recovery rate and a method for hydrolyzing a plant material has been widely studied. For example, a method for producing a sugar solution including a step of hydrolyzing cellulose-containing biomass such as bagasse using cellulose derived from filamentous fungi is disclosed in Patent Literature 2 and 3. Citation List Patent Literature

[0005]

[Patent Literature 1] Japanese Unexamined Patent Publication No. 2016-520093

[Patent Literature 2] PCT International Publication No. W02015/025927

[Patent Literature 3] PCT International Publication No. W02015/099109 Non Patent Literature

[0006]

[Non Patent Literature 1] Journal of the Society of Tropical Resources Technologists, Vol. 26, No. 1, pp. 23-27, 2010

[Non Patent Literature 2] Journal of Chemical Engineering of Japan, vol. 42, No. 3, pp. 131-135, 2016

[Non Patent Literature 3] Innovative Food Science and Emerging Technologies, 10, 253-259, 2009 Summary of Invention Technical Problem

[0007] In order to obtain sugar from a plant material, it is necessary to separate the cell wall of the plant material into structures such as cellulose, matrix polysaccharides (hemicellulose and p-glucan), and lignin. After separating the cell wall to some extent, sugar can be obtained by hydrolyzing (performing an enzymatic treatment on) cellulose and matrix polysaccharides.

[0008] In the processes of producing a sugar solution disclosed in Patent Literature 2 and 3, a pretreatment with an alkaline solution is performed before hydrolyzing bagasse. Since a solid content obtained through the pretreatment contains cellulose and hemicellulose, a sugar solution can be obtained through a saccharification step in which cellulose and hemicellulose are hydrolyzed. However, a liquid component (pretreatment solution) after the pretreatment is unnecessary for obtaining a sugar solution, and therefore, has been discarded.

[0009] An object of the present invention is to provide a novel method for producing a polyphenol composition from bagasse. Solution to Problem

[0010] The present inventors have found that polyphenols such as coumaric acid and ferulic acid are contained in a pretreatment solution generated in a step of producing a sugar solution and that a polyphenol composition in the pretreatment solution can be extremely efficiently produced by treating the pretreatment solution through a predetermined method.

[0011] That is, the present invention provides a method for producing a polyphenol composition from bagasse, the method including: pretreating bagasse using at least one alkaline solution selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous ammonia solution to obtain a pretreatment solution; adjusting a pH of the pretreatment solution to be acidic with hydrochloric acid, and then filtering the pretreatment solution to recover a filtrate; and passing the filtrate through a column filled with an aromatic synthetic adsorbent and eluting a component adsorbed onto the aromatic synthetic adsorbent with a mixed solvent of ethanol and water to obtain an eluted fraction as the polyphenol composition.

[0012] A temperature of the alkaline solution is preferably 50°C to 1100C.

[0013] The alkaline solution is preferably an aqueous sodium hydroxide solution. A concentration of the aqueous sodium hydroxide solution may be 0.1 to 10% by mass.

[0014] The aromatic synthetic adsorbent in the elution step preferably consists of a styrene-divinylbenzene resin. Advantageous Effects of Invention

[0015] According to the present invention, it is possible to provide a novel method for producing a polyphenol composition from bagasse. Brief Description of Drawings

[0016] FIG. 1 is a chart obtained by analyzing a polyphenol composition according to Example 1 through HPLC. Description of Embodiments

[0017] Hereinafter, an embodiment of the present invention will be described. However, the present invention is not limited to the following embodiment.

[0018] A polyphenol composition produced in the present invention is a composition containing one or more polyphenols. Polyphenols in the present specification are phenolic compounds that can be measured through the Folin-Ciocalteu method. More specifically, the polyphenols may be phenylpropanoids such as p-coumaric acid or ferulic acid, flavonoids such as catechin or anthocyanin, and the like.

[0019] In the production method according to an embodiment of the present invention, bagasse is first pretreated using an alkaline solution to obtain a pretreatment solution (pretreatment step).

[0020] In the present specification, bagasse is sugar cane pomace and typically refers to bagasse discharged in a sugar production process in a sugar factory. Bagasse discharged in a sugar production process in a sugar factory includes not only final bagasse that has exited a final compressor but also shredded sugar cane cut in the first compressor and the subsequent compressors. Bagasse discharged after sugar juice is compressed through a compression step in a sugar factory is preferably used. Bagasse discharged from the compression step has different moisture contents, sugar contents, and compositional ratios depending on the type of sugar cane, harvest time, and the like, and can be used arbitrarily. Bagasse may be bagasse remaining after compressing sugar cane discharged in a brown sugar factory. In addition, in a small-scale implementation at a laboratory level, bagasse, after a sugar solution is compressed from sugar cane, may be used.

[0021] The pretreatment using an alkaline solution may be a treatment of bringing the alkaline solution into contact with bagasse in the embodiment. Examples of the method for bringing an alkaline solution into contact therewith include a method for sprinkling an alkaline solution on bagasse and a method for immersing bagasse in an alkaline solution. In the method for immersing bagasse in an alkaline solution, bagasse may be immersed while stirring a mixture of bagasse and an alkaline solution. In the pretreatment step, a part or the whole of a chemical structure of lignin, cellulose, and/or hemicellulose contained in bagasse is preferably broken.

[0022] The alkaline solution may be at least one selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous ammonia solution. The alkaline solution is preferably an aqueous sodium hydroxide solution from the viewpoints of being inexpensive and used in a food production step.

[0023] The concentration of an alkaline solution may be appropriately set according to the type of alkaline solution to be used, but is preferably higher than or equal to 0.1% by mass, more preferably higher than or equal to 0.2% by mass, and still more preferably higher than or equal to 0.3% by mass from the viewpoint of shortening the processing time taken for pretreatment. The concentration of an alkaline solution is preferably lower than or equal to 10% by mass, more preferably lower than or equal to 5% by mass, and still more preferably lower than or equal to 1.0% by mass from the viewpoint of improving extraction efficiency. The concentration of an alkaline solution may be 0.1 to 10 % by mass, 0.1 to 5% by mass, 0.1 to 1.0% by mass, 0.2 to 10% by mass, 0.2 to 5% by mass, 0.2 to 1.0% by mass, 0.3 to 10% by mass, 0.3 to 5% by mass, or 0.3 to 1.0% by mass from the same viewpoint.

[0024] An alkaline solution in the pretreatment step is preferably heated. The temperature (liquid temperature) of an alkaline solution is preferably higher than or equal to 50°C, more preferably higher than or equal to 60°C, and still more preferably higher than or equal to 80°C from the viewpoint of shortening the processing time taken for pretreatment. The temperature of an alkaline solution is preferably lower than or equal to 1100C, more preferably lower than or equal to 105°C, and still more preferably lower than or equal to 100°C from the viewpoint of preventing polysaccharides from remaining in a pretreatment solution. The temperature of an alkaline solution may be 50°Cto 110°C,50°C to 105°C,50°Cto 100°C,60°C to 110°C,60°C to 105°C, 60°C to 100°C, 80°C to 110°C, 80°C to 105°C, or 80°C to 100°C from the same viewpoint.

[0025] The amount of alkaline solution added may be greater than or equal to 50 parts by mass, greater than or equal to 100 parts by mass, or greater than or equal to 1,000 parts by mass with respect to 100 parts by mass of bagasse. In addition, the processing time in the pretreatment step may be appropriately adjusted according to the type, temperature, and addition amount of the alkaline solution, and may be, for example, 1 to 5 hours.

[0026] The pH of a pretreatment solution may be greater than or equal to 8 or 9 and less than or equal to 13 or 12.

[0027] In the pretreatment step according to the present embodiment, an insoluble component may be separated from a liquid component after performing the above-described alkali treatment. In this case, the separated liquid component can be used as a pretreatment solution.

The method for separating an insoluble component from a liquid component may include separation performed using a strainer and through filtration, centrifugation, decantation, and the like.

[0028] After the pretreatment step, the pH of the obtained pretreatment solution is adjusted to be acidic with hydrochloric acid, and the pretreatment solution is filtered to recover a filtrate (filtration step).

[0029] In the filtration step, hydrochloric acid is first added to the pretreatment solution to adjust the pH of the pretreatment solution to be acidic. The concentration of hydrochloric acid may be appropriately set as long as the pH of the pretreatment solution can be adjusted, and maybe, for example, 0.1 to 35% by mass. If hydrochloric acid is used for pH adjustment, a produced polyphenol composition can be used in the food industry field.

[0030] The pH of the pretreatment solution (hereinafter, also referred to as an "acidic pretreatment solution") after the addition of hydrochloric acid is preferably greater than or equal to 1.5, more preferably greater than or equal to 2.0, and still more preferably greater than or equal to 2.5, and preferably less than or equal to 4.5, more preferably less than or equal to 4.0, and still more preferably less than or equal to 3.5 from the viewpoint of achieving both suppression of coagulative precipitation of polyphenols and adsorption of a synthetic adsorbent. The pH of the acidic pretreatment solution may be 1.5 to 4.5, 1.5 to 4.0, 1.5 to 3.5, 2.0 to 4.5, 2.0 to 4.0, 2.0 to 3.5, 2.5 to 4.5, 2.5 to 4.0, or 2.5 to 3.5 from the same viewpoint.

[0031] In a case where the pH of the acidic pretreatment solution is greater than or equal to 1.5, polyphenols are less likely to be coagulated and precipitated. Therefore, polyphenols are less likely to be removed through filtration even if the filtration is performed after pH adjustment. On the other hand, in a case where the pH of the acidic pretreatment solution is less than or equal to 4.5, polyphenols can be made to be easily adsorbed onto an aromatic synthetic adsorbent in an elution step to be described below. That is, in the case where the pH of the acidic pretreatment solution is within the above-described ranges, it is possible to promote adsorption onto an aromatic synthetic adsorbent while suppressing coagulative precipitation of polyphenols.

[0032] In the case where the pH of the acidic pretreatment solution is adjusted to the above-described ranges, insoluble components are precipitated in the acidic pretreatment solution. In the filtration step, the precipitated insoluble components are removed through filtration. For the filtration, natural filtration, vacuum filtration, pressure filtration, centrifugal filtration, and the like may be performed, and pressure filtration is preferably performed. Pressure filtration may be performed using a pressure filter (filter press).

[0033] A filter aid may be added to the acidic pretreatment solution at the time of filtration. Examples of filter aids include diatomaceous earth, perlite, and cellulose. In the case where a filter aid is added, the content of the filter aid may be 0.2 to 2.0 mass% based on the total amount of the acidic pretreatment solution.

[0034] After the filtration step, an obtained filtrate is passed through a column filled with an aromatic synthetic adsorbent. Components adsorbed onto the aromatic synthetic adsorbent are eluted with a mixed solvent of ethanol and water, and eluted fractions are obtained to enable production of a polyphenol composition (elution step).

[0035] The aromatic synthetic adsorbent is a synthetic adsorbent consisting of an aromatic resin from the viewpoint of efficiently adsorbing a polyphenol composition contained in the filtrate. A styrene-divinylbenzene aromatic resin (styrene-divinylbenzene resin) is preferable as the aromatic resin. Examples of the styrene-divinylbenzene aromatic resin include a porous resin such as an aromatic resin having a hydrophobic substituent, an unsubstituted group-type aromatic resin, and an aromatic resin obtained by subjecting the unsubstituted group-type aromatic resin to a special treatment. As the styrene-divinylbenzene aromatic resin, an unsubstituted group-type aromatic resin or an aromatic resin obtained by subjecting the unsubstituted group-type aromatic resin to a special treatment of increasing a specific surface area is preferable and an aromatic resin obtained by subjecting an unsubstituted group-type aromatic resin to a special treatment of increasing a specific surface area is more preferable.

[0036] A specific surface area of the aromatic synthetic adsorbent is, as dry mass, preferably greater than or equal to 500 m 2 /g and more preferably greater than or equal to 700 m 2/g from the viewpoint of improving the adsorption rate. The specific surface area of the aromatic synthetic adsorbent can be calculated by applying a measured value of a gas adsorption method to a BET equation. The most frequent pore diameter of the aromatic synthetic adsorbent is preferably less than or equal to 600 A, more preferably less than or equal to 300A, and still more preferably less than or equal to 200 Afrom the viewpoints of high separation performance and high adsorption performance. The most frequent pore diameter can be measured through the gas adsorption method.

[0037] Such a synthetic adsorbent is commercially available, and examples thereof include DIAION (trademark) HP-10, HP-20, HP-21, HP-30, HP-40, and HP-50 (all of which are trade names of unsubstituted group-type aromatic resins and manufactured by Mitsubishi Chemical Corporation); SP-825, SP-800, SP-850, SP-875, SP-70, and SP-700 (all of which are trade names of aromatic resins obtained by subjecting an unsubstituted group-type aromatic resin to a special treatment and are manufactured by Mitsubishi Chemical Corporation); SP-900 (which is a trade name of an aromatic resin and manufactured by Mitsubishi Chemical Corporation); Amberlite (trademark) XAD-2, XAD-4, XAD-16, XAD-18, and XAD-2000 (all of which are trade names of aromatic resins and manufactured by ORGANO CORPORATION); DIAION (trademark) SP-205, SP-206, and SP-207 (all of which are trade names of aromatic resins having a hydrophobic substituent and manufactured by Mitsubishi Chemical Corporation); and HP-2MG and EX-0021 (all of which are trade names of aromatic resins having a hydrophobic substituent and manufactured by Mitsubishi Chemical Corporation). Among these, DIAION (trademark) SP-850 is preferable. These synthetic adsorbents may be used alone or in combination of two or more thereof.

[0038] The amount of aromatic synthetic adsorbent with which a column is filled can be appropriately determined depending on the size of the column, the type of synthetic adsorbent, and the like.

[0039] When a filtrate is passed through a column, the temperature of the filtrate may be 25°C to 45°C. The liquid passage amount and the liquid passage rate when passing a filtrate through a column can be appropriately determined depending on the type of aromatic synthetic adsorbent, and the like.

[0040] In the elution step, the components adsorbed onto the column are eluted with a mixed solvent of ethanol and water after the completion of passing the filtrate. The mixing volume ratio (ethanol:water) of the mixed solvent may be 50:50 to 99:1, and is preferably within a range of 50:50 to 70:30 from the viewpoint improving the elution efficiency. The elution rate can be appropriately determined depending on the size of the column, the type of aromatic synthetic adsorbent, and the like. In order to efficiently elute the components adsorbed onto the column, it is preferable to wash the inside of the column with water before passing the filtrate through the column.

[0041] A polyphenol composition derived from bagasse can be produced by obtaining eluted fractions in the elution step.

[0042] After the elution step, a step (concentration step) of concentrating eluted fractions (polyphenol composition) may be further provided as necessary. In the concentration step, the eluted fractions may be concentrated, for example, 5 to 20-fold using a centrifugal thin-film vacuum evaporator. Accordingly, a concentrated liquid containing a polyphenol composition can be obtained.

[0043] The polyphenol composition that can be produced through the method of the present embodiment may mainly contain coumaric acid and ferulic acid as polyphenols. The fact that the polyphenol composition contains polyphenols can be confirmed by measuring a polyphenol content through the Folin-Ciocalteu method. In addition, the composition of the polyphenol composition can be confirmed by qualitatively and quantitatively analyzing the obtained polyphenol composition through high-performance liquid chromatography (HPLC).

[0044] The polyphenol composition to be obtained through the method of the present embodiment is obtained by performing elution with a mixed solvent of ethanol and water, particularly using an aromatic synthetic adsorbent in the elution step, and therefore can be suitably used as a food material.

[0045] The method of the present embodiment is a novel method different from a method in the related art in which a polyphenol composition is produced from bagasse, and is a useful method particularly from the viewpoint that a polyphenol composition can be produced from a pretreatment solution (waste liquid) generated in the step of producing a sugar solution from bagasse.

[0046] For example, the above-described method of Patent Literature 1 is a method for increasing the purity of ferulic acid to recover ferulic acid as a crystal in order to use the ferulic acid as a raw material of vanillin, and is different from the method of the present embodiment in that a treatment liquid in a state in which ferulic acid and polysaccharides are mixed with each other is obtained using a twin-screw extruder and a grinder/homogenizer as a method for subjecting waste corn to alkaline extraction through boiling.

[0047] In addition, the methods disclosed in Non Patent Literature 1 to

3 are methods for treating a plant material with an alkaline solution at a relatively low temperature for a long period of time. This is because monophenols ester-bonded to matrix polysaccharides are easily released and the purity of coumaric acid and ferulic acid increases if the alkali treatment is performed under mild conditions. However, in a case where such methods are used for a waste liquid generated in the saccharification step, the processing time becomes long. Therefore, there is a concern that the time required for the saccharification step in which a sugar solution is obtained from bagasse and the time required for treating a waste liquid may not be balanced. According to the method of the present embodiment, it is possible to efficiently produce a polyphenol composition from a waste liquid generated in the saccharification step while giving priority to the saccharification step.

[0048] Furthermore, according to the present embodiment, it is possible to effectively utilize a pretreatment solution, which has been discarded in the related art, without discarding the pretreatment solution in the step of producing a sugar solution from bagasse. Therefore, it is possible to reduce disposal costs of the pretreatment solution generated in the step of producing a sugar solution.

[0049] The polyphenol composition that can be produced through the method of the present embodiment can be used as a raw material for isolating and purifying polyphenols contained in the polyphenol composition at a high yield. The method for isolating and purifying polyphenols from a polyphenol composition may be a well-known method. That is, it can be said that the method of the present embodiment is a method for producing a raw material capable of isolating and purifying polyphenols such as ferulic acid and p-coumaric acid. Polyphenols isolated and purified from a polyphenol composition can also be suitably used as a food material similarly to the above-described polyphenol composition.

[Examples]

[0050] Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited by these examples.

[0051] [Test Example 1: Production Test of Polyphenol Composition] <Example 1> (Pretreatment Step) Pretreatment was performed by adding 3.2 kg of bagasse (with a moisture content of 50% by mass) which is sugar cane pomace and 20 L of a 0.5% (w/w) aqueous sodium hydroxide solution at 90°C to a cylindrical pot made of stainless steel and mixing them with each other for 2 hours. The pretreated mixed solution was separated into an insoluble component and a liquid component to obtain about 20 L of the liquid component. This was repeated twice to obtain 40 L of the liquid component (pretreatment solution).

[0052] (Filtration Step) 475 mL of 35% (w/w) hydrochloric acid was added to the total amount of the above-described pretreatment solution, and the pH was adjusted to 3.0. This was regarded as an acidic pretreatment solution. 395 g of diatomaceous earth was added to the acidic pretreatment solution (so as to become 1% (w/w) based on the total amount of the pretreatment solution) as a filter aid, and insoluble components were removed by filtering the mixture with a filter press to obtain 38 kg of a filtrate.

[0053] (Elution Step) The filtrate obtained from the filtration step was passed through a column (column capacity: IL) filled with 383 mL of an aromatic synthetic adsorbent (DIAION SP-850 manufactured by Mitsubishi Chemical Corporation) under the condition of a flow rate of 7.6 L/h (SV=20). Thereafter, washing was performed with 10 times as much water as the volume of the synthetic adsorbent, and elution was performed by passing 766 g of a 60% (v/v) aqueous ethanol solution at a SV of 2 to obtain eluted fractions. The pH of the eluted fractions was adjusted to 6.7 using a 48% (w/w) aqueous sodium hydroxide solution, and the concentration thereof was concentrated to a 10-fold concentration using a rotary evaporator to obtain 77 g of a polyphenol composition.

[0054] (Confirmation of Composition) The obtained polyphenol composition was analyzed through high-performance liquid chromatography (HPLC, Agilent 1260 Infinity LC manufactured by Agilent Technologies) to confirm the composition. The analysis conditions are as follows. Sample injection amount: 30 tL Eluent flow rate: 0.6 m/min Eluent: water (6% acetic acid) (eluent A), methanol (6% acetic acid) (eluent B) Column: LiChroCART (150 mm long x 4.6 mm inner diameter, 5 tm particle diameter, Merck KGaA)

Column temperature: 60°C Set wavelength of UV-VIS detector: 260 nm

[0055] In the analysis performed through HPLC, the conditions of a concentration gradient (gradient) are as shown in Table 1.

[Table 1] Retention time (RT, min) 0 10 60 70 90 120 Eluent A (%) 95 95 40 10 95 95 Eluent B (%) 5 5 60 90 5 5

[0056] The obtained chart is shown in FIG. 1. The presence of coumaric acid was confirmed as a peak at a retention time (RT) of 19 minutes, and the presence of ferulic acid was confirmed as a peak at RT of 25 minutes.

[0057] [Test Example 2: Examination of Aromatic Synthetic Adsorbent] <Examples 2 to 4> 20 L of each filtrate was obtained from about 3 kg of bagasse (with a moisture content of 50 mass%) using a filter press according to the same pretreatment step and filtration step as in Example 1. In the elution step, DIAION SP-850 (manufactured by Mitsubishi Chemical Corporation, Example 2), Amberlite XAD-4 (manufactured by ORGANO CORPORATION, Example 3), and Amberlite XAD-18 (manufactured by ORGANO CORPORATION, Example 4) were used as aromatic synthetic adsorbents. Columns (column capacity of 100 mL) respectively filled with 50 mL of adsorbents were prepared, and 5 L of each filtrate was passed through the columns under the condition of a flow rate of 1,000 mL/h (SV=20). Thereafter, washing was performed on each column with 10 times as much water as the volume of the synthetic adsorbent, and elution was performed by passing 100 mL of a 60% (v/v) aqueous ethanol solution at a SV of 2 to obtain eluted fractions. The solid content concentration (% by mass, based on the total amount of eluted fractions) and the polyphenol concentration (% by mass, based on the total amount of eluted fractions) of the eluted fractions according to Examples 2 to 4 are shown in Table 2.

[0058] [Table 2] Example Example Example 2 3 4 Characteristics of Type SP-850 XAD-4 XAD-18 aromatic synthetic Specific surface 930 876 905 adsorbent area (m2/g) Most frequent pore 90 122 184 diameter (A) Characteristics of eluted Solid content 3.2 1.9 3.3 fraction concentration (% by mass) Polyphenol 59 63 47 concentration (% by mass)

[0059] [Test Example 3: Effect of pH of Pretreatment Solution]

(Pretreatment Step and Filtration Step)

20 L of a pretreatment solution was obtained from about 3 kg of

bagasse (with a moisture content of 50 mass%) according to the same

pretreatment step as in Example 1. This liquid component was divided

into four, and pHs of three of them were respectively adjusted to 6

(Example 5), 5.5 (Example 6), and 3 (Example 7) using 35% (w/w) hydrochloric acid. In addition, the pH of one of the four divided

pretreatment solutions was not adjusted (Comparative Example 1).

The pH of the pretreatment solution of Comparative Example 1 of

which the pH was not adjusted was 10.8. The four pretreatment solutions were filtered through the same method as in Example 1.

[0060] (Elution Step) The filtrates obtained from the filtration step were passed through a column (column capacity: L) filled with 383 mL of an aromatic synthetic adsorbent (DIAION SP-850 manufactured by Mitsubishi Chemical Corporation) under the conditions of a flow rate SV of 10 and a liquid passage amount BV of 50. Thereafter, washing was performed with 10 times as much water as the volume of the synthetic adsorbent, and elution was performed by passing a 60% (v/v) aqueous ethanol solution at a SV of 2 and a BV of 2. Each of the recovery amounts (g) of total polyphenols, coumaric acid, and ferulic acid contained in a passed-through liquid (liquid component which had not been adsorbed onto the synthetic adsorbent) after passing the liquid through the column and eluted fractions (liquid components adsorbed onto the synthetic adsorbent) was measured to obtain each mass ratio (recovery rate) of the total polyphenols (polyphenol composition), coumaric acid, and ferulic acid contained in the passed-through liquid or the eluted fractions to the amount (g) of polyphenols contained in the filtrate before elution. The recovery amount of total polyphenols was measured through the Folin-Ciocalteu method, and the recovery amounts of coumaric acid and ferulic acid were measured through HPLC. The results are shown in Table 3.

[0061] [Table 3]

Recovery rate (%) I Total polyphenols Coumaric acid Ferulic acid Passed-through Eluted Passed-through Eluted Passed-through Eluted liquid fraction liquid fraction liquid fraction Example 5 69.0 10.7 78.3 4.3 59.7 26.5 Example 6 61.2 19.6 66.7 11.3 40.0 42.4 Example 7 6.6 25.2 9.4 35.6 3.6 46.6 Comparative 84.8 5.8 99.8 0.1 99.6 0.1 Example 1

Claims

1. A method for producing a polyphenol composition from bagasse, the method comprising: pretreating bagasse using at least one alkaline solution selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous ammonia solution to obtain a pretreatment solution; adjusting a pH of the pretreatment solution to be acidic with hydrochloric acid, and then filtering the pretreatment solution to recover a filtrate; and passing the filtrate through a column filled with an aromatic synthetic adsorbent and eluting a component adsorbed onto the aromatic synthetic adsorbent with a mixed solvent of ethanol and water to obtain an eluted fraction as the polyphenol composition.

2. The method according to claim 1, wherein a temperature of the alkaline solution is 50°C to 110°C.

3. The method according to claim 1 or 2, wherein the alkaline solution is an aqueous sodium hydroxide solution.

4. The method according to claim 3, wherein a concentration of the aqueous sodium hydroxide solution is 0.1 to 10% by mass.

5. The method according to any one of claims 1 to 4, wherein the aromatic synthetic adsorbent consists of a styrene-divinylbenzeneresin.