A method for isolating at least one substance selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass.

Abstract

The objective is to provide a method for isolating at least one substance selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complexes, cellulose, and hemicellulose-cellulose complexes from plant biomass. [Solution] The problem is solved by (A) a method for isolating at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass, which includes the step of contacting plant biomass with a solution containing organic acids and peracids.

Description

Technical Field

[0001] The present invention relates to a method for isolating at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complexes, cellulose, and hemicellulose-cellulose complexes from plant biomass, and the like. Background Art

[0002] Lignin, together with polysaccharides (cellulose and hemicellulose), is a main component constituting the plant cell wall. Lignin has attracted attention as an abundant naturally occurring aromatic polymer, and at present, most lignin is obtained as a by-product from paper pulp manufacturing processes and bioethanol manufacturing processes. Since these isolated lignins are denatured, it is considered difficult to impart high functionality thereto.

[0003] For this reason, various methods for isolating lignin while avoiding denaturation as much as possible have been proposed (Patent Document 1). Prior Art Literature Patent Literature

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2013-241391 Summary of Invention Problem to be Solved by Invention

[0005] An object of the present invention is to provide a method for isolating at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complexes, cellulose, and hemicellulose-cellulose complexes from plant biomass. Means for Solving the Problem

[0006] The inventors of the present invention conducted diligent studies to solve the above problems and conceived of a new method for isolating lignin by extracting it in the reverse order of wood biosynthesis, and found that this could solve the above problems. The present invention was completed by further studies based on this finding and includes the following embodiments.

[0007] Item 1. (A) A step of contacting plant biomass with a solution containing organic acids and peracids. A method for isolating at least one substance selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass.

[0008] Item 2. The above process (A) is, (A1) A step of contacting plant biomass with a solution containing organic acids and peracids at a temperature of 90°C or lower, and / or (A2) A process of contacting plant biomass with a solution containing organic acids and peracids at a temperature between 90°C and 160°C. The method described in item 1, including the method described in item 1.

[0009] Item 3. The method according to item 1 or 2, comprising obtaining at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, and hemicellulose-cellulose complex from the soluble portion obtained in step (A).

[0010] Item 4. The method according to any one of items 1 to 3, comprising obtaining at least one selected from the group consisting of cellulose, hemicellulose, and hemicellulose-cellulose composites from the insoluble portion obtained in step (A).

[0011] Item 5. The method according to any one of items 1 to 4, further comprising irradiating the plant biomass with microwaves or ultrasound in step (A).

[0012] Item 6. The method according to any one of items 1 to 5, wherein the plant biomass used in step (A) is an alkali-treated product of a plant or a mechanically processed product thereof.

[0013] Item 7. A lignin having a content of β-O-4 type ether structure of 50% or more, and a solubility of 2 w / v% or more in 60 to 80% ethanol at 25°C.

[0014] Item 8. A lignin obtainable by the method according to any one of Items 1 to 6.

[0015] Item 9. A lignin-polysaccharide complex having at least one bond selected from the group consisting of α-ether bonds between lignin and polysaccharide, α-ester bonds between lignin and polysaccharide, and γ-ester bonds between lignin and polysaccharide.

[0016] Item 10. The lignin-polysaccharide complex according to Item 9, having a solubility of 2 w / v% or more in 60 to 80% ethanol at 25°C.

[0017] Item 11. A lignin-polysaccharide complex obtainable by the method according to any one of Items 1 to 6.

[0018] Item 12. Cellulose obtainable by the method according to any one of Items 1 to 6.

[0019] Item 13. A hemicellulose-cellulose complex obtainable by the method according to any one of Items 1 to 6.

[0020] Item 14. Hemicellulose obtainable by the method according to any one of Items 1 to 6.

[0021] Item 15. A self-assembled body of at least one selected from the group consisting of the lignin according to Item 7 or 8 and the lignin-polysaccharide complex according to any one of Items 9 to 11.

[0022] Item 16. The self-assembled body according to Item 15, which is in a sheet shape or a particle shape.

[0023] Item 17. A phosphor comprising the self-assembled body according to Item 15 or 16.

[0024] Item 18. The phosphor according to Item 17, which exhibits anti-Stokes fluorescence.

[0025] Item 19. An ultraviolet absorber comprising at least one selected from the group consisting of the lignin according to Item 7 or 8 and the lignin-polysaccharide complex according to any one of Items 9 to 11. [Effects of the Invention]

[0026] The present invention can provide a method for isolating at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass. [Brief Description of Drawings]

[0027] [Figure 1-1] It is a drawing showing a flow chart of the method of the present invention (M-APA method). [Figure 1-2] It is a drawing showing a flow chart of the method of the present invention (A-APA method). [Figure 2] It is a drawing showing microwave irradiation conditions, output, temperature and pressure profiles related to lignocellulose component separation, the used apparatus is an Initiator+ 60 microwave synthesizer manufactured by Biotage, with conditions: stirring speed: 600 rpm, Cooling: On, Absorption: High. [Figure 3] It is a two-dimensional NMR spectrum of low-denaturation, high-purity, high ether content lignin obtained according to the present invention. This is an analysis result of lignin isolated by the M-APA method (50°C microwave treatment for 10 minutes, 1% peracetic acid in acetic acid condition) using eucalyptus as a starting material. [Figure 4] It is a drawing showing the partial chemical structures of inter-unit bonds between lignin units and covalent bonds between lignin and hemicellulose. [Figure 5]The two-dimensional NMR spectrum (ad) of the lignin-hemicellulose copolymer and magnified views (a'-d') of the interunit bonds and sugar regions are shown. Lignin-hemicellulose copolymers obtained from broadleaf trees (a, b) and coniferous trees (c, d) by M-APA were analyzed. The circles in the figure indicate LC bonds (ether and ester forms). [Figure 6] Synchronized fluorescence spectra in the near-infrared wavelength region of APA lignin derived from bagasse (sugarcane). This is the result of a synchronic scan measurement that detects a constant Stokes shift, i.e., detecting fluorescence wavelengths Em 80, 90, 150, 160, and 170 nm longer than the excitation wavelength Ex (scanning the excitation wavelength). [Figure 7] This shows the 3D fluorescence spectrum of Japanese red pine APA lignin in the near-infrared wavelength region. APA lignin obtained by treating Japanese red pine wood powder with the M-APA method (microwave 50°C, 10 min, acetic acid + 0.2M hydrogen peroxide) was measured in an 80% acetonitrile solution (concentration 0.1 wt%). [Figure 8] This graph shows a comparison of the synchronized scan fluorescence spectra of reagent lignin (Tokyo Chemical Industries TCI alkaline lignin, blue line) and lignin (APA lignin, red line). Fluorescence longer than the excitation wavelength (plus 90 nm) was detected (scanned across the excitation wavelength). Lignin (APA lignin) exhibits characteristic fluorescence in the long-wavelength region. [Figure 9] Synchronized antifluorescence spectra of lignin solid thin films and lignin-polysaccharide copolymer solid thin films are shown. Antifluorescence spectra (af) and control (g) were obtained by scanning the excitation wavelength and selectively detecting fluorescence with an anti-Stokes shift shorter than the excitation wavelength. The anti-Stokes shift is excitation wavelength minus 50 nm, except for spectrum (b), which is minus 40 nm. From a comparison of spectra (b) and (d), and (e) and (f), the antifluorescence intensity is higher when peracetic acid is used as the oxidizing agent than when hydrogen peroxide is used. From a comparison of spectra (b) and (c), the antifluorescence intensity of APA lignin is higher than that of lignin polysaccharide copolymer. [Figure 10-1] The results of simultaneous differential thermal and thermogravimetric measurements for APA lignin and lignin hemicellulose copolymer are shown. [Figure 10-2] The results of simultaneous differential thermal and thermogravimetric measurements for cellulose and eucalyptus wood powder are shown. [Figure 11] This table shows the ultraviolet absorption spectra of lignin and lignin-hemicellulose copolymers. The vertical axis represents absorbance, and the horizontal axis represents wavelength (nm). See Table 8 for explanations of the legend. [Figure 12] The NMR measurement results of the hemicellulose solution obtained in Test Example 7-1 are shown. [Figure 13] The results of solid-state CP / MAS NMR measurements are shown. Spectrum a is from cellulose fiber (derived from eucalyptus wood powder) obtained in Test Example 7-1, and spectrum b is from beech white wood chips obtained in 7-2, which were decolorized with acetic acid, washed with water, and then freeze-dried. Spectrum c is from beech white wood chips obtained in 7-2, which were freeze-dried after bleaching treatment in addition to the conditions in b. The solid-state 13C CP / MAS spectrum was measured using a solid-state NMR spectrometer (Varian, Inc., 400 MHz) under MAS conditions of 15 kHz, with the powdered white powder placed in a 4 mm pencil-type sample tube (50 μL capacity). Analysis was performed using Varian VnmrJ4.2. In solid-state 13C CP / MAS NMR spectroscopy, unbleached beech wood chips (Figure 13b) showed clear signals of carbonyl groups (172 ppm) and methyl groups (22 ppm) derived mainly from the acetyl groups and glucuronic acid side chains of acetylated glucuronoxylan, indicating a hemicellulose-cellulose complex. This suggests that hemicellulose firmly forms a complex structure with cellulose while retaining a high degree of acetyl groups and side chains. [Figure 14] The FT-IR measurement results of the white wood chips obtained in Test Example 7-2 are shown. a-c correspond to the explanations in Figure 13. The measurement conditions were as follows: PerkinElmer FT-IR spectrometer Spectrum Two diamond ATR, measuring white cellulose powder. 400-4000 cm⁻¹, 10 scans. [Figure 15]This is a magnified view of a portion of Figure 14. The circled areas represent peaks characteristic of hemicellulose. In spectrum b, the acetyl group-derived C=O stretching vibrations of acetylated glucuronoxylan and glucuronic acid at 1728 cm⁻¹, and the CO stretching vibrations of acetylated glucuronoxylan and glucuronic acid at 1243 cm⁻¹ were clearly observed. [Figure 16] These are photographs of the white wood chips and their processed products obtained in Test Example 7-2. In (a), the left side shows the state of the acetic acid peracid treated wood chip after acetic acid decolorization, and the right side shows the wood chip before being subjected to the alkali treatment in Test Example 7. (b) shows the state of the wood chip on the left side of (a) after decolorization, bleaching, and washing with water. (c) shows the state of the wood chip on the left side of (a) after freeze-drying. [Modes for carrying out the invention]

[0028] In this specification, the terms “contains” and “includes” include the concepts of “contains,” “includes,” “substantially consist of,” and “consist solely of.”

[0029] 1. Isolation method In one aspect, the present invention relates to a method for isolating at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass, comprising the step of (A) contacting the plant biomass with a solution containing an organic acid and a peracid (this may also be referred to as "the isolation method of the present invention" in this specification). This is described below.

[0030] The isolation method of the present invention, by including step (A), can produce high-quality (low-condensation) lignin with a high content of the β-O-4 type ether structure among the total bonding modes between monolignols.

[0031] The plant biomass is not particularly limited as long as it includes at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complexes, cellulose, and hemicellulose-cellulose complexes, and examples include the plant itself, mechanically processed plant products, etc.

[0032] Examples of plant materials include coniferous wood, broadleaf wood, and non-tree materials. Specifically, examples include Japanese cedar, pine, Yezo spruce, larch, Japanese black pine, Sakhalin fir, Japanese white pine, Japanese yew, Japanese cedar, Japanese fir, Japanese spruce, Japanese yew, Japanese cypress, Japanese fir, Japanese cypress, Japanese cypress, Japanese yew, Japanese yew, Japanese spruce, spruce, yellow cedar (Western cedar), Lowson cypress (Western cypress), Douglas fir (Western pine), Sitka spruce (Western spruce), Radiata pine, Eastern spruce, Eastern white pine, Western larch, Western fir, Western Examples of materials include coniferous woods such as hemlock and tamalac; hardwoods such as asbestos, American black cherry, yellow poplar, walnut, birch, zelkova, sycamore, silver cherry, ash, teak, Chinese elm, Chinese maple, oak, beech, hard maple, hickory, pecan, white ash, white oak, white birch, red oak, acacia, and eucalyptus; and non-tree materials such as rice, sugarcane, wheat, corn, pineapple, oil palm, kenaf, cotton, alfalfa, timothy, bamboo, dwarf bamboo, and sugar beet.

[0033] Examples of mechanically processed plant materials include logs, square timbers, planks, solid wood, wood-based materials, laminated timber, veneer laminated timber, plywood, wood-based boards, particleboard, fiberboard, wood chips, particulate wood (chips, particles, wood powder, etc.), fibrous wood, compressed materials, crushed materials, etc.

[0034] From the viewpoint of improving yield, the plant biomass is preferably wood powder. The volume-average particle size of the wood powder is, for example, 500 μm or less, preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and even more preferably 20 μm or less. The lower limit of the average particle size is not particularly limited and can be, for example, 1 μm, 2 μm, or 5 μm. By using wood powder with relatively small particle size, a high yield can be achieved without performing the following alkali treatment.

[0035] Wood powder can be obtained by grinding plant biomass. Grinding can be carried out according to or in accordance with known methods, for example, using various mills (e.g., ball mills, mixer mills, etc.).

[0036] From the viewpoint of improving yield, the plant biomass is preferably an alkali-treated product of a plant or its mechanically processed product. According to the present invention, by using an alkali-treated product, the target product can be efficiently obtained without crushing (even in cases where the specific surface area is relatively large, such as with wood chips). The alkali-treated product can be obtained by alkali-treating a plant or its mechanically processed product. Alkali treatment loosens the plant cell wall structure (reduction of intermolecular interactions and cleavage of hydrogen bonds) and also cleaves intramolecular ester bonds, thereby improving the yield. As a result, a high yield can be achieved even without or with minimal physical crushing of the plant biomass, and process costs can be reduced. Furthermore, the yield can be improved by 1.2 to 2 times. In addition, the cellulose fibers obtained through this alkali treatment have good crystallinity.

[0037] Alkaline treatment, specifically, for example (X) A step of bringing a plant body or a mechanically processed product thereof into contact with an alkaline solution. It is preferable that this be the case.

[0038] The alkaline solution is not particularly limited as long as it is an alkaline solution that can achieve the above objective. For example, the alkaline solution can be a solution with a pH of 12 to 15. The pH of the solution is preferably 13 to 14. The alkaline solution can also be a solution containing, for example, an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide, etc.) in an amount of 0.3 to 2% by mass (preferably 0.7 to 1.5% by mass).

[0039] The amount of alkaline solution used is not particularly limited, as long as it is an alkaline solution sufficient to achieve the above objective. The amount of alkaline solution can be, for example, 3 to 20 mL, preferably 5 to 12 mL, per 1 g of plant material or its mechanically processed product.

[0040] The manner in which the plant body or its mechanically processed product comes into contact with the alkaline solution is not particularly limited, but from the viewpoint of processing efficiency, it is preferable to immerse the plant body or its mechanically processed product in the alkaline solution.

[0041] The temperature of the alkaline solution is not particularly limited, as long as it is at a temperature sufficient to achieve the above objectives. The temperature of the alkaline solution can be, for example, 20 to 150°C, preferably 50 to 120°C, and more preferably 80 to 120°C. When heating is performed, methods include, for example, internal heating by microwave heating and external heating by an oil bath, but internal heating by microwave heating is preferred.

[0042] The processing time for process (X) is not particularly limited, as long as it is sufficient to achieve the above objective. The processing time is, for example, 5 to 120 minutes, preferably 15 to 60 minutes.

[0043] After step (X), the soluble and insoluble parts are separated, and the insoluble part can be used in step (A) as an alkali-treated product of plant material or its mechanically processed product.

[0044] Plant biomass can consist of a single species or a combination of two or more species.

[0045] A solution containing an organic acid and a peracid (organic acid-peracid solution) is a solution containing an organic acid and a peracid that can extract and solubilize at least one selected from the group consisting of lignin, hemicellulose, and lignin-polysaccharide complexes, and is not particularly limited in this respect.

[0046] The organic acids are not particularly limited and include, for example, acetic acid, formic acid, glyoxylic acid, maleic acid, propionic acid, folic acid, isobutyric acid, valeric acid, isovaleric acid, pyruvic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, ketoglutaric acid, adipic acid, lactic acid, tartaric acid, fumaric acid, oxaloacetic acid, malic acid, isocitric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, merophanic acid, prenitic acid, pyromellitic acid, melitic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, camphorsulfonic acid, p-toluenesulfinic acid, benzenesulfinic acid, etc. Among these, acetic acid, formic acid, glyoxylic acid, 3-oxopropanoic acid, 2-methyl-3-oxopropanoic acid, etc. are preferred, more preferably acetic acid, formic acid, glyoxylic acid, etc., and acetic acid is particularly preferred.

[0047] Organic acids can exist as a single entity or as a combination of two or more entities.

[0048] As peracids, there are no particular limitations as long as they are acids having a hydroperoxide group (-O-OH), and examples include organic peroxoacids such as percarboxylic acids, persulfuric acid, percarbonate, superphosphoric acid, and subperhalic acids. Examples of percarboxylic acids include peracetic acid, performic acid, perbenzoic acid, and metachloroperbenzoic acid, and examples of subperhalic acids include subperchloric acid, subperbromic acid, and subperiodic acid. In addition to the above, examples of peracids include hydrogen peroxide, lithium peroxide, sodium peroxide, potassium peroxide, sodium percarbonate, urea peroxide, sodium perborate, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, dimethyldioxirane, acetone peroxide, methyl ethyl ketone peroxide, and hexamethylene triperoxide diamine. Among these, preferred examples include organic peroxoacids, hydrogen peroxide, sodium percarbonate, urea peroxide, sodium perborate, and the like; more preferred examples include percarboxylic acids (especially peracetic acid), hydrogen peroxide, and the like; and particularly preferred is hydrogen peroxide.

[0049] A peracid can be a single acid or a combination of two or more acids.

[0050] The content of organic acid in the organic acid-peracid solution is, for example, 5 to 30 mol / L, preferably 8 to 25 mol / L, and more preferably 10 to 20 mol / L. The content of organic acid in the organic acid-peracid solution is preferably 3 to 10 g, more preferably 4 to 8 g, and even more preferably 5 to 7 g per 1 g of plant biomass that comes into contact with the organic acid-peracid solution.

[0051] The peracid content in the organic acid-peracid solution is, for example, 0.05 to 3 mol / L, preferably 0.08 to 2.5 mol / L, and more preferably 0.1 to 2 mol / L. The peracid content in the organic acid-peracid solution is preferably 0.03 to 0.1 g, more preferably 0.04 to 0.08 g, and even more preferably 0.05 to 0.07 g per 1 g of plant biomass that comes into contact with the organic acid-peracid solution.

[0052] The manner in which plant biomass comes into contact with the organic acid-peracid solution is not particularly limited, but from the viewpoint of processing efficiency, it is preferable to immerse the plant biomass in the organic acid-peracid solution.

[0053] The temperature of the organic acid-peracid solution is not particularly limited, as long as it is a temperature at which at least one selected from the group consisting of lignin, hemicellulose, and lignin-polysaccharide complexes can be extracted and solubilized. The temperature of the organic acid-peracid solution is, for example, 15 to 160°C (preferably 40 to 160°C). By using a temperature of this magnitude, high-quality (low-condensation) lignin with a high content of the β-O-4 type ether structure among the total bonding modes between monolignols, and a complex of said lignin with a polysaccharide can be obtained. In step (A), a complex of lignin with a polysaccharide tends to be obtained when processed at a high temperature, while lignin alone tends to be obtained when processed at a low temperature. For example, if the starting material is woody biomass, if step (A) is carried out with an organic acid-peracid solution at, for example, 90°C or below (preferably 40-90°C, more preferably 40-70°C, and even more preferably 40-60°C), pure lignin is more likely to be selectively obtained, and if step (A) is carried out with an organic acid-peracid solution at, for example, more than 90°C and 160°C or below (preferably 100-160°C, more preferably 120-160°C), a complex of lignin and polysaccharides is more likely to be obtained. For example, if the starting material is herbaceous biomass, if step (A) is carried out with an organic acid-peracid solution at, for example, 60°C or below (preferably 15-60°C), pure lignin is more likely to be selectively obtained, and if step (A) is carried out with an organic acid-peracid solution at, for example, more than 60°C and 150°C or below (preferably 70-150°C), a complex of lignin and polysaccharides is more likely to be obtained. When heating is required, methods include, for example, internal heating by microwave heating and external heating by an oil bath, but internal heating by microwave heating is preferred. Rapid internal heating by microwaves allows for quick and efficient pretreatment.

[0054] The processing time for step (A) is not particularly limited, as long as it is sufficient to achieve the above objective. The processing time is, for example, 1 to 60 minutes, preferably 1 to 30 minutes, and more preferably 5 to 20 minutes.

[0055] In step (A), it is preferable to perform microwave treatment while the biomass is immersed in the above solution. This improves the yield of lignin. The conditions for microwave treatment can be set as appropriate, but for example, it can be performed using a commercially available microwave synthesis apparatus while stirring the solution. The microwave treatment time can be, for example, 1 to 30 minutes, and preferably about 10 minutes. Since the isolation method of the present invention requires relatively short irradiation time when microwave treatment is performed, it is easy to construct not only a batch system but also a continuous system.

[0056] In step (A), it is preferable to irradiate the plant biomass with microwaves or ultrasound, as this can promote the penetration of the solution into the pores inside the plant cell wall and improve the efficiency. The irradiation time is the same as described above.

[0057] Step (A) may be carried out in multiple stages with varying conditions as needed. For example, the temperature of the solution may be varied, in which case it is preferable that the temperature of the solution be higher in the next stage when comparing a particular stage with the next stage. For example, step (A) may include (A1) a step of contacting plant biomass with a solution containing organic acids and peracids at a temperature of 90°C or lower, and / or (A2) a step of contacting plant biomass with a solution containing organic acids and peracids at a temperature between 90°C and 160°C. In step (A2), "plant biomass" includes the insoluble portion obtained in step (A1).

[0058] Step (A1) allows for the selective extraction and solubilization of lignin alone, while step (A2) allows for the extraction and solubilization of the lignin-polysaccharide complex. Therefore, by performing steps (A1) followed by (A2), both lignin alone and the lignin-polysaccharide complex can be efficiently obtained.

[0059] After step (A), a separation solvent is added as needed, and then the soluble and insoluble parts are separated. The method of separating the soluble and insoluble parts is not particularly limited, and methods such as decantation, spin-down, and filtration can be employed. As separation solvents, lignin and lignin-hemicellulose copolymers are isolated using various alcohols such as dioxane, ethanol, acetone, acetonitrile, DMSO, DMF, NMI, ethyl acetate, methanol, and butanol, as well as acetic acid, water, and mixed solvents thereof. From the viewpoint of extraction efficiency, selectivity, and environmental impact, organic solvents such as acetone, ethanol, and acetonitrile, and 10-20 v / v% water-mixed organic solvents are desirable.

[0060] Furthermore, using water-free extraction solvents (acetic acid-peracetic acid) and separation solvents allows for the acquisition of high-purity lignin-hemicellulose copolymers. When water-containing solvents are used, some of the polysaccharide hemicellulose component is also acquired simultaneously. The hydrolysis reaction can also be accelerated using catalysts in the presence of acid or alkali.

[0061] The soluble portion obtained in step (A) contains at least one selected from the group consisting of lignin, hemicellulose, and lignin-polysaccharide complexes. Therefore, the soluble portion can be obtained as is, or, if necessary, after other processing, as at least one selected from the group consisting of lignin, hemicellulose, and lignin-polysaccharide complexes.

[0062] Other possible processes include the following: After step (A), if necessary, moisture can be removed by evaporation and / or freeze-drying to obtain the target product as a dry powder. If desalting is required, the concentrated solution may be extracted with alcohol or acetone, and the solvent removed by distillation. This will allow the target product to be obtained as a dry powder.

[0063] If lignin is to be obtained selectively, for example, lignin can be obtained from the soluble portion obtained by step (A1).

[0064] If you want to selectively obtain the lignin-polysaccharide complex, for example, you can obtain the lignin-polysaccharide complex from the soluble portion obtained in step (A2), which uses the insoluble portion obtained in step (A1) as plant biomass.

[0065] To obtain hemicellulose, for example, a lignin-polysaccharide complex can be subjected to alkaline hot water extraction. If necessary, the hemicellulose can be purified by ethanol precipitation, ion exchange column chromatography, gel filtration, hydrophobic chromatography, etc.

[0066] Hemicellulose can also be obtained by contacting the insoluble portion obtained in step (A) (preferably step (A1)) with a hemicellulose extraction solution prepared by adding a peracid (type and final concentration as described in step (A) above) to an alkaline solution (composition, etc., as described in step (X) above). The contact conditions are as described in step (A) above. The soluble portion obtained in this step can be subjected to purification (dialysis, etc.), water removal, etc., as needed, to obtain hemicellulose. On the other hand, cellulose (cellulose fiber) can be obtained from the insoluble portion obtained in this step by subjecting it to bleaching, washing, etc., as needed.

[0067] The insoluble portion obtained in step (A) contains cellulose. Therefore, this insoluble portion can be used as is, or, if necessary, subjected to other treatments as described above, to obtain cellulose. For example, hemicellulose can be extracted from the insoluble portion by alkaline hot water extraction. However, if the objective is to obtain type I cellulose, it is preferable not to treat the insoluble portion with a high-concentration alkaline solution in order to prevent mercellation of the cellulose.

[0068] When lignin is selectively isolated from plant biomass by process (A1), the insoluble portion (residue) contains a hemicellulose-cellulose composite. When a material with a certain shape (e.g., wood chips) is used as the plant biomass, the hemicellulose-cellulose composite can be obtained as a relatively high-strength material piece. By decolorizing this material piece (by immersion in an organic acid solution, washing, bleaching, etc.), a white material piece can be obtained.

[0069] According to the present invention, a new paper pulp manufacturing process is available that is low-energy and does not produce harmful wastewater. This process uses cleanly deligninized polysaccharides and is a low-temperature, mild process, thus providing a new pretreatment method for plant biomass that contains fewer inhibitory substances in the recovered material that would otherwise cause problems during ethanol fermentation.

[0070] 2. Lignin, lignin-polysaccharide complex, cellulose, hemicellulose-cellulose complex According to the isolation method of the present invention, it is possible to obtain lignin having at least the following characteristics: a β-O-4 type ether-type structure content of 50% or more, and a solubility of 2 w / v% or more in 60-80% ethanol at 25°C.

[0071] According to the isolation method of the present invention, it is possible to obtain a lignin-polysaccharide complex having at least one bond selected from the group consisting of an α-ether bond between lignin and polysaccharide, an α-ester bond between lignin and polysaccharide, and a γ-ester bond between lignin and polysaccharide.

[0072] According to the isolation method of the present invention, it is possible to obtain cellulose that has at least fewer inhibitory substances that cause problems in ethanol fermentation.

[0073] According to the isolation method of the present invention, it is possible to obtain a hemicellulose-cellulose composite.

[0074] These will be explained below.

[0075] 2-1. Lignin In one embodiment, the present invention relates to lignin having a β-O-4 type ether structure content of 50% or more, and a solubility of 2 w / v% or more in 60-80% ethanol at 25°C, or to lignin that can be obtained by the isolation method of the present invention.

[0076] The lignin of this invention refers to lignin isolated from biomass (including natural lignin). Natural lignin exhibits a wide variety of binding modes. Representative binding modes of natural lignin include the following:

[0077] [ka]

[0078] The above is called a β-O-4 bond.

[0079] [ka]

[0080] The above is called a resinol (β-β) bond.

[0081] [ka]

[0082] The above is called a phenylcoumaran (β-5) bond.

[0083] [ka]

[0084] The above is called a 5-5 bond.

[0085] [ka]

[0086] The above is called a dibenzodioxin (DBDO 5-5 / 4-O-β) bond.

[0087] [ka]

[0088] The above is called a 4-O-5 bond.

[0089] [ka]

[0090] The above is called a β-1 bond.

[0091] [ka]

[0092] The above is called a spirodiene bond.

[0093] In natural lignin, although it varies depending on the plant species, the β-O-4 ether-type structure is the most abundant type of total bond between monolignols. For example, in coniferous trees, this structure is said to account for 40-60%. In broad-leaved trees, for example, in eucalyptus, this structure is said to account for about 45%.

[0094] The lignin of the present invention has a content of 50% or more of the β-O-4 type ether type structure among the total bonding modes between monolignols, preferably 60% or more, more preferably 65-85%, and even more preferably 70-80%.

[0095] The lignin of the present invention has a content (%) of β-O-4 type ether type structure among the total bonding modes between monolignols, which is preferably 1.2x% or more, more preferably 1.4x% or more, and even more preferably 1.6x% or more, when the content of the same structure in the lignin contained in the biomass used as raw material is x%. In the above, the upper limit is preferably 2x%.

[0096] The content of the β-O-4 type ether structure among the total bonding modes between monolignols in lignin is measured specifically as follows: The sample is dissolved in deuterated dimethyl sulfoxide (DMSO-d6) to a concentration of 1-10 wt%, and an NMR spectrum is obtained using a Bruker Avance III 600 MHz NMR spectrometer equipped with a low-temperature probe. The content of the β-O-4 type ether structure can be estimated from the signal volume on the HSQC (Heteronuclear single-quantum correlation spectroscopy) spectrum. The quantitative value obtained by the 2D NMR method is corrected according to the literature (Okamura, H. Nishimura, T. Nagata, T. Kigawa, T. Watanabe and M. Katahira, Accurate and molecular-size-tolerant NMR quantitation of diverse components in solution, Scientific Reports, 6, 21742. 2016) to calculate the accurate content.

[0097] The lignin of the present invention is characterized by having a solubility of 2 w / v% or more in 60-80% ethanol at 25°C. Therefore, by using the lignin of the present invention, the self-assembled material described later can be easily obtained, and a highly stable self-assembled material can be obtained. The solubility is preferably 4 w / v% or more, more preferably 5 w / v% or more, even more preferably 6 w / v% or more, and even more preferably 7 w / v% or more.

[0098] The method for measuring the solubility is as follows: The sample is dissolved by stirring in ethanol at 25°C, and then separated into an ethanol-soluble portion and an ethanol-insoluble portion by solid-liquid separation. An ethanol aqueous solution (1 / 1 = ethanol / water) at 25°C is added to the ethanol-insoluble portion and stirred to dissolve it, obtaining an ethanol aqueous solution-soluble portion. The ethanol aqueous solution-soluble portion is mixed with the ethanol-soluble portion to obtain the sample solution. The amount of ethanol aqueous solution added is adjusted so that the ethanol concentration of the sample solution is in the range of 60-80%. In the process of obtaining the soluble portion, dispersion and solubilization are performed using an ultrasonic cleaner for 3 minutes at 28kHz as needed. The maximum sample concentration at which the sample solution becomes transparent visually is defined as the "solubility in 60-80% ethanol at 25°C".

[0099] The lignin of the present invention preferably has a composition ratio of 5% or less of biphenyl-type lignin, which has a condensed structure.

[0100] The lignin of the present invention preferably has a number-average molecular weight (Mn) of 0.7 to 9 kDa, more preferably 1 to 5 kDa, and even more preferably 1.5 to 4 kDa.

[0101] The lignin of the present invention preferably has a weight-average molecular weight (Mw) of 1 to 10 kDa, more preferably 1.5 to 8 kDa, and even more preferably 2 to 6 kDa.

[0102] In this invention, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) of lignin are specifically measured as follows. The molecular weight of lignin can be determined by size exclusion chromatography (SEC), also known as GPC (gel permeation chromatography). The sample is dissolved in a solution of acetic anhydride and a base (such as pyridine), reacted for 3-6 hours to obtain an acetylated product. This is dissolved in tetrahydrofuran (THF) at a concentration of 2.0 mg / mL and separated by high-performance liquid chromatography. An HZ-M column (Tosoh 150 mm × 4.6 mm id, 4 μm, 3 columns connected in series) is used. The analysis is performed by injecting 10 μL of the sample, at a column temperature of 40°C, with tetrahydrofuran (THF) as the mobile phase, and at a flow rate of 0.35 mL / min. Using standard polystyrene, Tosoh PStQuickC (molecular weights (MW) of 2,110,000, 427,000, 37,900, and 5,970), pinoresinol (MW 352), and vanillin (MW 152), mass calibration curves were created to determine the Mw and Mn of the samples.

[0103] The lignin of the present invention preferably has a polydispersity (Mw / Mn) of 2.5 or less, and more preferably 2 or less.

[0104] 2-2. Lignin-Polysaccharide Complex In one aspect, the present invention relates to a lignin-polysaccharide complex having at least one bond selected from the group consisting of an α-ether bond between lignin and a polysaccharide, an α-ester bond between lignin and a polysaccharide, and a γ-ester bond between lignin and a polysaccharide, or a lignin-polysaccharide complex that can be obtained by the isolation method of the present invention.

[0105] The lignin-polysaccharide complex of the present invention refers to a lignin-polysaccharide complex isolated from biomass.

[0106] Polysaccharides include, for example, xylan and mannan, as well as glucomannan, galactoglucomannan, glucuronoxylan, and arabinoglucuronoxylan. Hemicellulose primarily consists of glucomannan in conifers, glucuronoxylan in broad-leaved trees, and arabinoxylan in herbaceous plants. The above includes xylose, arabinose, glucose, mannose, galactose, and uronic acid as monomers. It also contains acetyl and methoxy groups in its side chains. In herbaceous plants, hemicellulose includes ferulic acid and diferulic acid bonded to the arabinose side chain of arabinoxylan.

[0107] The lignin-polysaccharide complex of the present invention is a lignin-polysaccharide complex that can be uniformly dispersed in a separation solvent, and is characterized by a polymeric structure in which lignin and polysaccharide are copolymerized by covalent bonds. The lignin-polysaccharide complex of the present invention is isolated from the lignin-polysaccharide complex structure in plant cell walls by cleaving a small portion (less than 10% of the bonds) of the hemicellulose backbone through a hydrolysis reaction. By carrying out the hydrolysis reaction under mild conditions, over-decomposition, side reactions, and demolecular-weight breakdown can be suppressed.

[0108] The lignin-polysaccharide complex of the present invention is characterized by having at least one bond selected from the group consisting of an α-ether bond (LCα-ether bond) between lignin and polysaccharide, an α-ester bond (LCα-ester bond) between lignin and polysaccharide, and a γ-ester bond (LCγ-ester bond) between lignin and polysaccharide.

[0109] In the lignin-polysaccharide complex of the present invention, it is preferable that the α-ether bond (LCα-ether) between lignin and polysaccharide, which is the copolymerization site, is concentrated to 1.2 times or more compared to the original bonding unit composition ratio of the raw material biomass.

[0110] Within biomass, lignin and polysaccharides are also bound by non-covalent bonds. These non-covalent bonds result from hydrophobic interactions, hydrogen bonds, electrostatic interactions, and entanglement of polymer chains. Therefore, previous studies have not shown clear evidence that lignin and polysaccharides, polymers with different properties, form copolymers through covalent bonds in lignin-polysaccharide complexes. Furthermore, conventional methods for preparing lignin-polysaccharide complexes involve multiple steps and result in low yields (less than 5%) or low purity.

[0111] Clear evidence of copolymerization sites (covalent bonds) in lignin-hemicellulose copolymers can be confirmed by signal assignment using the two-dimensional NMR method HSQC (Figures 3 and 4). Further clear evidence can be confirmed by continuous correlation analysis using HMBC and TOCSY-HSQC. For more details, please refer to the literature (Nishimura et al., Direct evidence for α ether linkage between lignin and carbohydrates in wood cell walls, Sci Rep 2018).

[0112] LCα ether CH correlation signals at the α-position of lignin (in the region of LC ether, δH / δC = 4.50 ±0.15 ppm / 80.1 ±1 ppm) and (in the region of LC ether, δH / δC = 4.95 ±0.2 ppm / 81.5 ±1.5 ppm) originate from the ether bond between the hexose 6-position or pentose hydroxyl group and the α-position (benzyl position) of lignin.

[0113] LCα ester The CH correlation signal at the α-position of lignin (LC α ester, region of δH / δC = 5.88 ±0.15 ppm / 74.0 ±1.5 ppm) originates from the ester bond between the carboxyl group at position 6 of glucuronic acid (uronic acid) and the α-position (benzyl position) of lignin.

[0114] LCγ ester The CH correlation signal at the γ position of lignin (LC γester, δH / δC = 4.0 ±0.15 ppm, 4.4 ±0.15 ppm, / 64.8 ±1.5 ppm region) originates from the ester bond between the carboxyl group at position 6 of glucuronic acid (uronic acid) and the γ position of lignin.

[0115] The lignin-polysaccharide complex of the present invention is characterized by having a solubility of 2 w / v% or more in 60-80% ethanol at 25°C. Therefore, by using the lignin-polysaccharide complex of the present invention, the self-assembled product described later can be easily obtained, and a highly stable self-assembled product can be obtained. The solubility is preferably 4 w / v% or more, more preferably 5 w / v% or more, even more preferably 6 w / v% or more, and even more preferably 7 w / v% or more.

[0116] In the lignin-polysaccharide complex of the present invention, the bonding unit composition ratio of LCα ether and LCα ester, which are copolymerization sites, is preferably 5% or more, more preferably 10% or more, in terms of lignin aromatic ring ratio.

[0117] The lignin-polysaccharide complex of the present invention preferably has a polysaccharide composition ratio of 0.1 to 2 relative to lignin, and more preferably 0.3 to 1.

[0118] The lignin-polysaccharide complex of the present invention preferably has a molecular weight (Mw) of 2,000 to 15,000, and more preferably 3,000 to 7,000. The lignin-polysaccharide complex of the present invention preferably has a polydispersity (Mw / Mn) of 3.5 or less, and more preferably 2.5 or less.

[0119] The measurement methods for each of the above-mentioned parameters shall be in accordance with the measurement method for lignin of the present invention or the measurement methods of the examples described later.

[0120] 2-3. Cellulose In one embodiment, the present invention relates to cellulose that can be obtained by the isolation method of the present invention.

[0121] In this invention, cellulose refers to cellulose isolated from biomass.

[0122] The cellulose of this invention has a further reduction in inhibitory substances that pose problems during ethanol fermentation.

[0123] The cellulose of the present invention can be used in various fields, for example, as cellulose fibers, pulp for papermaking, pretreatment of plant biomass, and biofuels produced by saccharification and fermentation.

[0124] 2-4. Hemicellulose-cellulose complex In one embodiment, the present invention relates to a hemicellulose-cellulose composite that can be obtained by the isolation method of the present invention.

[0125] The hemicellulose-cellulose composite of this invention refers to a hemicellulose-cellulose composite in a state isolated from biomass.

[0126] The hemicellulose-cellulose composite of the present invention can be in the form of material pieces (material pieces having a certain shape and size). Furthermore, the hemicellulose-cellulose composite of the present invention can be white (see Figure 13).

[0127] The hemicellulose-cellulose composite of the present invention can be obtained under mild conditions (treatment at 60°C or below using a combination of a low-concentration alkaline solution, an organic acid, or a low-concentration peracid), thus retaining the natural hemicellulose structure. For example, in hardwoods, it is a hemicellulose-cellulose composite having hemicellulose with a high degree of retention of acetyl groups and side-chain glucuronic acid. (See Figures 13, 14, and 15) The hemicellulose-cellulose composite of the present invention can be used in various fields, such as thermal insulation materials, lightweight carbon materials, acoustics, soundproofing, and piezoelectric elements.

[0128] Furthermore, the hemicellulose-cellulose composite of the present invention can be impregnated with a resin to become a transparent material. From this viewpoint, in one aspect, the present invention relates to a transparent material comprising the hemicellulose-cellulose composite and a resin of the present invention. The method of resin impregnation and the resin to be used can be selected according to known information (e.g., JP 2020-515437). For example, the resin can be selected from poly(methyl methacrylate) (PMMA), epoxy, poly(glycidyl methacrylate) (PGMA), polydimethylsiloxane (PDMS), and polystyrene (PS), or copolymers or mixtures thereof, having a refractive index of 1.4 to 1.6 or 1.45 to 1.55.

[0129] 3.Self-organized body In one aspect, the present invention relates to at least one self-assembling material selected from the group consisting of the lignin of the present invention and the lignin-polysaccharide complex of the present invention.

[0130] The shape of the self-assembled material of the present invention is not particularly limited. The self-assembled material of the present invention can be, for example, sheet-like (e.g., coating film, etc.), particulate (e.g., fine particles, aggregates, etc.), etc.

[0131] The lignin and lignin-polysaccharide complex of the present invention can form self-assembly bodies. Self-assembly occurs easily, and the conditions for self-assembly can be appropriately set based on known conditions. For example, a sheet-like self-assembly body can be obtained by applying an aqueous solution containing at least one selected from the group consisting of the lignin and lignin-polysaccharide complex of the present invention onto a solid surface and evaporating the solvent of the aqueous solution.

[0132] In the above, as the aqueous solution, for example, a mixture of water with an organic solvent such as alcohol (preferably ethanol) or acetonitrile (the separation solvent described above can be used) can be used. Specifically, for example, a mixture of ethanol and water can be used, and the mixing ratio in such a mixture is not particularly limited and can be set as appropriate, but for example, the ethanol:water (volume ratio) can be 5:95 to 40:60.

[0133] The self-assembled material of the present invention exhibits fluorescence in the long-wavelength region. Specifically, it exhibits fluorescence in the wavelength region of 400 nm to 700 nm. Furthermore, the self-assembled material of the present invention exhibits fluorescence that is significantly shifted to a shorter wavelength compared to the excitation wavelength, so-called anti-Stokes fluorescence. Anti-Stokes fluorescence is exhibited even with weaker light sources than conventional ones, such as xenon lamps, as the excitation light source. For this reason, the self-assembled material of the present invention can be used as a phosphor (preferably a phosphor that exhibits anti-Stokes fluorescence). Specifically, the self-assembled material of the present invention can be used as an anti-Stokes fluorescent agent. In this case, for example, an agent containing the self-assembled material of the present invention can be used as an anti-Stokes fluorescent paint, ink, and identification agent, or as an upconversion / wavelength conversion molecular material.

[0134] The self-assembled material of the present invention can be stably dispersed in aqueous solution and can maintain the above-mentioned fluorescence even in a solid state after drying.

[0135] 4. UV absorbers The lignin and lignin-polysaccharide complex of the present invention can exhibit strong absorption of ultraviolet rays, particularly UV-B and UV-C. From this viewpoint, in one aspect, the present invention relates to an ultraviolet absorber comprising at least one selected from the group consisting of the lignin and lignin-polysaccharide complex of the present invention.

[0136] The UV absorber of the present invention can prevent the degradation of polymers by ultraviolet radiation, for example, when mixed with polymers. Furthermore, by incorporating the UV absorber of the present invention into topical compositions, the skin can be protected from ultraviolet radiation. [Examples]

[0137] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, units in the tables represent mass.

[0138] Test Example 1. Isolation of lignin, lignin-polysaccharide complex, hemicellulose, and cellulose. Lignin, lignin-polysaccharide complexes, hemicellulose, and cellulose were isolated from biomass using the M-APA method, the A-APA method, or methods for optimizing their conditions, and the yield and physical properties of the isolated products were measured. The isolation method of the present invention is a method that can efficiently isolate soluble lignin, lignin-polysaccharide complexes, hemicellulose, and cellulose from natural polymers in biomass, and includes a step (A) of contacting plant biomass with a solution containing organic acids and peracids. Specifically, it was carried out as follows.

[0139] <Test Example 1-1. Preparation of finely ground wood flour> Fine powder (finely ground wood powder) with a volume average particle size of 10 μm (1-100 μm) was prepared from wood flour of broad-leaved trees (eucalyptus or beech), coniferous trees (Japanese red pine, Japanese cedar, or Japanese cypress), or herbaceous plants (bagasse (sugarcane), or bamboo) using a ball mill or bead mill method.

[0140] An example of a preparation method using a ball mill is shown. A planetary ball mill (P-6, Fritsch) was used. 2g of wood powder and 100g of φ3mm zirconia beads were placed in an 80cc agate container and sealed in a double overpot. After vacuuming the overpot for 20 minutes, nitrogen gas, an inert gas, was injected. Milling was performed for 1 minute, followed by a 1 minute 20 second pause, for a total of 180 cycles (3 hours total) at 550 rpm. Under these conditions, fine wood powder can be obtained while suppressing oxidation and modification due to heating during grinding.

[0141] <Test Example 1-2. Preparation of Wood Powder> One g each of wood powder or wood chips (10 mm x 10 mm x 1 mm) from hardwoods (eucalyptus or beech), conifers (Japanese red pine, cedar or cypress), or herbaceous plants (bagasse (sugarcane) or bamboo) was placed in the two pots on the left and right of a mixer mill (MM301, manufactured by Retsch). The powder was ground for 5 minutes at a frequency of 1 / 15 sec to obtain a powder (wood powder) with a volume average particle size of 0.1 mm.

[0142] <Example Test 1-3. M-APA Method (Milling-Acid-Per-Acid Method)> As the starting material, the finely ground wood powder (average particle size 10 μm) obtained in Test Example 1-1 was used. 2 g of the finely ground wood powder and 10 mL of an acetic acid-peracetic acid-containing solution (composition: 99% acetic acid 17.4 M, slightly less than 1% peracetic acid 0.14 M, 0.01 M hydrogen peroxide, trace amount of water) were placed in an initiator vial, and microwave irradiation was performed for 10 min at 50°C, Initial Power 400 W, and stirring speed 600 rpm using a Biotage Initiator+ 60 microwave synthesizer. After microwave treatment, the soluble portion was separated by adding 10 mL of separation solvent (acetone) and spin-down (RCF 8000 x g, 5 min). The insoluble portion was extracted with 10 mL of separation solvent (acetone), washed three times, and combined with the soluble portion. This soluble lignin was designated as acid-peracid lignin (APA lignin).

[0143] For the insoluble portion, a second step was performed, similar to the extraction operation, but with the microwave heating conditions changed to 140°C. The soluble portion was identified as a lignin-hemicellulose copolymer. An insoluble portion mainly composed of cellulose was obtained.

[0144] <Example Test 1-4. A-APA Method (Alkali-Acid-PerAcid Method)> As the starting material, wood powder (average particle size 0.1 mm) obtained in Test Example 1-2 was used. A 0.25 M sodium hydroxide solution was prepared (1 N diluted 4 times). 2.4 mL of the 0.25 M sodium hydroxide solution was added to 0.3 g of wood powder, and microwave extraction treatment (100°C, 30 min) was performed. The required amount of alkali is approximately 1 mmol of NaOH per 1 g of wood powder.

[0145] After microwave treatment, the soluble and insoluble parts can be easily separated by decantation, spin-down, or filtration. Additional acetone (separation solvent) extraction was performed three times to combine with the soluble part. For the insoluble part, acid peracid lignin (APA lignin) and lignin-hemicellulose copolymer were obtained as soluble lignin using the same extraction method as the M-APA method in Test Example 1-3. An insoluble part mainly composed of cellulose was obtained.

[0146] <Test Example 1-5. Condition Examination> In addition to acetic acid, studies were conducted using other organic acids (formic acid, glyoxylic acid). Furthermore, in addition to peracetic acid, studies were conducted using other peracids (hydrogen peroxide). When using other peracids (hydrogen peroxide), the composition was acetic acid: 12M, and hydrogen peroxide concentration: as shown in the table below.

[0147] The study involved changing the contact temperature between plant biomass or insoluble material and organic acid + peracid from room temperature to 180°C. Furthermore, instead of internal heating by microwave, an external heating method using an oil bath was employed for the study.

[0148] <Test Example 1-6. Analysis and Measurement Methods> Lignin, lignin-polysaccharide complexes, and cellulose were analyzed and measured using the following methods.

[0149] <Test Example 1-6-1. Method for Measuring Molecular Weight (Mn, Mw, and Polydispersity)> The molecular weight was determined by size exclusion chromatography (SEC), also known as GPC (Gel Permeation Chromatography). The sample was dissolved in a solution of acetic anhydride and a base (such as pyridine), reacted for 3-6 hours, and acetylated was obtained. This was dissolved in tetrahydrofuran (THF) at a concentration of 2.0 mg / mL and separated by high-performance liquid chromatography (Shimadzu Corporation, high-pressure gradient SEC analysis system). The column used was an HZ-M column (Tosoh, 150 mm × 4.6 mm id, 4 μm, 3 columns connected in series). Analysis was performed by injecting 10 μL of sample, at a column temperature of 40°C, with tetrahydrofuran (THF) as the mobile phase, and at a flow rate of 0.35 mL / min. Mass calibration curves were created using standard polystyrene, Tosoh PStQuickC (molecular weights (MW) of 2,110,000, 427,000, 37,900, and 5,970), pinoresinol (MW 352), and vanillin (MW 152), and the weight-average molecular weight Mw and number-average molecular weight Mn of the samples were determined. Polydispersity was determined as Mw / Mn.

[0150] <Test Example 1-6-2. Method for Calculating the Composition Ratio of Molecular Bonding Units> The sample was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) to a concentration of 1-10 wt%, and NMR spectra were acquired using a Bruker Avance III 600 MHz NMR spectrometer equipped with a low-temperature probe. The composition ratio of lignin interunit bond units was calculated from the signal volume on the HSQC (Heteronuclear single-quantum correlation spectroscopy) spectrum. The composition ratio was calculated as the ratio per 100 lignin aromatic rings. The content of ether-type bond units was estimated from the sum of the integral values ​​of the CH correlation signals at the β position (in the regions of δH / δC = 4.0 ±0.2 ppm / 85.6 ±1.2 ppm and δH / δC = 4.3 ±0.2 ppm / 83.0 ±0.7 ppm). The quantification using 2D NMR was corrected using the TAF method described in the literature (Okamura, H. Nishimura, T. Nagata, T. Kigawa, T. Watanabe and M. Katahira, Accurate and molecular-size-tolerant NMR quantitation of diverse components in solution, Scientific Reports, 6, 21742. 2016) to accurately calculate the content.

[0151] The region to be integrated will shift slightly depending on the sample and measurement environment; therefore, the signal integration region should be adjusted as appropriate during analysis (this also applies to other measurement methods described herein).

[0152] <Test Example 1-6-3. Method for Calculating the Composition Ratio of Lignin and Polysaccharides> The sum of the integrated CH correlation signals at the anomeric position (position 1) of the polysaccharide was calculated using the NMR method described in the previous section, corrected using the TAF method, and then calculated as the ratio per 100 lignin aromatic rings.

[0153] <Test Example 1-6-4. Method for Calculating the Composition Ratio of Lignin-Polysaccharide Copolymer Sites> As described above, the sum of the integral values ​​of the CH correlation signals derived from the LCα ether and LCα ester bonding units (LC ether, δH / δC = 4.50 ±0.15 ppm / 80.1 ±1 ppm region) and (LC ester, δH / δC = 5.88 ±0.15 ppm / 74.0 ±1.5 ppm region) was calculated by two-dimensional HSQC NMR spectroscopy, corrected by TAF spectroscopy, and then calculated as the ratio per 100 lignin aromatic rings. In the case of the A-APA method, some of the ester bonds undergo hydrolysis due to alkali treatment, but it is also possible to obtain LCα ester-type lignin-hemicellulose copolymers.

[0154] <Test Example 1-6-5. Method for Calculating Yield from Raw Biomass> Each obtained component was confirmed using a pH meter, pH test paper, or peracid test paper (potassium iodide starch paper), and then neutralized or peracid quenched as necessary. Neutralization was performed by adding small amounts of 1N HCl or 1N NaOH. Peracid quenching was performed by dropwise adding 1M sodium sulfite aqueous solution. The organic solvent was removed using an evaporator. Then, a dry powder was obtained by freeze-drying. If a salt was formed during neutralization, the concentrated solution after removal of the organic solvent was re-extracted with a separation solvent (acetone) to remove the salt. After that, the solvent was removed again using an evaporator, and a dry powder was obtained by freeze-drying. Each obtained component was weighed, and the yield per unit of raw biomass was calculated.

[0155] <Result> The following conditions are desirable for the molecular structure, molecular weight, and yield of the obtained polymer. The results are shown in Tables 1-7.

[0156] Table 1 shows the peracid conditions and yields (by weight %) of each component of high molecular weight lignocellulose in the M-APA two-step microwave extraction reaction, using eucalyptus as the raw material.

[0157] [Table 1]

[0158] Table 2 shows the yield (by weight, relative to raw material biomass) of each high-molecular-weight lignocellulose component from various biomass materials in the A-APA two-step microwave extraction reaction.

[0159] [Table 2]

[0160] Table 3 shows the peracid conditions and molecular weights (acetylated GPC analysis values) of each component of high-molecular-weight lignocellulose in the M-APA two-step microwave extraction reaction.

[0161] [Table 3]

[0162] Table 4 shows the yield (by weight, relative to raw material biomass) of each high-molecular-weight lignocellulose component from various biomass materials in the M-APA two-step microwave extraction reaction.

[0163] [Table 4]

[0164] Solvent: Acetic acid (containing 1% peracetic acid, 0.14 mol / L) Microwave extraction conditions: APA lignin soluble portion obtained by 50°C, 10 min (first stage). Lignin hemicellol copolymer was obtained by 140°C for 10 minutes (second stage). Table 5 shows the yield (by weight, relative to raw material biomass) of each high-molecular-weight lignocellulose component from various biomass materials in the A-APA one-step microwave extraction reaction.

[0165] [Table 5]

[0166] Table 6 shows the molecular weight (acetylated GPC analysis value) of each component of high-molecular-weight lignocellulose obtained by the A-APA method from various biomass materials.

[0167] [Table 6]

[0168] As a result of the condition studies, it was found that when the starting material is woody biomass, a contact temperature of 40-90°C with organic acid + peracid is suitable for obtaining soluble lignin, and a contact temperature of 100-160°C is suitable for obtaining lignin-hemicellulose copolymer. Furthermore, as a result of the condition studies, it was found that when the starting material is herbaceous biomass, a contact temperature of room temperature to 60°C with organic acid + peracid is suitable for obtaining soluble lignin, and a contact temperature of 70-150°C is suitable for obtaining lignin-hemicellulose copolymer.

[0169] After investigating the conditions, it was found that the heating time by microwave irradiation should be 5-30 minutes, preferably 10 minutes. The net irradiation time was short. See Figure 2 for microwave profile and temperature and pressure data.

[0170] As a result of the condition studies, it was found that microwave heating yielded higher yields and selectivity compared to external heating methods under low temperature, short time, and low energy input conditions. In other words, the microwave effect, including local heating, internal heating, electron transfer, and drug penetration enhancement, was observed.

[0171] After investigating the conditions, lignin could be isolated using acetic acid, formic acid, and glyoxylic acid as organic acids, but acetic acid was deemed optimal from the standpoint of yield, purity, and industrial application.

[0172] Figure 3 shows the NMR results for Test Examples 1-6-2 and 1-6-3. Figure 3 shows the analysis results of lignin isolated by the M-APA method (microwave treatment at 50°C for 10 minutes, 1% acetic acid / peracetic acid) using eucalyptus as the starting material. The proportion of interunit bonds of lignocellulose was quantified by TAF-NMR, and it was found that 99% of the signals originated from lignin and 1% originated from polysaccharides (hemicellulose). The breakdown of interunit bonds of lignin was 81% ether-type β-O-4, 5% β-5, 11% β-β, 1% dibenzodioxosine, and 1% others. See Figure 4 for the partial chemical structures of interunit bonds of lignin and covalent bonds between lignin and hemicellulose.

[0173] Figure 5 shows the NMR results for Test Example 1-6-4. Figure 5 shows the analytical results of lignin-hemicellulose copolymers isolated by the M-APA method (microwave treatment at 50°C for 10 minutes, 1% acetic peracetic acid) using each plant as a starting material. The LC bonds (ether and ester types) shown by circles in the figure are the main branching structure, with an abundance ratio equal to or greater than that of the β-5 and β-β bonds, which are the main interunit bonds of lignin. The isolated lignin-hemicellulose copolymers are particularly characterized by having LCα-ester type bonds.

[0174] Test Example 2. Preparation of Self-Assembled Structures Self-assembled structures were prepared using lignin isolated by the M-APA method (microwave treatment at 50°C for 10 minutes, with 1% acetic acid-peracetic acid or acetic acid-0.2M hydrogen peroxide) using eucalyptus or bamboo as the starting material, or lignin-polysaccharide copolymers isolated by the M-APA method (microwave treatment at 140°C for 10 minutes, with 1% acetic acid-peracetic acid or acetic acid-0.2M hydrogen peroxide) using eucalyptus as the starting material. Specifically, the procedure was as follows.

[0175] A DMSO solution with a sample concentration of 1-2 wt% was prepared, and this was diluted to 0.01-0.02 wt% using a mixed solvent (1:1 or 2:1) of separation solvent (acetonitrile or ethanol) and water (or buffer solution) to obtain the sample solution. 0.1-0.2 mL of the sample solution was spread onto a glass slide or coverslip, and the solvent was evaporated under atmospheric pressure to obtain a thin film of self-assembled material. Under the above conditions, a high-concentration self-assembled material could be obtained by adding an equal volume of water (or buffer solution) to a 1 wt% sample concentration DMSO solution and spreading it.

[0176] Next, the optical properties of the obtained self-assembled material (lignin solid thin film or lignin-polysaccharide copolymer solid thin film) and a comparison sample (lignin obtained by the APA method (APA lignin)) were analyzed. Specifically, the analysis was carried out as follows.

[0177] The following was used for the measurement.

[0178] Ultraviolet-Visible Absorption Spectrum: UV-2700 (manufactured by Shimadzu Corporation) Fluorescence spectrum: Spectrofluorometer RF-6000 (Shimadzu Corporation) Fluorescence microscopy measurement: All-in-one fluorescence microscope BZ-X810 (manufactured by Keyence) The analysis was performed using the analysis software provided with each device.

[0179] UV-Vis absorption spectrum: Black quartz cell for spectroscopic measurement (optical path length: 10 mm) Fluorescence measurements were performed using a fully transparent synthetic quartz cell (optical path length: 10 mm) and a Starner triangular quartz cell SF3. For solid samples, a solid measurement unit was used, and the sample coated on a cover glass was sandwiched between quartz plates for measurement.

[0180] 3D fluorescence spectrum Excitation wavelength 310-800nm, data interval 5 nm; fluorescence wavelength 350-900nm, data interval 1 nm. Measurements were taken with a scan speed of 12000 nm / min, and a UV cut filter U310 was attached to the excitation side to reduce the effects of scattered light and higher-order light. The bandwidth was 5 nm on the excitation side and 15 nm on the fluorescence side, and the sensitivity setting was set to Low.

[0181] Synchro-scan spectroscopy is a scan mode in which the excitation and fluorescence spectrometers of a spectrofluorometer are simultaneously scanned with a fixed wavelength difference between them. Measurements were performed by varying the wavelength difference between the excitation light and fluorescence from -90 nm to 260 nm. When the wavelength difference is negative, i.e., fluorescence with a wavelength shorter than the excitation light is detected. In this case, fluorescence due to anti-Stokes shift can be selectively detected. The scan was set to cover the fluorescence wavelength range of 350-800 nm, with a data interval of 0.1 nm, a scan speed of 600 nm / min, a bandwidth of 15 nm on the excitation side and 20 nm on the fluorescence side, and a sensitivity setting of Low.

[0182] The ultraviolet-visible absorption spectrum was measured using a double monochromator UV-2700. A wavelength scan (200-900 nm) was performed.

[0183] The results are shown in Figures 6-9. From Figure 9, it was found that lignin solid thin films or lignin-polysaccharide copolymer solid thin films exhibit anti-Stokes fluorescence.

[0184] Test Example 3. Differential Thermal and Thermogravimetric Analysis Differential thermal and thermogravimetric measurements were performed on APA lignin, lignin-hemicellulose copolymer, and cellulose obtained by the APA method, along with their raw material, eucalyptus wood powder. A Shimadzu DTG-60 instrument was used. Approximately 10 mg of each powder sample was placed in a platinum cell, and after purging with nitrogen at 30°C for 15 minutes in a nitrogen atmosphere, the temperature was increased to 1000°C at 20°C / min for measurement. The results are shown in Figures 10-1 and 10-2.

[0185] Test Example 4. Solubility Measurement The solubility of lignin and lignin-hemicellulose copolymers obtained by the method of Test Example 1 or a similar method was measured in 60-80% ethanol at 25°C. Details of the measurement samples are shown in Table 7. The abbreviations in Table 7 are explained below. PA: Peracetic acid HP: Hydrogen Peroxide 50:MW50 ACTN, microwave 50°C treated high-quality polymer lignin 140:MW50-Mw140 ACTN, second stage of 140°C treatment of residue after microwave treatment at 50°C, lignin hemicellulose copolymer A50: Acetate-peracetic acid system, HP PA1%AA Mw50 ACN Microwave 50℃ treatment High-quality polymer lignin H50: Acetate peroxide system, HP 1M hydrogen peroxide Mw50 ACN microwave 50℃ treatment, high-quality polymer lignin.

[0186] [Table 7]

[0187] The solubility was measured as follows: The sample was dissolved by stirring in ethanol at 25°C, and then separated into an ethanol-soluble portion and an ethanol-insoluble portion by solid-liquid separation. An ethanol aqueous solution (1 / 1 = ethanol / water) at 25°C was added to the ethanol-insoluble portion and stirred to dissolve it, obtaining an ethanol aqueous solution-soluble portion. The ethanol aqueous solution-soluble portion was mixed with the ethanol-soluble portion to obtain the sample solution. The amount of ethanol aqueous solution added was adjusted so that the ethanol concentration of the sample solution was in the range of 60-80%. In the process of obtaining the soluble portion, dispersion and solubilization were performed using an ultrasonic cleaner for 3 minutes at 28kHz as needed. The maximum sample concentration at which the sample solution became transparent visually was defined as the "solubility in 60-80% ethanol at 25°C".

[0188] The results are shown in Table 8. It was found that the lignin and lignin-hemicellulose copolymer obtained by the method of the present invention exhibit good ethanol solubility.

[0189] [Table 8]

[0190] Test Example 5. Measurement of UV Absorption The ultraviolet absorption properties of lignin and lignin-hemicellulose copolymer used in Test Example 4 were measured. Specifically, the samples were dissolved in ethanol to a concentration of 0.005 w / v%, and the ultraviolet absorption spectrum of the resulting solution (clear) was measured using a spectrophotometer (Shimadzu Corporation, UV-2700) (optical path length 1 cm, quartz cell).

[0191] The results are shown in Figure 11. It was found that the lignin and lignin-hemicellulose copolymer obtained by the method of the present invention exhibit good ultraviolet absorption properties.

[0192] Test Example 6. Isolation of lignin from wood chips. Lignin was isolated using the A-APA method with wood chips from the broadleaf tree beech sapwood (size: 10 mm × 10 mm × 2 mm, 1.0 ± 0.1 g). Specifically, the procedure was as follows.

[0193] Wood chips were immersed in 10.0 mL of alkaline solution (0.25 M NaOH, 0.25 M KOH, 0.1 M NaOH, or 0.1 M KOH) and irradiated with ultrasound for 15 minutes (Honda Electronics ultrasonic cleaner, W-113 multimode, 28 kHz, 45 kHz, 100 kHz). After 1 hour, the alkaline cleaning solution was filtered off. After cleaning, the wood chips were immersed in 10 mL of acetic acid peroxide solution (prepared by adding 1 mL of 30% H2O2 to 9 mL of acetic acid, with a final hydrogen peroxide concentration of 3 v / v%) and irradiated with ultrasound for 30 minutes (Honda Electronics ultrasonic cleaner, W-113 multimode, 28 kHz, 45 kHz, 100 kHz). The immersion solution was collected, and the collected acetic acid peroxide solution was concentrated by evaporation and then freeze-dried to obtain lignin powder. The yield was 3%.

[0194] Test Example 7. Isolation of lignin and white wood chips (hemicellulose-cellulose complex) from wood chips. Lignin and hemicellulose-cellulose complexes were isolated using the A-APA method with wood chips of beech sapwood (size: 10 mm × 10 mm × 2 mm, 1.0 ± 0.1 g), a hardwood, and cedar sapwood (size: 10 mm × 10 mm × 2 mm, 0.7 ± 0.1 g), a softwood. Specifically, the procedure was as follows.

[0195] Wood chips were immersed in 10.0 mL of alkaline solution (0.25 M NaOH, 0.25 M KOH, 0.1 M NaOH, or 0.1 M KOH) and irradiated with ultrasound for 30 minutes (Honda Electronics ultrasonic cleaner, W-113 multimode, 28 kHz, 45 kHz, 100 kHz). During this time, the water in the ultrasonic cleaner was changed to maintain the liquid temperature, which rose due to the ultrasonic irradiation, at around 50°C (the same amount of water added was drained). After 1 hour, the alkaline cleaning solution was filtered off, and the resulting wood chips were immersed in 10 mL of acetic acid peracid solution (prepared by adding 1.0 mL of 30% H2O2 to 9 mL of Acetic Acid, with a final hydrogen peroxide concentration of 3 v / v%) and irradiated with ultrasound for 30 minutes (Honda Electronics ultrasonic cleaner, W-113, 28 kHz). After 10 hours, the immersion solution was collected, and 10 mL of acetic acid peracid solution was added again and the wood chips were immersed again, and similarly irradiated with ultrasound for 30 minutes. This process was repeated twice. The recovered acetic acid peracid solution was then concentrated in a fume hood (using a Convenience Evaporator from Biochromat Co., Ltd.), redissolved in 1.5 mL of 80% dioxane v / v solution, and freeze-dried. White lignin powder was obtained using the above method. The yield was 8%.

[0196] 7-1) After acetic acid peracid treatment, the wood chips were washed with pure water, immersed in 10 mL of 0.1 M NaOH solution, and 0.1 g of sodium percarbonate (Sigma-Aldrich, Na2CO31.5H2O2, CAS15630-89-4) was added. Ultrasonic irradiation was performed for 10 minutes (Honda Electronics ultrasonic cleaner, W-113 multimode 28kHz, 45kHz, 100kHz). This was repeated three times at 2-hour intervals. After dialysis of the immersion solution, glucrono xylan (4-O-Methyl-D-glucurono-D-xylan) was obtained from the sapwood of beech hardwood as hemicellulose (Figure 12). 1 H- and 1 H- 13The material was identified by 13C HSQC NMR analysis. Cellulose fibers were obtained by bleaching the residue, washing with pure water, and drying. Bleaching was performed by adding sodium hypochlorite (5 v / v%, 5 mL) and heating at 30°C, 1000 rpm, 1 hour (using an Eppendorf ThermoMixer C). The yield relative to the wood chips was 37%.

[0197] 7-2) Acetic acid was added to the acetic acid peracid treated wood chips, and decolorization progressed by continuing the immersion. After 3 days, the chips were washed with pure water and freeze-dried to obtain white wood chips. The white wood chips were hard, and after being powdered with a cutter, FT-IR and solid-state CP / MAS NMR measurements were performed. The results were compared with the cellulose obtained in 7-1. The results are shown in Figures 14-15. As a result, it was found that the white wood chips obtained in 7-2 (photographs are shown in Figures 16a and 16c) were cellulose-hemicellulose composites. The yield relative to the wood chips was 68%.

[0198] Furthermore, the white wood chips were ultrasonically treated and washed in a sodium percarbonate-containing NaOH solution, in the same manner as in 7-1. The resulting wood chips are shown in Figure 16b.

Claims

1. (A) A step of contacting plant biomass with a solution containing organic acids and peracids. A method for isolating at least one substance selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, cellulose, and hemicellulose-cellulose complex from plant biomass.

2. The above step (A) is, (A1) A step of contacting plant biomass with a solution containing organic acids and peracids at a temperature of 90°C or lower, and / or (A2) A process of contacting plant biomass with a solution containing organic acids and peracids at a temperature between 90°C and 160°C. The method according to claim 1, including the method described in claim 1.

3. The method according to claim 1 or 2, comprising obtaining at least one selected from the group consisting of lignin, hemicellulose, lignin-polysaccharide complex, and hemicellulose-cellulose complex from the soluble portion obtained in step (A).

4. The method according to any one of claims 1 to 3, comprising obtaining at least one selected from the group consisting of cellulose, hemicellulose, and hemicellulose-cellulose composite from the insoluble portion obtained in step (A).

5. The method according to any one of claims 1 to 4, further comprising irradiating the plant biomass with microwaves or ultrasound in step (A).

6. The method according to any one of claims 1 to 5, wherein the plant biomass used in step (A) is an alkali-treated product of a plant or a mechanically processed product thereof.

7. Lignin having a β-O-4 type ether structure content of 50% or more, and a solubility of 2 w / v% or more in 60-80% ethanol at 25°C.

8. Lignin that can be obtained by the method described in any one of claims 1 to 6.

9. A lignin-polysaccharide complex having at least one bond selected from the group consisting of an α-ether bond between lignin and polysaccharide, an α-ester bond between lignin and polysaccharide, and a γ-ester bond between lignin and polysaccharide.

10. The lignin-polysaccharide complex according to claim 9, wherein its solubility in 60-80% ethanol at 25°C is 2 w / v% or more.

11. A lignin-polysaccharide complex that can be obtained by the method described in any one of claims 1 to 6.

12. Cellulose that can be obtained by the method described in any one of claims 1 to 6.

13. A hemicellulose-cellulose composite that can be obtained by the method described in any one of claims 1 to 6.

14. Hemicellulose that can be obtained by the method described in any one of claims 1 to 6.

15. A self-assembling body selected from the group consisting of lignin according to claim 7 or 8 and a lignin-polysaccharide complex according to any one of claims 9 to 11.

16. The self-assembled body according to claim 15, which is in the form of a sheet or particulate matter.

17. A phosphor comprising the self-assembled body described in claim 15 or 16.

18. The phosphor according to claim 17, which exhibits anti-Stokes fluorescence.

19. A UV absorber comprising at least one selected from the group consisting of lignin according to claim 7 or 8 and a lignin-polysaccharide complex according to any one of claims 9 to 11.

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