Method for extracting lignin contained in herbs, composition containing separated lignin derived from herbs, and method for producing the same

Abstract

A method for extracting lignin contained in herbaceous plants, the method comprising feeding wood-eating termites with a herbaceous plant.

Description

Technical Field

[0001] The present invention relates to a method for extracting lignin contained in herbs, and a composition containing isolated lignin derived from herbs and a method for producing the same.

Background Art

[0002] Lignin is a high-molecular compound formed by the enzymatic oxidative polymerization of lignin monomers called monolignols, and is one of the main components constituting the plant cell wall. Although lignin has attracted attention as a renewable resource, it is difficult to separate the lignin contained in plants because it forms a strong composite material with polysaccharides (cellulose, hemicellulose) in the plant cell wall (Non-Patent Documents 1 and 2).

[0003] As a method for separating (extracting) lignin contained in herbs, methods such as using black liquor discharged during paper pulp production (Patent Document 1) and a method including subjecting a lignocellulosic raw material to saccharification treatment with an enzyme and then performing heat treatment in a specific solvent to obtain a lignin decomposition product (Patent Document 2) have been found so far.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The inventors have found that termites that feed on food can be made to ingest herbs, and that lignin contained in herbs can be extracted by a method including causing termites that feed on food to ingest herbs. The present invention is based on this new finding, and aims to provide a method for extracting lignin contained in herbs, a composition containing separated lignin derived from herbs, and a method for producing the same.

Means for Solving the Problems

[0007] One aspect of the present invention relates to a method for extracting lignin contained in herbs, which includes causing termites that feed on food to ingest herbs.

[0008] As a result of the study by the inventors, it has become clear that termites that feed on food can be made to ingest herbs. And it has been found that by causing termites that feed on food to ingest herbs, lignin can be concentrated and separated as excrement (feces) of the termites. Thus, lignin contained in herbs can be extracted by a method including causing termites that feed on food to ingest herbs.

[0009] Another aspect of the present invention relates to a method for producing a composition containing separated lignin derived from herbs, which includes causing termites that feed on food to ingest herbs.

[0010] Still another aspect of the present invention relates to a composition containing separated lignin derived from herbs.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a method for extracting lignin contained in herbs, a composition containing separated lignin derived from herbs, and a method for producing the same.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0014] In this specification, when lignin is "isolated", it means that it is in a state different from lignin in plants such as herbs. More specifically, lignin in plants is strongly complexed with polysaccharides (cellulose, hemicellulose), and when lignin is at least partially separated from those polysaccharides, it is called "isolated" lignin.

[0015] A method for extracting lignin contained in herbs according to an embodiment includes causing a food termite to ingest the herb.

[0016] Food termites are termites that mainly feed on woody plants and are not known to ingest herbs. However, through the studies of the present inventors, it has become clear that it is possible to cause food termites to ingest herbs. Termites can decompose and absorb polysaccharides in the complex of polysaccharides and lignin, and as a result, excrete the separated lignin derived from herbs as excrement (feces). Therefore, by causing food termites to ingest herbs, lignin contained in herbs as a complex with polysaccharides can be extracted into the excrement of food termites.

[0017] Conventionally, in order to separate lignin contained in herbs, a method has been used in which the herb is treated at high temperature and high pressure with an acid or an alkali, and the decomposed lignin is extracted into a liquid of the acid or the alkali. The lignin recovered by such a method is soluble in an acid or an alkali at least in a high temperature or high pressure state, and has undergone decomposition and reduction in molecular weight.

[0018] On the one hand, in the method according to the present embodiment, termites selectively consume the polysaccharides in the complex of lignin and polysaccharides in herbs, whereby the lignin is separated. Therefore, according to the method according to the present embodiment, lignin can be extracted in a state where decomposition does not proceed and chemical modification is small.

[0019] In addition, in the method according to the present embodiment, the digestive function of termites is used and high-temperature and high-pressure treatment is not required, so that lignin can be extracted at low cost and with low energy.

[0020] Feeding herbs to food-grade termites may include feeding food (hereinafter also simply referred to as "food") containing herbs to food-grade termites.

[0021] The herb may be a herb belonging to the monocotyledons. Examples of herbs belonging to the monocotyledons include herbs belonging to the order Poales. Examples of herbs belonging to the order Poales include herbs of the families Poaceae, Juncaceae, Cyperaceae, and Typhaceae. Examples of herbs of the family Poaceae include herbs of the genera Oryza, Leersia, Colpodium, Secale, Allium, Zizania, Triticum, Phragmites, Echinochloa, Setaria, Digitaria, Panicum, Eleusine, Urochloa, Zoysia, Sorghum, Pennisetum, etc. Examples of herbs of the genus Oryza include rice. Examples of herbs of the genus Leersia include cutgrass. Examples of herbs of the genus Colpodium include colpodium. Examples of herbs of the genus Secale include rye. Examples of herbs of the genus Allium include wild garlic. Examples of herbs of the genus Zizania include wild rice. Examples of herbs of the genus Triticum include wheat. Examples of herbs of the genus Phragmites include common reed. Examples of herbs of the genus Echinochloa include barnyard grass. Examples of herbs of the genus Setaria include foxtail millet. Examples of herbs of the genus Digitaria include crabgrass. Examples of herbs of the genus Panicum include panicgrass. Examples of herbs of the genus Eleusine include goosegrass. Examples of herbs of the genus Urochloa include signalgrass. Examples of herbs of the genus Zoysia include zoysiagrass. Examples of herbs of the genus Sorghum include sorghum. Examples of herbs of the genus Pennisetum include pearl millet. Sugarcane may be bagasse (the bagasse of sugarcane).

[0022] The feed may consist of herbs and may also contain components other than herbs. The content of the herbs contained in the feed may be 30% by volume or more, 40% by volume or more, or 45% by volume or more based on the total volume of the feed, and may be 100% by volume or less.

[0023] The feed may contain woody plants. Examples of woody plants include conifers such as Cryptomeria japonica, Chamaecyparis obtusa, and Pinus spp., and broad-leaved trees such as Quercus serrata, Quercus acutissima, and Quercus mongolica.

[0024] The content of woody plants contained in the bait may be 1% by volume or more, or 5% by volume or more, based on the total volume of the bait, and may be 80% by volume or less, 60% by volume or less, or 55% by volume or less.

[0025] The bait may contain other components other than herbaceous and woody plants. Examples of other components include okara, crab shells, shrimp shells, ant soil, spent mushroom beds, and bamboo powder.

[0026] The content of other components other than herbaceous and woody plants contained in the bait may be 0.1% by volume or more, based on the total volume of the bait, and may be 10% by volume or less, or 5% by volume or less.

[0027] The moisture content of the bait may be 10% by mass or more, or 30% by mass or more, based on the total mass of the bait, and may be 90% by mass or less, or 80% by mass or less.

[0028] The bait can be produced, for example, by compression molding a raw material containing herbs and, if necessary, components other than herbs. Compression molding can be performed, for example, by putting the raw material into a mold and applying pressure using a tabletop press.

[0029] Food-grade termites are termites that mainly feed on woody plants, and may be lower termites or higher termites. Examples of lower termites include termites of the families Rhinotermitidae, Kalotermitidae, Hodotermitidae, Reticulitermitidae, Termopsidae, and Rhinotermitidae. Examples of termites of the family Rhinotermitidae include Coptotermes formosanus and Coptotermes nevadensis. An example of a termite of the family Kalotermitidae is Kalotermes flavicollis. Examples of termites of the family Reticulitermitidae include Reticulitermes speratus and Reticulitermes flavipes. An example of a termite of the family Termopsidae is Zootermopsis nevadensis. Examples of termites of the family Rhinotermitidae include Coptotermes formosanus and Coptotermes formosanus.

[0030] The termite Macrotermes osimensis prefers decayed wood and inhabits only in deep forests with high precipitation in the natural world, and rarely damages wooden buildings, etc. Moreover, it has a large body size and a large food intake per individual. Therefore, Macrotermes osimensis is particularly suitable as the termite for food properties in one embodiment. When using Macrotermes osimensis, since the production of winged termites can be completely suppressed under artificial management, there is also an advantage that winged termites do not escape from the breeding environment.

[0031] Examples of higher termites include termites of the family Termitidae. Examples of termites of the family Termitidae include Coptotermes formosanus and Cryptotermes domesticus.

[0032] The method for extracting lignin contained in herbs according to one embodiment may further include collecting the excrement of termites for food properties. Collecting the excrement of termites for food properties can be carried out, for example, by collecting the termite soil formed by termites for food properties.

[0033] As described above, the excrement (feces) of termites for food properties that have eaten herbs contains separated lignin derived from herbs. That is, a composition containing separated lignin derived from herbs can be produced by the above method. Therefore, the above method can also be regarded as a method for producing a composition containing separated lignin derived from herbs. As specific embodiments and the like in the method, each of the above-described embodiments can be applied without particular limitation.

[0034] Another embodiment of the present invention is a composition containing lignin derived from separated herbs. Such a composition can be produced, for example, by the above-described production method. The composition may contain the excrement of food-grade termites that have ingested herbs. Specific examples of food-grade termites are as described above. The composition may contain, for example, the excrement of lower termites that have ingested herbs. Lower termites have bacteria and protists as intestinal symbionts. On the other hand, higher termites do not have protists as intestinal symbionts. Therefore, the excrement of lower termites and the excrement of higher termites differ particularly in terms of the constituent components (DNA, etc.) derived from intestinal symbionts.

[0035] The separated herb-derived lignin is different from the lignin obtained by a method that undergoes high-temperature and high-pressure treatment using an acid or an alkali. The decomposition and low-molecular-weight reduction of lignin in herbs are suppressed, and it is of low denaturation.

[0036] The weight-average molecular weight (Mw) of the separated lignin contained in the composition may be 18,000 or more, 19,000 or more, 20,000 or more, 21,000 or more, 22,000 or more, 23,000 or more, 24,000 or more, 26,000 or more, 28,000 or more, 30,000 or more, 32,000 or more, 34,000 or more, 36,000 or more, 38,000 or more, 40,000 or more, more than 40,000, 41,000 or more, 42,000 or more, 43,000 or more, 44,000 or more, 45,000 or more, 46,000 or more, 47,000 or more, 48,000 or more, 49,000 or more, or 50,000 or more, and may be 100,000 or less, 90,000 or less, or 80,000 or less. In this specification, the Mw of the separated lignin contained in the composition means a value determined by gel permeation chromatography using polyethylene glycol standard and polyethylene oxide standard as standard substances. The weight-average molecular weight (Mw) of the separated herb-derived lignin contained in the composition may be within the numerical range described above as the weight-average molecular weight (Mw) of the separated lignin contained in the composition.

[0037] Lignin is a polymer containing monolignols (p-hydroxycinnamic alcohol analogs) as monomer units. There are three types of monolignols: coniferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol. The aromatic nuclear units of lignin derived from each monolignol are referred to as guaiacyl nucleus (G nucleus), syringyl nucleus (S nucleus), and p-hydroxyphenyl nucleus (H nucleus) in order (Non-Patent Document 1). In addition, lignin may contain at least one of p-coumaric acid esterified products (for example, p-coumaric acid esterified product of coniferyl alcohol, p-coumaric acid esterified product of sinapyl alcohol, etc.) and tricin as monomer units (Non-Patent Document 2).

[0038] The structure of lignin contained in plants varies depending on the plant (Non-Patent Document 2). For example, lignin contained in coniferous trees contains coniferyl alcohol as a monomer unit, and lignin contained in broad-leaved trees contains coniferyl alcohol and sinapyl alcohol as monomer units. In addition, lignin contained in plants belonging to monocotyledons such as Gramineae plants contains coniferyl alcohol, sinapyl alcohol, p-coumaric acid esterified product, and tricin as monomer units.

[0039] In the composition, the mass ratio of the content of acid-insoluble lignin to the content of acid-soluble lignin (content of acid-insoluble lignin / content of acid-soluble lignin) may be 1 / 1 or more, 5 / 1 or more, 10 / 1 or more, 12 / 1 or more, or 15 / 1 or more, and may be 50 / 1 or less, 40 / 1 or less, 30 / 1 or less, or 20 / 1 or less. In this specification, the content of acid-soluble lignin and the content of acid-insoluble lignin mean the values obtained as dry mass by the Klason method, and more specifically, the values measured by the method described in the examples.

[0040] In the composition, the content of acid-insoluble lignin (dry mass) may be 20% by mass or more, 30% by mass or more, 40% by mass or more, or 43% by mass or more, and may be 100% by mass or less, 90% by mass or less, or 80% by mass or less, based on the total mass (dry mass) of the composition.

[0041] In the composition, the content (dry mass) of acid-soluble lignin may be 1% by mass or more, 1.5% by mass or more, 2% by mass or more, or 2.3% by mass or more, and may be 50% by mass or less, 30% by mass or less, or 10% by mass or less, based on the total mass (dry mass) of the composition.

[0042] In the composition, the content (dry mass) of alcohol-benzene soluble matter may be 1% by mass or more, 1.5% by mass or more, 2% by mass or more, or 2.3% by mass or more, and may be 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on the total mass (dry mass) of the composition. In this specification, the content of alcohol-benzene soluble matter means a value determined in accordance with JAPAN TAPPI Paper Pulp Test Method No. 63:2000.

[0043] The content (dry mass) of lignin in the composition measured by the detergent method may be 36% by mass or more, 40% by mass or more, 44% by mass or more, or 48% by mass or more, and may be 100% by mass or less, or 95% by mass or less, based on the total mass (dry mass) of the composition.

[0044] The content (dry mass) of cellulose in the composition measured by the detergent method may be 1% by mass or more, 5% by mass or more, 10% by mass or more, or 20% by mass or more, and may be 40% by mass or less, 30% by mass or less, or 25% by mass or less, based on the total mass (dry mass) of the composition.

[0045] The content (dry mass) of hemicellulose in the composition measured by the detergent method may be 1% by mass or more, 3% by mass or more, 5% by mass or more, or 7% by mass or more, and may be 20% by mass or less, 15% by mass or less, or 11% by mass or less, based on the total mass (dry mass) of the composition.

[0046] The mass ratio of the lignin content (dry mass) to the cellulose content (dry mass) in the composition, as measured by the detergent method (lignin content / cellulose content), may be 0.5 or more, 1 or more, 1.5 or more, or 2 or more, and may be 50 or less, 30 or less, 10 or less, 5 or less, or 3 or less.

[0047] The mass ratio of the lignin content (dry mass) to the hemicellulose content (dry mass) in the composition, as measured by the detergent method (lignin content / hemicellulose content), may be 1 or more, 2 or more, 3 or more, 4 or more, 4.5 or more, or 5 or more, and may be 50 or less, 30 or less, 20 or less, 10 or less, or 5.5 or less.

[0048] Generally, a composition containing lignin is obtained by subjecting a plant containing lignin to chemical treatment with an alkali or physical treatment such as blasting treatment and hydrothermal treatment. In these cases, since moisture is added during the chemical treatment or physical treatment, the resulting composition contains a large amount of moisture. On the other hand, the composition according to one embodiment can be obtained by a method that does not add moisture as described above. Therefore, the composition according to one embodiment may have a relatively low moisture content. The composition according to one embodiment may be a solid.

Examples

[0049] Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited by the following examples.

[0050] <Preparation of artificial feed> The following were prepared as materials for the artificial feed. · Bagasse · Cryptomeria powder · Okara

[0051] (Feed A) Using a tabletop press and a mold, the bagasse was compression-molded to produce a block-shaped Feed A. The moisture content of Feed A was 30 to 70% by mass based on the total mass of Feed A.

[0052] (Bait B) Using a tabletop press and a mold, a mixture of bagasse and sugi powder was compression-molded to produce block-shaped bait B. The mixing volume ratio of bagasse and sugi powder was bagasse:sugi powder = 1:1. The moisture content of bait B was 30 - 70% by mass based on the total mass of bait B.

[0053] (Bait C) Using a tabletop press and a mold, a mixture of bagasse, sugi powder, and okara was compression-molded to produce block-shaped bait C. The mixing volume ratio of bagasse, sugi powder, and okara was bagasse:sugi powder:okara (volume ratio) = 1:1:0.1. The moisture content of bait C was 30 - 70% by mass based on the total mass of bait C.

[0054] <Rearing experiment of Odontotermes formosanus using artificial bait> Colonies of Odontotermes formosanus were transplanted into each of baits A - C and reared at room temperature (25°C) for 4 weeks. Thereafter, Odontotermes formosanus and ant soil (solid matter) were collected respectively.

[0055] <Component analysis of ant soil> The component analysis of the ant soil collected in the system using bait A was carried out as follows. Note that the ant soil contains the feces of Odontotermes formosanus.

[0056] (Acid-insoluble lignin) The content of acid-insoluble lignin in the ant soil was determined by the acidolysis-gravimetric method (Klason method). As a result, the content of acid-insoluble lignin (dry mass) was 44.9% by mass based on the total amount (dry mass) of the ant soil. Note that the lower limit of quantification by this analysis method was 0.1% by mass in dry mass.

[0057] (Acid-soluble lignin) The content of acid-soluble lignin in the ant soil was determined by the acid decomposition-absorbance photometry (Klason method). As a result, the content of acid-soluble lignin (dry mass) was 2.6% by mass based on the total amount of the ant soil (dry mass). The lower limit of quantification by this analysis method was 0.2% by mass in terms of dry mass.

[0058] (Alcohol-benzene soluble matter) The alcohol-benzene soluble matter was determined in accordance with JAPAN TAPPI Pulp Test Method No.63:2000. As a result, the alcohol-benzene soluble matter (dry mass) was 2.4% by mass based on the total amount of the ant soil (dry mass). The lower limit of quantification by this analysis method was 0.1% by mass in terms of dry mass.

[0059] In addition, for each of the systems using feeds A to C, (a) the worker survival rate, (b) the weight loss rate per worker, (c) the feed consumption rate, and (d) the apparent digestibility and absorption rate were examined. The calculation formulas are as follows. (a) Worker survival rate (%) = 100×(the number of workers surviving after breeding) / (the number of workers before breeding) (b) Weight loss per worker (mg) ={(the sum of the weights of all workers before breeding (mg) / (the number of workers before breeding)}-{(the sum of the weights of all workers after breeding (mg) / (the number of workers after breeding)} (c) Feed consumption rate (%) = 100×(the amount of feed intake (dry mass g)) / (the amount of feed before breeding (dry mass g)) (d) Apparent digestibility and absorption rate (ADC) (%) = 100×{(the amount of feed intake (dry mass g))-(the weight of feces (dry mass g))} / (the amount of feed intake (dry mass g))

[0060] For each strain, the above breeding experiment was conducted in five test plots, and (a) to (d) were calculated for each. For (a), a generalized linear mixed model (GLMM) was used, and for (b) to (c), a linear mixed model (LMM) was used for statistical analysis. After that, a post hoc test was performed using the Tukey HSD Test (P<0.05). The results are shown in Fig. 1(a) to (d). In each graph of Fig. 1(a) to (d), each data represents the results of the strain using Feed A, the strain using Feed B, and the strain using Feed C in order from the left. Each data is assigned an alphabet, and it was determined that there was a significant difference between the data assigned different alphabets. Also, the error bars indicate the standard error.

[0061] <Preparation of Feed D> Bagasse and cedar powder were mixed, and Feed D was prepared by burying cedar wood in the bagasse and cedar powder mixture. The mixing volume ratio of bagasse and cedar powder was bagasse:cedar powder (volume ratio)=1:1. Also, the cedar wood was 20 to 40% by volume based on the total volume of Feed D. The moisture content of Feed D was 30 to 70% by mass based on the total mass of Feed D.

[0062] <Breeding experiment of Odontotermes formosanus using Feed D> A colony of Odontotermes formosanus was transplanted onto the above Feed D and bred at room temperature (25°C) for 4 months. After that, Odontotermes formosanus and ant soil (solid matter) were collected respectively.

[0063] <Component analysis of ant soil recovered in the system using Feed D> The contents of cellulose, hemicellulose, and lignin in the ant soil recovered in the system using bait D were determined by the detergent method. The ant soil contains the feces of O. flavus. As a result, based on the total amount (dry mass) of the ant soil, the content (dry mass) of cellulose was 22% by mass, the content (dry mass) of hemicellulose was 9.6% by mass, and the content (dry mass) of lignin was 49% by mass. The lower limit of quantification by this analysis method was 0.5% by mass in terms of dry mass. Generally, the cellulose content in plants is 40 to 50% by mass, and the contents of hemicellulose and lignin are each about 15 to 35% by mass (Non-Patent Document 2, RSC Adv., 12, 3946-3956, 2013). In the above composition, the content ratio of lignin was high, and it was confirmed that lignin was extracted.

Claims

1. A method for extracting lignin contained in herbs, comprising feeding herbs to termites that are food-eating agents.

2. The method according to claim 1 , wherein the herbaceous plant is a grass plant.

3. A method for producing a composition containing isolated lignin derived from herbaceous plants, comprising feeding on herbaceous plants to termites that are food-eating agents.

4. The method according to claim 3, wherein the herbaceous plant is a grass plant.

5. A composition comprising isolated herbaceous lignin, The composition, wherein the mass ratio of the content of acid-insoluble lignin to the content of acid-soluble lignin in the composition is 5 / 1 or more and 50 / 1 or less.

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