Method for hydrolyzing and saccharifying wood fiber biomass

Abstract

The invention discloses a method for hydrolyzing and saccharifying wood fiber biomass. The method is characterized by comprising the following steps: (1) washing and drying materials; (2) crushing the materials; (3) preparing a material pretreatment solvent; (4) delignification of the material in a pretreatment solvent; (5) filtering the reaction liquid at normal temperature and normal pressure to separate liquid from solid to obtain cellulose; and (6) adding cellulose and polypeptide into deionized water according to a ratio of 2: 1-1: 2 in a solid-to-liquid ratio of 1: 50-1: 100, adding a NaOH solution to adjust the pH value of the solution to 3-8, and reacting at 40-95 DEG C under the protection of nitrogen for 6-16 hours to obtain the product glucose.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of lignocellulose waste, and specifically relates to a method for improving the hydrolysis and saccharification efficiency of lignocellulose raw materials. Background Technology

[0002] With the ever-expanding demand for energy and the growing need for chemicals and materials derived from petroleum, fossil resources, which have long served as a primary source of energy and industrial raw materials for human society, are facing the severe challenge of increasing depletion. The environmental pollution and global climate anomalies caused by the overexploitation of fossil fuels are also becoming increasingly prominent. Therefore, the search for and development of new renewable energy sources and petroleum alternatives is urgently needed.

[0003] Lignocellulosic biomass, such as straw and branches, is currently the most abundant renewable resource on Earth. Converting it into chemicals or biofuels is of great significance in addressing current challenges such as energy depletion, resource scarcity, and environmental pollution. Glucose is an important platform compound capable of producing biofuels, chemicals, and high-molecular-weight compounds (such as bioethanol, lactic acid, 3-hydroxypropionic acid, and furfural). Therefore, the hydrolysis and saccharification of lignocellulosic biomass is considered one of the key bottlenecks in its development.

[0004] The main chemical components of lignocellulosic biomass are lignin, hemicellulose, and cellulose. Lignin and hemicellulose are covalently bonded and tightly surround cellulose, making it difficult for catalysts or enzymes to contact the cellulose, thus affecting its hydrolysis and saccharification. Therefore, pretreatment is necessary to separate or remove some lignin and hemicellulose, increasing the porosity of the lignocellulosic raw material and improving the specific surface area and accessibility for enzymes to contact cellulose. Thus, the saccharification of lignocellulosic biomass mainly includes two steps: pretreatment and hydrolysis-saccharification.

[0005] Existing physicochemical pretreatment methods, such as steam explosion and acid / alkali treatment, often involve harsh conditions including high temperature, high pressure, strong acids, and strong alkalis. These conditions, while disrupting the stubborn structure of lignocellulose, can also easily lead to excessive degradation or structural damage, resulting in significant losses of cellulose raw materials. Furthermore, the pretreatment process may generate byproducts such as furfural and hydroxymethylfurfural, affecting the efficiency of subsequent cellulose saccharification. In addition, to eliminate the impact of residual strong acids, alkalis, and byproducts on subsequent cellulose saccharification, extensive washing or neutralization of the pretreated material is required. This step not only significantly increases process water consumption, energy consumption, and wastewater treatment costs but also generates large amounts of wastewater containing acids, alkalis, and organic matter, thus putting pressure on the environment. Therefore, developing novel pretreatment technologies that are mild, highly selective, environmentally friendly, and do not require extensive washing is one of the key challenges that urgently needs to be overcome in the field of lignocellulose biorefining.

[0006] Currently, the most common methods for cellulose hydrolysis and saccharification are acid hydrolysis and enzymatic hydrolysis. Acid hydrolysis is further divided into concentrated acid hydrolysis and dilute acid hydrolysis. Concentrated acid hydrolysis is highly corrosive and requires sophisticated reactors. Dilute acid hydrolysis has milder reaction conditions, a faster reaction rate, and relatively lower cost, making it easier for industrial applications. However, the hydrolysis product sugars are prone to degradation in acidic media, resulting in complex hydrolysis products, low selectivity for the target product, and difficulties in separating and purifying the product sugars, making it difficult to achieve precise control over the target product. Enzymatic hydrolysis offers milder process conditions, fewer hydrolysis byproducts, and higher saccharification yields. However, cellulase has poor stability, high cost, and complex pretreatment processes, leading to higher costs. To overcome the drawbacks of acid hydrolysis and enzymatic hydrolysis, solid acid catalysts have been increasingly used in the catalytic hydrolysis of cellulose to glucose in recent years. Currently, the main types of solid acid catalysts include metal oxides, polymer solid acids, enzyme-like solid acids, sulfonated carbon-based solid acids, heteropoly acids, hydrogen-form molecular sieves, magnetic solid acids, supported metal oxides, solid superacids, and graphene derivatives. These solid acids have a certain catalytic effect on cellulose hydrolysis and saccharification, but their overall catalytic performance is still not ideal, with low glucose yield and selectivity. This is mainly because solid acid hydrolysis of cellulose is a heterogeneous catalysis (solid-solid reaction), which usually requires increasing the reaction temperature and extending the reaction time to achieve the ideal cellulose conversion rate. However, while increasing the reaction temperature and extending the reaction time, the stability of the solid acid becomes a problem. Acidic groups are easily leached and deactivated under hydrothermal conditions, reducing the catalytic effect of the solid acid. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the shortcomings and deficiencies in the pretreatment and hydrolysis-saccharification steps of the above-mentioned lignocellulosic biomass saccharification process. In the pretreatment stage, this invention provides a mild, highly efficient, environmentally friendly pretreatment method that eliminates the need for water washing. In the saccharification stage, this invention provides a saccharification method with high glucose yield and selectivity under ambient temperature, ambient pressure, and near-neutral conditions. This method can remove lignin from lignocellulosic biomass under near-room temperature and ambient pressure conditions, achieving a lignin removal rate of over 95%. The obtained cellulose only requires a small amount of water washing before directly entering the saccharification stage. The saccharification stage is carried out under ambient temperature, ambient pressure, and near-neutral conditions, resulting in high glucose selectivity and yield. The hydrolysate requires no further treatment and can be directly used for subsequent fermentation to produce bioethanol, overcoming the problems of strong corrosivity, difficulty in separating and purifying the product sugars, and low glucose yield and selectivity in existing methods. Furthermore, the pretreatment method of this invention uses a green solvent to remove lignin at ambient temperature and ambient pressure. The solvent can be reused through distillation, making this method green, environmentally friendly, and pollution-free.

[0008] The technical solution of the present invention is: a method for hydrolyzing and saccharifying lignocellulose biomass, comprising the following steps: (1) washing and drying the material; (2) crushing the material; (3) preparing a pretreatment solvent for the material; (4) removing lignin from the material in the pretreatment solvent; (5) filtering the reaction solution at room temperature and pressure to separate the liquid and solid, thereby obtaining cellulose; (6) adding cellulose and polypeptides to deionized water at a ratio of 2:1 to 1:2, with a solid-liquid ratio of 1:50 to 1:100, and adjusting the pH of the solution to between 3 and 8 with NaOH solution, and maintaining the pH at 40 to 95. o Under nitrogen protection, the reaction can be carried out for 6 to 16 hours to obtain the product glucose.

[0009] The materials in step (1) include corn stalks, rice stalks, wheat straw, tea tree pruning branches, various types of wood, branches, fruit shells and bamboo.

[0010] In step (2), the particle size of the material is 80-120μm.

[0011] The material pretreatment solvent is prepared by mixing organic acid and hydrogen peroxide in a volume ratio of 7:1 to 10:1; the organic acid includes saturated monocarboxylic acids such as formic acid, acetic acid, and propionic acid.

[0012] Step (4) is as follows: at normal pressure and temperature 50~90°C o C. Under the condition that the solid-liquid ratio of the material to the pretreatment solvent is 1:12~1:60, the material is pretreated with mechanical stirring at a speed of 90~150 rpm for 6-12 hours. The lignin and hemicellulose in the material depolymerize into low molecular weight organic compounds in the solution.

[0013] The peptides include histidine-glutamate hexapeptide (His-Glu-His-Glu-His-Glu), tyrosine-glutamate hexapeptide (Tyr-Glu-Tyr-Glu-Tyr-Glu), lysine-glutamate hexapeptide (Lys-Glu-Lys-Glu-Lys-Glu), tyrosine-histidine hexapeptide (Tyr-His-Tyr-His-Tyr-His), lysine-histidine hexapeptide (Lys-His-Lys-His-Lys-His), and dodecylhistidine-glutamate hexapeptide (C 12 H 25 -His-Glu-His-Glu-His-Glu), dodecyl tyrosine-glutamic acid hexapeptide (C 12 H 25 -Tyr-Glu-Tyr-Glu-Tyr-Glu), dodecyl lysine-glutamic acid hexapeptide (C 12 H 25-Lys-Glu-Lys-Glu-Lys-Glu), dodecyl tyrosine-histidine hexapeptide (C 12 H 25 -Tyr-His-Tyr-His-Tyr-His), dodecyl lysine-histidine hexapeptide (C 12 H 25 -Lys-His-Lys-His-Lys-His).

[0014] The glucose solution used in the hydrolysis and saccharification method of lignocellulose biomass is used for fermentation to prepare bioethanol.

[0015] The lignin depolymerization liquid obtained after pretreatment in the method of hydrolysis and saccharification of lignocellulose biomass is used as a conventional liquid fuel.

[0016] The beneficial effects of this invention are as follows: 1. This invention uses an organic acid / hydrogen peroxide green solvent method to pretreat lignocellulose biomass under normal pressure and near room temperature conditions, removing lignin and hemicellulose. The production conditions are mild, the equipment requirements are low, the process is simple, the operation is convenient and reliable, the safety is strong, the production cost is low, and it is easy to carry out large-scale industrial production.

[0017] 2. Organic acid / hydrogen peroxide hydrolysis solvent is green and environmentally friendly; organic acid can be reused through distillation. 3. Pretreated lignin fragments are easily soluble in organic solvents, which is beneficial for subsequent processing into biomass fuel; 4. The pretreated cellulose does not require further processing and can be used directly in the hydrolysis and saccharification process; 5. The hydrolysis saccharification process is carried out under normal pressure and near-neutral conditions. The reaction temperature is mild, and the reaction selectivity and yield are high. The product after hydrolysis saccharification can be directly used in subsequent sugar fermentation processes without further processing. Detailed Implementation

[0018] Example 1: A method for hydrolyzing and saccharifying lignocellulosic biomass, comprising the following steps: 1. Washing and drying of materials; Materials include all crop straws such as corn stalks, rice stalks, and wheat straw, as well as tea tree pruning branches, various types of wood, branches, bamboo, and fruit shells, and all lignocellulose biomass. Rinse thoroughly with tap water and air dry at room temperature or in a forced-air dryer (≤40°C). o C), avoid excessively high temperatures that could carbonize the material; 2. Crushing of materials; The particle size of the material should ideally be 80-120μm. If the particle size is too small, cellulose will remain in the pretreatment solvent during later filtration; if the particle size is too large, it will hinder the removal of lignin from the material. 3. Solvent preparation for material pretreatment; Organic acid: hydrogen peroxide (volume ratio) = 7:1; the hydrogen peroxide is commercially available and contains 30% hydrogen peroxide; the organic acids include saturated monocarboxylic acids such as formic acid, acetic acid, and propionic acid, with a purity of over 98%; 4. The material undergoes lignin removal in the pretreatment solvent; At normal pressure and a temperature of 70°C o C. Under the condition that the solid-liquid ratio of the material to the pretreatment solvent is 1:20, the material is pretreated with mechanical stirring at 100 rpm for 8 hours. The lignin and hemicellulose in the material depolymerize into low molecular weight organic compounds in the solution. 5. Filter the reaction solution at room temperature and pressure to separate the liquid and solid, and obtain cellulose; Cellulose is obtained by filtering and separating the low molecular weight organic matter solution of depolymerized lignin and hemicellulose with solid cellulose at room temperature and pressure. 6. Add cellulose and polypeptides, including histidine-glutamic acid hexapeptide, to deionized water at a 1:1 ratio, with a solid-liquid ratio of 1:50. Adjust the pH of the solution to between 3 and 6 using NaOH solution, and then heat at 85°C. o The product glucose was obtained by reacting under nitrogen protection for 6 hours, with a glucose selectivity of 90.6% and a yield of 93.8%.

[0019] Example 2: A method for hydrolyzing and saccharifying lignocellulosic biomass, comprising the following steps: 1. Washing and drying of materials; Materials include all crop straws such as corn stalks, rice stalks, and wheat straw; tea tree pruning branches; various types of wood, branches, bamboo, and fruit shells; and all lignocellulosic biomass. Rinse thoroughly with tap water and air dry at room temperature or in a forced-air dryer (≤40°C). o C), avoid excessively high temperatures that could carbonize the material; 2. Crushing of materials; The particle size of the material should ideally be 80-120μm. If the particle size is too small, cellulose will remain in the pretreatment solvent during later filtration; if the particle size is too large, it will hinder the removal of lignin from the material. 3. Solvent preparation for material pretreatment; Organic acid: hydrogen peroxide (volume ratio) = 9:1; the hydrogen peroxide is commercially available and contains 30% hydrogen peroxide; the organic acids include saturated monocarboxylic acids such as formic acid, acetic acid, and propionic acid, with a purity of over 98%; 4. The material undergoes lignin removal in the pretreatment solvent; At normal pressure and temperature 90 o C. Under the condition that the solid-liquid ratio of the material to the pretreatment solvent is 1:30, the material is pretreated with mechanical stirring at 120 rpm for 6 hours. The lignin and hemicellulose in the material depolymerize into low molecular weight organic compounds in the solution. 5. Filter the reaction solution at room temperature and pressure to separate the liquid and solid, and obtain cellulose; Cellulose is obtained by filtering and separating the low molecular weight organic matter solution of depolymerized lignin and hemicellulose with solid cellulose at room temperature and pressure. 6. Add cellulose and tyrosine-glutamic acid hexapeptide to deionized water at a ratio of 1:2, with a solid-liquid ratio of 1:80. Adjust the pH of the solution to between 5 and 10 by adding NaOH solution, and then heat at 90°C. o The product glucose can be obtained by reacting under nitrogen protection for 10 hours, with a glucose selectivity of 91.4% and a yield of 92.1%.

[0020] Example 3: A method for hydrolyzing and saccharifying lignocellulosic biomass, comprising the following steps: 1. Washing and drying of materials; Materials include all crop straws such as corn stalks, rice stalks, and wheat straw, as well as tea tree pruning branches, various types of wood, branches, bamboo, and fruit shells, and all lignocellulose biomass. Rinse thoroughly with tap water and air dry at room temperature or in a forced-air dryer (≤40°C). o C), avoid excessively high temperatures that could carbonize the material; 2. Crushing of materials; The particle size of the material should ideally be 80-120μm. If the particle size is too small, cellulose will remain in the pretreatment solvent during later filtration; if the particle size is too large, it will hinder the removal of lignin from the material. 3. Solvent preparation for material pretreatment; Organic acid: hydrogen peroxide (volume ratio) = 10:1; where the hydrogen peroxide is commercially available hydrogen peroxide containing 30% hydrogen peroxide; the organic acids include saturated monocarboxylic acids such as formic acid, acetic acid, and propionic acid, with a purity of over 98%; 4. The material undergoes lignin removal in the pretreatment solvent; At normal pressure and a temperature of 60°C o C. Under the condition that the solid-liquid ratio of the material to the pretreatment solvent is 1:50, the material is pretreated with mechanical stirring at 150 rpm for 12 hours. The lignin and hemicellulose in the material depolymerize into low molecular weight organic compounds in the solution. 5. Filter the reaction solution at room temperature and pressure to separate the liquid and solid, and obtain cellulose; Cellulose is obtained by filtering and separating the low molecular weight organic matter solution of depolymerized lignin and hemicellulose with solid cellulose at room temperature and pressure. 6. Add cellulose and lysine-glutamic acid hexapeptide to deionized water at a ratio of 1:2, with a solid-liquid ratio of 1:100. Adjust the pH of the solution to between 6 and 8 by adding NaOH solution, and then heat at 85°C. o Under nitrogen protection, the product glucose can be obtained after 12 hours of reaction, with a glucose selectivity of 90.4% and a yield of 89.6%. 7. The glucose solution can be directly fermented to produce bioethanol; The glucose reaction solution was directly poured into a shake flask, yeast was inoculated, and the shaker was kept at a constant temperature of 34-36°C. o C, adjust the pH of the solution to between 4 and 6, ferment for 60 to 80 h, and the bioethanol concentration is 29.3 g / L.

[0021] 8. The pretreated lignin depolymerization solution can be used as a conventional liquid fuel.

[0022] A conventional liquid fuel was prepared by mixing the pretreated lignin depolymerization solution with ethanol at a ratio of 1:20, with a calorific value of 5400 (Kcal / kg).

Claims

1. A method for hydrolyzing and saccharifying lignocellulosic biomass, characterized in that: The process includes the following steps: (1) washing and drying the materials; (2) crushing the materials; (3) preparing the pretreatment solvent for the materials; (4) removing the lignin from the materials in the pretreatment solvent; (5) filtering the reaction solution at room temperature and pressure to separate the liquid and solid, thereby obtaining cellulose; (6) adding cellulose and polypeptides to deionized water at a ratio of 2:1 to 1:2, with a solid-liquid ratio of 1:50 to 1:100, and adjusting the pH of the solution to between 3 and 8 with NaOH solution, and maintaining the pH at 40 to 95. o Under nitrogen protection, the reaction can be carried out for 6 to 16 hours to obtain the product glucose.

2. The method for hydrolyzing and saccharifying lignocellulosic biomass according to claim 1, characterized in that: The materials in step (1) include corn stalks, rice stalks, wheat straw, tea tree pruning branches, wood, branches, fruit shells and bamboo.

3. The method for hydrolyzing and saccharifying lignocellulosic biomass according to claim 1, characterized in that: In step (2), the particle size of the material is 80-120μm.

4. The method for hydrolyzing and saccharifying lignocellulosic biomass according to claim 1, characterized in that: The material pretreatment solvent is prepared by mixing organic acid and hydrogen peroxide in a volume ratio of 7:1 to 10:1; the organic acid includes saturated monocarboxylic acids such as formic acid, acetic acid, and propionic acid.

5. The method for hydrolyzing and saccharifying lignocellulosic biomass according to claim 1, characterized in that: Step (4) is as follows: at normal pressure and temperature 50~90°C o C. Under the condition that the solid-liquid ratio of the material to the pretreatment solvent is 1:12~1:60, the material is pretreated with a mechanical stirring speed of 90~150 rpm and a depolymerization time of 6-12 h. The lignin and hemicellulose in the material depolymerize into low molecular weight organic compounds in solution.

6. The method for hydrolyzing and saccharifying lignocellulosic biomass according to claim 1, characterized in that: The peptides include histidine-glutamate hexapeptide (His-Glu-His-Glu-His-Glu), tyrosine-glutamate hexapeptide (Tyr-Glu-Tyr-Glu-Tyr-Glu), lysine-glutamate hexapeptide (Lys-Glu-Lys-Glu-Lys-Glu), tyrosine-histidine hexapeptide (Tyr-His-Tyr-His-Tyr-His), lysine-histidine hexapeptide (Lys-His-Lys-His-Lys-His), and dodecylhistidine-glutamate hexapeptide (C 12 H 25 -His-Glu-His-Glu-His-Glu), dodecyl tyrosine-glutamic acid hexapeptide (C 12 H 25 -Tyr-Glu-Tyr-Glu-Tyr-Glu), dodecyl lysine-glutamic acid hexapeptide (C 12 H 25 -Lys-Glu-Lys-Glu-Lys-Glu), dodecyl tyrosine-histidine hexapeptide (C 12 H 25 -Tyr-His-Tyr-His-Tyr-His), dodecyl lysine-histidine hexapeptide (C 12 H 25 -Lys-His-Lys-His-Lys-His).

7. The reaction glucose solution in the method for hydrolysis and saccharification of lignocellulose biomass as described in claim 1 is used for fermentation to prepare bioethanol.

8. The pretreated lignin depolymerization liquid from the method for hydrolysis and saccharification of lignocellulose biomass as described in claim 1 is used as a conventional liquid fuel.