Functionalized lignin as well as preparation method and application thereof
Functionalized lignin was prepared by in-situ modification of lignocellulose, which solved the problems of mass transfer limitation and low enzymatic hydrolysis efficiency under high solid content fermentation conditions, and achieved efficient ethanol production, reduced costs and simplified the process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA AGRICULTURAL UNIVERSITY
- Filing Date
- 2025-12-18
- Publication Date
- 2026-05-05
AI Technical Summary
Under high solids content fermentation conditions, the lignin saccharification fermentation process for ethanol production suffers from mass transfer limitations and low enzymatic hydrolysis efficiency. Existing commercial surfactants are costly and increase production complexity.
Functionalized lignin was prepared by in-situ modification of lignocellulose with toluenesulfonic acid and ethylene glycol. It was then used as a surfactant to combine with cellulase and Saccharomyces cerevisiae for saccharification and fermentation, thereby increasing the ethanol concentration and yield.
It achieves an ethanol yield of over 90% at low solids content and over 80% at high solids content, reducing production costs and simplifying the process.
Smart Images
Figure CN121975147A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of biomass energy technology, and in particular to a functionalized lignin, its preparation method, and its application. Background Technology
[0002] High-solids fermentation technology refers to the process of using high-concentration solids (usually total solids content > 15%) as substrate for biotransformation during fermentation. Compared with traditional liquid fermentation, this technology can significantly improve product concentration and fermentation efficiency when processing viscous materials, and shows great potential, especially in the fields of agricultural waste treatment, biofuel production, and chemical production.
[0003] In the process of producing ethanol by lignin saccharification and fermentation, although the high solids content fermentation technology can improve the production efficiency and economy of bioethanol, the high viscosity of the high solids content system will cause serious mass transfer limitations. At the same time, the non-productive adsorption of cellulase by lignin after pretreatment will also significantly reduce the enzymatic hydrolysis efficiency.
[0004] Currently, to address these issues, commercial surfactants such as milk whey protein and the Tween system are typically added during fermentation. However, these exogenous surfactants are expensive, and their use increases the additional investment and complexity of the production process, resulting in unsatisfactory economics for lignin saccharification fermentation to produce ethanol.
[0005] Therefore, there is an urgent need for a method that can effectively improve the yield of ethanol production by saccharification and fermentation under high solids fermentation conditions. Summary of the Invention
[0006] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and to provide a functionalized lignin, its preparation method, and its application.
[0007] The primary objective of this invention is to provide a method for preparing functionalized lignin.
[0008] The second objective of this invention is to provide functionalized lignin prepared by the above-described preparation method.
[0009] A third objective of this invention is to provide the application of the above-mentioned functionalized lignin in improving the yield of ethanol produced by saccharification and fermentation.
[0010] The fourth objective of this invention is to provide a method for improving the yield of ethanol produced by saccharification and fermentation.
[0011] To achieve the above objectives, the present invention is implemented through the following solution: This invention seeks protection for a method for preparing functionalized lignin, comprising the following steps: S1. Mix the lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid in a ratio of 10-30g: 100-300mL: 2.5-7.5g until fully reacted, then separate the solid and liquid components and collect the liquid. S2. Add the liquid obtained in step S1 to water with pH=2 to 4 to allow it to precipitate fully. Collect the solid by solid-liquid separation, wash the solid thoroughly with water, and freeze-dry it to obtain functionalized lignin.
[0012] Preferably, the lignocellulose raw material in step S1 is wheat straw, corn straw, corn cob, or miscanthus.
[0013] More preferably, the lignocellulose raw material in step S1 is wheat straw.
[0014] Preferably, in step S1, the lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid are mixed evenly at a ratio of 25g:250mL:6.25g.
[0015] More preferably, the volume concentration of the ethylene glycol is 50-100%.
[0016] More preferably, the volume concentration of the ethylene glycol is 60%.
[0017] Preferably, the complete reaction is carried out at 140–170°C for 20–60 min.
[0018] More preferably, the reaction is carried out at 160°C for 30 minutes.
[0019] Preferably, before the precipitation in step S2, the pH of the liquid obtained in step S1 is adjusted to 5.5 to 5.8.
[0020] Preferably, step S2 involves adding the liquid obtained in step S1 to water with pH=2.
[0021] Preferably, the thorough cleaning in step S2 involves washing the solid with water until the pH of the cleaning solution is neutral.
[0022] In this preparation method, by using p-toluenesulfonic acid and ethylene glycol to modify lignocellulose in situ, functionalized lignin with surface activity can be obtained; using this functionalized lignin as a surfactant can effectively increase the ethanol concentration and ethanol yield during saccharification and fermentation.
[0023] Therefore, the present invention also seeks protection for the functionalized lignin prepared by the above preparation method.
[0024] This invention also claims protection for the use of the above-mentioned functionalized lignin in improving the yield of ethanol produced by saccharification and fermentation.
[0025] This invention also claims protection for a method for improving the yield of ethanol produced by saccharification and fermentation, comprising the following steps: S11. Mix lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid at a ratio of 10-30g: 100-300mL: 2.5-7.5g until homogeneous. After the mixture has fully reacted, separate the solid and liquid components to obtain liquid and pretreated lignocellulose raw material. S12. Add the liquid obtained in step S11 to water with pH=2 to 4 to fully precipitate, collect the solid by solid-liquid separation, wash the solid thoroughly with water, and freeze-dry to obtain functionalized lignin. S13. Mix the pretreated lignocellulose raw material and nutrient solution obtained in step S11 at a ratio of 5-15g: 50-100mL evenly, and add cellulase with a final concentration of 10-30FPU / g and brewing yeast with a final concentration of 1-4g / L to obtain the fermentation system. The nutrient solution contains 1–3 g / L of yeast extract, 0.5–1.5 g / L of NH4Cl, 0.5–1.5 g / L of KH2PO4, and 0.2–0.4 g / L of MgSO4·7H2O; S14. Add the functionalized lignin obtained in step S12 to the fermentation system obtained in step S13, carry out saccharification fermentation, and collect ethanol. The mass ratio of functionalized lignin to pretreated lignocellulose raw material in the fermentation system is 1–5 mg: 1 g.
[0026] Preferably, in step S13, the pretreated lignocellulose raw material and nutrient salt obtained in step S11 are mixed evenly at a ratio of 5-12.5g:50mL.
[0027] Preferably, in step S13, cellulase with a final concentration of 15 FPU / g and brewer's yeast with a final concentration of 3.3 g / L are added.
[0028] Preferably, the nutrient salt in step S13 contains 2 g / L yeast extract, 1 g / L NH4Cl, 1 g / L KH2PO4 and 0.3 g / L MgSO4·7H2O.
[0029] Preferably, the mass ratio of the functionalized lignin to the pretreated lignocellulose raw material in the fermentation system in step S14 is 2 mg: 1 g.
[0030] Preferably, the saccharification and fermentation in step S14 is carried out at 30-35°C for 24-96 hours.
[0031] When performing simultaneous saccharification and fermentation with low solids content using the method described above, the ethanol yield can reach over 90%, which is about 15% higher than that of traditional saccharification and fermentation. Furthermore, the ethanol yield also reaches over 80% when performing simultaneous saccharification and fermentation with high solids content.
[0032] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing functionalized lignin. By in-situ modifying lignocellulose with p-toluenesulfonic acid and ethylene glycol, surface-active functionalized lignin is obtained. Simultaneously, using this functionalized lignin as a surfactant effectively increases ethanol concentration and yield during saccharification and fermentation, achieving an ethanol yield of over 90%. Furthermore, this functionalized lignin can be prepared simultaneously during the pretreatment of lignocellulose raw materials, simplifying the entire process from raw material to product. Moreover, since the functionalized lignin is a byproduct of the lignocellulose raw material pretreatment process, it is cheaper than commercially available surfactants, effectively reducing the overall cost of ethanol production through saccharification and fermentation. Attached Figure Description
[0033] Figure 1 This is a graph showing the free enzyme content at various time points during the fermentation process of the experimental and control groups in Example 2. Figure 2 The graph shows the viscosity results at various time points during the fermentation process of the experimental group and the blank group in Example 3. Detailed Implementation
[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.
[0035] The yeast extract used in this embodiment of the invention was purchased from Guangdong Huankai Microbial Technology Co., Ltd., product number 050090.
[0036] Example 1: A method for preparing functionalized lignin A method for preparing functionalized lignin includes the following steps: S1. In a 500mL high-temperature and high-pressure reactor, 25g of oven-dried wheat straw (WS) and 250mL of 60% ethylene glycol (ethylene glycol and water are mixed at a volume ratio of 60:40) are mixed. Then, 6.25g of p-toluenesulfonic acid (TsOH, 2.5%, w / v) is added and mixed evenly. The mixture is then reacted at 160℃ for 30min. After the reaction is completed, the mixture is cooled to 50℃ with running water, and the solid and liquid are separated and the liquid is collected. S2. Adjust the pH of the liquid collected in step S1 to 5.5-5.8 using 6M HCl, then pour it into deionized water with pH=2.0 and precipitate for 24 hours (pre-cooled at 4℃). Then, separate the solid and liquid to collect the solid. Wash the solid repeatedly with deionized water and centrifuge until the pH of the washing solution is neutral. After washing, freeze-dry the solid for 24 hours to obtain functionalized lignin powder.
[0037] Comparative Example 1: A method for preparing lignin A method for preparing lignin, as detailed below: Place 1g of wheat straw (40 mesh, oven-dry substrate) into a 150mL Erlenmeyer flask, then add 50mL of acetate-sodium acetate buffer (pH=4.8), and add 15 FPU / g of the buffer solution. 绝干底物 The cellulase was mixed evenly and placed in a constant temperature shaker. The temperature was set at 50℃ and the shaking speed at 150 rpm for the first enzymatic hydrolysis. After 72 hours of enzymatic hydrolysis, the hydrolysate was centrifuged and the solid 1 was collected.
[0038] Place solid 1 in a 150 mL Erlenmeyer flask, then add 50 mL of acetate-sodium acetate buffer (pH=4.8), and add 15 FPU / g. 绝干底物 Cellulase was mixed evenly and placed in a constant temperature shaker. The temperature was set at 50℃ and the shaking speed at 150 rpm for a second enzymatic hydrolysis. After 72 hours of enzymatic hydrolysis, the hydrolysate was centrifuged and solid 2 was collected to obtain crude lignin. Dioxane was used to extract the crude lignin and the extract was collected. After centrifugation, the extract was poured into deionized water at pH=2 to precipitate. Solid 3 was collected by solid-liquid separation. Solid 3 was repeatedly washed with deionized water and centrifuged until the pH of the washing solution was neutral. After freeze-drying the washed solid 3 for 24 hours, lignin 1 was obtained.
[0039] Comparative Example 2: A method for preparing lignin The preparation method shown in this comparative example differs from the preparation method of functionalized lignin shown in Example 1 only in that: the 250 mL of 60% ethylene glycol (ethylene glycol and water are mixed in a volume ratio of 60:40) in step S1 is replaced with an equal volume of water. The rest of the preparation process is exactly the same, and lignin 2 is prepared.
[0040] Comparative Example 3: A method for preparing lignin The preparation method shown in this comparative example differs from the preparation method of functionalized lignin shown in Example 1 only in that p-toluenesulfonic acid is not added in step S2, while the other preparation processes are exactly the same, and lignin 3 is obtained.
[0041] Example 2: A method for producing ethanol by saccharification and fermentation with low solids content I. Ethanol Yield Determination in Ethanol Production via Saccharification and Fermentation under Low Solid Content 1. Experimental Methods The experimental group (10% TsOH-L) was used to produce ethanol through saccharification and fermentation using the functionalized lignin shown in Example 1. The specific steps included: S11. In a 500 mL high-temperature and high-pressure reactor, 25 g of oven-dried wheat straw (WS) and 250 mL of 60% ethylene glycol (ethylene glycol and water were mixed at a volume ratio of 60:40) were mixed. Then, 6.25 g of p-toluenesulfonic acid (TsOH, 2.5%, w / v) was added and mixed evenly. The mixture was then reacted at 160 °C for 30 min. After the reaction was completed, the mixture was cooled to 50 °C with running water. The solid and liquid were then separated, and the liquid and pretreated wheat straw (solid) were collected. S12. Adjust the pH of the liquid collected in step S11 to 5.5-5.8 using 6M HCl, then pour it into deionized water with pH=2.0 and precipitate for 24h (pre-cooled at 4℃). Then, separate the solid and liquid to collect the solid. Wash the solid repeatedly with deionized water and centrifuge until the pH of the washing liquid is neutral. After washing, freeze-dry the solid for 24h to obtain functionalized lignin powder. S13. Mix 5g of pretreated wheat straw (substrate, accounting for 10% of the fermentation system, w / v) obtained in step S11 and 25mL of nutrient solution (composed of 2g / L yeast extract, 1g / L NH4Cl, 1g / L KH2PO4 and 0.3g / L MgSO4·7H2O) evenly, add water to 50mL, and then add cellulase with a final concentration of 15FPU / g and brewer's yeast with a final concentration of 3.3g / L to obtain the fermentation system (pH = 5.5, 50mL). S14. Add the functionalized lignin obtained in step S12 to the fermentation system obtained in step S13, and saccharify and ferment at 34℃ and 150rpm for 72h. The mass ratio of functionalized lignin to pretreated wheat straw in the fermentation system was 2 mg: 1 g.
[0042] The difference between the control group (10% control) and the experimental group is that no functionalized lignin is added in step S14, while the rest of the steps are the same, and saccharification and fermentation are carried out.
[0043] The difference between control group 1 and experimental group is that the functionalized lignin in step S14 is replaced with an equal amount of lignin 1 prepared in comparative example 1, while the other steps are the same, and saccharification and fermentation are carried out.
[0044] The difference between control group 2 and experimental group is that the functionalized lignin in step S14 is replaced with an equal amount of lignin 2 prepared in comparative example 2, while the other steps are the same, and saccharification and fermentation are carried out.
[0045] The difference between control group 3 and experimental group is that the functionalized lignin in step S14 is replaced with an equal amount of lignin 3 prepared in comparative example 3, while the other steps are the same, and saccharification and fermentation are carried out.
[0046] For the experimental group, blank group, and control groups 1 to 3, after 24 hours of saccharification and fermentation, the fermentation broth of each group was collected and centrifuged at 6000 rpm for 5 minutes. The supernatant was then taken and the ethanol concentration of each group was detected by liquid chromatography. The ethanol yield of each group was calculated according to formula I. Formula I: Ethanol yield (%) = {Ethanol concentration (g / L) * System volume (L)} / {Cellulose content in pretreated wheat straw (g) * 1.11 * 0.511} × 100%; The cellulose content in the pretreated wheat straw was determined by component analysis of 5g of pretreated wheat straw obtained in step S11, according to the method described in the existing technology (Pei, X., Fan, M., Zhang, H. et al. Assessment for industrial production of poplar ethanol after analysis of influencing factors and predicted yield. Cellulose 31, 10801–10829 (2024). https: / / doi.org / 10.1007 / s10570-024-06236-6).
[0047] 2. Experimental Results The ethanol concentration and ethanol yield after saccharification and fermentation in each group are shown in Table 1.
[0048] Table 1. Ethanol concentration and ethanol yield of each group after 24 h of saccharification and fermentation.
[0049] The results showed that in the process of producing ethanol by saccharification and fermentation with low solid content (substrate content accounts for 10% of the fermentation system, w / v), the functionalized lignin shown in Example 1 can effectively improve the yield of ethanol produced by fermentation. After 24 hours of fermentation, the ethanol yield can reach 93.4%, which is much higher than the ethanol yield of the blank group and control groups 1 to 3 after saccharification and fermentation (all around 80%).
[0050] The functionalized lignin shown in Example 1 has a significant synergistic effect in the saccharification and fermentation production of ethanol, and can effectively improve the efficiency of saccharification and fermentation production of ethanol.
[0051] II. Determination of Free Enzyme Content in Ethanol Production via Saccharification and Fermentation under Low Solid Content 1. Experimental Methods According to the description in "I. Determination of Ethanol Yield in Ethanol Production by Saccharification and Fermentation under Low Solid Content", an experimental group (10% TsOH-L) and a blank group (10% control) were constructed for saccharification and fermentation. At 0h, 6h, 12h, 24h, 48h and 72h of saccharification and fermentation, 0.5mL of supernatant was taken and the free enzyme content at each time point was determined by the Bradford method combined with Formula II using an enzyme-linked immunosorbent assay (ELISA) reader. Formula II: Free enzyme content (%) = (protein concentration in supernatant / original protein concentration) × 100%; The original protein concentration is the protein concentration in the supernatant at 0 h of saccharification and fermentation.
[0052] 2. Experimental Results The results of free enzyme content at various time points during fermentation in the experimental and control groups are shown in the figure below. Figure 1 As shown.
[0053] The results showed that the free enzyme content in the experimental group (saccharification and fermentation with the functionalized lignin shown in Example 1) was consistently higher than that in the control group during the fermentation process. After 12 hours of fermentation, the free enzyme content in the experimental group was still 20.20%, while that in the control group was only 10.93%.
[0054] Results show that in the process of saccharification and fermentation to produce ethanol, the functionalized lignin shown in Example 1 can act as a surfactant, which can bind to the fermentation substrate through its porous structure and surface functional groups, reduce the non-productive adsorption of enzymes by the fermentation substrate, enhance the accessibility of cellulase, and thus improve fermentation efficiency.
[0055] Example 3: A method for producing ethanol by saccharification and fermentation with high solids content. I. Ethanol Yield Determination in Saccharification and Fermentation Production of Ethanol under High Solid Content 1. Experimental Methods The only difference between experimental group ' (25% TsOH-L) and experimental group ' (10% TsOH-L) in Example 2 is that the mass of the pretreated wheat straw in step S13 was adjusted to 12.5g (accounting for 25% of the fermentation system, w / v), while the other methods and steps were the same, and saccharification and fermentation were carried out for 96h.
[0056] The only difference between the blank group (25% control) and the blank group (10% control) in Example 2 is that the mass of the pretreated wheat straw in step S13 is adjusted to 12.5g (accounting for 25% of the fermentation system, w / v), and the other steps are the same, and saccharification and fermentation are carried out for 96h.
[0057] The only difference between control group 1' and control group 1 in Example 2 is that the mass of the pretreated wheat straw in step S13 is adjusted to 12.5g (accounting for 25% of the fermentation system, w / v), while the other steps are the same, and saccharification and fermentation are carried out for 96h.
[0058] The only difference between control group 2' and control group 2 in Example 2 is that the mass of the pretreated wheat straw in step S13 is adjusted to 12.5g (accounting for 25% of the fermentation system, w / v), while the other steps are the same, and saccharification and fermentation are carried out for 96h.
[0059] The only difference between control group 3' and control group 3 in Example 2 is that the mass of the pretreated wheat straw in step S13 is adjusted to 12.5g (accounting for 25% of the fermentation system, w / v), while the other steps are the same, and saccharification and fermentation are carried out for 96h.
[0060] Next, following the method shown in Example 2, the ethanol concentration and ethanol yield of each group were measured after 48 hours of saccharification and fermentation.
[0061] 2. Experimental Results The ethanol concentration and ethanol yield results for each group are shown in Table 2.
[0062] Table 2. Ethanol concentration and ethanol yield of each group after 48 hours of fermentation.
[0063] The results showed that in the process of producing ethanol by saccharification and fermentation with high solid content (substrate content accounts for 25% of the fermentation system, w / v), the functionalized lignin shown in Example 1 can effectively improve the ethanol concentration and ethanol yield during fermentation. The ethanol yield can reach 84.35% after 48 hours of saccharification and fermentation, and the corresponding ethanol concentration is 75.80 g / L, which is significantly better than the ethanol yield of the blank group' and control groups 1' to 3'.
[0064] Results show that the functionalized lignin shown in Example 1 has a significant synergistic effect in both low-solids-content and high-solids-content saccharification and fermentation processes, and can effectively improve the efficiency and yield of ethanol production during saccharification and fermentation.
[0065] II. Determination of Rheological Properties of Ethanol Production by Saccharification and Fermentation under High Solid Content 1. Experimental Methods According to the description in "I. Determination of Ethanol Yield in Ethanol Production by Saccharification and Fermentation under High Solid Content", experimental group '(25%TsOH-L)' and blank group '(25%control)' were constructed for saccharification and fermentation. The viscosity of the fermentation broth was measured at 0h, 6h, 12h, 24h, 48h, 72h and 96h using a 25# spindle digital rotational viscometer (LV-SSR, Shanghai Fangrui Instrument Co., Ltd.).
[0066] 2. Experimental Results The viscosity results at various time points during the fermentation process of the experimental group and the control group are shown in the figure below. Figure 2 As shown.
[0067] The results showed that the viscosity of the experimental group (saccharification and fermentation using the functionalized lignin shown in Example 1) was consistently lower than that of the control group during fermentation. At 12 hours of fermentation, the viscosity of the experimental group was 28.21% lower than that of the control group. This indicates that during the saccharification and fermentation process for ethanol production, the functionalized lignin shown in Example 1 can act as a surfactant, creating a steric hindrance effect in the fermentation system, effectively blocking the distance between particles, thereby improving fermentation efficiency.
[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description and ideas, and it is neither necessary nor possible to exhaustively describe all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing functionalized lignin, characterized in that, Includes the following steps: S1. Mix the lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid in a ratio of 10-30g: 100-300mL: 2.5-7.5g until fully reacted, then separate the solid and liquid components and collect the liquid. S2. Add the liquid obtained in step S1 to water with pH=2 to 4 to allow it to precipitate fully. Collect the solid by solid-liquid separation, wash the solid thoroughly with water, and freeze-dry it to obtain functionalized lignin.
2. The preparation method according to claim 1, characterized in that, The lignocellulose raw material mentioned in step S1 is wheat straw, corn straw, corn cob, or miscanthus.
3. The preparation method according to claim 1, characterized in that, In step S1, the lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid are mixed evenly at a ratio of 25g:250mL:6.25g.
4. The preparation method according to claim 1, characterized in that, The complete reaction described in step S1 is: reacting at 140–170°C for 20–60 min.
5. Functionalized lignin prepared by any of the preparation methods described in claims 1 to 4.
6. The application of the functionalized lignin according to claim 5 in improving the yield of ethanol produced by saccharification and fermentation.
7. A method for improving the yield of ethanol produced by saccharification and fermentation, characterized in that, Includes the following steps: S11. Mix lignocellulose raw material, ethylene glycol and p-toluenesulfonic acid at a ratio of 10-30g: 100-300mL: 2.5-7.5g until homogeneous. After the mixture has fully reacted, separate the solid and liquid components to obtain liquid and pretreated lignocellulose raw material. S12. Add the liquid obtained in step S11 to water with pH=2 to 4 to fully precipitate, collect the solid by solid-liquid separation, wash the solid thoroughly with water, and freeze-dry to obtain functionalized lignin. S13. Mix the pretreated lignocellulose raw material and nutrient solution obtained in step S11 at a ratio of 5-15g: 50-100mL evenly, and add cellulase with a final concentration of 10-30FPU / g and brewing yeast with a final concentration of 1-4g / L to obtain the fermentation system. The nutrient solution contains 1–3 g / L of yeast extract, 0.5–1.5 g / L of NH4Cl, 0.5–1.5 g / L of KH2PO4, and 0.2–0.4 g / L of MgSO4·7H2O; S14. Add the functionalized lignin obtained in step S12 to the fermentation system obtained in step S13, carry out saccharification fermentation, and collect ethanol. The mass ratio of functionalized lignin to pretreated lignocellulose raw material in the fermentation system is 1–5 mg: 1 g.
8. The method according to claim 7, characterized in that, In step S13, the pretreated lignocellulose raw material and nutrient salt solution obtained in step S11 are mixed evenly at a ratio of 5-12.5g:50mL.
9. The method according to claim 7, characterized in that, The mass ratio of the functionalized lignin to the pretreated lignocellulose raw material in the fermentation system in step S14 is 2 mg: 1 g.
10. The method according to claim 7, characterized in that, The saccharification and fermentation described in step S14 is carried out at 30-35°C for 24-96 hours.