A method for pretreating lignocellulose

Abstract

A method for pretreating lignocellulose is provided, which is to add ethylenediamine and sodium carbonate solution to straw and pretreat at 75-85°C for 2-6 hours. The invention belongs to a raw material cellulose separation technology, which promotes efficient degradation of lignin in the straw by pretreating the straw at medium temperature and normal pressure with ethylenediamine and sodium carbonate, effectively separates cellulose from the raw material, increases the accessibility of cellulose to cellulase, hemicellulase, etc., thereby improving the enzymatic hydrolysis efficiency of the straw, and the glucose yield is increased to 92.57%. In addition, the pretreatment is carried out at medium temperature and normal pressure, which reduces environmental pollution, reduces processing energy consumption, and simplifies processing steps.

Description

Technical Field

[0001] The invention relates to the technical field of bioresource utilization, and in particular to a method for pretreating lignocellulose. Background Art

[0002] Lignocellulose is a renewable resource that is ubiquitous in nature and has the characteristics of wide distribution and high yield. The efficient utilization of this type of material is crucial to improving biorefining technology, achieving sustainable development and alleviating energy shortages. Lignocellulose can be converted into fermentable sugars through biological, chemical, physical and other means, and then further converted into various chemical substances through microorganisms. The whole process includes pretreatment, enzymatic hydrolysis and fermentation. Among them, pretreatment is a key step in improving the enzymatic hydrolysis conversion rate of lignocellulose, which can destroy the cell wall structure of lignocellulose and improve the accessibility of cellulose.

[0003] Biological, chemical and physical methods are commonly used pretreatment methods. Biological methods are not suitable for large-scale industrial production applications because of their long treatment cycle and low efficiency. Although physical methods can effectively increase the specific surface area and pore size of raw materials, they have the disadvantages of high energy consumption and insignificant lignin removal effect. Chemical methods based on acid pretreatment, alkali pretreatment, ionic liquid pretreatment, etc. are widely studied because of their efficient lignin degradation effect and good economy. In the prior art, alkali pretreatment to remove lignin often uses strong alkalis such as sodium hydroxide and potassium hydroxide, which have significant effects on removing lignin, but the use of such chemical reagents causes serious environmental pollution and equipment corrosion. Due to the recyclability of ammonia, pretreatment using it as a catalyst has attracted attention. Ethylenediamine is a typical alkaline fatty diamine with excellent lignin removal ability. It can be pretreated with high solid content without adding water, which can effectively reduce operating costs. Compared with strong alkalis such as sodium hydroxide and potassium hydroxide, the pollution rate of ethylenediamine is relatively small. Therefore, ethylenediamine is an excellent reagent for pretreating lignin. However, at present, the research on ethylenediamine pretreatment is limited, and most of the treatment methods have high temperatures, which increases energy consumption to a certain extent; therefore, it is critical to seek a pretreatment method with mild conditions and obvious effects. In the prior art, ammonia water and ethylenediamine are used together to pretreat straw to increase the glucose yield. Although this effect is achieved, the combination is a step-by-step treatment, the ammonia water treatment time is long, the energy consumption is increased, and the steps are cumbersome. Summary of the invention

[0004] The present invention aims to provide a method for pretreating lignocellulose. The method is carried out at medium temperature and normal pressure, effectively improving the glucose yield while reducing energy consumption and reducing the pollution of reagents to the environment.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for pretreating lignocellulose, characterized in that ethylenediamine and sodium carbonate solution are added to straw, and pretreated at 75-85°C for 2-6 hours.

[0007] More preferably, the pretreatment temperature is 80° C. and the pretreatment time is 4 h.

[0008] Furthermore, the addition amount of ethylenediamine is 0.5-2 mL / g straw, the mass percentage concentration of sodium carbonate is 1-10%, and the addition amount is 0.4-0.6 mL / g straw.

[0009] Further preferably, the added amount of ethylenediamine is 1 mL / g straw, and the mass percentage concentration of sodium carbonate is 5%, and the added amount is 0.5 mL / g straw.

[0010] A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw, characterized by comprising straw pretreatment and enzymatic hydrolysis, wherein the pretreatment is to add ethylenediamine and sodium carbonate solution to the straw and pretreat at 75-85°C for 2-6 hours.

[0011] More preferably, the pretreatment temperature is 80° C. and the pretreatment time is 4 h.

[0012] Furthermore, the addition amount of ethylenediamine is 0.5-2 mL / g straw, the mass percentage concentration of sodium carbonate is 1-10%, and the addition amount is 0.4-0.6 mL / g straw.

[0013] Further preferably, the added amount of ethylenediamine is 1 mL / g straw, and the mass percentage concentration of sodium carbonate is 5%, and the added amount is 0.5 mL / g straw.

[0014] Compared with the pretreatment with sodium carbonate alone or ethylenediamine alone, the combined pretreatment showed a serious fragmentation structure on the surface of corn straw, and the connection between the fiber bundles showed an obvious loose structure with the appearance of holes. These changes in morphology and structure have greatly destroyed the physical structure barrier on the surface of corn straw, increased the specific surface area and pore structure of cellulose, and helped to improve the subsequent enzymatic hydrolysis conversion rate of corn straw. The synergistic effect between ethylenediamine and sodium carbonate cut off the connection between lignin and cellulose and hemicellulose, effectively destroying the lignin structure. The aromatic skeleton of lignin was broken under the action of ethylenediamine-sodium carbonate reagent. The polymer was degraded into dimer, and the main connection bond between lignin monomers was broken. The C on the side chain of the monomer α -C βThe bonds are broken, and the benzene ring polymer is split into more monomer structures. Under the action of the intermediate product, a further ring-opening reaction occurs, causing the lignin structure to break into long-chain fatty hydrocarbons, exposing more enzyme action sites and improving the efficiency of subsequent enzymatic hydrolysis reactions. This effect cannot be achieved by single sodium carbonate or single ethylenediamine pretreatment.

[0015] Furthermore, the enzymatic hydrolysis is to use the composite enzyme Cellic CTec 3 to enzymatically hydrolyze the pretreated straw, the enzymatic hydrolysis temperature is 50°C, the pH is 5.4, the glucan loading is 2-2.5%, the enzyme addition amount is 10 FPU / g glucan, and the enzymatic hydrolysis is carried out for 72 hours.

[0016] Most specifically, a method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw is characterized by comprising the following steps:

[0017] (1) Preprocessing

[0018] Add ethylenediamine and sodium carbonate solution to the straw and pretreat at 75-85°C for 2-6 h, wherein the amount of ethylenediamine added is 0.5-2 mL / g straw, the mass percentage concentration of sodium carbonate is 1-10%, and the amount of addition is 0.4-0.6 mL / g straw;

[0019] (2) Enzymatic hydrolysis

[0020] Citrate buffer was added to the pretreated straw to adjust the pH to 5.4, and the composite enzyme CellicCTec 3 was added with 2.5% glucan loading and 10 FPU / g glucan. The straw was enzymatically hydrolyzed at 50°C for 72 h. After the enzymatic hydrolysis, the straw was centrifuged at 12,000 rpm for 10 min and the supernatant was collected.

[0021] The present invention has the following technical effects:

[0022] The present invention pre-treats straw at medium temperature and normal pressure by using ethylenediamine and sodium carbonate in combination, thereby promoting efficient degradation of lignin in the straw, increasing the accessibility of cellulose to cellulase, hemicellulase, etc., thereby improving the efficiency of straw enzymolysis and the yield of glucose. The yield of glucose is improved by 92.57% compared with the yield of glucose in straw pre-treated with single ethylenediamine at high temperature. In addition, the pre-treatment is carried out at medium temperature and normal pressure, which reduces environmental pollution, reduces processing energy consumption, and simplifies the pre-treatment steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Flow chart of ethylenediamine-sodium carbonate pretreatment of straw in Example 2 of the present invention.

[0024] Figure 2: The effects of sodium carbonate concentration, pretreatment time and temperature on glucose concentration, yield and lignin removal rate in the ethylenediamine-sodium carbonate pretreatment of straw of the present invention.

[0025] Figure 3 : SEM images of corn stover with different treatments.

[0026] Figure 4 : XRD patterns of corn stover with different treatments.

[0027] Figure 5 : FT-IR characterization of corn stover with different treatments.

[0028] Figure 6 : Changes in percentage content of main substances after pretreatment of corn stover with different reagents. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0030] The strong entanglement between lignin and cellulose and the covering of cellulose by hemicellulose have caused obstacles to the complete utilization of lignocellulose. Lignin is also regarded as the main limiting factor for the efficient enzymatic hydrolysis of lignocellulose in biorefining technology. In the current pretreatment method, the lignin removal effect is usually used as an evaluation indicator. Under the same pretreatment conditions, four weak alkaline reagents, sodium carbonate, sodium bicarbonate, urea, and ammonium carbonate, were mixed with ethylenediamine to pretreat corn stover in one step, and the lignin removal rate was used as an indicator to evaluate the pretreatment effect. The results are shown in Table 1.

[0031] Table 1: Changes in the content of components in corn straw pretreated with different weak bases and ethylenediamine coupling

[0032]

[0033] Compared with single reagent pretreatment, the lignin removal rate of the four combined pretreatment methods was significantly improved; among them, the effect of combined pretreatment with ethylenediamine-sodium carbonate was the most obvious, which was increased by about 2.7 times compared with single sodium carbonate pretreatment and about 1.1 times compared with single ethylenediamine pretreatment. Based on the results, sodium carbonate was selected as the combined reagent for subsequent experiments.

[0034] Example 1

[0035] A method for pretreating lignocellulose by using ethylenediamine-sodium carbonate in combination with medium temperature and normal pressure, comprising the following steps:

[0036] Ethylene diamine and sodium carbonate solution were added to corn straw and pretreated at 80°C for 4 h, wherein the amount of ethylenediamine added was 1 mL / g straw, and the mass percentage concentration of sodium carbonate was 5%, and the amount added was 0.5 mL / g straw.

[0037] Example 2

[0038] A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw comprises the following steps:

[0039] (1) Preprocessing

[0040] Ethylenediamine and sodium carbonate solution were added to the straw and pretreated at 80℃ for 4 h, wherein the amount of ethylenediamine added was 1 mL / g straw, the mass percentage concentration of sodium carbonate was 5%, and the amount of sodium carbonate added was 0.5 mL / g straw;

[0041] (2) Enzymatic hydrolysis

[0042] Citrate buffer was added to the pretreated straw to adjust the pH to 5.4, and the composite enzyme Cellic CTec3 was added with 2.5% glucan loading and 10 FPU / g glucan. The straw was enzymatically hydrolyzed at 50°C for 72 h. After the enzymatic hydrolysis, the straw was centrifuged at 12000 rpm for 10 min and the supernatant was collected.

[0043] The glucose content was analyzed using a kit and the yields of the two were calculated:

[0044] Glucose yield (%) = glucose content in the enzymatic hydrolysis system / (glucan content in the solid substrate * 1.11)

[0045] Among them, 1.11 is the coefficient of cellulose conversion to glucose. The above formula was used to calculate the concentration and yield of glucose after enzymatic hydrolysis of single sodium carbonate (concentration 5%, 0.5 mL / g straw addition, 80℃ for 4 h), single ethylenediamine (1 mL / g straw addition, 80℃ for 4 h) and ethylenediamine-sodium carbonate pretreatment of straw in Example 2, as shown in Table 2, where the CK group is enzymatic hydrolysis of straw without any pretreatment.

[0046] Table 2: Glucose concentration and yield of enzymatic hydrolysis of corn straw with different pretreatments

[0047]

[0048] It can be seen that the combined pretreatment of corn straw with ethylenediamine and Na2CO3 effectively promoted the final enzymatic hydrolysis efficiency, and the glucose yield was increased to 92.57%.

[0049] Effect of pretreatment on enzymatic saccharification:

[0050] In order to verify the effect of sodium carbonate-ethylenediamine pretreatment on enzymatic hydrolysis of corn straw under different conditions and to clarify the key factors affecting the enzymatic hydrolysis conversion rate, three factors including sodium carbonate concentration, pretreatment time and temperature during the pretreatment process were investigated.

[0051] (1) Effect of sodium carbonate concentration on enzymatic saccharification

[0052] Depend on Figure 2 As can be seen from (a) and (b), there are significant differences in glucose production and yield between the groups with and without ethylenediamine-sodium carbonate pretreatment. After enzymatic hydrolysis of corn straw without pretreatment, 6.93 g / L glucose was obtained, with a yield of 49.81%. In contrast, after treatment with 5% sodium carbonate (0.5 mL / g straw) and ethylenediamine (1.0 mL / g straw) at 80°C for 4 h, the glucose concentration and glucose yield increased to 25.92 g / L and 90.86%, respectively, and the lignin removal rate reached 85.11%. This indicates that this alkaline pretreatment is an effective lignin removal process, which can effectively destroy the alkyl aryl bonds of lignin and improve the efficiency of enzymatic hydrolysis.

[0053] (2) Effects of pretreatment temperature and time on enzymatic saccharification

[0054] Depend on Figure 2 As can be seen from (c) and (d), under the same pretreatment time, when the temperature increased from 40℃ to 80℃, the glucose concentration increased from 14.2 g / L to 25.92 g / L, and the glucose yield increased from 66.19% to 90.86%. When the temperature rose to 100℃, the glucose yield decreased.

[0055] With the increase of treatment time, the glucose yield and glucose production showed a trend of first increasing and then decreasing. When the treatment time was 4 h, the glucose content obtained after enzymatic saccharification at 40, 60, 80, and 100 °C was higher than that at 2 h and 6 h at the same temperature. This shows that the ethylenediamine-sodium carbonate coupling pretreatment time is too short, resulting in incomplete reaction, which is not enough to break the chemical bonds of the lignin structure of corn straw; while the pretreatment time is too long, which weakens the degree of reaction to a certain extent. During the experiment, single ethylenediamine and single sodium carbonate were used to pretreat corn straw at the same temperature and time, and then the same enzymatic treatment was carried out. It was found that with the increase of temperature or time, the concentration and yield of glucose showed an upward trend. This is different from the results obtained by enzymatic hydrolysis after the corn straw was pretreated with ethylenediamine-sodium carbonate. It shows that the combination of ethylenediamine and sodium carbonate has played a synergistic role, so that the pretreatment can achieve excellent pretreatment effect at a specific temperature and time.

[0056] Changes in the microstructure of corn stalk surface:

[0057] Scanning electron microscopy (SEM) was used to observe the microstructural changes of corn stalks before and after pretreatment with different reagents. Figure 3 It can be seen that there are significant differences in the surface structure of corn straw before and after pretreatment. The surface of corn straw without pretreatment is smooth and flat, and the structure is relatively complete; this ordered and dense network structure gives lignocellulose inherent resistance to the entry of pretreatment solvents and enzymes. The surface of corn straw after pretreatment is damaged, the internal structure is exposed, and obvious wrinkles and holes appear. This is due to the removal of a large amount of lignin, and the straw exposes more fiber bundles. Small cracks appeared on the surface of corn straw after sodium carbonate reagent pretreatment, which may be caused by the breakage of the connecting bonds between the fiber bundles. The surface of corn straw after ethylenediamine pretreatment became rougher and showed obvious fragmented structure. Compared with the pretreatment of sodium carbonate and ethylenediamine reagents alone, the surface of corn straw after the combined pretreatment of the two showed serious fragmented structure, the connection between the fiber bundles showed obvious loose structure, and there were holes, which may be caused by the gasification of ethylenediamine and sodium carbonate. These changes in morphological structure have greatly destroyed the physical structure barrier on the surface of corn straw, increased the specific surface area and pore structure of cellulose, and helped to improve the subsequent enzymatic conversion rate of corn straw. From the above results, it can be seen that the effect of sodium carbonate-ethylenediamine reagent combined pretreatment is indeed better than the effect of single reagent pretreatment on lignin degradation, which is consistent with the experimental results described above.

[0058] Changes in crystallinity of corn stalks:

[0059] Crystallinity (CrI) is a physical parameter that reflects the relative content of crystalline cellulose in lignocellulose raw materials, and its change is mainly related to the removal of amorphous components (hemicellulose and lignin). The effects of different pretreatments on the crystallinity of corn stover are shown in Table 3, where the CK group is the crystallinity of corn stover without any pretreatment.

[0060] Table 3: Changes in crystallinity of corn straw before and after different pretreatments

[0061]

[0062] As shown in Table 3 and Figure 4As shown in the figure, compared with the original corn stalks, the crystallinity of the alkaline reagent pretreatment increased to varying degrees. This may be because the alkali treatment destroyed the dense structure inside the corn stalks to a certain extent, resulting in the degradation of amorphous components such as lignin, which exposed more cellulose. In the combined pretreatment group of the two reagents, the crystallinity of corn stalks increased from 44.25% to 49.23%, which was 2.9% and 0.46% higher than that of the sodium carbonate alone and ethylenediamine alone treatment groups, respectively. This result shows that the combined pretreatment effectively removed the amorphous component (lignin). Experiments have shown that the synergistic effect between ethylenediamine and sodium carbonate cuts off the connection between lignin and cellulose and hemicellulose, exposing more enzyme action sites and improving the efficiency of subsequent enzymatic hydrolysis reactions.

[0063] Changes in the chemical structure and functional groups on the surface of corn stalks:

[0064] The changes in the functional groups of corn stalks before and after pretreatment were analyzed by FT-IR spectroscopy to further determine the effects of different reagent pretreatments on the structure of corn stalks. Figure 5 As shown, 1510 cm -1 and 1604 cm -1 The absorption peaks are respectively attributed to CC stretching and CO stretching of lignin aromatic skeleton vibration. Compared with the untreated group, the corresponding peaks are observed to weaken or even disappear in the three pretreatment groups, indicating that a large amount of lignin is removed. -1 The absorption peak corresponds to the conjugated carbonyl and CC stretching vibrations in lignin. The peak weakened in the sodium carbonate treatment group and disappeared in the ethylenediamine and ethylenediamine-sodium carbonate treatment groups. These phenomena indicate that the bonds between the benzene rings are broken and the connected carbonyl structures are deconstructed. In the two groups of experiments with ethylenediamine, the 1604 cm -1 , 1240 cm -1 、1650 cm -1 The corresponding absorption peak disappeared after pretreatment, indicating that EDTA has superior lignin removal ability in combined pretreatment and plays a major role in combined pretreatment, which is consistent with the previous analysis. -1 The absorption peak is attributed to the non-conjugated absorption (C=O) of the acetyl group in hemicellulose and the ester bond between lignin and carbohydrates. In the two treatment groups of ethylenediamine and ethylenediamine-sodium carbonate, the absorption peak disappeared, indicating that the acetyl group and lignin connected to hemicellulose fell off, indicating that the ester bond breakage in the experimental group with ethylenediamine was the main reason for the removal of lignin, which is consistent with previous studies. The characteristic absorption peak of cellulose appears at 1161 cm -1 , 1030 cm -1 and 896cm -1, these peaks became stronger after pretreatment, indicating that lignin was removed and cellulose was exposed. In the ethylenediamine and ethylenediamine-sodium carbonate treatment groups, 1651 cm -1 The characteristic absorption peak of NH vibration in the amino group appeared, indicating that the participation of ethylenediamine caused the amino group to appear in the structure of corn straw. According to the FT-IR results, it can be seen that ethylenediamine-sodium carbonate pretreatment can effectively remove lignin, and ethylenediamine plays a major role in the whole system, which corresponds to the above results.

[0065] In order to analyze the changes in chemical composition before and after pretreatment, the degradation products of three pretreatment methods, sodium carbonate, ethylenediamine, and ethylenediamine-sodium carbonate, were analyzed using gas chromatography-mass spectrometry (GC-MS) to obtain mass spectra. The chromatograms were retrieved using the NIST spectrum library to qualitatively identify each chromatographic peak. On this basis, various substances were classified, and the percentage of chromatographic peak area to total was used to express the substance content. After GC-MS analysis, the results are shown in Tables 4 and 5.

[0066] Table 4: Main components of corn straw washing liquid with different pretreatments

[0067]

[0068] Table 5: Main components of corn straw washing liquid with different pretreatments

[0069]

[0070] Lactic acid, erythritol-1,4-lactone, p-hydroxyacetophenone, 4-hydroxyphenylethanol / tyrosol, vanillyl acetophenone / acetyl vanillone and 2-hydro-pyran-2-one were detected in the corn straw products after single sodium carbonate pretreatment, single ethylenediamine pretreatment, and ethylenediamine-sodium carbonate pretreatment. The products of single sodium carbonate pretreatment and single ethylenediamine pretreatment all contained acetylmethyl carbinol / 3-hydroxy-2-butanone, succinic acid, 2'-deoxyribonucleic acid lactone, 4-hydroxybenzoic acid, but the above components were not detected in the corn straw products pretreated with ethylenediamine-sodium carbonate. In addition, characteristic products of lignin depolymerization such as geranyl coniferyl alcohol, acetyl vanillone, 3-hydroxyphenylpropionic acid, coumaric acid, and syringaldehyde were detected in the products of ethylenediamine-sodium carbonate pretreatment of corn straw, which were not found in single sodium carbonate and single ethylenediamine pretreatment, indicating that in this pretreatment method, ethylenediamine and sodium carbonate play a synergistic role and effectively destroy the lignin structure. The aromatic skeleton of lignin is broken under the action of ethylenediamine-sodium carbonate reagent. The polymer is degraded into dimer, and the main connecting bonds between lignin monomers are broken. Among them, acetovanillone, vanillic acid, syringaldehyde, coniferyl alcohol, etc. are all important products formed by oxidation of lignin phenol propane monomer structure.

[0071] Combining Table 4, Table 5 and Figure 6 It can be seen that the main components after pretreatment with sodium carbonate alone include acids, alcohols, and a small amount of ketones and esters. Among them, acids account for the largest proportion of 50.09%, followed by alcohols (43.24%). The proportion of aromatic compounds is relatively small. Although aliphatic compounds account for a large proportion, the products are mainly concentrated in simple short-chain compounds such as lactic acid, glycerol, and 2-hydroxyisocaproic acid. This may be due to the weak alkalinity and oxidizing properties of sodium carbonate. In the delignification stage, it can only effectively break some modified structures of lignin. The oxidation ability of non-phenolic β-O-4 structure is weak, and the aromatic products produced are relatively small. When pretreated with ethylenediamine, the main products include aldehydes, acids, alcohols, esters, and a small amount of ketones. Among them, the proportion of aromatic compounds such as vanillin, syringaldehyde, and geranyl coniferyl alcohol increased, which is due to the cleavage of the connecting bonds between the benzene rings under the catalysis of ethylenediamine. This pretreatment method produces more aromatic aldehydes. This is because ethylenediamine has strong oxidizing properties and can further oxidize the phenolic hydroxyl group produced by the break of the β-O-4 ether bond into aromatic aldehyde compounds. A lot of aliphatic hydrocarbons are produced in this stage. The increase of these substances may be caused by the opening of the benzene ring structure. During the ethylenediamine pretreatment process, there are fewer esters, indicating that ethylenediamine can break the ester bond and further aminize to produce substances such as p-hydroxybenzamide and 3,4,5-trimethoxybenzamide. Compared with ethylenediamine pretreatment, the ethylenediamine-sodium carbonate combined pretreatment produces fewer aromatic compounds and more aliphatic hydrocarbons, indicating that the combination of the two reagents increases the pretreatment effect, making the C on the side chain of the monomer α -C β The bonds are broken, and the benzene ring polymer is split into more monomer structures. Under the action of the intermediate products, further ring-opening reactions occur, causing the lignin structure to break into long-chain aliphatic hydrocarbons.

[0072] Example 3

[0073] A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw comprises the following steps:

[0074] (1) Preprocessing

[0075] Ethylenediamine and sodium carbonate solution were added to the straw and pretreated at 75°C for 5 h, wherein the amount of ethylenediamine added was 2 mL / g straw, the mass percentage concentration of sodium carbonate was 10%, and the amount of sodium carbonate added was 0.6 mL / g straw;

[0076] (2) Enzymatic hydrolysis

[0077] Citrate buffer was added to the pretreated straw to adjust the pH to 5.4, and the composite enzyme Cellic CTec3 was added with 2.5% glucan loading and 10 FPU / g glucan. The straw was enzymatically hydrolyzed at 50°C for 72 h. After the enzymatic hydrolysis, the straw was centrifuged at 12000 rpm for 10 min and the supernatant was collected.

[0078] In this embodiment, the glucose concentration of corn stalks after enzymatic hydrolysis after pretreatment is 0.69 g / g stalk, and the glucose yield is 93.24%.

[0079] Example 4

[0080] A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw comprises the following steps:

[0081] (1) Preprocessing

[0082] Ethylenediamine and sodium carbonate solution were added to the straw and pretreated at 85°C for 3 h, wherein the amount of ethylenediamine added was 0.5 mL / g straw, the mass percentage concentration of sodium carbonate was 1%, and the amount of sodium carbonate added was 0.4 mL / g straw;

[0083] (2) Enzymatic hydrolysis

[0084] Citrate buffer was added to the pretreated straw to adjust the pH to 5.4, and the composite enzyme Cellic CTec3 was added with 2.0% glucan loading and 10 FPU / g glucan. The straw was enzymatically hydrolyzed at 50°C for 72 h. After the enzymatic hydrolysis, the straw was centrifuged at 12000 rpm for 10 min and the supernatant was collected.

[0085] In this embodiment, the glucose concentration of corn straw after enzymatic hydrolysis after pretreatment is 0.66 g / g straw, and the glucose yield is 91.31%.

Claims

1. A method for pretreating lignocellulose, characterized in that: Add ethylenediamine and sodium carbonate solution to the straw, and pretreat at 75-85° C. for 2-6 h, wherein the amount of ethylenediamine added is 0.5-2 mL / g straw, the mass percentage concentration of sodium carbonate is 1-10%, and the amount of sodium carbonate added is 0.4-0.6 mL / g straw.

2. A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw, characterized in that: The method comprises straw pretreatment and enzymolysis. The pretreatment comprises adding ethylenediamine and sodium carbonate solution into the straw and pretreating the straw at 75-85°C for 2-6 hours.

3. A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw as claimed in claim 2, characterized in that: The added amount of ethylenediamine is 0.5-2 mL / g straw, the mass percentage concentration of sodium carbonate is 1-10%, and the added amount is 0.4-0.6 mL / g straw.

4. A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw as claimed in claim 2 or 3, characterized in that: The added amount of ethylenediamine is 1 mL / g straw, and the mass percentage concentration of sodium carbonate is 5%, and the added amount is 0.5 mL / g straw.

5. A method for improving the efficiency of preparing glucose by enzymatic hydrolysis of straw as claimed in any one of claims 2 to 4, characterized in that: The enzymatic hydrolysis is to perform enzymatic hydrolysis on the pretreated straw, the enzymatic hydrolysis temperature is 50° C., the pH is 5.4, the glucan loading is 2-2.5%, the enzyme addition amount is 10 FPU / g glucan, and the enzymatic hydrolysis is performed for 72 hours.

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