Method for improving straw enzymolysis saccharification effect

Abstract

The invention relates to the technical field of agricultural raw materials, in particular to a method for improving the straw enzymolysis saccharification effect. The method for improving the straw enzymolysis saccharification effect provided by the invention comprises the following steps: carrying out enzymolysis treatment after carrying out chemical pretreatment on a straw raw material by adopting a pretreatment solution; wherein the pretreatment liquid comprises the following components in percentage by mass: 3%-8% of sodium bicarbonate, 0.1%-0.5% of sucrose fatty acid ester, 0.01%-0.05% of manganese sulfate, 0.5%-1% of sodium hydroxide and the balance of water. According to the method, a chemical pretreatment method is improved, the pretreatment liquid composed of sodium bicarbonate, sucrose fatty acid ester, manganese sulfate and sodium hydroxide is adopted for carrying out chemical pretreatment on the straw raw materials, the content of reducing sugar after enzymolysis is increased, the sugar conversion rate is increased, the reducing sugar after enzymolysis can reach 50%-60%, and the sugar conversion rate can reach 70%-95%.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural raw materials, and in particular to a method for improving the enzymatic hydrolysis and saccharification effect of straw. Background Art

[0002] In China, the annually collectable crop straw resources are nearly 900 million tons. Utilizing straw resources to develop animal husbandry, realizing "returning straw to the field through livestock", substituting crops, reducing the pressure on feed demand, and promoting the virtuous cycle of the agricultural and animal husbandry systems have important practical significance. More than half of the photosynthesis products are contained in straw, which is rich in mineral elements such as nitrogen, phosphorus, potassium, calcium, and magnesium. Although straw has certain nutritional value and is suitable for feeding ruminants, there are also many problems and it is affected by various factors such as species and texture. The cellulose in straw is tightly wrapped by hemicellulose and lignin, forming a structure such as "reinforced concrete". Due to the protective effect of lignin and hemicellulose on cellulose and the crystalline structure of cellulose itself, the digestibility of directly feeding straw to animals is relatively low. Therefore, straw can break the barrier of plant cell walls against the action of enzymes through the combination of chemical pretreatment and enzymatic method to improve the enzymatic hydrolysis efficiency of cellulase. The main role of chemical pretreatment is to degrade lignin, destroy the crystal structure of cellulose, increase the porosity and specific surface area of biomass, and increase the accessibility of cellulase to cellulose, thereby improving the degradation rate of the substrate. Therefore, chemical pretreatment is an essential and crucial step in the biorefinery process of lignocellulosic raw materials.

[0003] Currently, the chemical pretreatment methods include alkalization, acidification, oxidation, and ammoniation, and the addition amount is relatively large, but the effect is often not good. The content of reducing sugar after degradation is only 30% - 40%, and the total sugar content is calculated as 65%. The sugar conversion rate is only 50% - 60%. Therefore, it is necessary to find a suitable chemical pretreatment method to increase the content of reducing sugar and degrade cellulose and lignin to the greatest extent.

[0004] In view of this, this invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the enzymatic hydrolysis and saccharification effect of straw, which improves the content of reducing sugar and sugar conversion rate after enzymatic hydrolysis of straw by optimizing the chemical pretreatment method, and fully utilizes straw resources.

[0006] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0007] The present invention provides a method for improving the enzymatic hydrolysis and saccharification effect of straw, including the following steps:

[0008] After chemically pretreating the straw raw material with a pretreatment solution, perform enzymatic hydrolysis treatment;

[0009] Among them, the pretreatment liquid, by mass percentage, comprises the following components:

[0010] Sodium bicarbonate 3% - 8%, sucrose fatty acid ester 0.1% - 0.5%, manganese sulfate 0.01% - 0.05%, sodium hydroxide 0.5% - 1%, and the balance is water.

[0011] Furthermore, the straw raw material includes at least one of corn straw, wheat straw, and rice straw.

[0012] Furthermore, before the chemical pretreatment, it also includes: sequentially washing and drying the straw raw material.

[0013] Furthermore, the chemical pretreatment includes: after mixing the straw raw material and the pretreatment liquid, obtaining material A; reacting the material A at 25 - 30°C for 10 - 15 days to obtain material B.

[0014] Furthermore, the water content in the material A is 30wt% - 50wt%.

[0015] Furthermore, the enzymatic hydrolysis treatment includes: after adjusting the pH of the material B to 4.0 - 5.0, adding an enzyme component and mixing to obtain material C; subjecting the material C to enzymatic hydrolysis.

[0016] Furthermore, the enzyme component includes cellulase, xylanase, β - glucosidase, mannanase, and pectinase.

[0017] Furthermore, the dosage of the cellulase is 200 - 1000U / g, the dosage of the xylanase is 100 - 500U / g, the dosage of the β - glucosidase is 50 - 200U / g, the dosage of the mannanase is 50 - 200U / g, and the dosage of the pectinase is 50 - 200U / g.

[0018] Furthermore, the water content in the material C is 50wt% - 80wt%.

[0019] Furthermore, the temperature of the enzymatic hydrolysis is 30 - 50°C, and the time of the enzymatic hydrolysis is 24 - 48h.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] By improving the method of chemical pretreatment, the present invention uses a pretreatment liquid composed of sodium bicarbonate, sucrose fatty acid ester, manganese sulfate, and sodium hydroxide to chemically pretreat the straw raw material, improving the content of reducing sugar and the sugar conversion rate after enzymatic hydrolysis. The reducing sugar after enzymatic hydrolysis can reach 50% - 60%, and the sugar conversion rate can reach 70% - 95%. Detailed implementation manners

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0023] The following specifically describes a method for improving the enzymatic hydrolysis and saccharification effect of straw in an embodiment of the present invention.

[0024] In some embodiments of the present invention, a method for improving the enzymatic hydrolysis and saccharification effect of straw is provided, including the following steps:

[0025] After chemically pretreating the straw raw material with a pretreatment solution, enzymatic hydrolysis treatment is carried out;

[0026] Among them, the pretreatment solution, calculated by mass percentage, includes the following components:

[0027] Sodium bicarbonate (NaHCO3) 3% - 8%, sucrose fatty acid ester 0.1% - 0.5%, manganese sulfate (MnSO) 0.01% - 0.05%, sodium hydroxide (NaOH) 0.5% - 1%, and the balance is water.

[0028] By improving the method of chemical pretreatment, the present invention chemically pretreats the straw raw material with a pretreatment solution composed of sodium bicarbonate, sucrose fatty acid ester, manganese sulfate, and sodium hydroxide, improving the content of reducing sugar and the sugar conversion rate after enzymatic hydrolysis. The reducing sugar after enzymatic hydrolysis can reach 50% - 60%, and the sugar conversion rate can reach 70% - 95%.

[0029] In the pretreatment solution of the present invention, sucrose fatty acid ester and manganese sulfate can make lignin better separate from cellulose and hemicellulose under alkaline conditions, combine with the phenolic hydroxyl groups on lignin, quickly separate lignin, and can reduce the barrier effect on the action of enzymes; thereby increasing the content of reducing sugar and the sugar conversion rate after enzymatic hydrolysis of straw, and degrading cellulose and lignin to the greatest extent.

[0030] In some embodiments of the present invention, in the pretreatment liquid, typically but not restrictively, for example, the mass percentage of sodium bicarbonate can be 3%, 4%, 5%, 6%, 7%, 8% or a range value composed of any two of them; the mass percentage of sucrose fatty acid ester can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or a range value composed of any two of them; the mass percentage of manganese sulfate can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05% or a range value composed of any two of them; the mass percentage of sodium hydroxide can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range value composed of any two of them.

[0031] In some embodiments of the present invention, the straw raw material includes at least one of corn straw, wheat straw and rice straw.

[0032] In some embodiments of the present invention, before chemical pretreatment, it further includes: washing the straw raw material with water and drying it in sequence; preferably, washing the straw raw material with water, and the mass of water is 5-8 times the mass of the straw raw material, and then using a drum screen to remove the liquid; drying includes air drying.

[0033] In some embodiments of the present invention, the chemical pretreatment includes: after mixing the straw raw material and the pretreatment liquid, obtaining material A; reacting material A at 25-30 °C (for example, it can be 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, 30 °C, etc.) for 10-15 days (for example, it can be 10 days, 11 days, 12 days, 13 days, 14 days, 15 days, etc.), obtaining material B.

[0034] In some embodiments of the present invention, the water content in material A is 30wt% - 50wt%; typically but not restrictively, for example, the water content in material A can be 30wt%, 35wt%, 40wt%, 45wt%, 50wt% or a range value composed of any two of them.

[0035] In some embodiments of the present invention, the pretreatment liquid is sprayed into the straw raw material through a sprayer, adding the liquid and mixing at the same time to make the straw raw material and the pretreatment liquid fully contact, obtaining material A, and the water content in material A is 30wt% - 50wt%; loading material A into a ton bag and storing it in a room at 25-30 °C for 10-15 days, obtaining material B.

[0036] In some embodiments of the present invention, the enzymatic hydrolysis treatment includes: after adjusting the pH of material B to 4.0-5.0, adding an enzyme component and mixing to obtain material C; subjecting material C to enzymatic hydrolysis.

[0037] In some embodiments of the present invention, 98% concentrated sulfuric acid is added to material B to adjust the pH to 4.0-5.0.

[0038] In some embodiments of the present invention, the enzyme components include cellulase, xylanase, β-glucosidase, mannanase, and pectinase.

[0039] In some embodiments of the present invention, the dosage of cellulase is 200 - 1000 U / g, the dosage of xylanase is 100 - 500 U / g, the dosage of β-glucosidase is 50 - 200 U / g, the dosage of mannanase is 50 - 200 U / g, and the dosage of pectinase is 50 - 200 U / g; typically but not restrictively, for example, the dosage of cellulase can be 200 U / g, 400 U / g, 600 U / g, 800 U / g, 1000 U / g, or a range value composed of any two of them; the dosage of xylanase can be 100 U / g, 200 U / g, 300 U / g, 400 U / g, 500 U / g, or a range value composed of any two of them; the dosage of β-glucosidase can be 50 U / g, 100 U / g, 150 U / g, 200 U / g, or a range value composed of any two of them; the dosage of mannanase can be 50 U / g, 100 U / g, 150 U / g, 200 U / g, or a range value composed of any two of them; the dosage of pectinase can be 50 U / g, 100 U / g, 150 U / g, 200 U / g, or a range value composed of any two of them.

[0040] The dosages of the cellulase, xylanase, β-glucosidase, mannanase, and pectinase of the present invention are the dosages required per gram of straw raw material (dry).

[0041] In some embodiments of the present invention, the water content in material C is 50 wt% - 80 wt%; typically but not restrictively, for example, the water content in material C can be 50 wt%, 60 wt%, 70 wt%, 80 wt%, or a range value composed of any two of them.

[0042] In some embodiments of the present invention, the temperature of enzymatic hydrolysis is 30 - 50 °C, and the time of enzymatic hydrolysis is 24 - 48 h; typically but not restrictively, for example, the temperature of enzymatic hydrolysis can be 30 °C, 40 °C, 50 °C, or a range value composed of any two of them; the time of enzymatic hydrolysis can be 24 h, 30 h, 36 h, 42 h, 48 h, or a range value composed of any two of them.

[0043] In some embodiments of the present invention, in the method for improving the enzymatic hydrolysis and saccharification effect of straw, the reducing sugar content after enzymatic hydrolysis treatment is 50% - 60%, and the sugar conversion rate is 70% - 95%; preferably, in the method for improving the enzymatic hydrolysis and saccharification effect of straw, the reducing sugar content after enzymatic hydrolysis treatment is 55% - 60%, and the sugar conversion rate is 85% - 95%.

[0044] Example 1

[0045] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this example includes the following steps:

[0046] S1. Wash the corn straw with water, where the mass of water is 5 - 8 times that of the corn straw. Then use a drum sieve to remove the liquid, dry it, and transfer it to a mixer. Spray the pretreatment liquid into the corn straw through a sprayer, adding the liquid while mixing to make the corn straw fully contact with the pretreatment liquid, obtaining material A with a water content of 30 wt% in material A. Load material A into a ton bag and store it in a 25°C room for 10 days to obtain material B;

[0047] Among them, the pretreatment liquid, by mass percentage, includes the following components:

[0048] Sodium bicarbonate 3%, sucrose fatty acid ester 0.1%, manganese sulfate 0.01%, sodium hydroxide 0.5%, and the balance is water;

[0049] S2. Adjust the pH of material B to 4.0 - 5.0, then add 200 U / g of cellulase, 100 U / g of xylanase, 50 U / g of β - glucosidase, 50 U / g of mannanase, and 50 U / g of pectinase to obtain material C with a water content of 50 wt% in material C. React material C at 30°C for 24 h to obtain the enzymatic hydrolysis product.

[0050] Example 2

[0051] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this example includes the following steps:

[0052] S1. Wash the corn straw with water, where the mass of water is 5 - 8 times that of the corn straw. Then use a drum sieve to remove the liquid, dry it, and transfer it to a mixer. Spray the pretreatment liquid into the corn straw through a sprayer, adding the liquid while mixing to make the corn straw fully contact with the pretreatment liquid, obtaining material A with a water content of 50 wt% in material A. Load material A into a ton bag and store it in a 30°C room for 15 days to obtain material B;

[0053] Among them, the pretreatment liquid, by mass percentage, includes the following components:

[0054] Sodium bicarbonate 8%, sucrose fatty acid ester 0.5%, manganese sulfate 0.05%, sodium hydroxide 1%, and the balance is water;

[0055] S2. Adjust the pH of Material B to 4.0 - 5.0, then add 1000 U / g of cellulase, 500 U / g of xylanase, 200 U / g of β-glucosidase, 200 U / g of mannanase, and 200 U / g of pectinase to obtain Material C, with the water content in Material C being 80 wt%; react Material C at 50 °C for 48 h to obtain the enzymatic hydrolysis product.

[0056] Example 3

[0057] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this example includes the following steps:

[0058] S1. Wash corn straw with water, where the mass of water is 5 - 8 times the mass of corn straw, then use a drum sieve to remove the liquid, dry it, and transfer it to a mixer; spray the pretreatment liquid into the corn straw through a sprayer, adding the liquid while mixing to ensure full contact between the corn straw and the pretreatment liquid to obtain Material A, with the water content in Material A being 40 wt%; place Material A in a ton bag and store it in a room at 28 °C for 12 days to obtain Material B;

[0059] Among them, the pretreatment liquid, by mass percentage, includes the following components:

[0060] Sodium bicarbonate (NaHCO3) 6%, sucrose fatty acid ester 0.3%, manganese sulfate 0.03%, sodium hydroxide (NaOH) 0.8%, with the balance being water;

[0061] S2. Adjust the pH of Material B to 4.0 - 5.0, then add 600 U / g of cellulase, 300 U / g of xylanase, 120 U / g of β-glucosidase, 120 U / g of mannanase, and 120 U / g of pectinase to obtain Material C, with the water content in Material C being 65 wt%; react Material C at 40 °C for 36 h to obtain the enzymatic hydrolysis product.

[0062] Comparative Example 1

[0063] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this comparative example refers to Example 2, with the only difference being that in step S1, the pretreatment liquid, by mass percentage, includes the following components: sodium bicarbonate 8%, sodium hydroxide 1%, with the balance being water.

[0064] Comparative Example 2

[0065] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this comparative example refers to Example 2, with the only difference being that in step S1, the pretreatment liquid, by mass percentage, includes the following components: sucrose fatty acid ester 0.5%, manganese sulfate 0.05%, with the balance being water.

[0066] Comparative Example 3

[0067] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this comparative example refers to Example 2, with the only difference being that in step S1, the pretreatment liquid, by mass percentage, comprises the following components: sodium bicarbonate 2%, sucrose fatty acid ester 0.05%, manganese sulfate 0.005%, sodium hydroxide 3%, and the balance is water.

[0068] Comparative Example 4

[0069] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this comparative example refers to Example 2, with the only difference being that in step S2, mannanase is not added.

[0070] Comparative Example 5

[0071] The method for improving the enzymatic hydrolysis and saccharification effect of straw provided in this comparative example refers to Example 2, with the only difference being that in step S2, 100 U / g of cellulase, 50 U / g of xylanase, 25 U / g of β-glucosidase, 25 U / g of mannanase, and 25 U / g of pectinase are added.

[0072] Test Example

[0073] The reducing sugar content and transglycosylation rate after enzymatic hydrolysis of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1.

[0074] Method for detecting the reducing sugar content after enzymatic hydrolysis: Refer to GB / T 5513-2019;

[0075] Method for detecting the total sugar content of straw: GBT15672-2009;

[0076] Straw transglycosylation rate: Reducing sugar content / Total sugar content (cellulose + hemicellulose).

[0077] Table 1

[0078]

[0079]

[0080] As can be seen from Table 1, chemical pretreatment of straw raw materials with the pretreatment liquid containing sodium bicarbonate, sucrose fatty acid ester, manganese sulfate, and sodium hydroxide of the present invention improves the reducing sugar content and transglycosylation rate after enzymatic hydrolysis; removing sucrose fatty acid ester and manganese sulfate from the pretreatment liquid results in poor enzymatic hydrolysis effect and low reducing sugar content; and sucrose fatty acid ester and manganese sulfate must be chemically pretreated under alkaline conditions to achieve better effects.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the enzymatic saccharification effect of straw, characterized in that: The following steps are involved: The straw raw material is chemically pretreated with a pretreatment liquid and then subjected to enzymatic hydrolysis; Wherein, the pretreatment solution comprises the following components in terms of mass percentage: Sodium bicarbonate 3%-8%, sucrose fatty acid ester 0.1%-0.5%, manganese sulfate 0.01%-0.05%, sodium hydroxide 0.5%-1%, and the balance is water.

2. The method for improving the enzymatic saccharification effect of straw according to claim 1, characterized in that: The straw raw material includes at least one of corn straw, wheat straw and rice straw.

3. The method for improving the effect of enzymatic saccharification of straw according to claim 1, characterized in that: Before the chemical pretreatment, the method further includes: washing and drying the straw raw material in sequence.

4. The method for improving the enzymatic saccharification effect of straw according to claim 1, characterized in that: The chemical pretreatment comprises: mixing the straw raw material and the pretreatment liquid to obtain material A; reacting the material A at 25-30° C. for 10-15 days to obtain material B.

5. The method for improving the effect of enzymatic saccharification of straw according to claim 4, characterized in that: The water content in the material A is 30 wt% to 50 wt%.

6. The method for improving the enzymatic saccharification effect of straw according to claim 4, characterized in that: The enzymatic hydrolysis treatment comprises: adjusting the pH of the material B to 4.0-5.0, adding enzyme components and mixing to obtain material C; and enzymatically hydrolyzing the material C.

7. The method for improving the effect of enzymatic saccharification of straw according to claim 6, characterized in that: The enzyme components include cellulase, xylanase, β-glucosidase, mannanase and pectinase.

8. The method for improving the enzymatic saccharification effect of straw according to claim 7, characterized in that: The dosage of the cellulase is 200-1000 U / g, the dosage of the xylanase is 100-500 U / g, the dosage of the beta-glucosidase is 50-200 U / g, the dosage of the mannanase is 50-200 U / g, and the dosage of the pectinase is 50-200 U / g.

9. The method for improving the enzymatic saccharification effect of straw according to claim 6, characterized in that: The water content of the material C is 50 wt% to 80 wt%.

10. The method for improving the enzymatic saccharification effect of straw according to claim 6, characterized in that: The temperature of the enzymolysis is 30-50° C., and the time of the enzymolysis is 24-48 hours.

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