Method for improving enzymolysis efficiency of cellulose in corn cob residues

Abstract

The invention relates to the technical field of biomass resource utilization, in particular to a method for improving the enzymolysis efficiency of cellulose in corn cob residues. According to the method disclosed by the invention, the corn cob residues are treated by adopting gas explosion, an intertwined space structure in the corn cob residues is opened in a steam explosion manner, and then the corn cob residues subjected to steam explosion are crushed, so that efficient enzymolysis of cellulose in a subsequent enzymolysis process is facilitated; according to the method disclosed by the invention, treatment is carried out through steam explosion, so that relatively high water content can be kept in the subsequent drying process of the corn cob residues, the energy consumption of production is reduced, and meanwhile, the corn cob residues do not need to be crushed into relatively fine granularity in the crushing process, so that on one hand, the problem of blockage of crushing equipment does not need to be worried about; and on the other hand, the energy consumption of the equipment and the production cost can be effectively reduced, and application in industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of biomass resource utilization, and in particular to a method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue. Background Art

[0002] Xylose residue is the leftover material after xylose products are made from agricultural waste such as corn cobs, bagasse, and bamboo. Its main components are cellulose and lignin. Its main use is to replace part of the coal for biomass power generation. Another part is bought by farmers for edible fungus cultivation. Its utilization value is relatively low. Solving the high added value utilization of xylose residue is an urgent issue that all companies need to solve.

[0003] The traditional method for treating xylose residue is alkali dissolution. Through alkali dissolution, lignin in xylose residue can be dissolved, and the remaining components mainly contain cellulose, thereby achieving the separation of lignin and cellulose; in the subsequent treatment, lignin products and cellulose glucose can be obtained to achieve the comprehensive utilization of xylose residue. However, the existing alkali dissolution process has poor dissolution effect on lignin, low lignin yield, and correspondingly leads to low cellulose content in the cellulose component. Since lignin also consumes cellulase, this leads to an increase in the amount of cellulase used in the enzymatic hydrolysis stage of the cellulose component, thereby increasing production costs and also leading to a decrease in product purity.

[0004] In actual production operations, the xylose residue can also be directly enzymatically hydrolyzed, but the xylose residue is required to be crushed to a finer particle size. Experimental research has found that when the xylose residue is dried and crushed to more than 100 meshes, cellulase is directly added for enzymatic hydrolysis, and the conversion rate of cellulose in the xylose residue can reach more than 97%; however, in actual industrial applications, there are a series of problems. First, the moisture content in the xylose residue is high, which can reach about 60%. Drying equipment is used for drying and then crushing. In order to be able to crush to 100 meshes while avoiding clogging of the crushing equipment, the moisture content of the xylose residue must be at least dried to less than 10%. Huge energy consumption is generated in the process, which is completely unfavorable for application in industrial production. When the particle size after crushing is small, such as about 60 meshes, the measured cellulose conversion rate is only 70.91%, which is low and not suitable for industrial applications. Therefore, a method for efficient enzymatic hydrolysis and conversion of cellulose in xylose residue is a technical problem that needs to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the efficiency of enzymatic hydrolysis of cellulose in xylose residue, so as to solve the problem that the existing method has harsh process conditions and high energy consumption when enzymatic hydrolyzing cellulose in xylose residue, which is not conducive to industrial application.

[0006] To achieve the above object, the present invention adopts the following technical scheme: A method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residues, comprising the following steps:

[0007] S1, performing steam explosion treatment on xylose residue to obtain xylose residue after steam explosion treatment;

[0008] S2, drying and crushing the xylose residue after the gas explosion treatment in S1, and then screening, collecting the xylose residue powder with a suitable particle size, and storing it for later use;

[0009] S3, mixing the xylose residue powder obtained in S2 with cellulase to perform efficient enzymatic hydrolysis on the xylose residue powder.

[0010] Furthermore, in the S1, the steam explosion pressure is 2-4 MPa, the treatment time is 1-2 min, and the stirring intensity is 60-100 rpm.

[0011] Furthermore, in the above S2, the drying temperature is 120-150° C., the drying time is 2-6 hours, and the moisture content of the xylose residue after drying is 20-30%.

[0012] Furthermore, the drying equipment used in the drying includes but is not limited to a flash dryer and a drum dryer.

[0013] Furthermore, the particle size of the xylose residue powder is 40-80 meshes.

[0014] Furthermore, the crushing machines used include but are not limited to hammer crushers, tooth crushers and cutting crushers.

[0015] Furthermore, in S3, the xylose residue powder is mixed with water to form a slurry before adding cellulase, and the solid-liquid ratio of the xylose residue powder to water is 1:5-15.

[0016] Furthermore, in the S3, the added amount of cellulase is 0.5-1.5% of the absolute dry weight of the xylose residue powder.

[0017] Furthermore, in the S3, the enzymatic hydrolysis temperature is 52-54° C., the pH is 4.7-5.3, the time is 60-80 h, and the stirring intensity is 60-100 rpm.

[0018] Furthermore, in the above-mentioned S3, the conversion rate of cellulose in the xylose residue powder can reach more than 98%.

[0019] Beneficial effects of the present invention:

[0020] 1. Reduced the process requirements and energy consumption of crushing; the method of the present invention performs steam explosion treatment on xylose residue, so that the molecular spatial structure of the xylose residue is looser, and in the subsequent enzymatic hydrolysis process, it is not necessary to crush to a finer particle size, thereby reducing the process requirements of crushing and further reducing the energy consumption of crushing;

[0021] 2. Reduced energy consumption for drying; since the method of the present invention reduces the process requirements for crushing, the crushing operation can be achieved at a higher moisture content, so when drying the material, it is not necessary to dry it to a lower moisture content, which ultimately greatly reduces the cost of drying;

[0022] 3. It helps to reduce equipment costs; since the method of the present invention greatly reduces the process adjustment requirements compared to crushing to a finer particle size, the load on the production equipment is greatly reduced, which helps to ensure the service life of the equipment. In addition, the production is more efficient, which helps to improve production efficiency. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0024] Example 1

[0025] A batch of xylose residue obtained after the factory's straw acidification to produce xylose was tested. The test showed that the moisture content was 61.27%. Samples were taken from the batch of xylose residue, and after drying to absolute dryness, the components therein were tested. The cellulose content was 71.03%, the lignin content was 19.3%, the hemicellulose content was 6.16%, and the remainder was ash.

[0026] 100 kg of xylose residue from this batch was taken and added into the reactor, and high-pressure steam was introduced into the reactor to perform steam explosion treatment on the xylose residue, wherein the steam pressure was 3 MPa, the pressure holding time was 90 s, the stirring intensity was 80 rpm, and the pressure was instantly lost to normal pressure after the pressure holding ended, completing the steam explosion process.

[0027] The steam-exploded xylose residue material is added to a drying device for drying. In this embodiment, the drying device is a drum dryer, the drying temperature is 130° C., the drying time is 5 h, and the final mass of the dried xylose residue is about 53 kg (there is loss during material transfer), and the moisture content is 28.12%.

[0028] The dried xylose residue was crushed by a universal crusher (hammer mill). The particle size after crushing was controlled to be 60 meshes. The mass of the xylose residue powder after crushing was 52.64 kg.

[0029] Add 400L of water to the reactor (the solid-liquid ratio of the present invention is the ratio of solid mass to liquid volume), add the above-mentioned crushed powder to the reactor and stir into slurry at a stirring intensity of 60rpm, then control the temperature at 53°C±1°C, and adjust the pH value to 5±0.2, dissolve 0.4kg of cellulase and slowly add it to the reactor, and then react for 72h at a stirring intensity of 80rpm to complete the enzymatic hydrolysis process.

[0030] After the enzymatic hydrolysis was completed, the cellulose was filtered and separated to obtain 408 L of cellulose glucose syrup, in which the glucose content was 65.1 g / L and the cellulose conversion rate was 98.83%.

[0031] Comparative Example 1

[0032] In this comparative example, the steam explosion treatment is not performed, and the material is directly dried.

[0033] During the process, 100 kg of the same batch of materials as in Example 1 were taken and dried in a drum dryer under the same drying conditions as in Example 1, and the obtained dried xylose residue had a mass of about 52 kg and a moisture content of 26.52%.

[0034] The obtained dried xylose residue was crushed by a hammer mill. During the process, the particle size after crushing was controlled to be 60 meshes. The mass of the xylose residue powder after crushing was 51.45 kg.

[0035] The subsequent steps are the same as in Example 1.

[0036] 406 L of cellulose glucose syrup was obtained, in which the glucose content was 46.9 g / L and the cellulose conversion rate was 70.91%.

[0037] It can be seen that, without steam explosion treatment, although the xylose residue was crushed to 60 mesh in this comparative example, the cellulose conversion rate was significantly inferior to that of Example 1, indicating that steam explosion played a significant role in promoting the cellulose conversion rate.

[0038] Comparative Example 2

[0039] 500 kg of xylose residue from the same batch as Example 1 was taken and dried directly in a drum dryer without steam explosion. The drying temperature was 150° C. and the drying time was 3 h. After the drying, the mass of the obtained xylose residue was about 256 kg, and the moisture content was 25.64%.

[0040] The xylose residue was divided into three batches and crushed by a hammer mill, a tooth mill and a cutting mill respectively. During the actual operation, when the xylose residue was crushed to 100 mesh, the mill was severely blocked and had to be stopped.

[0041] It can be seen that when the moisture content of the material is high and needs to be crushed to a finer particle size, it is a considerable burden on the operation of most crushers, which is not conducive to its application in industrial production.

[0042] Comparative Example 3

[0043] 100 kg of xylose residue from the same batch as in Example 1 was taken and dried directly to a lower moisture content using a flash dryer without using steam explosion treatment, and finally about 40 kg of material was obtained, wherein the moisture content was 3.57%.

[0044] The xylose residue material was crushed into 100 meshes by a hammer mill to obtain 39.51 kg of crushed material.

[0045] The other subsequent conditions are the same as those in Example 1.

[0046] 389 L of cellulose glucose syrup was obtained, in which the glucose content was 67.7 g / L and the cellulose conversion rate was 97.31%.

[0047] It can be seen that when the material is directly dried to a lower moisture content and crushed to a finer particle size, the final result is closer to the technical solution of the present invention.

[0048] Energy consumption analysis was performed on this comparative example and Example 1:

[0049] In Example 1 and this comparative example, the effective volume of the reactor is 1000L.

[0050] In Example 1, steam explosion consumes about 32 kg of steam; the steam cost is 235 yuan / ton; the steam cost is about 7.52 yuan, equivalent to 0.283 yuan / kg of glucose.

[0051] In Example 1, the power consumption during the xylose residue drying process is about 4.4KW, the steam is 47 kg, and the drying cost is 15.45 yuan, which is equivalent to 0.581 yuan / kg glucose; the power consumption during the xylose residue crushing process is about 0.5KW, and the crushing cost is 0.5 yuan, which is equivalent to 0.019 yuan / kg glucose.

[0052] The cost of Example 1 converted into glucose is 0.883 yuan / kg glucose.

[0053] The subsequent steps of Example 1 are consistent with this comparative example and are not calculated any more.

[0054] In this comparative example, the power consumption in the drying process is about 24.7 KW, the steam is 211 kg, and the drying cost is 74.29 yuan, which is equivalent to 2.821 yuan / kg of glucose; the power consumption in the crushing process is about 2.8 KW, and the crushing cost is 2.8 yuan, which is equivalent to 0.106 yuan / kg of glucose.

[0055] The cost of glucose converted into this comparative ratio is 2.927 yuan / kg glucose.

[0056] The current market price of glucose is generally 3000 to 4000 yuan / ton, that is, 3 to 4 yuan / kg. It can be seen that the cost of using this comparative example is significantly higher. If it is used in actual production, excluding the costs of subsequent processing, labor, equipment, sales, etc., there is basically no profit. However, the method of the present invention has significantly lower costs and is convenient for industrial utilization, thus opening up a new path for the industrial utilization of xylose residues.

[0057] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue, characterized in that: The following steps are involved: S1, performing steam explosion treatment on xylose residue to obtain xylose residue after steam explosion treatment; S2, drying and crushing the xylose residue after the gas explosion treatment in S1, and then screening, collecting the xylose residue powder with a suitable particle size, and storing it for later use; S3, mixing the xylose residue powder obtained in S2 with cellulase to perform efficient enzymatic hydrolysis on the xylose residue powder.

2. A method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the above-mentioned S1, the steam explosion pressure is 2-4 MPa, the treatment time is 1-2 min, and the stirring intensity is 60-100 rpm.

3. A method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the above-mentioned S2, the drying temperature is 120-150° C., the drying time is 2-6 hours, and the moisture content of the xylose residue after drying is 20-30%.

4. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: The drying equipment used in the drying includes but is not limited to a flash dryer and a drum dryer.

5. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: The particle size of the xylose residue powder is 40-80 meshes.

6. A method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 5, characterized in that: The crushing machines used include but are not limited to hammer crushers, tooth crushers and cutting crushers.

7. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the above-mentioned S3, the xylose residue powder is mixed with water to form a slurry before adding the cellulase, and the solid-liquid ratio of the xylose residue powder to water is 1:5-15.

8. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the S3, the added amount of cellulase is 0.5-1.5% of the absolute dry weight of the xylose residue powder.

9. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the S3, the enzymatic hydrolysis temperature is 52-54° C., the pH is 4.7-5.3, the time is 60-80 hours, and the stirring intensity is 60-100 rpm.

10. The method for improving the enzymatic hydrolysis efficiency of cellulose in xylose residue according to claim 1, characterized in that: In the above-mentioned S3, the conversion rate of cellulose in the xylose residue powder can reach over 98%.