Use of Manganese-Based Nanozymes and Method for Low-Temperature Degradation of Corn Straw Based on Manganese-Based Nanozymes

Abstract

The present invention discloses the use of manganese-based nanozymes and a method for low-temperature degradation of corn straw based on manganese-based nanozymes. The manganese-based nanozymes are MnBTC, MnO2 or Mn3O4. The degradation of corn straw in a low-temperature range is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of straw degradation, and specifically relates to the use of manganese-based nanozymes and a method for low-temperature degradation of corn straw based on manganese-based nanozymes. Background Art

[0002] Corn straw is an abundant renewable resource, and the lignocellulose it contains is the most valuable bioenergy. Corn straw lignocellulose is mainly composed of cellulose, hemicellulose, and lignin. The three main component monomers of them are various sugars and aromatic compounds, which are expected to be used to produce liquid fuels and chemical products. In addition, corn straw is also an effective raw material for restoring soil fertility. Therefore, the efficient utilization of corn straw is of great practical significance for the development of green chemistry and the maintenance of land security. However, the lignin, cellulose, and hemicellulose in corn straw form the cell wall structure in an intertwined manner, and this intertwined manner poses a huge challenge to the utilization and degradation of lignocellulose, hindering the effective utilization of lignocellulose in corn straw, and the key to the effective utilization of lignocellulose is whether lignin can be degraded.

[0003] Currently, the most promising method for degrading lignin is the degradation strategy based on natural enzymes, such as lignin peroxidase, versatile peroxidase, manganese peroxidase, and laccase. The above natural enzymes are all members of the natural lignin degradation enzyme system in nature, which can change the hydrophobicity and porosity of lignin, promote the dissociation of lignin macromolecules, and improve the biological utilization of lignocellulose by microorganisms. Unfortunately, the current production cost of relevant natural enzymes is high, the stability is poor, and it is difficult to adapt to extreme environmental changes during use, so the industrial application is not extensive. The most crucial thing is that the northern part of China and the black soil area in Northeast China are in a low-temperature environment for a long time, and the straw yield in relevant regions can account for 80% of the total output in China. The long-term low-temperature environment below 40°C greatly limits the activity of natural enzymes, making the straw decomposition rate in winter and spring in relevant regions only 30%. Therefore, developing a strategy for efficiently degrading corn straw under low-temperature conditions has become an urgent problem to be solved, and it is also of great significance for the popularization of straw returning technology. Summary of the Invention

[0004] The purpose of the present invention is to provide the use of manganese-based nanozymes and a method for low-temperature degradation of corn straw based on manganese-based nanozymes, realizing the degradation of corn straw in the low-temperature range.

[0005] The present invention adopts the following technical solutions: the use of manganese-based nanozymes for degrading lignin; the manganese-based nanozymes are MnBTC, MnO2 or Mn3O4.

[0006] Further, the MnO2 is α-MnO2, β-MnO2, γ-MnO2, ε-MnO2, δ-MnO2 or λ-MnO2.

[0007] Furthermore, the Mn3O4 is Mn3O4 nanoflowers, Mn3O4 nanosheets, Mn3O4 nanospheres or Mn3O4 nanowires.

[0008] The present invention also discloses a method for low-temperature degradation of corn straw based on manganese-based nanozymes. The above method includes:

[0009] Mix the manganese-based nanozyme and fragmented corn straw, and add deionized water to make the manganese-based nanozyme suspended in deionized water; incubate at 0-40 °C and change the air at intervals to complete the degradation of corn straw.

[0010] Furthermore, the mass ratio of the manganese-based nanozyme to the fragmented corn straw is 1:3, 1:2, 1:1, 2:1 or 3:1.

[0011] Furthermore, incubation is carried out by static placement or stirring for 7-21 days.

[0012] Furthermore, when incubating by stirring, a rotor is used for stirring, and the oscillation speed is 200 revolutions per minute.

[0013] Furthermore, the manganese-based nanozyme is MnBTC, the mass ratio of the manganese-based nanozyme to the corn straw is 1:2, the stirring incubation temperature is 4 °C, the stirring incubation is carried out for 14 days, and the pH is 7.

[0014] Furthermore, the fragmented corn straw is the material passing through a 80-mesh sieve.

[0015] The beneficial effects of the present invention are as follows: 1. The reaction conditions of the manganese-based nanozyme are milder than those of chemical catalysis, and it has the characteristics of low-temperature catalysis, and can be used as a substitute for enzymes in the degradation of corn straw. 2. The manganese-based nanozyme has stable performance, has a constant lignin degradation ability in the low-temperature range of 0-40 °C, and after six cycles, the manganese-based nanozyme still has 92% activity. Description of the Drawings

[0016] Figure 1 SEM images of corn straw before and after degradation; a is before degradation; b is after degradation;

[0017] Figure 2 The nanozyme activities of different manganese-based nanozymes at different temperatures;

[0018] a. is MnBTC, b. is β-MnO2, c. is λ-MnO2, d. is Mn3O4 nanowires, e. is Mn3O4 nanoflowers, f. is Mn3O4 nanosheets, g. is γ-MnO2, h. is Mn3O4 nanospheres.

[0019] Figure 3 Degradation rate diagrams of different nanozymes on corn straw at 0 °C with different mass ratios; and after treatment at 0 °C for 14 days, the highest degradation rate reached over 35%.

[0020] Figure 4 Degradation rate diagram of different nanozymes on corn straw at 0 °C with a mass ratio of 1:2;

[0021] Figure 5 Degradation activity diagram of MnBTC nanozyme on lignin at different temperatures;

[0022] Figure 6 Infrared spectrum diagram of lignin;

[0023] Figure 7 For lignin 1 H-NMR diagram;

[0024] Figure 8 Catalytic activity of MnBTC nanozyme recycled six times. Detailed implementation manners

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0026] The present invention discloses the use of manganese-based nanozymes for degrading lignin, and the manganese-based nanozymes are MnBTC, MnO2 or Mn3O4.

[0027] MnO2 is α-MnO2, β-MnO2, γ-MnO2, ε -MnO2, δ-MnO2 or λ-MnO2.

[0028] Mn3O4 is Mn3O4 nanoflowers, Mn3O4 nanosheets, Mn3O4 nanospheres or Mn3O4 nanowires.

[0029] The present invention also discloses the method for low-temperature degradation of corn straw based on the above-mentioned manganese-based nanozymes, and the method includes:

[0030] Mix the manganese-based nanozyme and fragmented corn straw, and add deionized water to make the manganese-based nanozyme suspended in the deionized water; incubate at 0-40 °C and ventilate at intervals to complete the degradation of corn straw; use the method of static or stirring for incubation for 7-21 days. When stirring and incubating, use a rotor to stir with an oscillation speed of 200 revolutions / min.

[0031] The above-mentioned manganese-based nanozymes are MnBTC, MnO2 or Mn3O4.

[0032] The mass ratio of the manganese-based nanozyme to the fragmented corn straw is 1:3, 1:2, 1:1, 2:1 or 3:1.

[0033] The manganese-based nanozyme is MnBTC. The mass ratio of the manganese-based nanozyme to corn straw is 1:2. The stirring and incubation temperature is 4°C, and the stirring and incubation lasts for 14 days with a pH of 7.

[0034] The fragmented corn straw is the material passing through a 80-mesh sieve.

[0035] The above-mentioned nanozymes all have the activity of degrading corn straw at low temperature, and the activity order is MnBTC > β-MnO2 > γ-MnO2 > Mn3O4 nanowires > Mn3O4 nanoflowers > Mn3O4 nanosheets > ε -MnO2 > γ-MnO2 > δ-MnO2 > α-MnO2 > Mn3O4 nanometers.

[0036] To further illustrate the uses of the above-mentioned manganese-based nanozymes and the method for low-temperature degradation of corn straw based on manganese-based nanozymes, the following specific examples are adopted, in which the manganese-based nanozymes are prepared by the methods in the prior art.

[0037] First, the nanozyme activities of the manganese-based nanozymes at different temperatures are detected. As Figure 2 shown, it can be seen from Figure 2 that within the low-temperature range of 0 - 40°C, the manganese-based nanozymes maintain stable enzyme activities. They can effectively catalyze the ring-opening of lignin, thereby causing the spontaneous degradation of lignin. The linkages between lignins are broken, and the benzene rings are opened, as Figure 6 shown. During the degradation process, the phenolic hydroxyl groups increase, indicating that lignin is decomposed into small-molecule substances, as Figure 7 shown.

[0038] Example 1

[0039] The method for low-temperature degradation of corn straw based on manganese-based nanozymes includes the following steps:

[0040] Step 1: The corn straw is mechanically crushed to obtain fragmented corn straw, which is passed through an 80-mesh sieve. The material passing through the sieve is taken to obtain homogenized corn straw powder, which is then dried at 105°C and reserved for later use.

[0041] Step 2: Weigh 5 mg of the manganese-based nanozyme and corn straw. Among them, the mass ratios of the manganese-based nanozyme to corn straw are 1:3, 1:2, 1:1, 2:1, and 3:1 respectively. Each is added to a 10-ml glass bottle, and 5 ml of deionized water is added to each glass bottle. Ultrasonic treatment is carried out for 10 minutes to fully suspend the nanozyme; then a rotor is added and stirred and incubated at 0°C for 14 days, with air exchange once every 12 hours.

[0042] The manganese-based nanozyme is MnO2, Mn3O4, or MnBTC, where MnO2 is α-MnO2, β-MnO2, γ-MnO2, ε-MnO2, δ-MnO2 or λ-MnO2; Mn3O4 is Mn3O4 nanoflowers, Mn3O4 nanosheets, Mn3O4 nanospheres or Mn3O4 nanowires;

[0043] Step 3: After being treated in Step 2, the mixed solution is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0044] After detection, when the manganese-based nanozyme uses MnBTC and the mass ratio of the manganese-based nanozyme to corn straw is 1:2, the degradation of corn straw is better.

[0045] The degradation activities of the 11 manganese-based nanozymes in Example 1 on corn straw at low temperature were tested. The results showed that the selected manganese-based nanozymes all exhibited low-temperature corn straw degradation activity. Among them, the MnBTC nanozyme showed the best corn straw degradation activity. As shown in Figure 3, the results showed that in the range of 0-40 °C, the enzyme-like activities of the manganese-based nanozymes had no obvious difference, and they had excellent corn straw degradation performance at low temperature. The highest corn straw degradation rate within 14 days reached 3625%.

[0046] In addition, the effects of different mass ratios of nanozymes and corn straw on the degradation efficiency were also investigated. Finally, it was optimized that the best degradation efficiency could be obtained when the mass ratio of the manganese-based nanozyme MnBTC to corn straw was 1:2, as Figure 4 shown

[0047] Corn straw degradation rate = (X1 - X2) / X × 100%;

[0048] where X1 represents the total weight of corn straw and catalyst after the reaction, X2 represents the remaining mass of the catalyst under the same operating conditions, and X represents the dry weight of corn straw before the reaction.

[0049] In Example 1, the manganese-based nanozyme MnBTC and the optimal mass ratio with corn straw were determined. In the following examples, the optimal mass ratio was used to verify the undetermined parameters in the method for low-temperature degradation of corn straw based on manganese-based nanozymes.

[0050] Example 2

[0051] The method for low-temperature degradation of corn straw based on manganese-based nanozymes includes the following steps:

[0052] Step 1: The corn straw is mechanically crushed to obtain fragmented corn straw, passed through an 80-mesh sieve, and the material under the sieve is taken to obtain homogenized corn straw powder, which is then dried at 105 °C for later use.

[0053] Step 2: Weigh 5 mg of manganese-based nanozyme MnBTC and 10 mg of the corn straw obtained in Step 1 into a 10 mL glass bottle, for a total of 15 mg. Add 5 mL of deionized water and ultrasonicate for 10 minutes to fully suspend the nanozyme. Then add a rotor and stir and incubate at 0 °C for 14 days, with air replacement every 12 hours.

[0054] Step 3: After the treatment in Step 2, the mixture is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0055] Example 3

[0056] The method for low-temperature degradation of corn straw based on manganese-based nanozyme includes the following steps:

[0057] Step 1: Mechanically crush the corn straw to obtain fragmented corn straw, pass through an 80-mesh sieve, collect the undersize fraction to obtain homogenized corn straw powder, and then dry it at 105 °C for later use.

[0058] Step 2: Weigh 5 mg of manganese-based nanozyme MnBTC and 10 mg of the corn straw obtained in Step 1 into a 10 mL glass bottle, add 5 mL of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozyme. Then add a rotor and stir and incubate at 20 °C for 14 days, with air replacement every 12 hours.

[0059] Step 3: After the treatment in Step 2, the mixture is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0060] Example 4

[0061] The method for low-temperature degradation of corn straw based on manganese-based nanozyme includes the following steps:

[0062] Step 1: Mechanically crush the corn straw to obtain fragmented corn straw, pass through an 80-mesh sieve, collect the undersize fraction to obtain homogenized corn straw powder, and then dry it at 105 °C for later use.

[0063] Step 2: Weigh 5 mg of manganese-based nanozyme MnBTC and 10 mg of the corn straw obtained in Step 1 into a 10 mL glass bottle, add 5 mL of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozyme. Then add a rotor and stir and incubate at 30 °C for 14 days, with air replacement every 12 hours.

[0064] Step 3: After the treatment in Step 2, the mixture is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0065] Example 5

[0066] The method for low-temperature degradation of corn straw based on manganese-based nanozyme includes the following steps:

[0067] Step 1: Mechanically crush corn straw to obtain fragmented corn straw, pass it through an 80-mesh sieve, take the material under the sieve to obtain homogenized corn straw powder, and then dry it at 105°C for later use.

[0068] Step 2: Weigh 5 mg of manganese-based nanozyme MnBTC and 10 mg of the corn straw obtained in Step 1 into a 10-ml glass bottle, add 5 ml of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozyme; then add a rotor and stir and incubate at 40°C for 14 days, with air exchange every 12 hours during this period.

[0069] Step 3: After the treatment in Step 2, the mixture is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0070] Calculate the degradation rates in Examples 2 - 5. It is known that Figure 5 in the low-temperature range of 0 - 40°C, the MnBTC nanozyme can effectively degrade lignin.

[0071] Example 6

[0072] The method for low-temperature degradation of corn straw based on manganese-based nanozyme includes the following steps:

[0073] Step 1: Mechanically crush corn straw to obtain fragmented corn straw, pass it through an 80-mesh sieve, take the material under the sieve to obtain homogenized corn straw powder, and then dry it at 105°C for later use.

[0074] Step 2: Weigh 5 mg of manganese-based nanozyme and 10 mg of the corn straw obtained in Step 1 into a 10-ml glass bottle, add 5 ml of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozyme; then add a rotor and stir and incubate at 4°C for 14 days, with air exchange every 12 hours during this period.

[0075] Step 3: After the treatment in Step 2, the mixture is filtered, washed, dried, weighed, and the degradation rate is calculated.

[0076] Analyze the corn straw after low-temperature degradation by the manganese-based nanozyme in Example 6. Use SEM to analyze the changes in the surface structure of the corn straw before and after degradation by the manganese-based nanozyme, as shown in Figure 1 a and b respectively. The SEM results show that after the corn straw is treated with the manganese-based nanozyme, its surface becomes rough, porous and disordered, and the small-volume corn straw changes from having a regular morphology and a smooth surface to having a rough morphology and being fragmented.

[0077] The results of the enzyme-like catalytic activity and degradation activity of the manganese-based nanozyme at different temperatures are as shown in Figure 2 and Figure 3As shown, a method for the efficient catalytic degradation of corn straw by manganese-based nanozymes at low temperature. The manganese-based nanozymes have a constant lignin degradation ability in the range of 0 to 40 °C.

[0078] The corn straw after low-temperature degradation by the manganese-based nanozymes in Example 6 was analyzed. SEM was used to analyze the changes in the surface structure of the corn straw before and after degradation by the manganese-based nanozymes, as shown in Figure 1 Figures a and b respectively. The SEM results show that after the corn straw was treated with the manganese-based nanozymes, its surface became rough, porous and disordered, and the small-volume corn straw changed from regular and smooth surface morphology to rough and fragmented morphology. As Figure 8 shown, after six cycles, the manganese-based nanozymes still had 92% activity.

[0079] Example 7

[0080] The method for the low-temperature degradation of corn straw based on manganese-based nanozymes includes the following steps:

[0081] Step 1: The corn straw was mechanically crushed to obtain fragmented corn straw, passed through an 80-mesh sieve, and the undersize was taken to obtain homogenized corn straw powder, which was then dried at 105 °C and reserved for use.

[0082] Step 2: Weigh 5 mg of the manganese-based nanozymes and 10 mg of the corn straw obtained in Step 1 into a 10-ml glass bottle, add 5 ml of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozymes; then add a rotor and stir and incubate at 0 °C for 14 days, with air exchange every 12 hours.

[0083] Step 3: After the treatment in Step 2, the mixture was filtered, washed, dried, weighed, and the degradation rate was calculated.

[0084] Example 8

[0085] The method for the low-temperature degradation of corn straw based on manganese-based nanozymes includes the following steps:

[0086] Step 1: The corn straw was mechanically crushed to obtain fragmented corn straw, passed through an 80-mesh sieve, and the undersize was taken to obtain homogenized corn straw powder, which was then dried at 105 °C and reserved for use.

[0087] Step 2: Weigh 5 mg of the manganese-based nanozyme MnBTC and 10 mg of the corn straw obtained in Step 1 into a 10-ml glass bottle, add 5 ml of deionized water, and ultrasonicate for 10 minutes to fully suspend the nanozymes; then add a rotor and stir and incubate at 0 °C for 21 days, with air exchange every 12 hours.

[0088] Step 3: After the treatment in Step 2, the mixture was filtered, washed, dried, weighed, and the degradation rate was calculated.

[0089] Example 9

[0090] The method for low-temperature degradation of corn straw based on manganese-based nanozyme comprises the following steps:

[0091] Step 1: Mechanically crush corn straw to obtain fragmented corn straw, sieve it through a 80-mesh sieve, take the material under the sieve to obtain homogenized corn straw powder, and then dry it at 105 °C for later use.

[0092] Step 2: Weigh 5 mg of manganese-based nanozyme MnBTC respectively and mix it with corn straw according to the mass ratios of 1:3, 1:2, 1:1, 2:1 and 3:1, transfer the mixture to a 2-ml centrifuge tube, add 200 μl of deionized water to fully mix the materials and straw; then leave it to stand and incubate at 0 °C for 14 days, and ventilate once every 12 hours during this period.

[0093] Step 3: After the treatment in Step 2, the mixture is filtered, washed and dried, then weighed and the degradation rate is calculated.

[0094] In Example 9, the influence of the static incubation method on the degradation efficiency is given. It can be seen from the experimental results that stirring incubation can accelerate the degradation efficiency of nanozyme on corn straw; however, although the degradation efficiency of corn straw under static incubation conditions is lower than that under stirring incubation, this method is closer to the actual operation procedure of in-situ straw returning to the field of corn straw, which is beneficial to solving the problem of straw degradation in winter.

Claims

1. Use of manganese-based nanozyme for low-temperature degradation of lignin, characterized in that, The manganese-based nanozyme is MnBTC, MnO2 or Mn3O4; the low temperature is 0 to 40 °C; The MnO2 is α-MnO2, β-MnO2, γ-MnO2, ε -MnO2, δ-MnO2 or λ-MnO2; The Mn3O4 is Mn3O4 nanoflowers, Mn3O4 nanosheets, Mn3O4 nanospheres or Mn3O4 nanowires.

2. Method for low-temperature degradation of corn straw based on manganese-based nanozyme, using the manganese-based nanozyme of claim 1, characterized in that, The method includes: Mix the manganese-based nanozyme and fragmented corn straw, add deionized water to make the manganese-based nanozyme in a suspended state in the deionized water; incubate at 0 to 40 °C and change the air at intervals, then the degradation of corn straw is completed.

3. The method for low-temperature degradation of corn straw based on manganese-based nanozyme according to claim 2, characterized in that, The mass ratio of the manganese-based nanozyme to the fragmented corn straw is 1:3, 1:2, 1:1, 2:1 or 3:

1.

4. The method for low-temperature degradation of corn straw based on manganese-based nanozyme according to claim 3, characterized in that, Incubate by static placement or stirring for 7 to 21 days.

5. The method for low-temperature degradation of corn straw based on manganese-based nanozyme according to claim 4, characterized in that, When incubating by stirring, use a rotor to stir, and the oscillation speed is 200 revolutions / min.

6. The method for low-temperature degradation of corn straw based on manganese-based nanozyme according to claim 5, characterized in that, The manganese-based nanozyme is MnBTC, the mass ratio of the manganese-based nanozyme to corn straw is 1:2, the stirring incubation temperature is 4 °C, the stirring incubation is 14 days, and the pH is 7.

7. The method for low-temperature degradation of corn straw based on manganese-based nanozyme according to claim 6, characterized in that, The fragmented corn straw is the material passing through a 80-mesh sieve.

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