Method for removing compound enzyme system and degrading starch in pulping process of waste box board

Abstract

The invention discloses a method for removing and degrading starch by a compound enzyme system in a pulping process of waste box boards, which comprises alpha-amylase, beta-amylase, glucoamylase, pullulanase and pectinase. OCC white water and OCC paper pulp are subjected to enzymolysis through alpha-amylase and another three kinds of compound enzymes (beta-amylase, pullulanase and glucoamylase) which are compounded (the enzyme activity is conventional enzyme activity), and when the dosage of the compound enzymes is 1000 mL * t <-1 >, the enzymolysis rate of the compound enzymes is far superior to that of single alpha-amylase with the dosage of 5000 mL * t <-1 > at the same enzymolysis time; the starch decomposition rate of the waste paper pulp is increased by 3.75 times and reaches 42.8%, and the white water is correspondingly increased by 38% and reaches 42.8%.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a method for removing and degrading starch using a composite enzyme system during the pulping process of waste cardboard. Background Technology

[0002] Corrugated cardboard is a packaging material with a unique layered structure of "corrugated core paper + linerboard" formed by mechanically bonding boxboard and corrugated base paper together. Due to its recyclability, biodegradability, low price, superior performance, and the demands of e-commerce and logistics, the demand for corrugated cardboard is huge.

[0003] However, due to restrictions on imported waste paper and a shortage of raw materials for papermaking in China, the raw materials for corrugated paperboard in China—boxboard and corrugated base paper—are all produced by the secondary use of waste boxboard (OCC) and require multiple reuses. Therefore, paper and paperboard made from OCC fibers need to have a large amount of starch added to the wet end of the pulp or to the surface sizing to make the paper made from fibers damaged by multiple reuses meet the strength requirements. At the same time, the layers of corrugated paperboard need to be bonded together with starch, so its starch content reaches 8-12%.

[0004] However, the use of large amounts of starch in the OCC pulping process leads to a significant amount of starch entering the white water during papermaking, which reduces the pulp's absorbability. This starch is highly susceptible to fermentation, leading to pulp spoilage. Simultaneously, fermentation easily generates anions, resulting in reduced filler retention and thus lower chemical utilization. Furthermore, the large amount of anions generated can neutralize cationic retention aids, further reducing filler retention. Moreover, undissolved starch continues to coat the fiber surface, affecting the binding of subsequent additives to the fiber. Therefore, it is necessary to remove starch from the fiber as much as possible and decompose the starch entering the white water into oligomers with fewer than 7 carbon atoms to make it a true solution, thereby reducing the viscosity of the white water and improving absorbability.

[0005] Therefore, completely removing starch from OCC pulp, reducing the starch in white water to a low molecular weight so it can no longer settle onto the pulp, and improving its filtration properties are among the core requirements for improving the quality and pulping efficiency of OCC pulp. Amylases are widely used in textile desizing; in waste paper pulping, the use of amylases can purify the pulp while improving its filtration performance. Currently, α-amylase is mainly used for white water and pulp removal in waste paper pulping, but there are few reports on combining multiple amylases to improve the efficiency of enzymatic pulping processes. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of existing technologies that use a single α-amylase, which have low enzymatic hydrolysis efficiency, and to provide a composite enzyme system for the pulping process of waste cardboard.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a composite enzyme system for the pulping process of waste cardboard, comprising α-amylase, β-amylase, saccharifying enzyme, pullulanase and pectinase; wherein the enzyme activities of α-amylase, β-amylase, saccharifying enzyme, pullulanase and pectinase in the system are 2000u / ml, 700000u / ml, 10000u / ml, 2000u / ml and 10000u / ml, respectively.

[0010] As a preferred embodiment of the complex enzyme system described in this invention, the complex enzyme system includes α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase. The contents of α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase in the system relative to the amount of starch are 1-10 U / g, 500-50000 U / g, 50-5000 U / g, 1-10 U / g, and 1-15 U / g, respectively.

[0011] Another object of the present invention is to overcome the shortcomings of the prior art and provide a method for pulping waste cardboard, comprising, Tear the waste corrugated paper into shreds, soak them in deionized water to soften them, pour the soaking solution into a pulper, and then add deionized water to pulp the shredded paper. The pulping liquor is filtered through a 200-400 mesh screen to obtain white water and waste paper pulp. The waste paper pulp is washed two or three times with clean water and then filtered again. The filtrate and white water are combined, and the filter residue is waste paper pulp. Take white water into a reaction vessel, add enzyme at 60°C and react for a certain time, then raise the temperature to 95°C and react for 30 minutes to inactivate the enzyme, and obtain white water enzymatic hydrolysate; Waste paper pulp residue is diluted to a mass concentration of 1% in a reaction vessel, and enzyme is added at 60°C for a certain period of time. Then the temperature is raised to 95°C and reacted for 30 minutes to inactivate the enzyme, thus obtaining an enzymatic hydrolysate of waste paper pulp.

[0012] In a preferred embodiment of the method described in this invention, the white water enzymatic hydrolysate contains four or five types of enzymes: α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase.

[0013] As a preferred embodiment of the method described in this invention, the contents of α-amylase (enzyme activity 2000u / ml), β-amylase (700000u / ml), saccharifying enzyme (enzyme activity 10000u / ml), pullulanase (enzyme activity 2000u / ml) and pectinase (enzyme activity 10000u / ml) in the system are 1-10U / g, 500-50000U / g, 50-5000U / g, 1-10U / g, and 1-15U / g, respectively.

[0014] In a preferred embodiment of the method described in this invention, the waste paper pulp enzymatic hydrolysate contains four or five types of enzymes: α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase.

[0015] As a preferred embodiment of the method described in this invention, the contents of α-amylase (enzyme activity 2000u / ml), β-amylase (700000u / ml), saccharifying enzyme (enzyme activity 10000u / ml), pullulanase (enzyme activity 2000u / ml) and pectinase (enzyme activity 10000u / ml) in the system are 1-10U / g, 500-50000U / g, 50-5000U / g, 1-10U / g, and 1-15U / g, respectively.

[0016] In a preferred embodiment of the method described in this invention, the soaking and softening time is 2-24 hours.

[0017] In a preferred embodiment of the method described in this invention, the enzyme reaction time is 10-60 min.

[0018] Beneficial effects of this invention: (1) In this invention, OCC white water and OCC pulp are enzymatically hydrolyzed at 60°C by α-amylase and three other compound enzymes (β-amylase, pullulanase and saccharifying enzyme) (commercially available conventional enzymes with conventional enzyme activity). When the amount of each compound enzyme is 1000 mL·t-1, the starch hydrolysis rate is much better than that of α-amylase alone at 5000 mL·t-1. The starch decomposition rate of waste paper pulp is increased by 3.75 times to 42.8%, and the white water is increased by 38% to 42.8%.

[0019] (2) Based on the quaternary complex enzyme system, pectinase was selected to be added to form a pentagonal enzyme (commercially available conventional enzyme with conventional enzyme activity). The enzymatic data of 1000 mL·t-1 of each complex enzyme at the same enzymatic hydrolysis time showed that compared with 5000 mL·t-1 of α-amylase, the effect of the complex enzyme was far superior to that of the single enzyme. The starch decomposition rate of waste paper pulp by α-amylase increased by seven times to 72.3%, and the corresponding increase in white water was 63% to 95.0%. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a diagram of the OCC pulping process in an embodiment of the present invention.

[0021] Figure 2 This is a comparison chart of the starch decomposition efficiency of a single enzyme and different complex enzyme systems in the embodiments of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0023] In this embodiment of the invention, the α-amylase (enzyme activity 2000u / ml), liquid, was purchased from Buckman Laboratories Chemical (Shanghai) Co., Ltd.; the β-amylase (enzyme activity 70000u / ml), pullulanase (enzyme activity 2000u / ml), saccharifying enzyme (enzyme activity 10000u / ml), and pectinase (enzyme activity 10000u / ml) were all liquids purchased from Weifang Ruichen Biotechnology Co., Ltd.; and the corrugated paper was purchased from Zhejiang Jingxing Paper Co., Ltd.

[0024] The enzyme activity of α-amylase was determined according to GB / T 24401—2009 (2000 U / mL), the enzyme activities of pullulanase, pectinase and saccharifying enzyme were determined according to GB1886.174—2016 (2000, 10000, and 100000 U / mL, respectively), and the enzyme activity of β-amylase was determined according to LDZJ 03.04—2010 (700000 U / mL).

[0025] Measure absorbance: Take 1g of corn starch, add 80mL of deionized water and heat at 95℃ for 10min to fully dissolve the corn starch. Take out the gelatinized corn starch and let it cool, then make up to 100mL. Take 5mL of starch gelatinization solution and make up to 100mL in a volumetric flask to dilute the starch gelatinization solution 20 times. Take 0.04mL, 0.06mL, 0.08mL, 1.00mL and 1.20mL of the diluted starch solution and add them to five test tubes respectively to prepare a standard curve. Then add 0.5mL of hydrochloric acid and 5mL of dilute iodine solution to each tube for color development and read the absorbance.

[0026] Pulp enzymatic hydrolysis absorbance measurement: Add 1.00 mL of the diluted enzyme solution to be tested, start timing immediately, shake well, and react accurately for 5 minutes. Immediately afterward, take 1.00 mL of the reaction solution and add it to a test tube containing 0.5 mL of hydrochloric acid solution and 5.00 mL of dilute iodine solution. Shake well, and use 0.5 mL of hydrochloric acid solution and 5.00 mL of dilute iodine solution as blanks. Quickly measure the absorbance at 660 nm using a 10 mm cuvette. Calculate the concentration of the enzyme solution based on the absorbance.

[0027] Starch decomposition rate determination: Dilute the white water enzymatic hydrolysate or the starch enzymatic hydrolysate from waste paper pulp to a certain factor, measure the absorbance and ensure it is within the range of the standard curve, calculate the starch mass fraction in the starch enzymatic hydrolysate, and calculate the starch decomposition rate according to the following formula: Example 1 (1) Take a whole piece of corrugated paper weighing 5.0g from a three-layer waste corrugated cardboard, tear it into pieces smaller than 1×1cm, soak it in 150ml of deionized water overnight, and the next day pour the soaking liquid into a pulping machine and add 350mL of deionized water. Pulp the paper at 10000 rpm for 5 minutes. Filter the liquid through a 350 mesh filter, and wash the filter residue three times with 350ml of deionized water, filtering each time. Combine the filtrate with the white water from the previous step and bring the volume to 2L. Bring the waste paper pulp to a volume of 500ml. See the pulping process diagram. Figure 1 ; The starch content of the white water and pulp was measured separately after separation. The starch content was 3.6% and 6% of that of the original paperboard, totaling 9.6%, which is consistent with the starch content of general corrugated paper, which is about 8-12%. This indicates that the detection method is effective.

[0028] (2) Take 300 mL of water to a reaction vessel and add enzymes (α-amylase, β-amylase, saccharifying enzyme, pullulanase) at 60°C. The amount of each enzyme added is 500 mL·t-1. React for 30 minutes, then raise the temperature to 95°C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 500 mL. Take 10 mL of the solution into a glass test tube for testing.

[0029] (3) Add enzymes (α-amylase, β-amylase, saccharifying enzyme, pullulanase) to 500 mL of waste paper pulp solution in a reaction vessel at 60 °C. The amount of each enzyme added is 500 mL·t-1. React for 30 minutes, then raise the temperature to 95 °C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 600 mL. Take 5 mL of the supernatant into a glass test tube and make up to 10 mL with deionized water for testing.

[0030] (4) Add α-amylase to the white water and waste paper pulp hydrolysate of (2) and (3) above, with an addition amount of 2500 mL·t-1, and repeat the same steps.

[0031] The starch decomposition rates of (2) and (3) were 43.8% and 13.6%, respectively, while those of (4) were 35.1% and 3.9%, respectively. The quaternary complex enzymes at 500 mL·t⁻¹ were 24.8% higher than the single 2500 mL·t⁻¹ α-amylase in white water, and the starch decomposition rate of waste paper pulp was increased by 2.48 times.

[0032] Example 2 (1) Prepare white water enzymatic hydrolysate and waste paper pulp enzymatic hydrolysate as in Example 1.

[0033] (2) Take 300 mL of water to a reaction vessel and add enzymes (α-amylase, β-amylase, saccharifying enzyme, pullulanase) at 60°C. The amount of each enzyme added is 1000 mL·t-1. React for 30 minutes, then raise the temperature to 95°C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 500 mL. Take 10 mL of the solution into a glass test tube for testing.

[0034] (3) Add enzymes (α-amylase, β-amylase, saccharifying enzyme, pullulanase) to 500 mL of waste paper pulp solution in a reactor at 60 °C. The amount added is 1000 mL·t-1. React for 30 minutes, then raise the temperature to 95 °C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 600 mL. Take 5 mL of the supernatant into a glass test tube and make up to 10 mL with deionized water for testing.

[0035] (4) Add α-amylase to the white water and waste paper pulp hydrolysate of (2) and (3) above, with an addition amount of 5000 mL·t-1, and repeat the same steps.

[0036] The starch decomposition rates of (2) and (3) were 81.0% and 42.8%, respectively, while those of (4) were 58.6% and 9.0%, respectively. The quaternary complex enzymes at 1000 mL·t⁻¹ were 38% higher than those of the single 5000 mL·t⁻¹ α-amylase in white water, and the starch decomposition rate of waste paper pulp was increased by 3.75 times.

[0037] Example 3 (1) Prepare white water enzymatic hydrolysate and waste paper pulp enzymatic hydrolysate as in Example 1.

[0038] (2) Take 300 mL of water to a reaction vessel and add enzymes (α-amylase, β-amylase, saccharifying enzyme, pectinase, pullulanase) at 60°C. The amount of each enzyme added is 1000 mL·t-1. React for 30 minutes, then raise the temperature to 95°C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 500 mL. Take 10 mL of the solution into a glass test tube for testing.

[0039] (3) Add enzymes (α-amylase, β-amylase, saccharifying enzyme, pectinase, pullulanase) to 500 mL of waste paper pulp solution in a reactor at 60 °C. The amount added is 1000 mL·t-1. React for 30 minutes, then raise the temperature to 95 °C and react for 30 minutes to inactivate the enzymes. Take out the reaction solution and make up to 600 mL. Take 5 mL of the supernatant into a glass test tube and make up to 10 mL with deionized water for testing.

[0040] (4) Add α-amylase to the white water and waste paper pulp hydrolysate of (2) and (3) above, with an addition amount of 5000 mL·t-1, and repeat the same steps.

[0041] The starch decomposition rates of (2) and (3) were 95.0% and 72.3%, respectively, while those of (4) were 63% and 9.0%, respectively. The five-element complex enzymes at 1000 mL·t⁻¹ showed a 38% increase in white water efficiency compared to the single 5000 mL·t⁻¹ α-amylase, and a 7.0-fold increase in starch decomposition rate of waste paper pulp. See the results below. Figure 2 .

[0042] Table 1. Enzyme dosage for each component (relative to starch dosage, — represents 0).

[0043] It can be seen that, with the same amount of enzyme, the starch decomposition rate of white water is always higher than that of waste paper pulp. This may be because the starch in the pulp is encapsulated and shielded by plant cell structures, resulting in poor enzyme accessibility. The reaction typically occurs on the solid surface and within internal pores, and is severely limited by mass transfer, leading to an even lower starch decomposition rate. The combined enzymes are more effective than single enzymes, possibly because the synergistic effect of the combined enzymes can eliminate steric hindrance.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A composite enzyme system for the pulping process of waste cardboard boxes, characterized in that: include, Four or five types of enzymes: α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase; The enzyme activities of α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase were 2000 u / ml, 700000 u / ml, 10000 u / ml, 2000 u / ml, and 10000 u / ml, respectively.

2. The composite enzyme system as described in claim 1, characterized in that: include, α-Amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase; The contents of α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase in the system relative to the amount of starch are 1-10 U / g, 500-50000 U / g, 50-5000 U / g, 1-10 U / g, and 1-15 U / g, respectively.

3. A method for pulping waste cardboard boxes, characterized in that: include, Tear the waste corrugated paper into shreds, soak them in deionized water to soften them, pour the soaking solution into a pulper, and then add deionized water to pulp the shredded paper. The pulping liquor is filtered through a 200-400 mesh screen to obtain white water and waste paper pulp. The waste paper pulp is washed two or three times with clean water and then filtered again. The filtrate and white water are combined, and the filter residue is waste paper pulp. Take white water into a reaction vessel, add enzyme at 60°C for a certain time, then raise the temperature to 95°C and react for 30 minutes to inactivate the enzyme, thus obtaining white water enzymatic hydrolysate; Waste paper pulp filter residue is diluted to a mass concentration of 1% in a reaction vessel, and enzyme is added at 60°C for a certain period of time. Then the temperature is raised to 95°C and reacted for 30 minutes to inactivate the enzyme, thus obtaining the enzymatic hydrolysate of waste paper pulp.

4. The method as described in claim 3, characterized in that: The white water enzymatic hydrolysate contains four or five types of enzymes: α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase.

5. The method as described in claim 4, characterized in that: The contents of α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase in the system relative to the amount of starch are 1-10 U / g, 500-50000 U / g, 50-5000 U / g, 1-10 U / g, and 1-15 U / g, respectively.

6. The method as described in claim 3, characterized in that: The enzymatic hydrolysate of the waste paper pulp contains four or five enzymes: α-amylase, β-amylase, saccharifying enzyme, pullulanase, and pectinase.

7. The method as described in claim 6, characterized in that: The contents of α-amylase, β-amylase, saccharifying enzyme, pullulanase and pectinase in the system are 1-10 U / g, 500-50000 U / g, 50-5000 U / g, 1-10 U / g and 1-15 U / g, respectively.

8. The method as described in claim 3, characterized in that: The soaking and softening time is 2 to 24 hours.

9. The method as described in claim 3, characterized in that: The enzyme addition reaction time is 10-60 min.

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