Preparation process of deodorization modified enteromorpha-based papermaking fiber

Abstract

This invention provides a preparation process for deodorized and modified seaweed-based papermaking fibers. The preparation process includes physical pre-deodorization, alkaline protease-based deodorization, neutral lipase removal of oxidized lipids, synergistic cellulolysis by pectinase and hemicellulase, and mild oxidative decolorization. The preparation process of the deodorized and modified seaweed-based papermaking fibers provided by this invention includes: S1 physical pre-deodorization, utilizing Raoult's law and Dalton's law of partial pressures, under conditions of 80°C hot water combined with vacuum or [other conditions], causing a large amount of low-boiling-point volatile amines such as trimethylamine and dimethyl sulfide to escape; and 80°C being far below the thermal degradation temperature of cellulose, resulting in zero damage to cellulose. In S2, alkaline protease-based deodorization efficiently hydrolyzes fishy-smelling proteins at the optimal pH of 8.0–9.0. In S3, neutral lipase specifically hydrolyzes oxidized lipids and free fatty acids, and oxidative decolorization removes the visual fishy smell caused by pigments. This multi-step deodorization process achieves excellent deodorization results.

Description

Technical Field

[0001] This invention relates to the field of pulp and paper technology, and in particular to a preparation process for deodorized modified seaweed-based papermaking fibers. Background Technology

[0002] Ulva prolifera is the dominant algae species in the large-scale green tides that occur in the Yellow Sea. Every summer, large amounts of Ulva prolifera are washed ashore and decompose, which not only seriously damages the marine ecological environment and coastal landscape, but also causes a huge waste of resources. Ulva prolifera contains 7% to 21% cellulose, 8% to 15% protein and 5% to 15% unsaturated fatty acids in its dry weight, making it a potential high-quality paper fiber raw material. However, seaweed has a strong fishy smell, which severely limits its application in food, feed and papermaking. Currently, there are two main technical routes for deodorizing seaweed: the soda ash method and the enzymatic method. The soda ash method is the earliest deodorization method. Its principle is to use high concentration of NaOH to hydrolyze proteins and destroy pigment structures under high temperature conditions. The typical process is to boil at 70-90℃ with 1% to 3% NaOH for 30 to 90 minutes. Although the soda ash method can remove fishy smell and pigment to a certain extent, the strong alkali will simultaneously trigger the alkaline peeling reaction of cellulose and hemicellulose under high temperature conditions, resulting in a large number of glycosidic bonds breaking and low cellulose yield. To overcome the damage to fiber caused by the soda ash method, an enzymatic method is currently used instead of strong alkali. The core logic is that the fishy smell of seaweed mainly comes from protein degradation products. When using it, it is first treated with 1500U / g of protease at 45℃ and pH 6.0 for 1.5 hours to specifically hydrolyze the fishy smell protein without damaging the cellulose. Then, it is combined with 80U / g of cellulase to open the cell wall and release polysaccharides. The final dietary fiber content can reach 82.13%, the yield is 40.22%, the water holding capacity is increased to 1250%, the temperature is reduced from 70℃ to 45℃, and the time is shortened from 90 minutes to 1.5 hours, which greatly improves the cellulose retention rate. However, in actual use, it was found that both the soda ash method and the original enzyme method assume that the fishy smell comes only from proteins, while ignoring low molecular weight volatile amines such as trimethylamine and dimethyl sulfide. These substances have low boiling points, and although some can escape during high-temperature alkaline boiling, the cost is that cellulose is degraded at the same time, resulting in the treated product still having a noticeable ammonia smell, which causes inconvenience in actual use.

[0003] Therefore, it is necessary to provide a new preparation process for deodorized and modified seaweed-based papermaking fibers to solve the above-mentioned technical problems. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a preparation process for deodorized modified seaweed-based papermaking fibers.

[0005] The preparation process of deodorized modified seaweed-based papermaking fiber provided by the present invention includes the following steps: S1. Physical pre-treatment for deodorization: First, chop the raw material of seaweed and add it to 80℃ hot water at a material-to-liquid ratio of 1:8 to 1:10. Then, reduce the pressure to 0.06 to 0.08 MPa or introduce... Under saturated conditions, stir quickly and blanch for 30-60 seconds, then remove and rinse with cold water to cool to room temperature; S2, alkaline protease for deodorization: Disperse the S1-treated *Ulva prolifera* at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 8.0 to 9.0 with buffer solution, and add 800 to 1200 ml of alkaline protease. The dried seaweed was reacted, and the solid filter cake after the reaction was collected by filtration. S3, neutral lipase removal of oxidized lipids: redisperse the solid filter cake from S2 at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 6.5 to 7.5 with buffer solution, add 500 to 1000 U / g of neutral lipase to react, and filter and collect the solid filter cake after reaction. S4. Synergistic cell wall opening by pectinase and hemicellulase: Redisperse the solid filter cake from S3 at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 4.5 to 5.0 with buffer solution, and add 150 to 250 μL of pectinase. Dried seaweed and xylanase 80-150 The dried seaweed was reacted, the solid filter cake was collected by filtration and washed with deionized water 2 to 4 times to obtain seaweed fiber filter cake; S5 Mild oxidative decolorization: Disperse the S4-washed Ulva prolifera fiber filter cake at a material-to-liquid ratio of 1:8 to 1:12, and add 1.0% to 2.0% of the solution. The reaction was carried out, and after the reaction was completed, the product was washed with deionized water until neutral. The solid was collected by filtration and dried under vacuum at 60°C until constant weight, thus obtaining the deodorized modified seaweed-based papermaking fiber product.

[0006] Preferably, in step S1, the raw material of *Ulva prolifera* is fresh *Ulva prolifera* or frozen-thawed *Ulva prolifera*, chopped into 1-5 cm pieces; the decompression is achieved by vacuum pumping, with an absolute system pressure of 0.06-0.08 MPa; or by continuous airflow. The method of saturation is used to replace vacuum pumping.

[0007] Preferably, in step S2, the alkaline protease is an alkaline protease derived from Bacillus subtilis; the buffer solution is... Buffer solution.

[0008] Preferably, in step S3, the neutral lipase is a lipase derived from Candida albicans; and the buffer solution is Tris-HCl buffer.

[0009] Preferably, the cellulose content of the *Ulva prolifera* raw material is 7%–21% of dry weight, the protein content is 8%–15% of dry weight, and the total content of EPA and DHA is 5%–15% of dry weight.

[0010] Preferably, the alkaline protease in step S2 is an alkaline protease derived from Bacillus subtilis, whose active center contains a Ser-His-Asp catalytic triplet.

[0011] Preferably, the oxidized lipids removed by the neutral lipase in step S3 include short-chain aldehydes such as chlorophyll aldehyde, heptanal, and nonanal generated from the oxidation of EPA and DHA in seaweed, wherein the olfactory threshold of chlorophyll aldehyde is 0.006 mg / L.

[0012] Preferably, in step S4, the ratio of pectinase to xylanase is 2:1 to 2.5:1, wherein pectinase cleaves the α-1,4 glycosidic bonds of the pectin backbone through a β-elimination mechanism, and xylanase cleaves the β-1,4 glycosidic bonds of the xylan backbone through an endoglucosinolate mechanism. The two work together to dissolve the cell wall, thereby exposing and releasing cellulose microfibrils.

[0013] Compared with related technologies, the preparation process of deodorized modified seaweed-based papermaking fiber provided by the present invention has the following beneficial effects: 1. In this invention, the S1 physical pre-deodorization process utilizes Raoult's law and Dalton's law of partial pressures, using 80℃ hot water in conjunction with a vacuum or Under these conditions, a large amount of low-boiling-point volatile amines such as trimethylamine and dimethyl sulfide are released, removing 30%–40% of the total fishy odor. Furthermore, the temperature of 80℃ is far below the thermal degradation temperature of cellulose, causing zero damage to cellulose. In S2, alkaline protease primarily removes the fishy odor, efficiently hydrolyzing fishy odor proteins at the optimal pH of 8.0–9.0, removing 25%–30% of the total fishy odor. In S3, neutral lipase specifically hydrolyzes oxidized lipids and free fatty acids. Oxidation and decolorization remove the visual fishy smell caused by pigments. The multi-step deodorization process has a good deodorization effect. 2. This invention adjusts the pH to 8.0-9.0, so that the His residues are in a deprotonated state, and the catalytic efficiency reaches the optimal level. The actual hydrolysis rate of the protease at 1000 U / g is higher than that of the existing technology at 1500 U / g at pH 6.0. The enzyme dosage is reduced by more than 30%, while the deodorization efficiency is improved by more than 30%, which significantly reduces the production cost. This invention solves the problems in the existing technology where the protease reaction pH is set at 6.0, but the optimal pH of Bacillus subtilis alkaline protease is 8.0-9.0. At pH 6.0, most of the imidazole ring of the His residues in the enzyme active center of the catalytic triplet is in a protonated state, resulting in low catalytic efficiency. 3. In this invention, pectinase is used to cleave the α-1,4 glycosidic bonds of the pectin backbone and xylanase is used to cleave the β-1,4 glycosidic bonds of the xylan backbone. After dissolution, the cell wall naturally loosens, and the cellulose microfibrils are exposed and released, while their β-1,4 glycosidic bonds are not affected. The pectinase and xylanase act on the polysaccharides in the amorphous region, and the reaction rate is much faster than the rate at which cellulase attacks the cellulose in the crystalline region. 4. This invention uses Hydroxyl radicals are generated at pH 10.0–11.0, preferentially attacking the chlorophyll conjugated double bond system and carotenoid polyene chains, while the attack rate on cellulose glycosidic bonds is much lower than that on conjugated double bonds. Therefore, under mild conditions of 45–55℃ and 20–40 minutes, the pigments are fully oxidized while cellulose degradation is negligible. It replaces NaOH to adjust the pH to 10.0–11.0 instead of 13–14, resulting in a milder alkalinity. and Formation of hydrogen peroxide adduct, slowing down Self-decomposition makes the oxidation reaction more uniform and controllable, avoiding fiber damage caused by local high concentrations; 5. In the deodorization and modification process of this invention, no strong alkali is used throughout the entire process. The decomposition products are only water and oxygen, eliminating the need for waste alkali treatment. It is cheaper than NaOH, and the overall production cost is significantly lower than the existing soda ash process. Moreover, the process is mild, with the highest temperature throughout the process being only 85-95℃ and the reaction temperature controlled at 40-55℃, making it suitable for industrial-scale production. Attached Figure Description

[0014] Figure 1 A schematic diagram of the process for preparing a product using an enzymatic method to replace a strong alkali method in existing technologies; Figure 2 This is a schematic flowchart illustrating the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Comparative Example 1 For reference Figure 1 As shown, the specific preparation process of the existing enzymatic method for replacing strong alkali is as follows; Step 1: Raw material pretreatment and dispersion: Take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed to room temperature water at a material-to-liquid ratio of 1:10. Stir and disperse the seaweed under normal conditions at room temperature to ensure that the seaweed raw material is fully moistened and evenly dispersed in the water. Step 2, hydrolysis of the fishy smell by protease: Add alkaline protease to the dispersed seaweed solution in Step 1. The amount of enzyme used is 1500 U / g dried seaweed. Adjust the pH of the system to 6.0 with conventional buffer solution. Heat the solution to 45°C and stir the reaction for 1.5 hours at 45°C and pH 6.0. After the reaction is completed, heat the solution to 90°C and keep it for 10 minutes to inactivate the protease. Then filter and collect the solid filter cake. Among them, trimethylamine has a boiling point of 2.9℃ and dimethyl sulfide has a boiling point of 37.3℃; It should be noted that in this step, the protease specifically hydrolyzes the fishy-smelling proteins in *Ulva prolifera*, including free amino acids, short peptides, and medium-molecular-weight fishy-smelling protein fragments. Cellulose is not lost because the protease does not attack glycosidic bonds. However, since pH 6.0 is not the optimal pH for *Bacillus subtilis* alkaline protease (8.0–9.0), at this pH, most of the imidazole ring of the His residue in the Ser-His-Asp catalytic triplet in the enzyme's active site is in a protonated state, resulting in a catalytic efficiency of only 40%–60% of the optimal condition. Therefore, 1500… The actual effective workload is only equivalent to 600-900 U / g. Meanwhile, volatile amines such as trimethylamine and dimethyl sulfide, as well as lipid oxidation products such as cyanaldehyde, heptanal, and nonanal, are completely left untreated in this step. Step 3: Cellulase releases polysaccharides through cellulase cellulase: The solid filter cake obtained from step 2 is redispersed in water at a material-to-liquid ratio of 1:10. Cellulase is added at a dosage of 80 U / g of dried Ulva lactuca. The pH of the system is adjusted to 4.8. The reaction is carried out at 45°C with conventional stirring for 1.5 hours. After the reaction is completed, the solid filter cake is collected by filtration. It should be noted that in this step, cellulase cuts part of the cell wall structure to release polysaccharides. However, the substrate of cellulase is precisely cellulose itself. While opening the cell wall, it also continuously cuts the β-1,4 glycosidic bonds of cellulose. The cellulose content of the raw material of *Ulva prolifera* is only 7% to 21% of its dry weight. Every cut of cellulase cuts the already scarce cellulose matrix, causing damage to the fiber. After this step, the dietary fiber content can reach 82.13%, and the water-holding capacity can be increased to 1250%, but the yield is only 40.22%. Step 4, NaOH alkaline washing, bleaching and decolorization: Disperse the filter cake obtained from step 3 in water, add 1% NaOH solution, stir and react at 70℃ for 45 minutes until the pH of the system reaches 13.5, which is strongly alkaline. After the alkaline washing is completed, wash with water until neutral, filter and collect the solid filter cake. It should be noted that in this step, NaOH causes the chlorophyll porphyrin ring to open and the carotenoids to saponify under alkaline conditions, thereby removing pigments and achieving decolorization. However, the strong alkali also attacks the glycosidic bonds of cellulose and hemicellulose, resulting in an alkaline peeling reaction, i.e., alkaline degradation. The structure of cellulose and hemicellulose is destroyed, which reduces the yield of cellulose. Step 5: Drying to obtain the finished product: The solid filter cake washed in Step 4 is dried using conventional methods. The drying temperature is generally 70℃, without vacuum conditions, until constant weight is achieved.

[0017] Based on experimental analysis, the final product specifications of the existing technology are as follows:

[0018] in conclusion: The existing enzymatic hydrolysis method, which replaces the strong alkali preparation method, yields a dry-based cellulose yield of more than 85 kg of seaweed per 100 kg of dried seaweed during the deodorization process. According to the obtained fishy smell removal rate, the final product still has a fishy smell. Example 1

[0019] For reference Figure 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention includes the following steps: S1. Physical pre-treatment to remove fishy smell: First, take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:9. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.07MPa. Blanch for 45 seconds under rapid stirring and then immediately remove it. Rinse it with cold water to cool it to room temperature. Filter and collect the solid filter cake for later use. It is worth noting that the blanching time mentioned above should be strictly controlled between 30 and 60 seconds: when the blanching time exceeds 60 seconds, the heat loss of the seaweed cellulose in 80℃ hot water increases significantly; when the blanching time is less than 30 seconds, the escape of trimethylamine and dimethyl sulfide is insufficient, and the removal rate of total fishy smell is less than 30%. When saturating and replacing vacuum pumping, Ventilation rate to make the system The minimum flow rate required to reach saturation should be used as the standard. Carbonic acid is formed in water, causing the system's pH to drop to 5.5–6.0, while high concentrations... Further reduce the partial pressure of volatile amines to enhance the deodorization effect; S2, alkaline protease for deodorization: Disperse the S1-treated *Ulva prolifera* at a material-to-liquid ratio of 1:7, and use... Adjust the pH of the buffer solution to 8.5, then add 1000 kJ of alkaline protease. The dried seaweed was reacted, and the solid filter cake after the reaction was collected by filtration. The active site of the Bacillus subtilis alkaline protease contains a Ser-His-Asp catalytic triplet. Adjusting the pH to 8.5 deprotonates the imidazole ring of the His residue in the catalytic triplet, allowing it to act as a generalized base to accept protons from the Ser residue, thereby activating the nucleophilic attack of the Ser residue on the peptide bond. This achieves optimal catalytic efficiency, exceeding 50% compared to the pH 6.0 condition. The alkaline protease dosage is 1000... The amount of dried seaweed was lower than the original scheme of 1500 U / g, but under the optimal conditions of pH 8.3 to 8.7, the actual hydrolysis rate of 1000 U / g was higher than that of the original scheme of 1500 U / g at pH 6.0. Moreover, pH 8.3 to 8.7 is within the stable range of cellulose, pH 6 to 10, and does not induce alkaline degradation of cellulose. S3, neutral lipase removal of oxidized lipids: The solid filter cake obtained in S2 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The reaction was carried out at 43°C with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. The mechanism of action of neutral lipase in *Candida albicans* is interfacial activation: after a conformational change at the oil-water interface, the active site Ser residue is exposed, and it specifically hydrolyzes the ester bonds of triglycerides via an acyl-enzyme intermediate. It is inactive with proteins, cellulose, and glycosidic bonds, removing only oxidized lipids and free fatty acids. The hydrolysis products are glycerol and fatty acids, the latter of which are removed in subsequent washing. *Ulva prolifera* contains EPA and DHA at a dry weight of 5%–15%. These polyunsaturated fatty acids contain multiple double bonds and are easily attacked by lipoxygenases to generate hydroperoxides, which are then broken down into short-chain aldehydes such as styraldehyde, heptanal, and nonanal. These short-chain aldehydes are the main source of the grassy, ​​fishy odor of *Ulva prolifera*. It should be noted that the olfactory threshold of quinalloaldehyde is 0.006 mg / L; S4. Synergistic cell wall opening by pectinase and hemicellulase: The filter cake obtained in S3 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva prolifera and 100 U / g dried Ulva prolifera were added. The ratio of pectinase to xylanase was 2:1. The reaction was carried out by conventional stirring at 45℃ for 1.0 hour. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake was collected by filtration and washed 3 times with deionized water. In this process, pectinase cleaves the α-1,4 glycosidic bonds of the pectin backbone through a β-elimination mechanism, while xylanase cleaves the β-1,4 glycosidic bonds of the xylan backbone through an endoglucosamine mechanism. Cellulose microfibrils in the cell wall structure of *Ulva prolifera* act as building blocks, while pectin and hemicellulose act as the cement binding these blocks. Pectinase and xylanase work together to dissolve the cement components in the cell wall, exposing and releasing the cellulose microfibrils. The cellulose β-1,4 glycosidic bonds have never been cleaved by any enzyme. Furthermore, the buffer pH is adjusted to 4.7, which is the intersection of the optimal pH for pectinase (4.5–5.5) and xylanase (4.5–5.0), allowing both enzymes to achieve high catalytic efficiency simultaneously. This pH value is also far from the cellulase's optimal pH range (4.8–5.0), ensuring that cellulose is not degraded. This step demonstrates superior cellulase ... S5 Mild oxidative decolorization: Disperse the S4 washed seaweed fiber filter cake in water at a material-to-liquid ratio of 1:10, and add 1.5% (based on dry seaweed) ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0020] in, Under weakly alkaline conditions of pH 10.3–10.7, superoxide hydroxide ions are generated (…). The chlorophyll undergoes a Fenton-like reaction to generate hydroxyl radicals (·OH). These hydroxyl radicals preferentially attack the conjugated double bond system of chlorophyll (π bond energy approximately 260 kJ / mol) and carotenoid polyene chains, while the attack rate on cellulose glycosidic bonds (bond energy approximately 350 kJ / mol) is much lower than the attack rate on conjugated double bonds. Therefore, under mild conditions of 48–52 °C and 25–35 minutes, the pigments are fully oxidized while cellulose degradation is negligible. Adjusting the pH to 10.5 instead of using NaOH to adjust the pH to 13.5 in the original scheme reduced the alkalinity of the system by more than an order of magnitude. and Formation of hydrogen peroxide adduct, slowing down The self-decomposition rate makes the oxidation reaction more uniform and controllable, avoiding localized high concentrations. This can cause fiber damage; the washing temperature should be at room temperature to ensure that residual fibers are not damaged. and The moisture is completely removed, and the drying temperature is below 70°C to avoid thermal degradation of cellulose. Vacuum conditions allow the moisture to evaporate at low temperatures. The standard for drying to constant weight is that the difference between two consecutive weighings does not exceed 0.1%.

[0021] Based on experimental analysis, the final product indicators for Example 1 are as follows:

[0022] in conclusion: Compared with Comparative Example 1, the dry cellulose yield of Example 1 increased from 13.2% to 28%, an increase of 112%. For every 100 kg of dried seaweed processed, 86.8 kg of Comparative Example 1 was wasted, while only 72 kg was wasted, resulting in an additional 14.8 kg of usable fiber. The total odor removal rate increased from 65% to 88%, and the odor of the finished product was basically eliminated. The swelling power increased from 6.52 mL / g to 16 mL / g, resulting in a more fluffy fiber skeleton and better papermaking performance.

[0023] Specifically, in this invention, the S1 physical pre-deodorization process utilizes Raoult's law and Dalton's law of partial pressures, using 80°C hot water in conjunction with a vacuum or... Under these conditions, a large amount of low-boiling-point volatile amines such as trimethylamine and dimethyl sulfide are released, removing 30%–40% of the total fishy odor. Furthermore, the temperature of 80℃ is far below the thermal degradation temperature of cellulose, causing zero damage to cellulose. In S2, alkaline protease primarily removes the fishy odor, efficiently hydrolyzing fishy odor proteins at the optimal pH of 8.0–9.0, removing 25%–30% of the total fishy odor. In S3, neutral lipase specifically hydrolyzes oxidized lipids and free fatty acids. Oxidation and decolorization remove the visual fishy smell caused by pigments. The multi-step deodorization process has a good deodorization effect. Specifically, this invention adjusts the pH to 8.0–9.0, so that the His residues are in a deprotonated state, achieving the optimal catalytic efficiency. The actual hydrolysis rate of the protease at 1000 U / g is higher than that of the existing technology at 1500 U / g at pH 6.0. While reducing the enzyme dosage by more than 30%, the deodorization efficiency is improved by more than 30%, significantly reducing production costs. This invention solves the problems in the existing technology where the protease reaction pH is set at 6.0, but the optimal pH for Bacillus subtilis alkaline protease is 8.0–9.0. At pH 6.0, most of the imidazole ring of the His residues in the enzyme active center of the catalytic triplet is in a protonated state, resulting in low catalytic efficiency. Furthermore, this invention employs pectinase to cleave the α-1,4 glycosidic bonds of the pectin backbone and xylanase to cleave the β-1,4 glycosidic bonds of the xylan backbone. After dissolution, the cell wall naturally loosens, exposing and releasing cellulose microfibrils, while their β-1,4 glycosidic bonds remain unaffected. Pectinase and xylanase act on the polysaccharides in the amorphous region, and the reaction rate is much faster than that of cellulase attacking the cellulose in the crystalline region. Furthermore, the present invention uses Hydroxyl radicals are generated at pH 10.0–11.0, preferentially attacking the chlorophyll conjugated double bond system and carotenoid polyene chains, while the attack rate on cellulose glycosidic bonds is much lower than that on conjugated double bonds. Therefore, under mild conditions of 45–55℃ and 20–40 minutes, the pigments are fully oxidized while cellulose degradation is negligible. It replaces NaOH to adjust the pH to 10.0–11.0 instead of 13–14, resulting in a milder alkalinity. and Formation of hydrogen peroxide adduct, slowing down Self-decomposition makes the oxidation reaction more uniform and controllable, avoiding fiber damage caused by local high concentrations; Furthermore, this invention does not use strong alkalis throughout the deodorization and modification process. The decomposition products are only water and oxygen, eliminating the need for waste alkali treatment. It is cheaper than NaOH, and the overall production cost is significantly lower than the existing soda ash process. Moreover, the process is mild, with the highest temperature throughout the process being only 85-95℃ and the reaction temperature controlled at 40-55℃, making it suitable for industrial-scale production.

[0024] Example 2 For reference Figures 1 to 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: The raw material is frozen and thawed seaweed, and S1 uses a method of introducing... Physical pre-deodorization is performed by replacing vacuum pumping with saturation, and the remaining steps and parameters are the same as in Example 1. The specific steps are as follows: Step 1, Physical pre-treatment for deodorization: First, take the frozen and thawed seaweed and chop it into 3-4 cm pieces. Add the chopped seaweed to 80℃ hot water at a material-to-liquid ratio of 1:9 and continuously circulate the solution. To saturate, the ventilation rate is approximately 1.5 L / min, and ventilation lasts approximately 15 seconds until the system is saturated. Once the concentration reaches saturation, blanch for 45 seconds under rapid stirring, then immediately remove and rinse with cold water to cool to room temperature. Filter and collect the solid filter cake for later use. Step 2, alkaline protease deodorization: The *Ulva prolifera* filter cake treated in Step 1, i.e., the solid filter cake, is redispersed in water at a material-to-liquid ratio of 1:7, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.1 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step a3, neutral lipase removal of oxidized lipids: The solid filter cake obtained in Step a2 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The mixture was stirred at 43°C for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. Step 4, synergistic cell wall opening by pectinase and hemicellulase: The solid filter cake obtained in Step 3 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva prolifera and 100 U / g dried Ulva prolifera xylanase were added, with a pectinase to xylanase ratio of 2:1. The reaction was carried out at 45℃ with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake was collected by filtration and washed 3 times with deionized water. Step 5 Mild oxidative decolorization: Disperse the Stepa4 washed seaweed fiber filter cake in water at a material-to-liquid ratio of 1:10, and add 1.5% (based on dry seaweed) ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0025] Based on experimental analysis, the final product indicators for Example 2 are as follows:

[0026] in conclusion: Example 2 uses frozen and thawed seaweed as raw material, and... The physical pre-deodorization method, which replaces vacuum, achieved essentially the same performance as Example 1 and significantly outperformed Comparative Example 1 in all aspects, demonstrating that this process is effective regardless of the raw material state (fresh or frozen) or the degassing method (vacuum or...). It has good adaptability. Saturation treatment can also effectively reduce the partial pressure of volatile amines, and its deodorization effect is comparable to that of vacuum treatment. It has a wide range of sources and is easy to operate.

[0027] Example 3 For reference Figures 1 to 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: Adjust the parameters for each step to conservative values; The specific steps are as follows: Step b1, Physical pre-treatment to remove fishy smell: First, chop the seaweed into 2-3 cm pieces with a knife. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:10. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.07MPa. Blanch for 50 seconds under rapid stirring and then immediately remove it. Rinse with cold water to cool to room temperature. Filter and collect the solid filter cake for later use. Step b2, alkaline protease deodorization: The *Ulva prolifera* filter cake treated in Step b1, i.e., the solid filter cake, is redispersed in water at a material-to-liquid ratio of 1:8, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.1 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step b3, neutral lipase removal of oxidized lipids: The solid filter cake obtained in Step b2 was redispersed in water at a material-to-liquid ratio of 1:8. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The reaction was carried out at 43°C with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. Step b4, synergistic cell wall opening by pectinase and hemicellulase: The solid filter cake obtained in Step b3 was redispersed in water at a material-to-liquid ratio of 1:8. The pH of the system was adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva prolifera and 100 U / g dried Ulva prolifera xylanase were added, with a pectinase to xylanase ratio of 2:1. The reaction was carried out at 45℃ with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake was collected by filtration and washed 3 times with deionized water. Step 5 Mild oxidative decolorization: Disperse the *Ulva prolifera* fiber filter cake washed in Step b4 in water at a material-to-liquid ratio of 1:10, and add 1.5% (based on dry *Ulva prolifera*) ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0028] Based on experimental analysis, the final product indicators for Example 3 are as follows:

[0029] in conclusion: In Example 3, the parameters of each step were adjusted to conservative values. The blanching time in Step 1 was extended to 50 seconds, the reaction time in Steps 2 to 4 was kept to 1.0 to 1.1 hours, and the reaction time in Step 5 was kept to 30 minutes. All the indicators of the finished product were still within the range of Example 1 and were all significantly better than those of Comparative Example 1. No indicators deteriorated, proving that the process can still operate stably under non-optimal parameter conditions, with a wide process window and strong fault tolerance.

[0030] Example 4 For reference Figures 1 to 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: S5 The dosage was too high and the reaction time was too long. The specific steps are as follows: Step c1, Physical pre-treatment to remove fishy smell: First, take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:9. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.07MPa. Blanch for 40 seconds under rapid stirring and then immediately remove it. Rinse it with cold water to cool it to room temperature. Filter and collect the solid filter cake for later use. Step c2, alkaline protease deodorization: The *Ulva prolifera* filter cake treated in Step c1 is redispersed in water at a material-to-liquid ratio of 1:7, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.1 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step c3, neutral lipase removal of oxidized lipids: The filter cake obtained in Step c2 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The mixture was stirred at 43°C for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. Step c4, synergistic cell wall opening by pectinase and hemicellulase: The filter cake obtained in Step c3 is redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system is adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva lactuca and 100 U / g dried Ulva lactuca are added. The ratio of pectinase to xylanase is 2:1. The reaction is carried out by conventional stirring at 45℃ for 1.0 hour. After the reaction is completed, the temperature is raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake is collected by filtration and washed 3 times with deionized water. Step c5 Mild oxidative decolorization: Disperse the *Ulva prolifera* fiber filter cake washed in Step c4 in water at a material-to-liquid ratio of 1:10, and add 1.8% (based on dry *Ulva prolifera*) , The dosage was too high. The pH of the system was adjusted to 10.7, and the reaction was carried out at 52℃ with conventional stirring for 35 minutes. The stirring time was a bit long. After the reaction was completed, the mixture was washed with deionized water until neutral, filtered and collected. The solid was then vacuum dried at 60℃ and 0.09MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0031] Based on experimental analysis, the final product specifications for Example 4 are as follows:

[0032] in conclusion: Example 4 Increasing the dosage to 1.8% and extending the reaction time to 35 minutes, the total odor removal rate remained the same as in Example 1 at 88%, but the water-holding capacity decreased from 1020% to 980% and the swelling power decreased from 16 mL / g to 14 mL / g, indicating that... Excessive dosage or excessively long reaction time may cause slight damage to the pore structure of the fiber. In summary, A dosage of 1.2%–1.8% and a reaction time of 25–35 minutes represent the optimal balance between decolorization and fiber protection. Example 1, with its chosen dosage of 1.5% and reaction time of 30 minutes, represents the best value within this range. All indicators are still superior to those of Comparative Example 1.

[0033] Example 5 For reference Figures 1 to 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: The ratio of pectinase to xylanase in S4 was adjusted to 2.4:1.

[0034] The specific steps are as follows: Step 1, Physical pre-treatment to remove fishy smell: First, take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:9. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.07MPa. Blanch for 45 seconds under rapid stirring and then immediately remove it. Rinse it with cold water to cool it to room temperature. Filter and collect the solid filter cake for later use. Step 2, Alkaline protease deodorization: The *Ulva prolifera* filter cake treated in S1 was redispersed in water at a material-to-liquid ratio of 1:7, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.1 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step 3: Neutral lipase removal of oxidized lipids: The filter cake obtained in S2 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The mixture was stirred at 43°C for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. Step 4: Synergistic cell wall opening by pectinase and hemicellulase: The filter cake obtained in S3 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 4.8 with acetate-sodium acetate buffer. 220 U / g dried Ulva prolifera and 90 U / g dried Ulva prolifera were added. The ratio of pectinase to xylanase was 2.4:1. The proportion of pectinase was increased here. The reaction was carried out by conventional stirring at 46℃ for 1.1 hours. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzyme. The solid filter cake was collected by filtration and washed 3 times with deionized water. Step 5 Mild oxidative decolorization: Disperse the S4 washed seaweed fiber filter cake in water at a material-to-liquid ratio of 1:10, and add 1.5% (based on dry seaweed) ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0035] Based on experimental analysis, the final product indicators for Example 5 are as follows:

[0036] in conclusion: In Example 5, the ratio of pectinase to xylanase was increased from 2:1 to 2.4:1. The dry-basis cellulose yield increased from 28% in Example 1 to 30%, and the swelling power increased from 16 mL / g to 17 mL / g, both superior to Example 1. This indicates that appropriately increasing the pectinase ratio is beneficial for more fully dissolving the pectin cement components in the cell wall, resulting in more complete exposure of cellulose microfibers and better cell wall opening. However, the pectinase ratio should not exceed 2.5:1; otherwise, insufficient xylanase will lead to xylan residue and incomplete cell wall opening. All indicators were still superior to Comparative Example 1.

[0037] Example 6 For reference Figures 1 to 2As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: The blanching time in S1 is adjusted to the upper limit of 60 seconds, and the material-to-liquid ratio is adjusted to 1:8. The specific steps are as follows: Step 1, Physical pre-treatment to remove fishy smell: First, take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:8. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.06MPa. Blanch for 60 seconds under rapid stirring and then immediately remove it. Rinse it with cold water to cool it to room temperature. Filter and collect the solid filter cake for later use. The blanching time is extended to 60 seconds, which is the upper limit of this step. At this time, trimethylamine and dimethyl sulfide are released most fully, and the proportion of total fishy smell removal can reach more than 40%. However, the blanching time is close to the critical point of cellulose heat loss. The material-liquid ratio of 1:8 is more concentrated than the 1:7 in Example 1, which is conducive to improving the reaction efficiency of subsequent steps, but at the same time, it also puts forward higher requirements for the thermal stability of the fiber. Step 2, alkaline protease deodorization: The *Ulva prolifera* filter cake treated in Step 1 is redispersed in water at a material-to-liquid ratio of 1:6, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.2 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step 3: Removal of oxidized lipids with neutral lipase: The solid filter cake obtained in Step 2 was redispersed in water at a material-to-liquid ratio of 1:6. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 750 U / g of neutral lipase from Candida albicans was added. The mixture was stirred at 43°C for 1.0 hour. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was then collected by filtration. Step 4, synergistic cell wall opening by pectinase and hemicellulase: The solid filter cake obtained in Step 3 was redispersed in water at a material-to-liquid ratio of 1:6. The pH of the system was adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva prolifera and 100 U / g dried Ulva prolifera xylanase were added, with a pectinase to xylanase ratio of 2:1. The reaction was carried out at 45℃ with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake was collected by filtration and washed 3 times with deionized water. Step 5 Mild oxidative decolorization: Disperse the *Ulva prolifera* fiber filter cake washed in Step 4 in water at a material-to-liquid ratio of 1:8, and add 1.5% (based on dry *Ulva prolifera*). ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0038] Based on experimental analysis, the final product specifications for Example 6 are as follows:

[0039] in conclusion: In Example 6, extending the blanching time in Step 1 to the upper limit of 60 seconds and tightening the liquid-to-material ratio to 1:8 actually increased the overall odor removal rate to 90%, indicating that more thorough physical deodorization helps reduce the burden on subsequent enzyme treatment. However, the dry-basis cellulose yield decreased to 25% and the water-holding capacity decreased to 1000%, indicating that while the combination of 60-second blanching and a 1:8 concentrated liquid ratio maximized the deodorization effect, it also slightly increased the heat loss and mechanical damage to the fibers. In summary, a blanching time of 40-50 seconds and a liquid-to-material ratio of 1:8-1:9 in Step 1 represent the optimal balance between deodorization and fiber protection. The 45-second blanching time and 1:9 ratio selected in Example 1 represent the optimal value within this range, and all indicators are still superior to those of Comparative Example 1.

[0040] Example 7 For reference Figures 1 to 2 As shown, the preparation process of the deodorized modified seaweed-based papermaking fiber provided by the present invention differs from that in Example 1 in that: The amount of lipase in S3 was increased to the upper limit of 900 U / g, and the reaction time was extended to the upper limit of 1.2 hours. The specific steps are as follows: Step 1, Physical pre-treatment to remove fishy smell: First, take fresh seaweed and chop it into 2-3 cm pieces. Add the chopped seaweed raw material to 80℃ hot water at a material-to-liquid ratio of 1:9. Turn on the vacuum pump to draw the system pressure to an absolute pressure of 0.07MPa. Blanch for 45 seconds under rapid stirring and then immediately remove it. Rinse it with cold water to cool it to room temperature. Filter and collect the solid filter cake for later use. Step 2, alkaline protease deodorization: The *Ulva prolifera* filter cake treated in Step 1 is redispersed in water at a material-to-liquid ratio of 1:7, and then... Adjust the pH of the buffer system to 8.5, add 1000 U / g of alkaline protease from Bacillus subtilis to dried Ulva lactuca, and stir the reaction at 53℃ for 1.1 hours. After the reaction is completed, raise the temperature to 90℃ and hold for 10 minutes to inactivate the enzyme. Filter and collect the solid filter cake. Step 3: Removal of oxidized lipids with neutral lipase: The solid filter cake obtained in Step 2 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 7.0 with Tris-HCl buffer. 900 U / g of neutral lipase from Candida albicans was added, and the amount of lipase was increased to the upper limit of the range. The reaction was carried out at 43°C with normal stirring for 1.2 hours. The reaction time was extended to the upper limit of the range. After the reaction was completed, the temperature was raised to 80°C and held for 10 minutes to inactivate the enzyme. The solid filter cake was collected by filtration. The experiment involved increasing the lipase dosage from 750 U / g to 900 U / g and extending the reaction time from 1.0 hour to 1.2 hours. The aim was to maximize the hydrolysis of hydroperoxides and short-chain aldehydes generated from the oxidation of EPA and DHA in *Ulva prolifera*, including styraldehyde, heptanal, and nonanal, to verify whether the lipid oxidation pathway for fishy odor could be more thoroughly blocked. Step 4, synergistic cell wall opening by pectinase and hemicellulase: The solid filter cake obtained in Step 3 was redispersed in water at a material-to-liquid ratio of 1:7. The pH of the system was adjusted to 4.7 with acetate-sodium acetate buffer. 200 U / g dried Ulva prolifera and 100 U / g dried Ulva prolifera xylanase were added, with a pectinase to xylanase ratio of 2:1. The reaction was carried out at 45℃ with conventional stirring for 1.0 hour. After the reaction was completed, the temperature was raised to 90℃ and held for 10 minutes to inactivate the enzymes. The solid filter cake was collected by filtration and washed 3 times with deionized water. Step 5 Mild oxidative decolorization: Disperse the *Ulva prolifera* fiber filter cake washed in Stepf4 in water at a material-to-liquid ratio of 1:10, and add 1.5% (based on dry *Ulva prolifera*) ,use The pH of the system was adjusted to 10.5, and the reaction was carried out by stirring at 50°C for 30 minutes. After the reaction was completed, the mixture was washed with deionized water until neutral, the solid was collected by filtration, and vacuum dried at 60°C and 0.09 MPa to constant weight to obtain the deodorized modified seaweed-based paper fiber product.

[0041] Based on experimental analysis, the final product specifications for Example 7 are as follows:

[0042] in conclusion: In Example 7, the amount of lipase used in Step 3 was increased to 900 U / g and the reaction time was extended to 1.2 hours. The total odor removal rate reached 91%, which was further improved from 88% in Example 1. This shows that appropriately increasing the amount of lipase and extending the reaction time is beneficial to more thoroughly removing lipid oxidation odor substances such as sine leaf aldehyde, heptanal, and nonanal. However, the dry basis cellulose yield was 27%, the water holding capacity was 1030%, and the swelling power was 16 mL / g, which were basically the same as in Example 1. No indicators deteriorated, indicating that lipase is indeed inactive against cellulose and glycosidic bonds under the conditions of pH 6.8-7.2 and 42-45℃. Extending the reaction time and increasing the amount will not cause any damage to the fiber body. All indicators are still better than those of Comparative Example 1. Based on this, the present invention prepares deodorized modified papermaking fibers using seaweed as raw material, compared with Comparative Example 1: First, in terms of deodorization effect, the total odor removal rate of Comparative Example 1 was only 65%, and the finished product still had a noticeable odor. The total odor removal rate of each embodiment of the present invention was 86% to 91%, which was 21 to 26 percentage points higher than that of Comparative Example 1. The odor of the finished product was basically eliminated, meeting the quality requirements of papermaking grade fiber. Secondly, in terms of fiber retention, the dry-based cellulose yield of Comparative Example 1 was only 13.2%, meaning that 86.8 kg of cellulose was wasted for every 100 kg of dried seaweed processed. The dry-based cellulose yield of each embodiment of the present invention was 25% to 30%, which is 90% to 127% higher than that of Comparative Example 1. Each 100 kg of dried seaweed processed yielded an additional 11.8 to 16.8 kg of usable fiber, significantly improving the utilization rate of raw materials. Third, in terms of fiber functional properties, the swelling force of Comparative Example 1 was only 6.52 mL / g; the swelling force of each embodiment of the present invention was 14 to 17 mL / g, an increase of 115% to 161%, indicating that the exposure degree and pore structure of cellulose microfibers after synergistic cellulase and xylanase opening the cell walls were better than those of Comparative Example 1 when cellulase opened the cell walls, and the fiber skeleton was more fluffy. When mixed with wood pulp at a mass ratio of 15:85 to 25:75 for papermaking, it can provide better papermaking performance. Fourth, this invention does not use strong alkalis throughout the entire process. The decomposition products are only water and oxygen, eliminating the need for waste alkali treatment. It is cheaper than NaOH, and the overall production cost is significantly lower than that of the soda ash process in Comparative Example 1. Moreover, the process is mild, with the highest temperature throughout the process being only 90℃ and the reaction temperature controlled at 40-55℃, making it suitable for industrial-scale production.

[0043] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for the preparation of deodorized modified Enteromorpha-based papermaking fibers, characterized by, Includes the following steps: S1. Physical pre-treatment for deodorization: First, chop the raw material of seaweed and add it to 80℃ hot water at a material-to-liquid ratio of 1:8 to 1:

10. Then, reduce the pressure to 0.06 to 0.08 MPa or introduce... Under saturated conditions, stir quickly and blanch for 30-60 seconds, then remove and rinse with cold water to cool to room temperature; S2, alkaline protease for deodorization: Disperse the S1-treated *Ulva prolifera* at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 8.0 to 9.0 with buffer solution, and add 800 to 1200 ml of alkaline protease. The dried seaweed was reacted, and the solid filter cake after the reaction was collected by filtration. S3, neutral lipase removal of oxidized lipids: redisperse the solid filter cake from S2 at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 6.5 to 7.5 with buffer solution, add 500 to 1000 U / g of neutral lipase to react, and filter and collect the solid filter cake after reaction. S4. Synergistic cell wall opening by pectinase and hemicellulase: Redisperse the solid filter cake from S3 at a material-to-liquid ratio of 1:6 to 1:8, adjust the pH to 4.5 to 5.0 with buffer solution, and add 150 to 250 μL of pectinase. Dried seaweed and xylanase 80-150 The dried seaweed was reacted, the solid filter cake was collected by filtration and washed with deionized water 2 to 4 times to obtain seaweed fiber filter cake; S5 Mild oxidative decolorization: Disperse the S4-washed Ulva prolifera fiber filter cake at a material-to-liquid ratio of 1:8 to 1:12, and add 1.0% to 2.0% of the solution. The reaction was carried out, and after the reaction was completed, the product was washed with deionized water until neutral. The solid was collected by filtration and dried under vacuum at 60°C until constant weight, thus obtaining the deodorized modified seaweed-based papermaking fiber product.

2. The preparation process of the deodorized modified seaweed-based papermaking fiber according to claim 1, characterized in that, In step S1, the raw material for *Ulva prolifera* is fresh *Ulva prolifera* or frozen-thawed *Ulva prolifera*, chopped into 1-5 cm pieces; the decompression is achieved by vacuum pumping, with an absolute system pressure of 0.06-0.08 MPa; or by continuous airflow. The method of saturation can replace vacuum pumping.

3. The preparation process of the deodorized modified seaweed-based papermaking fiber according to claim 1, characterized in that, In step S2, the alkaline protease is an alkaline protease derived from Bacillus subtilis; the buffer solution is... Buffer solution.

4. The preparation process of the deodorized modified seaweed-based papermaking fiber according to claim 1, characterized in that, In step S3, the neutral lipase is a lipase derived from Candida albicans; the buffer solution is Tris-HCl buffer.

5. The preparation process of the deodorized modified seaweed-based papermaking fiber according to any one of claims 1-4, characterized in that, The raw material of *Ulva prolifera* has a cellulose content of 7%–21% by dry weight, a protein content of 8%–15% by dry weight, and a total EPA and DHA content of 5%–15% by dry weight.

6. The preparation process of deodorized modified seaweed-based papermaking fiber according to claim 1 or 3, characterized in that, The alkaline protease in step S2 is an alkaline protease derived from Bacillus subtilis, whose active center contains the Ser-His-Asp catalytic triplet.

7. The preparation process of deodorized modified seaweed-based papermaking fiber according to claim 1 or 4, characterized in that, The oxidized lipids removed by the neutral lipase in step S3 include short-chain aldehydes such as chlorophyll aldehyde, heptanal, and nonanal generated from the oxidation of EPA and DHA in seaweed, wherein the olfactory threshold of chlorophyll aldehyde is 0.006 mg / L.

8. The preparation process of the deodorized modified seaweed-based papermaking fiber according to claim 5, characterized in that, In step S4, the ratio of pectinase to xylanase is 2:1 to 2.5:

1. Pectinase cleaves the α-1,4 glycosidic bonds of the pectin backbone through a β-elimination mechanism, while xylanase cleaves the β-1,4 glycosidic bonds of the xylan backbone through an endoglucosinolate mechanism. The two work together to dissolve the cell wall, exposing and releasing cellulose microfibrils.

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