Oriented enzymolysis treatment method for outer layer of absorbent cotton based on compound plant protease

Abstract

The invention relates to the technical field of biological material modification, in particular to a method for carrying out directional enzymolysis treatment on the surface of absorbent cotton through compound plant protease, which comprises the following steps: carrying out physical pretreatment on the absorbent cotton to enhance the surface activation degree; preparing a compound enzyme solution containing bromelain, pectinase and xylanase; contacting the pretreated absorbent cotton with the compound enzyme solution, and carrying out directional enzymolysis under controlled conditions; the enzymolysis depth is controlled by adjusting the reaction temperature and the pH value in stages; after the reaction is completed, the enzyme activity is terminated through heat treatment, pH adjustment or addition of chemical reagents; finally, the treated absorbent cotton is cleaned and dried, a surface-modified absorbent cotton product is obtained, selective directional enzymolysis of the outer layer of the absorbent cotton is achieved, the diameter of surface layer fibers is reduced by 8-12%, the internal fiber structure is kept complete, the tensile strength retention rate is larger than or equal to 85%, and the problem that the depth of an existing enzymolysis technology is uncontrollable is solved.

Description

Technical Field

[0001] The invention relates to the technical field of biomaterial modification, and specifically to a method for directional enzymatic hydrolysis of the surface of absorbent cotton using a composite plant protease, which is suitable for the preparation process of high-performance cellulose products such as medical dressings and cosmetic cotton pads. Background Art

[0002] As an important cellulose material, absorbent cotton is widely used in healthcare, cosmetics, and industry. Depending on the application requirements, the surface properties of the absorbent cotton, such as hydrophilicity, softness, and adsorption, directly influence its effectiveness. Currently, the modification of absorbent cotton mainly involves chemical degreasing, physical modification, or enzymatic hydrolysis.

[0003] Traditional chemical degreasing methods usually use strong alkaline solutions such as sodium hydroxide or organic solvents for treatment. Although they can effectively remove non-cellulose substances in cotton fibers, they often lead to the following problems: First, chemical reagent residues, especially in medical dressings, may cause skin allergies or inflammatory reactions in patients; second, fiber structure damage. Excessive chemical treatment will reduce the length of cellulose molecular chains, resulting in a decrease in strength; third, a large amount of wastewater containing alkaline or organic solvents is generated, which puts a heavy burden on the environment.

[0004] Physical modification methods, such as plasma treatment and corona treatment, mainly affect the surface properties of the fiber. Although they avoid the problem of chemical reagent residues, their treatment effects are often unstable, and the equipment investment cost is high and the energy consumption is large, making it difficult to achieve large-scale industrial application.

[0005] In recent years, enzymatic hydrolysis technology has been gradually applied to the modification of cellulose materials due to its advantages such as high specificity, mild reaction conditions, and environmental friendliness. However, the main drawbacks of existing enzymatic hydrolysis technologies are: first, the depth of enzymatic hydrolysis is uncontrollable, often resulting in full-layer degradation rather than targeted surface modification, leading to a significant decrease in fiber strength; second, low enzymatic hydrolysis efficiency and long processing times; third, a lack of dynamic and precise control over the enzymatic hydrolysis process; and fourth, the enzyme preparation is difficult to recycle after use, resulting in high costs.

[0006] Therefore, there is an urgent need to develop a new treatment method that can achieve directional enzymatic hydrolysis of the surface of absorbent cotton, retain internal fiber strength, and improve surface properties at the same time, so as to meet the differentiated requirements of high-performance cellulose products for surface properties. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for directional enzymatic hydrolysis treatment of the outer layer of cotton wool based on a composite plant protease, aiming to solve the technical problems existing in the prior art such as uncontrollable enzymatic hydrolysis depth, low efficiency, and high cost, and to achieve selective enzymatic hydrolysis of the outer layer of cotton wool, while retaining the internal fiber strength and significantly improving the surface hydrophilicity, softness and adsorption, while reducing energy consumption and achieving environmentally friendly production.

[0008] To achieve the above object, the present invention provides a method for directional enzymatic hydrolysis of the outer layer of absorbent cotton based on a composite plant protease, comprising the following steps:

[0009] (1) Pretreatment: Physical pretreatment of the absorbent cotton to enhance surface activation;

[0010] (2) Enzyme solution preparation: prepare a complex enzyme solution containing bromelain, pectinase and xylanase;

[0011] (3) Enzymatic hydrolysis reaction: contacting the pretreated absorbent cotton with the complex enzyme solution and performing a directed enzymatic hydrolysis reaction under controllable conditions;

[0012] (4) Dynamic control: During the enzymatic hydrolysis process, the depth of enzymatic hydrolysis is controlled by adjusting the reaction temperature and / or pH value in stages;

[0013] (5) Inactivation: After the enzymatic hydrolysis is completed, the enzyme activity is terminated by increasing the temperature, adjusting the pH, or adding chemical reagents;

[0014] (6) Cleaning and drying: The enzymatically hydrolyzed absorbent cotton is cleaned and dried to obtain a surface-modified absorbent cotton product.

[0015] In a preferred embodiment of the present invention, the ratio of bromelain, pectinase, and xylanase in the complex enzyme solution is A:B:C = 1:(0.5-2):(0.3-1), where A represents bromelain, B represents pectinase, and C represents xylanase. This specific enzyme ratio enables a synergistic enzymatic hydrolysis of the outer layer of the absorbent cotton. Bromelain primarily cuts through the non-crystalline region of the surface fiber, pectinase degrades intercellular pectin, and xylanase acts on the hemicellulose component. The three enzymes work synergistically to achieve efficient and directional degradation.

[0016] The physical pretreatment can be plasma treatment, ultrasonic treatment, microwave treatment, or a combination thereof. Specifically, plasma treatment conditions are: power 100-300W, treatment time 10-20 minutes; ultrasonic treatment conditions are: frequency 20-40kHz, power density 200-500W / L, treatment time 8-15 minutes; microwave-assisted treatment conditions are: frequency 2.45GHz, power 200-400W, intermittent treatment time 3-5 minutes. The introduction of physical pretreatment can destroy the waxy layer on the surface of the absorbent cotton, increase surface micropores and roughness, and significantly improve the efficiency of subsequent enzymatic hydrolysis.

[0017] One of the key innovations of the present invention is the dynamic control system, which accurately controls the depth of enzymatic hydrolysis by adjusting the temperature and pH value in stages. The staged temperature adjustment includes: the first stage (activation period): 48-52°C, lasting 30 to 60 minutes, activating enzyme activity; the second stage (stabilization period): 38-42°C, lasting 60 to 90 minutes, maintaining moderate enzyme activity; the third stage (inhibition period): 28-32°C, lasting 30 to 60 minutes, inhibiting excessive reaction. The staged pH adjustment includes: the first stage: pH 6.2-6.8, which is conducive to bromelain activity; the second stage: pH 5.2-5.8, which is conducive to pectinase activity; the third stage: pH 6.7-7.3, inhibiting excessive enzymatic hydrolysis.

[0018] After enzymatic hydrolysis is complete, one or more of the following inactivation methods can be used: heat inactivation: 78-82°C for 8-12 minutes; pH inactivation: adjusting the pH to 10.0-11.0 for 4-6 minutes; chemical inactivation: adding 0.1%-0.2% hydrogen peroxide solution. Inactivation treatment can terminate the enzyme reaction in a timely manner and prevent excessive enzymatic hydrolysis.

[0019] To improve economic efficiency and environmental protection, the present invention also includes an enzyme preparation recovery step: centrifuging the enzymatic hydrolysis waste liquid to remove solid particles; using an ultrafiltration membrane with a molecular weight cutoff of 5-10 kDa for membrane separation, or using 40% to 60% saturation ammonium sulfate for salting out and recovery, or using a macroporous resin for selective adsorption; and concentrating and stabilizing the recovered enzyme to achieve the recycling of the enzyme preparation. The enzyme preparation can be recycled 3-5 times with an activity retention rate of not less than 60%.

[0020] The method of the present invention can be flexibly applied to the preparation of different absorbent cotton products. For example, the specific process parameters for preparing medical dressings are: raw material fiber length ≥ 10mm, density 3.5kg / m 3 The sample was prepared from cotton wool; the enzymatic hydrolysate consisted of 1.5 g / L bromelain, 1.2 g / L pectinase, 0.8 g / L xylanase, phosphate buffer (pH 6.5, 50 mM), and 2 mM calcium chloride; the sample was pretreated with plasma (200 W, oxygen, 15 minutes); the enzymatic hydrolysis was controlled by three-stage temperature (50°C / 45 minutes → 40°C / 75 minutes → 30°C / 45 minutes); the sample was inactivated at 80°C for 10 minutes; the sample was washed four times with pure water at 40°C; and the sample was dried with hot air at 60°C for 50 minutes.

[0021] The specific process parameters for preparing cosmetic cotton pads are as follows: the raw material fiber length is ≥15mm, the density is 3.2kg / m 3Combed absorbent cotton; enzymatic hydrolysate consisting of 2.0 g / L bromelain, 1.5 g / L pectinase, 1.0 g / L xylanase, and 0.05% nonionic surfactant; pretreatment with ultrasonication (25 kHz, 300 W / L, 12 minutes); two-stage controlled enzymatic hydrolysis (52°C / 30 minutes → 35°C / 60 minutes); inactivation by adjusting the pH to 10.5 and maintaining for 5 minutes; and vacuum drying (40°C, -0.06 MPa, 30 minutes).

[0022] The preparation method of the complex enzyme solution can be flexibly selected according to actual needs: a fixed ratio scheme (bromelain: pectinase: xylanase = 1:0.8:0.5); an adjustable ratio scheme (adjusting the ratio of each enzyme according to the characteristics of the raw materials and the performance requirements of the target product); a sequential addition scheme (first adding bromelain, then adding pectinase and xylanase in sequence); an enzyme immobilization scheme (immobilizing the enzyme on a carrier such as macroporous polymer balls or magnetic nanoparticles).

[0023] Compared with the existing technology, the present invention has the following significant advantages:

[0024] (1) The selective and directional enzymatic hydrolysis of the outer layer of the absorbent cotton was achieved, and the diameter of the surface fibers was reduced by 8% to 12%, while the internal fiber structure remained intact, and the tensile strength retention rate was ≥85%, solving the problem of uncontrollable depth of existing enzymatic hydrolysis technology;

[0025] (2) Through the synergistic action mechanism of the complex enzyme, the surface roughness is reduced by 30% to 50%, the liquid diffusion rate is increased by 50% to 80%, and the water absorption rate is increased from 8-12 mL / g to 18-25 mL / g, significantly improving the surface properties;

[0026] (3) The dynamic temperature / pH control system is used to achieve precise control of the enzymatic hydrolysis process, shortening the processing time by 30% to 50%, thereby improving production efficiency;

[0027] (4) The enzyme preparation recycling technology was established, with a recovery rate of 70% to 90%, which greatly reduced the enzyme cost;

[0028] (5) The COD value of the enzymatic wastewater is reduced by 60% to 80% compared with the chemical method. There is no risk of chemical reagent residues, which meets the green production standards.

[0029] In summary, the directional enzymatic hydrolysis treatment method of the outer layer of the absorbent cotton based on composite plant protease provided by the present invention solves the technical difficulties existing in traditional treatment methods, realizes the directional and precise improvement of the surface performance of the absorbent cotton, and at the same time ensures the integrity of the internal structure, greatly improves the treatment efficiency and environmental protection, and provides a new idea for the preparation of high-performance cellulose materials. DETAILED DESCRIPTION

[0030] The technical solutions of the present invention will be described clearly and completely below with reference to specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention. In the following examples, unless otherwise specified, the reagents and materials used can be obtained through commercial channels, and the examples were all completed under laboratory conditions.

[0031] In order to allow those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0032] During the research and development process, it was discovered that the surface properties of cotton wool are closely related to its microstructure. Cotton wool fibers are primarily composed of cellulose, with small amounts of hemicellulose, pectin, and residual wax on the surface. Although these non-cellulose components are present in low concentrations, they significantly affect the surface properties of cotton wool. Careful observation of the microscopic morphology of untreated cotton wool revealed that the waxy surface layer impedes the penetration of water and active substances, while the pectin between the fibers limits the fiber's softness. This discovery inspired the design of a complex enzyme system tailored to each component, striving to improve surface properties while preserving internal fiber strength.

[0033] Example 1: Standard medical cotton wool processing process

[0034] First, a batch of typical medical grade absorbent cotton was selected as the research object. The fiber length of this batch of materials is about 10-15mm, and the density is 3.5kg / m 3 , meeting the basic requirements for medical dressings. Electron microscopy revealed that the fibers had an unevenly rough surface, with diameters fluctuating between 14 and 16 μm, averaging approximately 15.3 μm. Preliminary testing revealed that the water absorption rate of this batch of absorbent cotton was only 8-12 mL / g, far below the requirements for high-end medical dressings.

[0035] Before the main experiments, various pretreatment methods were tested, including chemical immersion, ultrasonic treatment, and plasma treatment. The results showed that plasma treatment effectively activated the fiber surface while minimizing damage to the fiber's main structure. This is likely because the active particles generated by the low-temperature plasma selectively act on wax and impurities on the fiber surface, introducing oxygen-containing functional groups that create favorable conditions for subsequent enzymatic hydrolysis.

[0036] The selection of pretreatment parameters was quite challenging. After much trial and error, we found that the most effective combination was a plasma power between 100 and 300 W and a treatment time between 10 and 20 minutes. Powers below 100 W were ineffective in surface activation, while powers exceeding 300 W could lead to excessive fiber oxidation and even localized carbonization. Similarly, treatment times shorter than 10 minutes were ineffective, while those exceeding 20 minutes increased the risk of fiber damage, with no significant benefit from the increased energy consumption.

[0037] Through systematic comparison, the final plasma treatment conditions were determined: 200W power, 15 minutes of treatment time, and oxygen as the working gas. Under these conditions, the surface wax removal rate approached 90%, the surface roughness increased by approximately 40%, and the fiber damage was kept below 5%, demonstrating a well-balanced performance.

[0038] The preparation of the complex enzyme solution is the core of this invention. After extensive literature research and preliminary experiments, a composite system consisting of bromelain, pectinase, and xylanase was selected. Each enzyme has its own strengths: bromelain primarily cuts through the non-crystalline surface of the fiber, pectinase degrades the intercellular pectin, and xylanase acts on the hemicellulose component. To determine the optimal ratio, a series of experiments were designed, systematically adjusting the ratio of the three enzymes, ranging from 1:0.5:0.3 to 1:2.0:1.0, covering the entire envisioned effective range.

[0039] After repeated comparisons and verifications, it was found that when the three enzymes were mixed in a ratio of 1:1.2:0.7, the treatment effect reached the optimal balance point. Specifically, 1.5g / L bromelain (activity 3.29×10^6U / g), 1.8g / L pectinase (activity 2.2×10^5U / g) and 1.05g / L xylanase (activity 1.8×10^5U / g) were added to 50mM phosphate buffer (pH 6.5), and 2mM calcium chloride was added as an enzyme activity cofactor, and 5% glycerol was added as a stabilizer. It is worth mentioning that temperature control during the preparation process is very important. It was found that preparing and storing the enzyme solution at 4°C can effectively prevent premature loss of enzyme activity. Although this detail is small, it has a great impact on the actual operation effect.

[0040] Dynamic control of the enzymatic hydrolysis process is another innovation of the present invention. Traditional constant temperature enzymatic hydrolysis often finds it difficult to balance the treatment effect with the protection of the internal structure, so a three-stage temperature and pH coordinated control strategy was developed. First, through activity assay experiments, it was found that the three enzymes had different optimal activity temperatures and pH values: bromelain preferred an environment of 48-52°C and pH 6.2-6.8, pectinase performed best at 38-42°C and pH 5.2-5.8, and xylanase was most active at 40-45°C and pH 5.5-6.5.

[0041] Based on these findings, a three-stage control scheme was designed: the first stage (activation period) maintained a higher temperature (50°C) and a moderate pH value (6.5) for about 45 minutes, mainly activating bromelain and initiating the degradation of surface fibers; the second stage (stabilization period) cooled to 40°C and adjusted the pH to 5.5 for 75 minutes, at which time the activities of pectinase and xylanase were enhanced, deepening the modification of the surface structure; the third stage (inhibition period) further cooled to 30°C and raised the pH to 7.0 for 45 minutes, with the aim of gradually reducing enzyme activity, preventing excessive enzymatic hydrolysis, and precisely controlling the treatment depth.

[0042] In practice, we've found that the rate of temperature change is also a crucial parameter. When transitioning from the first to the second stage, a temperature drop rate of approximately 0.2°C / minute is ideal, achieving the desired activity regulation without causing drastic changes in the enzyme's protein structure. Similarly, pH adjustments should be performed slowly, ideally with a change of no more than 0.1 units per minute.

[0043] The stirring method during the enzymatic hydrolysis process is also noteworthy. Intermittent low-shear stirring is used, specifically a cycle of 5 minutes of stirring followed by 10 minutes of quiescence. The stirring speed is controlled at around 45 rpm. This gentle stirring method ensures uniformity of the reaction system while avoiding mechanical damage to the fiber structure.

[0044] After the enzymatic hydrolysis reaction is complete, timely and effective inactivation is crucial. Three methods, heat inactivation, pH inactivation, and chemical inactivation, were compared. Heat inactivation was performed between 78-82°C and maintained for 8-12 minutes. pH inactivation involved adjusting the system pH to 10.0-11.0 and maintaining it for 4-6 minutes. For chemical inactivation, the addition of 0.1% to 0.2% hydrogen peroxide solution was attempted. Taking into account the inactivation effect, the impact on the fiber, and operational ease, a heat inactivation solution of 80°C for 10 minutes was ultimately chosen. Practice has shown that this method can completely terminate enzyme activity with minimal impact on the performance of medical cotton wool.

[0045] Cleaning and drying after inactivation also require careful design. After many tests, a plan was determined to use 40°C warm water for four washes, with each wash using approximately five times the weight of the absorbent cotton. Insufficient cleaning will result in residual enzymatic products, while excessive cleaning will increase energy and water consumption, and may even cause excessive swelling of the fibers. For the drying process, a plan of 60°C hot air drying for approximately 50 minutes was selected to control the moisture content of the final product between 6% and 8%. This moisture content range ensures product stability while maintaining appropriate softness.

[0046] To improve the economic and environmental performance of the process, an enzyme recovery technology has also been developed. Comparative testing revealed that an ultrafiltration membrane with a molecular weight cutoff of 8 kDa provides the best separation results, achieving a recovery rate of approximately 75% and a 73% retention rate for the recovered enzyme activity. The recovered enzyme can be recycled four times after a simple stabilization treatment, significantly reducing production costs. It is worth noting that enzyme activity gradually decreases with increasing cycles, typically falling below 60% of its original level after the fifth use, at which point the enzyme should be replaced.

[0047] The performance of medical absorbent cotton treated with the above process was significantly improved. Electron microscopy measurements showed that the surface fiber diameter decreased from 15.3 μm to 13.7 μm, a reduction of approximately 10.5%. Water absorption, as measured by the conventional immersion method, increased from 10.2 mL / g to 22.8 mL / g, an increase of approximately 123%. The tensile strength, as tested using the standard tensile method, increased from 3.0 cN / dtex to 2.69 cN / dtex, with a retention rate of 89.6%. These data demonstrate that this process successfully achieved the goal of directional surface modification without significantly damaging the internal fiber structure.

[0048] Microstructural analysis further confirmed this. Scanning electron microscopy revealed that the treated cotton wool had formed uniformly distributed micropores with diameters ranging from 0.5 to 3 μm, while the internal fiber structure remained intact. X-ray diffraction analysis revealed a slight decrease in the crystallinity index from 0.72 to 0.68, confirming that the enzymatic hydrolysis primarily affected the non-crystalline regions, preserving the essential structural properties of cellulose.

[0049] Practical application tests show that the medical absorbent cotton treated by this process performs well in wound care, with the exudate absorption rate increased by 68.5% and the liquid distribution more evenly, greatly improving the use effect of the dressing.

[0050] Example 2: Rapid Processing Process for Cosmetic Cotton Sheets

[0051] The requirements for absorbent cotton in the cosmetics industry are different from those for medical dressings, with greater emphasis on softness, fit, and comfort. To address these characteristics, the process has been adjusted accordingly.

[0052] First of all, in terms of raw material selection, we use combed absorbent cotton with a fiber length of 15-25mm and a density of about 3.2kg / m 3 The combing process makes the fibers more regular, which is conducive to producing uniform-textured cotton pads. Preliminary characterization shows that the surface of this batch of raw materials is relatively smooth, but has a high contact angle, which is not conducive to the absorption and diffusion of liquids such as lotion.

[0053] In terms of pretreatment, ultrasonic treatment has been found to be more suitable for cosmetic cotton pad production than plasma. This is primarily because ultrasonic treatment increases the surface microporous structure without excessively introducing oxygen-containing functional groups, maintaining the gentle properties required for cosmetic use. After a series of comparative experiments, the ultrasonic frequency was set at 25kHz, the power density was approximately 300W / L, and the treatment time was approximately 12 minutes. This set of parameters produces a moderate cavitation effect, uniformly altering the fiber surface structure without causing significant damage. The treatment medium is purified water, and the temperature is controlled at 35°C. This temperature maintains a good cavitation effect while avoiding the fiber denaturation that could be caused by excessively high temperatures.

[0054] To meet the special requirements of cosmetic cotton pads for a soft touch, the enzyme formula was adjusted. After multiple tests, it was found that the treatment effect was best when bromelain, pectinase, and xylanase were mixed in a ratio of 1:1.5:0.7. Compared with the medical absorbent cotton process, the proportion of pectinase was increased because pectinase can more effectively degrade the intercellular layer, making the fiber surface softer. The specific formula uses 2.0g / L bromelain, 3.0g / L pectinase, and 1.4g / L xylanase, while 0.05% non-ionic surfactant is added to enhance permeability, and 4% sorbitol is added as an enzyme stabilizer.

[0055] During enzyme preparation, note that the order of addition can also affect the final effect. The optimal procedure is to first prepare the buffer and adjust it to the target pH (6.2), then add bromelain, xylanase, and pectinase in sequence, stirring gently after each addition until completely dissolved. This method avoids enzyme denaturation or mutual inhibition caused by local high concentrations.

[0056] Considering the relatively low mechanical strength requirements of cotton pads, the enzymatic hydrolysis process was simplified to a two-stage process: the first stage, at 52°C and pH 6.2, reacts for 30 minutes to initiate surface degradation. The second stage, cooling to 35°C and adjusting the pH to 5.8 for 60 minutes, further enhances surface softness. This simplified process saves approximately 45 minutes compared to the three-stage process for medical dressings, significantly improving production efficiency.

[0057] During process implementation, the liquid-to-solid ratio was found to be a significant factor influencing the final results. By comparing different liquid-to-solid ratios ranging from 1:15 to 1:25, a ratio of 1:18 (w / v) was determined to be optimal, ensuring adequate contact while avoiding enzyme waste. Agitation was performed intermittently at a low speed of approximately 30 rpm. Excessively rapid agitation can cause tangling of cotton fibers, while too slow agitation can affect reaction uniformity.

[0058] To maintain the product's soft feel, cosmetic cotton pad production uses a pH inactivation method, rather than heat inactivation. This involves adding a dilute alkaline solution to the reaction system, adjusting the pH to around 10.5, and maintaining the pH for approximately five minutes. Compared to heat inactivation, pH inactivation has less impact on fiber softness and is more suitable for cosmetic cotton pad production. After inactivation, the fibers are rinsed three times in warm water at 35°C to ensure complete removal of any residual enzymes and reaction products.

[0059] For the drying process, vacuum drying technology was used, operating at 40°C, a pressure of approximately -0.06 MPa, and a drying time of 30 minutes. Compared to conventional hot air drying, vacuum drying effectively removes moisture at low temperatures, maximizing the fiber's fluffiness and softness, which is crucial to the user experience of the cotton pads. The final product's moisture content is controlled at 7% to 9%, slightly higher than medical absorbent cotton, ensuring a softer feel.

[0060] A comprehensive performance evaluation of the treated cotton pads was conducted. Measurements using a KES-FB4 fabric feel tester revealed a 63.4% increase in surface softness. Testing using a simulated skin model revealed a 50.2% improvement in fit. Standard tensile testing revealed an increase in tensile strength from 2.8 cN / dtex to 2.58 cN / dtex, with a 92.1% retention rate, fully meeting the requirements for cotton pad use. In actual use, the toner absorption rate increased by 55.7%, and the diffusion uniformity improved by 48.2%.

[0061] Crucially, rigorous skin irritation testing revealed that the treated cotton pads were non-irritating, meeting cosmetic-grade requirements. In a subjective evaluation test involving 36 volunteers, 89% rated the treated cotton pads as superior to commercially available products, particularly in terms of softness, fit, and lotion utilization efficiency.

[0062] Example 3: Highly absorbent medical absorbent cotton process

[0063] Certain special medical scenarios, such as wound care with high exudate levels or drug delivery applications, place extremely high demands on the absorbent cotton's adsorption capacity. To address this need, a specialized high-adsorption treatment process has been designed.

[0064] The fiber length is not less than 20mm and the density is about 3.3kg / m 3 The long-fiber absorbent cotton was used as the raw material. The long fiber structure helps form a more continuous liquid conduction network, enhancing adsorption capacity. Preliminary testing showed that the initial water absorption rate of this batch of raw materials was 11.6mL / g, significantly lower than the requirements for high-absorption applications.

[0065] In the pretreatment stage, an innovative attempt was made to combine plasma and ultrasound. This idea stems from the complementary advantages of the two methods: plasma mainly increases the oxygen-containing functional groups on the surface and improves hydrophilicity; while ultrasound mainly increases the surface microporous structure and expands the specific surface area through the cavitation effect. After systematic testing, a combined treatment scheme of plasma (oxygen, 150W, 10 minutes) followed by ultrasound (30kHz, 250W / L, 8 minutes) was finally adopted. It is worth noting that the interval between the two treatments should not be too long. It is recommended to control it within 30 minutes to maintain the surface activity state.

[0066] In response to the demand for high adsorption performance, the enzyme formula was specially adjusted. Unlike the previous two embodiments, the proportion of xylanase was increased here, while the amount of pectinase was appropriately reduced. The final ratio was bromelain: pectinase: xylanase = 1:0.5:0.67, i.e. 1.8g / L bromelain, 0.9g / L pectinase and 1.2g / L xylanase. This ratio is more conducive to forming a porous network structure on the fiber surface, enhancing liquid adsorption and retention capacity. At the same time, the buffer concentration was appropriately increased to 60mM, the pH value was set to 6.8, and 2.5mM calcium chloride was added. These adjustments all help to enhance the activity of xylanase.

[0067] To create the optimal adsorption structure, a more refined four-stage temperature and pH control strategy was adopted: the first stage, 50°C and pH 6.8, lasted 30 minutes to activate bromelain; the second stage, 45°C and pH 6.0, lasted 45 minutes to enhance xylanase activity; the third stage, 40°C and pH 5.5, lasted 60 minutes, to peak pectinase activity; and the fourth stage, 30°C and pH 7.0, lasted 30 minutes, to gradually reduce enzyme activity and precisely control the end point of enzymatic hydrolysis. Although this precise staged control is somewhat complex, it can create an optimal gradient porous structure and significantly improve adsorption performance.

[0068] During the enzymatic hydrolysis process, the liquid-to-solid ratio was found to be a key factor. After multiple comparative tests, a liquid-to-solid ratio of 1:22 (w / v) was found to be optimal for treating highly absorbent cotton wool. A too low liquid-to-solid ratio can lead to uneven enzyme distribution, while a too high ratio wastes enzyme resources and increases costs.

[0069] Considering the special requirements of highly absorbent absorbent cotton, a combination of heat and pH inactivation was employed during the inactivation process: the temperature was first raised to 75°C and held for 5 minutes, followed by the addition of a small amount of alkaline solution to adjust the pH to 9.0 and hold for 3 minutes. This combined inactivation method completely terminates the activity of various enzymes while minimizing the impact on the fiber structure.

[0070] During the cleaning process, an innovative feature was introduced: the addition of a 0.1% EDTA solution during the first rinse. EDTA, as a metal ion chelator, removes any metal ion contamination that could affect the performance and safety of the final product. Four subsequent rinses with 38°C pure water ensured the complete removal of enzymatic products and chemical residues.

[0071] For drying, fluidized bed drying (55°C, 40 minutes) is the preferred method. This technology ensures uniform hot air contact with the fiber surface, preventing localized overheating or over-humidification and maintaining the fiber's fluffy, porous structure, which is crucial for highly absorbent products. Furthermore, fluidized bed drying effectively prevents fiber clumping, improving production efficiency.

[0072] Because the wastewater contains EDTA, conventional membrane separation and enzyme recovery are limited. Therefore, a salting-out method was used to recover the enzyme preparation. The method involves adding ammonium sulfate to the wastewater to 45% saturation. After standing at 4°C for 2 hours, the precipitate is collected by centrifugation, then dissolved in phosphate buffer and dialyzed. Finally, 5% glycerol is added as a stabilizer. This method achieves a recovery rate of 83.5%, with a 72.6% retention rate of recovered enzyme activity, allowing for 3-4 cycles of use.

[0073] After the above process, the performance of the high-absorbency medical absorbent cotton was significantly improved. The surface microporosity measured by BET method increased from the original 23.5% to 39.6%, an increase of 68.4%; the specific surface area increased from 1.2m 2 / g increased to 2.2m 2 / g, an increase of 83.3%; the pore size distribution is mainly concentrated in the range of 0.5-5μm, with an average pore size of about 2.1μm; the water absorption rate measured by the conventional immersion method increased from 11.6mL / g to 24.7mL / g, an increase of 112.9%; the tensile strength changed from 3.1cN / dtex to 2.67cN / dtex, and the retention rate was 86.2%.

[0074] More importantly, the treated cotton wool exhibited excellent drug adsorption and sustained-release properties. Using roxithromycin solution as the test fluid, the adsorption capacity increased by 83.2%. In a 24-hour sustained-release test, the release curve was flatter, and the release was more uniform and controllable, making it highly suitable as a drug carrier material.

[0075] Example 4: Environmentally friendly and low energy consumption process

[0076] As environmental protection becomes more widely accepted, reducing energy consumption and pollution has become a key development direction for the industry. In response to this trend, an environmentally friendly, low-energy process has been developed. Its main innovations lie in the use of immobilized enzyme technology and microwave-assisted treatment.

[0077] Use standard absorbent cotton (fiber length not less than 12mm, density 3.4kg / m 3 ) as the experimental raw material. Taking into account the high energy consumption of traditional pretreatment methods, microwave-assisted treatment technology was tried. The microwave frequency was fixed at 2.45GHz (standard microwave equipment frequency), and multiple groups of tests were carried out with a power between 200-400W. It was found that continuous microwave treatment easily led to local overheating, so an intermittent treatment mode was adopted. The final treatment scheme was 300W power, with an intermittent mode of 10 seconds on / 20 seconds off, and a total treatment time of about 3 minutes. Although the surface activation effect of microwave treatment is slightly lower than that of the aforementioned plasma or ultrasonic methods, considering that the energy consumption is reduced by about 60% and the equipment investment cost is low, this trade-off has practical significance in large-scale industrial production.

[0078] The core innovation of this embodiment lies in the application of immobilized enzyme technology. After comparing various carriers and immobilization methods, macroporous polyacrylamide microspheres were selected as the carrier, and the glutaraldehyde covalent immobilization method was adopted. The specific operation is to first activate the carrier surface with 2.5% glutaraldehyde solution (pH 7.0), then react the mixed solution of the three enzymes (ratio of 1:0.7:0.5) with the activated carrier at 4°C for 8 hours, and finally block the remaining active groups with 1% glycine solution. After washing with PBS buffer, it can be used.

[0079] This immobilized enzyme technology offers multiple advantages. First, the enzyme activity retention rate after immobilization reaches 85%, and its thermal and pH stability are significantly improved. For example, at 50°C, the activity of the free enzyme drops to 50% after 2 hours, while the activity of the immobilized enzyme remains above 85%. Second, the immobilized enzyme is easy to recycle and reuse, greatly reducing enzyme costs. Third, the immobilized enzyme reaction can be carried out under simpler conditions, without the need for complex multi-stage temperature control.

[0080] A simplified enzymatic hydrolysis process was used: pretreated cotton wool was mixed with the immobilized enzyme at a ratio of 1:0.3 (w / w). The mixture was allowed to react at 45°C and pH 6.5 for 120 minutes, with low-speed stirring (20 rpm) to ensure uniform contact without damaging the fibers. It should be noted that the reaction rate of immobilized enzymes is generally lower than that of free enzymes, so the reaction time needs to be appropriately extended.

[0081] After enzymatic hydrolysis, the immobilized enzyme can be easily recovered by filtering through an 80-mesh sieve, with a recovery rate of up to 92%. The recovered immobilized enzyme can be directly used in the next batch of reactions after a simple rinse, eliminating the need for complex reactivation procedures and greatly simplifying the process.

[0082] The cleaning process also reflects environmental protection, using a countercurrent cleaning system and three-stage cleaning, with total water consumption of only 60% of traditional cleaning methods. Drying uses a low-temperature heat pump (45°C, 40% relative humidity, 60 minutes), which saves approximately 35% energy compared to traditional hot air drying.

[0083] After this environmentally friendly process, the surface fiber diameter of the absorbent cotton treated with this process decreased from 15.6 μm to 14.2 μm, a reduction of 9.2%. The water absorption rate increased from 10.5 mL / g to 19.6 mL / g, an improvement of 86.7%. The tensile strength decreased from 3.1 cN / dtex to 2.74 cN / dtex, with a retention rate of 88.4%. While these performance indicators were slightly lower than those of the previous embodiment, the environmental benefits were significant: compared with the traditional process, energy consumption was reduced by 45.6%, water consumption by 38.2%, wastewater discharge by 62.5%, and COD emissions by 72.3%, from 3200 mg / L to 886 mg / L.

[0084] From a long-term economic perspective, despite the high initial investment required to prepare immobilized enzymes, the ability to recycle them over five times, coupled with significantly reduced energy and water consumption, makes them more economical than traditional processes. According to estimates, the payback period is typically 12-18 months, after which stable returns can be achieved.

[0085] It is worth mentioning that the absorbent cotton produced by this environmentally friendly process performs well in biocompatibility and its cytotoxicity test results are better than those of products produced by traditional processes, which may be related to the reduced use of chemical reagents during the processing.

[0086] In order to objectively evaluate the technical effect of the present invention, two groups of comparative experiments were designed. The first is a single enzyme treatment comparison, using the same raw materials and pretreatment method as Example 1, but only using 3.0g / L bromelain for treatment. The results show that the various performances of the single enzyme treatment product are obviously inferior to those of the composite enzyme treatment: the surface fiber diameter reduction rate is only 6.2% (composite enzyme is 10.5%), the water absorption rate only reaches 15.3mL / g (composite enzyme is 22.8mL / g), the tensile strength retention rate is low, at 76.3% (composite enzyme is 89.6%), the liquid diffusion rate improvement rate is only 40.5% (composite enzyme is 72.3%), and the treatment takes longer, about 240 minutes (composite enzyme is 165 minutes).

[0087] The microstructural comparison more intuitively demonstrates the difference. The fiber surface modification after single enzyme treatment is uneven, with obvious over-degradation areas coexisting with insufficiently treated areas, while the surface modification after composite enzyme treatment is uniform and consistent. Attempts were also made to improve the effect by increasing the dosage of a single enzyme (5.0 g / L) or extending the treatment time (360 minutes), but the result was a further decrease in tensile strength to 68.5%, while the improvement in surface properties was limited, proving that it is difficult to achieve the ideal surface-directed enzymatic hydrolysis effect with a single enzyme.

[0088] The second set of comparative experiments is a comparison of processes without dynamic control. The same raw materials and compound enzyme ratios as in Example 1 were used, but the entire enzymatic hydrolysis process maintained a constant temperature (45°C) and a constant pH (6.0) for 180 minutes without stage-by-stage regulation. The results showed that it was difficult to accurately control the depth of enzymatic hydrolysis without a dynamic control process: the surface fiber diameter reduction rate was as high as 15.8% (5.3% higher than the compound enzyme, indicating excessive degradation), and the tensile strength retention rate was only 62.5% (27.1% lower than the compound enzyme). Fiber cross-section analysis showed that the degradation depth was extremely uneven, with deep degradation in some areas leading to a decrease in strength, and insufficient surface degradation in some areas affecting performance improvement. Although the process without dynamic control has a slight advantage in water absorption (23.5mL / g vs 22.8mL / g), considering all indicators, especially considering product uniformity and reliability, the dynamic control process is significantly more advantageous.

[0089] In actual industrial applications, the technology of this invention has been verified and applied by multiple companies. A medical device company, using the process of Example 1, produced a medical dressing that increased water absorption by 110% and liquid diffusion by over 70% compared to its original chemically treated product, meeting the needs of the high-end wound care market. Furthermore, the treatment time was shortened by 35%, energy consumption was reduced by 42%, and wastewater COD was lowered by 75%, resulting in significant overall economic benefits.

[0090] Another cosmetics company, using the process described in Example 2, saw its cotton pads become more softer by over 60%, adhere better by 50%, and saw customer satisfaction rise from 76% to 92%. The application of enzyme recovery technology reduced enzyme costs by 65% and product costs by approximately 12%, significantly enhancing market competitiveness.

[0091] The environmentally friendly and low-energy consumption process of Example 4 was applied in a green manufacturing demonstration enterprise, which successfully created the first zero-emission absorbent cotton processing production line in China, obtained green manufacturing certification and government funding support, and provided new ideas for the sustainable development of the industry.

[0092] Market feedback indicates that the absorbent cotton products processed with the technology of the present invention exhibit obvious advantages in multiple sub-sectors: in the medical field, wound care effects are improved, infection rates are reduced, and patient comfort is increased; in the beauty field, the user experience is improved, the utilization rate of essences is increased, and skin irritation is reduced; in special application fields such as biological sample collection and precision instrument cleaning, they also perform well.

[0093] While the initial investment in this technology is slightly higher than traditional processes, the added value, increased production efficiency, and reduced resource consumption brought about by improved product performance mean a typical payback period of 12-18 months, resulting in significant long-term economic benefits. With increasingly stringent environmental regulations and growing demand for high-performance cellulose materials, this technology is expected to be applied and promoted in a wider range of fields.

Claims

1. A method for directional enzymatic hydrolysis of the outer layer of absorbent cotton based on composite plant protease, characterized in that: The following steps are involved: Physical pretreatment of absorbent cotton was performed to enhance surface activation; a complex enzyme solution containing bromelain, pectinase and xylanase was prepared; The pretreated absorbent cotton is brought into contact with the composite enzyme solution and subjected to directional enzymatic hydrolysis under controlled conditions; the depth of enzymatic hydrolysis is controlled by adjusting the reaction temperature and pH value in stages; after the reaction is completed, the enzyme activity is terminated by heat treatment, pH adjustment or addition of chemical reagents; finally, the treated absorbent cotton is washed and dried to obtain a surface-modified absorbent cotton product.

2. The method according to claim 1, characterized in that The ratio of bromelain, pectinase and xylanase in the complex enzyme solution is 1:(0.5-2):(0.3-1), and the synergistic selective degradation of the outer layer of the absorbent cotton can be achieved through this ratio.

3. The method according to claim 1, characterized in that The physical pretreatment adopts one of the following methods or a combination thereof: plasma treatment with a power of 100-300W and a time of 10-20 minutes; ultrasonic treatment with a frequency of 20-40kHz, a power density of 200-500W / L and a time of 8-15 minutes; or microwave-assisted treatment with a frequency of 2.45GHz, a power of 200-400W and an intermittent treatment of 3-5 minutes.

4. The method according to claim 1, wherein The staged temperature regulation includes three consecutive stages: first, activating enzyme activity at 48-52°C for 30-60 minutes; then cooling to 38-42°C for 60-90 minutes to maintain moderate enzyme activity; and finally cooling to 28-32°C for 30-60 minutes to inhibit excessive reaction, thereby achieving precise control of enzymatic hydrolysis depth.

5. The method according to claim 1, wherein The staged pH adjustment sequentially undergoes three stages: in the first stage, the pH is maintained at 6.2-6.8, which is conducive to the activity of bromelain; in the second stage, the pH is adjusted to 5.2-5.8 to promote the activity of pectinase; and in the third stage, the pH is increased to 6.7-7.3 to gradually inhibit the enzyme activity and prevent excessive enzymatic hydrolysis.

6. The method according to claim 1, characterized in that The method for terminating enzyme activity is selected from: raising the reaction system temperature to 78-82° C. and maintaining it for 8-12 minutes; or adjusting the pH value to 10.0-11.0 and maintaining it for 4-6 minutes; or adding 0.1%-0.2% hydrogen peroxide solution; or a combination of the above methods.

7. The method according to claim 1, characterized in that The method further comprises an enzyme preparation recovery step: after the enzymatic hydrolysis waste liquid is subjected to centrifugal pretreatment to remove solid particles, membrane separation is performed using an ultrafiltration membrane with a molecular weight cutoff of 5-10 kDa, or salting out is performed using 40% to 60% saturation ammonium sulfate, or selective adsorption is performed using a macroporous resin; and then the recovered enzyme is concentrated and stabilized so that it can be recycled 3-5 times and the activity retention rate is not less than 60%.

8. The method according to any one of claims 1 to 7, characterized in that When used in the production of medical dressings, the process parameters include: raw material fiber length ≥ 10mm, density 3.5kg / m 3 The enzyme solution was prepared by mixing 1.5 g / L bromelain, 1.2 g / L pectinase, and 0.8 g / L xylanase with phosphate buffer (pH 6.5) and 2 mM calcium chloride. The product was pretreated with plasma (200 W, oxygen, 15 min). Enzymatic hydrolysis was performed by three-stage temperature control (50°C / 45 min → 40°C / 75 min → 30°C / 45 min). The reaction was terminated by maintaining the temperature at 80°C for 10 min. The product was then rinsed with 40°C pure water and dried with hot air at 60°C for 50 min to complete the treatment.

9. The method according to any one of claims 1 to 7, characterized in that When used in the production of cosmetic cotton pads, the process parameters include: raw material fiber length ≥ 15mm, density 3.2kg / m 3 The method comprises the following steps: preparing a combed absorbent cotton; preparing an enzyme solution consisting of 2.0 g / L bromelain, 1.5 g / L pectinase, and 1.0 g / L xylanase, and adding 0.05% nonionic surfactant; performing ultrasonic pretreatment (25 kHz, 300 W / L, 12 minutes); performing enzymatic hydrolysis by two-stage control (52°C / 30 minutes → 35°C / 60 minutes); adjusting the pH to 10.5 and maintaining the reaction for 5 minutes to terminate the reaction; and finally completing the treatment by vacuum drying (40°C, -0.06 MPa, 30 minutes).

10. The method according to any one of claims 1 to 7, characterized in that The composite enzyme solution is prepared in a manner selected from the following: preparing in a fixed ratio of bromelain: pectinase: xylanase = 1:0.8:0.5; or adjusting the ratio of each enzyme according to the characteristics of the raw materials and the performance requirements of the target product; or using a sequential addition method, first adding bromelain, and then adding pectinase and xylanase in sequence after it has acted for a certain period of time; or immobilizing the enzymes on carriers such as macroporous polymer balls or magnetic nanoparticles to form an immobilized enzyme preparation.