The application of cellulase in cellulose fiber fabric finishing, including cotton fabric refining processing, cellulose fiber fabric softening finishing, polishing finishing, denim fabric rejuvenation finishing, Lyocell fiber defibrillation treatment, pointed out that cellulase Problems in textile processing applications.
Introduction to cellulase
Biological enzyme preparations are widely used due to their high efficiency, specificity, mild action conditions and environmentally friendly processing. In textile dyeing and finishing processing, cellulase is the most widely used and most successful enzyme preparation.
Cellulase is a general term for a group of enzymes that catalyze the hydrolysis of cellulose and produce glucose. At present, commercial cellulases are mainly produced by fermentation of strains of two genera, Trichodermaspp and Aspergillusniger.
According to their properties and functions, each component of the cellulase system can be divided into three major categories:
(1) Endoglucanase (endo-1, 4 -D-vlucanase, EC3.2.1.4, abbreviated as EG from fungi, abbreviated as Cen from bacteria). This enzyme can randomly hydrolyze p-l, 4-glycosidic bonds in the cellulose macromolecular chain to form new reducing ends;
(2) Exoglucanase (exo-l, 4-p-D- jucanase, EC3.2.1.91, abbreviated as CBH from fungi, abbreviated as Cex from bacteria). The enzyme hydrolyzes along the ends of the cellulose chain and releases cellobiose in sequence;
(3) p-glucosidase (3-D-~lucosidase, EC3.2.1.2l, referred to as BG), also known as Cellobiase. The enzyme mainly hydrolyzes cellobiose, oligosaccharides and oligosaccharides produced by endoglucanase and exoglucanase to generate glucose.
In the 1980s, American scientists first applied cellulase to cotton fabric finishing. Subsequently, researchers from various countries conducted many studies on the application of cellulase in textile processing. At present, cellulase has been successfully used in the pre-scouring treatment, softening finishing, polishing finishing and denim finishing of cellulose fiber fabrics.
Application of cellulase in finishing of cellulose fiber fabrics
1. Application of cellulase in scouring of cotton fabrics
After desizing, cotton fabrics still have most of the natural impurities (cotton seed hulls, pectin, waxy substances, proteins, etc.), sizing and oil residues, resulting in poor wettability and yellowing of the fabric, affecting the fabric. appearance, feel and subsequent processing. Therefore, cotton fabrics need to be scouring after desizing to remove natural impurities. The traditional alkali scouring process of cotton fabrics has shortcomings such as high energy consumption, large wastewater emissions, and serious fiber damage, and it no longer meets the requirements of modern green textile processing.
Using cellulase for refining processing is an important research direction for scientists from various countries. Cellulase can hydrolyze cellulose, causing the tiny fibers with impurities attached to them to hydrolyze and weaken, and then fall off from the fabric under mechanical action to achieve the purpose of removing impurities. Cellulase can also degrade cotton seed hulls on cotton fibers.
Hu Yingqing’s research on the degradation of cotton seed husks by cellulase found that when cellulase treated pure cotton seed husk scraps, the degradation rate was as high as 80%, which provided a theory for cellulase to remove residual cotton seed husks from cotton fabrics. support. Csiszfir et al. began studying the application of cellulase in cotton fabric scouring in 1998, and found that cellulase pretreatment of cotton fabrics can improve the effect of alkali scouring. After combined treatment, the weight loss rate of cotton seed hulls reached about 80%. The team also conducted research on the degradation of cotton seed hulls by commercial cellulase and found that commercial cellulase can directly degrade cotton seeds on the surface of cotton fabrics. They also found that the chelating agent EDTA can increase the ability of cellulase to degrade cotton seed hulls.
Although cellulase treatment of cotton fabrics can achieve the purpose of removing impurities to a certain extent, the effect is not very ideal. In order to further improve the effect of enzyme scouring, more and more studies are using cellulase combined with other enzyme preparations (pectinase, protease, lipase, xylanase, cutinase, etc.) for scouring cotton fabrics. In complex enzyme preparations, the synergistic effect between various enzyme components enables impurities to be hydrolyzed more and faster.
At present, enzymatic scouring of cotton fabrics has not been widely promoted and applied, mainly because the treatment effect of enzyme scouring, especially in the removal of cotton seed hulls, cannot achieve the effect of traditional alkali scouring, and thus cannot replace it. Alkali refining.
There are many reasons for the poor enzymatic refining effect. First, the impurity components on cotton fabrics are very complex, which makes it difficult for a single enzyme component to degrade them, requiring the synergistic action of multiple enzymes; secondly, , when multiple enzymes work synergistically, due to the inconsistent optimal conditions for various enzyme-catalyzed reactions, it is difficult to ensure that each component enzyme can play a good catalytic hydrolysis effect; finally, some enzyme preparations have not yet been commercialized, such as if The enzymatic activity of laboratory engineered enzymes such as gelatinase and cutinase is not high yet, which limits the research on enzymatic refining. In short, enzymatic refining still requires further research and exploration by scientists.
2. Application of cellulase in softening and finishing of cellulose fiber fabrics
Biological softening is the use of cellulase to soften cellulose. The hydrolysis of fibers reduces the stiffness of the fibers and improves the softness of the fabric.
Yanv et al.’s research shows that using cellulase to treat cotton fabrics after durable pressing can improve the feel of the fabrics, but will result in a decrease in the strength and wear resistance of the fabrics. In his doctoral thesis, Wu Zanmin studied the use of a combined bio-chemical method to achieve ultra-soft finishing of cotton fabrics. In this researchApplication
Lyocell fiber, also known as Tencel fiber, uses NMMO, a tertiary amine oxide, as a solvent to dissolve cellulose to produce a spinning liquid, and then spins it into shape. Because the solvent can be recycled, it does not pollute the environment. , known as the green fiber of the new century. In addition, Lyocell fiber also has the advantages of soft hand feel, good hygroscopicity, and good strength.
The fibrillation of fibers refers to the process in which some giant fibrils on the fiber surface are peeled off from the main body of the fiber and then split into fine microfibrils after wet friction between fibers or other objects. Cellulose fibers commonly suffer from fibrillation problems, among which Lyocell fiber has the most serious degree of fibrillation during use. After the fibers in the fabric are fibrillated, the fabric is prone to pilling and has poor dyeing gloss, which seriously affects the quality and wearing performance of the fabric.
Cellulase is used to hydrolyze the microfibrils on the surface of Lyocell fiber, gradually weakening them. Under the synergistic effect of machinery, they can be broken and removed to achieve the purpose of fiber defibrillation. Research by Morgado and others found that short-term treatment of Lyocell fabrics with cellulase cannot remove microfibrils and villi on the fiber surface of the fabric, but has a tendency to aggravate fibrillation. However, after extending the cellulase treatment time, the microfibrils and villi on the fiber surface will be removed. In addition, research has confirmed that mechanical action plays a very important role in this finishing process. Kumar et al. used cellulase to treat Lyocell fabric and found that the handle, drape and surface gloss of the treated fabric were improved. Research by Younsook et al. shows that dilute alkali pretreatment can further improve the defibrillation effect of cellulase treatment on Lyocell fibers.
6. Problems in the application of cellulase in textile processing
Although cellulase has many advantages in textile processing applications, there are still Some problems restrict its further large-scale application.
1. The fabric strength loss is large after treatment
Cellulase contains three different enzyme components, endoglucanase, exoglucanase, fiber disaccharidase. Under the synergistic action of the three enzyme components, the amorphous and crystalline regions of cellulose fibers can be hydrolyzed. When three enzyme components exist at the same time, they tend to gather together and act on the same location on the fiber. Therefore, after the fiber is hydrolyzed by cellulase, “potholes” and partial cracks will appear in local areas of the fiber. In addition, cellulase molecules can diffuse into the fiber and cause damage to the inside of the fiber. Since the hydrolysis of cellulase will destroy the cellulose fibers that make up the fabric without restriction, the strength loss of the fabric after enzyme treatment will be excessive.
2. The cost of enzyme preparations is high
Compared with the cost of traditional chemical treatment, the price of enzyme preparations is relatively high. The profits of the textile industry are not high, and the high price of enzyme preparations affects their widespread application.
3. The enzyme has poor stability and poor process reproducibility
Since cellulase enzyme activity is difficult to maintain stable, changes in storage conditions and storage time The length, etc. will have an impact on it. In addition, cellulase enzyme activity is very sensitive to processing temperature and pH, and slight fluctuations will affect it. In textile processing, although the conditions for enzyme treatment are kept the same for each batch, the quality of the fabric after processing is difficult to remain consistent.
Summary: Although there are still some problems in the application of cellulase in textile processing, with the continuous development of commercial cellulases and the continuous advancement of technology and technology, its The application range in cellulose fiber fabric finishing will be expanded, and it has great development potential and broad application prospects in textile processing.
Author: Yu Yuanyuan, Wang Qiang, Fan Xuerong, School of Textile and Clothing, Jiangnan University</p
