Industrial enzyme for textile applications .
Enzymatic treatments have gained popularity in the textile industry because of environmental friendly and energy conserving alternatives. Advancement in biotechnology and modification of enzymes has been focused based on various textile process applications. All the manufacturing steps of textile chemical processing, enzymes are using for implementations of the green technology to meet up the challenge of fourth industrial revolution. In this category, amylases, peroxidase used for desizing and bleaching, cellulase activates for bio polishing and denim finishing. This chapter summarizes the current developments of enzyme technology and highlights the environment-friendly and sustainable enzymatic textile processing in the textile industry.
- textile fibre
Enzymes are biocatalysts obtained from living cells through biochemical reactions specifically metabolic process of the cells . Enzymes obtained from the natural source since ancient times in the production of food products, such as cheese, sourdough, beer, wine, vinegar and indigo formation . The development of fermentation processes has grown during the last century, specifically for the production of purified enzymes in a large scale . The use of recombinant gene technology has improved enzyme-manufacturing processes. Most industrial enzymes occurred hydrolysis for degrading the natural substances . Enzymes are used in not only food production but also pharmaceuticals, textiles, leather processing [5, 6, 7]. There are prominent enzyme manufacturer for textile processing are listed in Table 1.
|Protease, xylanase, glucoamylase||Novozymes, Denmark||1921||Household care, textiles, food and beverages, oil and fats|
|Amylase, protease, phytase, xylanase, β-mannanase||Genencor, Denmark||1982||Food and Beverages, Textiles, Detergents, Biofuels|
|Amylases, Proteases, Cellulases, Xylanase, Pectinase||AB Enzymes, Germany||1907||Feed additives, food, textile, detergent, pulp and paper, biofuels|
|Protease, Amylase, Laccase, Catalase, Cellulase, Lipases||Dyadic, USA||1979||Food, brewing and animal feed enzymes, pulp and paper, textile enzymes|
2. Enzyme structure and its mechanism
Enzymes are amino acid based globular proteins that range in size from less than 100 to more than 2000 amino acid residues. One or more polypeptide chains can be arranged and folded to form a specific three-dimensional structure, called active site incorporate with substrate. The active site may involve a small number (less than 10) of the constituent amino acids  (Figure 1).
The hypothesis of an enzyme-substrate complex was first proposed by the German chemist Emil Fischer in 1894. The lock and key theory explained, as a key is the substrate and lock is an enzyme. Enzyme are not shown rigid structures in a crystallographic x-ray but quite flexible in shape. In 1958, Daniel Koshland presented the ‘induced-fit model’ of substrate and enzyme binding, which is also known as ‘hand-in-glove model’ .
3. Enzyme classification for textile processing
Enzymes are biocatalysts, which can speed up the chemical processes . Enzymes activates like other inorganic catalysts such as acids, bases, metals, and metal oxides. The molecule that an enzyme acts on is known as its substrate, which is converted into a product. The original attempt to classify enzymes was done according to different function. The International Commission on Enzymes (EC) was established in 1956 by the International Union of Biochemistry (IUB) in consultation with the International Union of Pure and Applied Chemistry (IUPAC) recommended hundreds of enzymes that had been discovered. The EC classification system is divided into six categories :
EC1 Oxidoreductases: catalyze oxidation/reduction reactions.
EC 2 Transferases: transfer a functional group.
EC 3 Hydrolases: catalyze the hydrolysis of various bonds.
EC 4 Lyases: cleave various bonds by means other than hydrolysis and oxidation.
EC 5 Isomerases: catalyze isomerization changes within a single molecule.
EC 6 Ligases: Join two molecules with covalent bonds.
In textile industry mainly hydrolases and Oxidoreductases are engage for various enzymatic applications. Most of the enzyme applications in textiles are confined to cotton processing: removal of impurities (desizing, scouring, bleaching); bio-finishing to improve appearance; bio-stoning or stone washing of denims to produce the fashionable aged look; bleaching cleanup to remove residual H2O2 before dyeing [13, 14, 15, 16, 17]. In addition to that there are efforts to substitute conventional processes of anti-shrinking, anti-pilling wool & degumming of silk with protease enzyme, retting of bast fibers with pectinase or hemicelluloses the several studies have been reported on modification of synthetics using hydrolases class of enzymes to impart hydrophilicity and antistatic properties [18, 19]. Moreover, detergent with the mixture of enzymes to remove varieties of stains in garments laundering . Textile chemical processing is highly chemical intensive, and a variety of complex chemicals & auxiliaries are regularly used. So, mixed color to water causes toxicity for different form of life. It is essential to treat the effluent specially the residual colorants before discharging in environment. Hence, different enzymes employed for the textile effluent treatment containing synthetic dyes as colorants has been used. International Union of Biochemistry and Molecular Biology set up the Enzyme Commission for solving the complexity of and inconsistency in the naming of enzymes. They proposed almost 7000 enzymes; however, 75 are commonly used in the textile industry  According to the use of enzymes in textile industries, enzyme can be classified as shown in Table 2.
The group of hydrolases enzyme includes amylases, cellulases, pectinases, proteases and lipases. In addition, hydrolases enzymes mainly act as hydrolysis. For isolating microbial strains that produce the desired enzyme and optimizing the conditions for growth, commercial quantities can be obtained. This technique, well known for more than 3,000 years is called fermentation .
α-amylases are produced from different fungi, yeasts and bacteria. The different microorganisms from α-amylases are listed in Table 3.
|EC digit||Enzyme groups||Enzyme class||Reaction type|
α-amylases are quite stable over a wide range of pH from 4 to 11. Optimum temperature for the activity of α-amylases is usually applied for modified microorganism. Addition of Ca2+ cans enhances thermo stability .
Commercial desizing compound under name Rhozyme DX, Rhozyme GC, Diastafor LCD (Bacterial α-Amylases) is more suitable for desizing compared to β-amylase from crude Barley & amyloglucosidase from (
Cellulases are hydrolytic enzymes that breakdown the cellulose to form oligosaccharides and finally glucose. Cellulase combining at least three types of enzyme for working synergistically on cotton (Figure 3).
The length of cellulose chains cleaves endogluconases or endocellulases in the middle of the amorphous region. However, exo-cellulases start their action from the crystalline ends of cellulose chains and convert to glucose by β-4-glucosidase . These enzymes are commonly produced by soil-dwelling fungi and bacteria (Table 4).
A temperature range from 30 to 60o C is an active condition for cellulase. According to pH sensitivity, cellulase enzymes are classified in different categories such as acid stable (pH 4.5–5.5), neutral (pH 6.6–7) or alkali stable (pH 9–10) . Cellulase obtained from
Alkali Cellulase (
Suhong 89 from Acid cellulase efficiently removes indigo from denim surface with minimum hydrolysis & possibility of cellulase reuse .
Pectinase are complex enzymatic group that degrade the pectic substances. They are produced from saprophytes and plant pathogens which can degrade the plant cell walls. There are three major classes of pectin degrading enzymes are pectin esterases, polygalacturonases and polygalacturonate lyases .
Pectin Esterases: Pectin esterases liberate pectin and methanol by de-esterifying the methyl ester. Their activity is highest on 65–75% methylated pectin, is to act on methoxy group adjacent to free carboxyl group. Its action has very little effect on the molecular weight of the pectin (Figure 4).
Pectin esterases active in the pH range of 4–8 and optimal temperature range for maximum activity is 40-50o C.
Polygalacturonases: Polygalacturonases reduce the molecular weight of the pectins. They catalyze the hydrolytic cleavage with the introduction of water across the oxygen. They are classified further as endo-galacturonases and exo-galacturonases (Figure 5).
Polygalacturonases obtained from different natural sources with respect to physiochemical and biological properties as well as their mode of actions.
Pectin Lyases: Pectin lyases depolymerise the pectin. These catalyse the trans-eliminative cleavage of the galacturonic acid polymer. It can break down the glycosidic linkages at C-4 and eliminate H from C-5 position (Figure 6).
Pectin esterases, polygalacturonases and pectin lyases are mainly produced in plants such as banana, citrus fruits and tomato, but also by bacteria and fungi (Table 5).
Bioprep 3000 L, Novozyme acts as alkaline pectinase are efficiently remove impurities formed uniform dyeing consistency & equivalent color depth with different direct dyes . Pectinase from
Proteolytic enzymes produced by microorganisms are mixtures of endo-peptidases and exopeptidases. The simplified form the action of the proteases are (Figure 7).
Microbial proteases obtained from the plant source such as papain, ficin, and the animal proteases obtained from pepsin and trypsin. Microbial proteolytic enzymes obtained from different fungi and bacteria. Most fungal proteases activate in a pH range (about 4 to 8), and bacterial proteases generally work best over a range of about pH 7 to 8  (Table 6).
Proteases with cellulase (Commercial Enzyme) mixture perform for bioscouring and optimized using ANN technique to achieve desired absorbency and pectin removal . Proteases (
Esterases represent a group of hydrolases that catalyse the cleavage of fats, oils and formed ester bonds. They are widely obtained from animals, plants and microorganisms. These enzymes make attractive biocatalysts for the production of optically pure compounds in fine-chemicals synthesis. Lipases have three-dimensional structure with the characteristic α/β-hydrolase fold . The phenomenon of interfacial activation can be distinguished by lipases and esterases. The interfacial activation is due to hydrophobic domain covering the lipase active site and the presence of a substrate concentration will lid open, making the active site accessible. It can be used for elimination of natural triglycerides in scouring and tallow compounds in desizing process . The phytopahthogenic fungus is the best examples of lipases are shown in Table 7.
Arylesterase obtained from Bio-bleach system HUNTSMAN and H2O2 in situ generate peracetic acid for mild temperature at 65o C, neutral bleaching of cotton . Lipase enzymes perform both bio-scouring and bio-bleaching, which provide high degree of whiteness .
The enzymes catalyze oxido reduction reactions, transfer electrons through substrates like cellulose. In the majority of cases, the substrate that is oxidized is regarded as a hydrogen donor. The systematic name of oxidoreductases is based on donor acceptor groups. The enzymes named oxidase, which contains molecular oxygen (O2) is the acceptor.
Oxidoreductases enzymes categorize two nonhydrolytic enzymes such as peroxidase and catalase.
3.2.1 Peroxidase/glucose oxidase
Glucose oxidase or peroxidase acts in the presence of oxygen to convert glucose to gluconic acid and hydrogen peroxide. It can oxidize only β-D-glucose (Figure 8).
The galactose oxidase (GO) from
Peroxidase is synthesized in several species of fungi and bacteria are illustrated in Table 8.
Glucose-Oxidase desize cotton fabric and enzymatically produce peroxide for bleaching at elevated temperature with high pH . Combined glucose, glucose-oxidase & peroxidase for cotton bleaching . Glucose-oxidase (Commercial Novo Nordisk- Denmark) optimized bio-bleaching of cotton, linen and their blends with 25 U/ml GOE, 10 g/l D-glucose at 85o C & pH 10 for 90 min . Glucose-Oxidase (
Catalases are ubiquitous oxidoreductases enzymes present in archaea, bacteria, fungi, plants and most have optimum temperatures (20-50o C) and neutral pH. Catalases obtained from animal sources (bovine liver) are generally cheap; therefore, the production of microbial catalase will be economically advantageous when recombinant technology is used. Catalases have special properties such as thermosatbility and operate both in alkaline or acidic pH. The chloroperoxidase from
Glucose-oxidase (multifect GO 5000 L, Genecor), Catalase (Terminox Ultra 10 L) integrated desizing, bleaching and reactive dyeing of cotton towel was performed .
Laccase originated from blue-multicopper oxidase family. It oxidizes a variety of aromatic and non-aromatic phenolic compound also depolymerizes the substrate by a radical-catalyze reaction mechanism.
Laccases have been found in plants, fungi, insect and bacteria. However, more than 60 fungal strains have found laccase activity. Fungal laccase is a protein approximately 60–70 KDa, which activate in the acidic pH range and optimal temperature between 50 and 70o C. Few laccases enzymes activate with optimum temperature below 35o C (Table 10).
Combined laccase/peroxide bleaching applied in batch & pad dry method . Laccase from
4. Textile applications
The enzymatic textile processing has started in the middle of nineteenth century. The enzymes were introduced in de-sizing purposes for the first time in 1857; however, enzymatic de-sizing process was successfully introduced in 1912 . In addition, cellulases were introduced in 1980s for de-pilling and de-fuzzing of cellulose-based fabrics . In the early 1990s, catalases were entered into the bleaching and pectin-degrading enzymes to replace traditional alkaline scouring . In biotechnological research is underway, around the globe, introduce environmental friendlier strategies for textile processing is extensively to the modern industry. The potential of enzymatic textile processing is illustrated in Figure 11.
5. Enzyme used in textile wet processing
The cotton warp yarns are sized to improve the yarn strength. Besides help in the interweaving during the procedure, it protects yarn against abrasion and snagging. Mostly starch-based products are used to apply sizes, synthetic and semi-synthetic sizes are polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) used [104, 105, 106]. The purpose of size is to protect the yarn from the abrasive action of weaving loom.
Desizing is the first step for wet processing in textile finishing technology employed to remove sizing material from the fabric. The size must be removed before bleaching and dyeing, for uniformity of wet processing. Chemically, starch is poly-α-glucopyranose in which amylase and amylopectin are present. However, they are insoluble in water. They can be solubilized by hydrolyzing them to shorter chain compounds. The object of desizing is to convert starch to soluble dextrin. The stages of hydrolyzing are mentioned below:
Starch (insoluble) → dextrin (insoluble) → dextrin (soluble) → maltose (soluble) → α-glucose (soluble)
Types of desizing methods
Enzyme desizing is the most widely practiced method of desizing starch.
In textile terminology “scouring” applies to the impurities removal process. Raw cotton contains about 90% of cellulose and various non-fibrous impurities such as dirt, oils, waxes, gums and seed fragments. Pectins are complex polysaccharides comprised of α-(1, 4) linked D-galacturonic acid backbone. Pectin is non-cellulosic substance in cotton acts as cementing/adhesive material; therefore, removing pectin, will enhance to remove other non-cellulosic substances. In scouring process, the target fabric is usually boiled in the presence of alkali solution using large iron-made vessels called kiers. Classic alkaline scouring using sodium hydroxide removes most of such contaminations, essential to achieve satisfactory wet-ability. In textile processing, the process based on extensive alkali consumption requires heavy rinsing which ultimately leads several by-products in the wastewater effluent and poses severe damage to the cellulose contents of the fabric [110, 111].
The process of bio scouring is based on the concept of decomposition of pectin using enzyme. Bio scouring is ecofriendly, energy conserving alternative based on the idea of specially targeting the non-cellulosic impurities with appropriate enzymes without adversely affecting the substrate. Natural properties of the cotton fiber are preserved; the fabric is softer to the touch than after classic scouring. Pectinases enzyme activate in two medium acidic and alkaline. Acidic pectinases that function in a slightly acidic medium (pH between 4 and 6), as well as alkaline pectinases that function in a slightly alkaline medium (pH between 7 and 9) . Optimum enzyme concentration varies from pectinase to pectinase but in general, pectinases are effective in low concentrations 0.005–2% range. In addition, the optimum temperature of pectinases application is form 40-60o C beyond which enzyme reduces its activity . A high temperature rinsing after bio scouring is required for the removal of waxes (Figure 12).
Mixed enzymatic treatments of unscoured cotton fabric conducted by German scientists involved pectinase, cellulase, protease, and lipase. Beside the temperature, the pH of the environment is crucial for the activity and stability of the enzyme. An assistance of lipases removes natural fats & lubricants for better absorbency and levelness in dyeing. Bio-scouring for mutations containing lipase are more effective in attaining good hydrophilicity for cellulosic textiles . In recent years, pectinases have been immobilized by ion exchange resins, aminated silica gel and macroporuos polyacrylamide for cotton scouring.
Bleaching is a process for improving the whiteness of textile materials with or without removing the natural coloring matter or extraneous substances. Bleaching produces permanent and basic white effect on fabric, which is required for level dyeing and sharp printing. Among the different oxidizing and reducing bleaching agent, H2O2 is mostly used as a universal bleaching agent from last two decades. The dissociation of hydrogen peroxide increased with rising temperature and form perhydroxyl anion shown in Figure 2. Perhydroxyl ions (HO2−) demobilize the mobile electrons of conjugated double bonds in chromophores and caused decolorization. However, hydrogen peroxide bleaching process required high temperature and long processing time, which leads to higher energy consumption and increased fiber damage, which would cause problems in dyeing  (Figure 13).
Many researchers explored the alternative eco-friendly bleaching method for cotton processing, such as laccase/mediator or glucose-oxidase/peroxidase and bleaching with enzymatically in situ generated per acids. Lacasses with copper containing oxidoreductases enzymes used for bio bleaching to bleach textiles, modify fabric surfaces and coloration of cotton . Another important bio-bleaching method for producing H2O2 is glucose oxidase. Generation of peroxidase with glucose oxidase requires slightly acidic to neutral conditions at low temperatures, however these conditions is insignificant. In addition, at the temperature 80-90o C and alkaline pH 11, glucose oxidase provides efficient results for improving the whiteness of the cotton fabric . On the other hand, in addition of bleach activators such as Tetraacetylethylenediamine (TAED), nanoyloxybenzene sulphonate (NOBS), N-[4-(triethyl ammoniomethyl) benzoyl] caprolactum chloride (TBCC) enhances the bleaching performance. Combined laccase and glucose oxidase can perform better bleaching effect on linen fabric (Table 11).
5.4 Bleach clean up
In textile industry, bleaching is carried out by H2O2 after scouring and before dyeing. However, 10–15% of H2O2 retains on fabric, which can degrade the cellulose and formed pinhole on the fabric surface, it can reduce the strength of fiber. Different reducing agent is used to destroy the hydrogen peroxide, or water to rinse out the hydrogen peroxide bleach. However, catalase enzyme can now be used to decompose excess H2O2 . This eliminates the use of strong reducing agent and minimizes the water consumption. The cost of enzyme for degradation of hydrogen peroxide in bleaching effluents could be reduced by the immobilized catalase enzymes . The process of bleach clean-up is very straightforward. A summary of the methodology is- 1) Drain the bleach liquor after bleaching 2) Fresh cold water filled 3) Maintain the pH is in the range 6.5–7 and the temperature 45o C 4) Add catalase (
5.5 Removal of excess dye
The dye removal process from over dyed fabric is called as “back stripping” or “destructive stripping”. Bio-enzymes used for decolorization is lignin peroxidase, manganese peroxidase and laccase. Previous studies have been investigated for color stripping from dyed textile fabric by microbial strains and their non-specific enzymatic system. The catalase enzymes from
The enzymes used for textile ETP are laccase, manganese peroxidase, lignin peroxidase and tyrosinase. These enzymes can catalyze the chlorinated phenolic compounds and halogenated organic compounds .
The process of removal of micro, fuzzy fibrils from the fabric surfaces through the action of cellulase enzyme is called bio polishing. It enhances the color brightness, hand feel, water absorbance property of fibers; strongly reduce the tendency for pill formation . Cellulase enzymes are widely used for bio polishing.
Cellulases enzymes hydrolyze the cellulose structure by degrading β-(1-4) glycosidic linkages. Endocellulases cleave bonds along the length of cellulose chains in the middle of the amorphous region, exoglucanases act from the crystalline ends of cellulose chains and convert soluble oligosaccharides to glucose. Commercially available cellulases enzyme for bio polishing are a mixture of endogluconases, exoglucanases & cellobioses (Table 14).
Bio polishing is done before or after dyeing to the cotton, fabrics influence dye-ability, besides improving the appearance and handle properties. Cellulase enzyme treatment enhances the post dyeing effect and resin finishing with increases softness. Endoglucanases with acid cellulase are suited for bio polishing of cellulosic fabrics . The enzymatic hydrolysis of cotton also enhanced by mechanical action with the addition of surfactant. For bio polishing acid and neutral cellulases bath is maintained at 4.5–5.5 and 7 respectively, the process is heated at 55o C. Finally, the process is terminated at the temperature 85o C. The immobilization of cellulase can restrict its action to fiber surface. Various immobilization of cellulases enzyme methods improve thermal stability and reusability .
6. Denim manufacturing
Due to special fading effect and aging process, denims became the most popular fashion trends in recent times. For increasing softness of denim garments usually pumice stones washing are using. However, the use of natural pumice stones has many disadvantages; it can cause severe physical damage to garments, machine and stone dust can clog the machine drainage lines and large amount of back staining on the fabric. In addition, the complete rid of pumice stones; several wash is required for denim fabrics. It causes high water consumptions [126, 127].
6.1 Denim wash using neutral cellulase
Cellulase enzyme application on denim finishing has started in the late 1980s. Cellulase enzyme can remove trapped indigo dye from the denim fabric, which causes non uniform shade fading & worn looking. Bio washing with cellulase enzyme is an ecofriendly and superior quality for denim fabric. Application of neutral cellulases enzyme is active in a wide temperature range from 30o to 60o C and based upon their application pH 6.6–7 cellulase [128, 129].
6.2 Denim bleaching using laccase/mediator
Eco friendly denim bleaching has been originated in the late 1980s due to adverse effect of the conventional chemical bleaching process. By oxidizing the flavonoids of denim fabric, laccase enzyme can enhance the whiteness of the fabric. Enzymatic bleaching system leads not only damage of the denim fabric but also save water consumption. There are some successful industrial laccase enzymes for denim bleaching are used as DenLite®from Novozyme (Novo Nordisk, Denmark) and Zylite from the company Zytex (Zytex Pvt. Ltd., Mumbai, India) .
7. Modification of synthetic fiber by enzyme
Even though synthetic fibers are mostly hydrophobic, however improving the hydrophilicity along with some properties such as weaving comfort, anti- pilling, dyeability, antistatic charge generation by Enzymes are used. Different classes of enzymes such as cutinases, lipases and esterases are suitable for polyester modification. Less potential for surface hydrolysis of polyester modification were esterases. Esterases from
Laccases with a mediator have been performed to increase the hydrophilicity of nylon 66 fabrics . For improving dye bath exhaustion with reactive and acid dyes on Nylon 66 fabrics were treated by proteases from
8. Enzymatic treatments of ETP in textile industry
Textile effluents are usually highly colored, presenting different chemical substances when discharged into waters after finishing processes. Textile effluents can be discolored through physical, chemical and biological technologies. Several researches have been carried out for the removal of dyes from industrial effluents by chemical, physical and biological techniques. The decoloration dyestuffs and recalcitrant compounds using some biological techniques such as anaerobic, aerobic and combined process . WRF are the principal organisms which have been investigated for dye degradation and decolorization purposes. The major lignin mineralizing enzymes of WRF are LiP, MnP and laccase that are involved in dye degradation . Other than these enzymes many oxidase including versatile peroxidase, glyoxal oxidase, aryl alcohol oxidase and oxalate decarboxylase can perform dye degradation . Toxic organic compounds can be detoxified through oxidative coupling is mediated with oxidoreductases. The detoxification of toxic organic compounds through oxidative coupling is mediated with oxidoreductases . Enzymes like laccase, manganese peroxidase and lignin peroxidase catalyze the removal of chlorinated phenolic compounds . Microbial oxygenases, such as monooxygenases and dioxygenases are active against a wide range of compounds .
Enzymes have tremendous progress in textile chemical processing to meet up the green and sustainable demand in 21st century. There are several commercially successful enzymes are amylases, cellulases, pectinases and catalase for textile wet processing. Enzyme immobilization is another important technique for highly efficient textile processes. This chapter highlights the integration of enzyme based bio-treatments in textile processing. In this context, different enzymatic processes have already been developed or in the process of development for textile processing. In this regard, this chapter summarizes current developments and highlights the environment-friendly enzymatic applications. So, extensive research is required for the implementation of enzyme-based processes for both synthetic and natural fibers. Due to wide variations in the properties of individual enzymes and their reaction mechanism, there are still considerable and reliable tools for potential applications in different textile processing.
Conflict of interest
The authors have declared no conflicts of interest.