Application of Enzyme in Textile Wet Processing Technology

Last Updated on 23/08/2021

What is Enzyme?
Enzyme is a living organism. Enzymes are active compounds characterized by their function as well as by their molecular structure. In previous article, we have discussed about enzymes in details. Now we will explain uses or application of enzymes in textile chemical processing. Enzymes vital to existence of life also plays important role in many aspects of life. Humankind has used enzymes for thousands of years to carry out important chemical reactions for making products such as cheese, beer, and wine. Bread and yogurt also owe their flavor and texture to a range of enzyme producing organisms that were domesticated many years ago. Enzymes are proteins, which act as a catalyst in many chemical reactions present in almost all life forms.

different types of enzymes
Fig: Different types of enzymes and their microscopic structures

With the increasingly important requirement for textile manufacturers to reduce pollution in textile manufacturing, the use of enzymes in the chemical processing of fibers and textiles is rapidly gaining wider recognition because of their non-toxic and eco-friendly characteristics. They can be safely used in a wide selection of textile processes such as de-sizing, scouring, bleaching, dyeing and finishing, where the alternatives are very harsh chemicals whose disposal into the environment causes many problems.

Textile processing with enzymes aims to provide the textile technologist with an understanding of enzymes and their use with textile materials and in process engineering. It covers all the relevant aspects of textile processing with enzymes, from the chemical constitution and properties of textile materials as potential substrates for enzymes, to the processing of these materials; from basic biochemistry and enzymology to the industrial application of these biocatalysts.

Uses / Application of Enzymes in Textile Chemical Industry:
In different chemical process of textile wet processing, enzymes are widely used, the important sectors are highlighted below:

  1. Enzymatic Desizing
  2. Bio-Scouring
  3. Bleaching
  4. Garment Washing
  5. Dyeing
  6. Finishing
enzyme in textile processing
Fig: Enzyme in textile processing

A. Enzymatic Desizing:
Previously, in order to remove the size, textiles were treated with acid, alkali or oxidising agents, or soaked in water for several days so that naturally occurring microorganisms could break down the starch. However, both of these methods were difficult to control and sometimes damaged or discoloured the material. But by using enzymes, which are specific for starch, the size can be removed without damaging the fibers. This process is called enzymatic desizing.

Enzymatic desizing is the process of degrading starch size on cotton fabrics using enzymes. Enzymes are complex organic, soluble biocatalysts formed by living organisms that catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a particular substance. A small quantity of enzyme is able to decompose a large quantity of the substance it acts upon. Enzymes are usually named by the kind of substance degraded in the reaction it catalyzes.

Amylases are the enzymes that hydrolyze and reduce the molecular weight of amylose and amylopectin molecules in starch, rendering it water soluble enough to be washed off the fabric. Amylase enzymes are highly effective catalysts for the hydrolysis of the amylose and amylopectin components of the starch.

Effective enzymatic desizing requires strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant. Normal types are applied for several hours at 65–70°C.

Thermostable hydrolytic enzymes have been introduced, allowing brief dwell times at temperatures up to 120°C. Common salt and calcium ions increase the rate of hydrolysis but amylase is deactivated by copper or zinc ions, as well as most anionic surfactants.

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There is some interest in the use of pectinases as scouring agents and lignases to degrade the lignin in bast fibers, but as yet no commercial processes have been developed.

Enzymatic desizing represented great progress, therefore, when crude enzyme extracts in the form of malt extract, or later, in the form of pancreas extract, were first used to carry out desizing. Bacterial amylase derived from Bacillus subtilis was used for desizing as early as 1917. Amylase is a hydrolytic enzyme which catalyses the breakdown of dietary starch to short chain sugars, dextrose and maltose.

B. Bioscouring:
Scouring (the process of removing natural waxes, pectins, fats and other impurities from the surface of fibers), which gives a fabric a high and even wet ability so that it can be bleached and dyed successfully. Today, highly alkaline chemicals (such as caustic soda) are used for scouring. These chemicals not only remove the non-cellulosic impurities from the cotton, but also attack the cellulose leading to heavy strength loss and weight loss in the fabric. Furthermore, using these hazardous chemicals result in high COD (chemical oxygen demand) and BOD (biological oxygen demand) in the wastewater.

Recently a new enzymatic scouring process known as ‘Bio-Scouring’ is being used in textile wet processing with which all non-cellulosic components from native cotton are completely or partially removed.

Bioscouring is a process in which alkali-stable pectinase as the enzyme is applied to selectively remove pectin and waxes from cotton fibers. By hydrolyzing the pectin material between the waxes and the fiber surface, the enzyme exposes the waxes to emulsification when the scouring bath temperature exceeds their melting range. Bioscouring does not eliminate motes (cottonseed fragments) or the natural colour of the cotton, which can be beneficial when scouring for a natural look.

After this Bio-Scouring process, the cotton has an intact cellulose structure, with lower weight loss and strength loss. The fabric gives better wetting and penetration properties, making the subsequent bleach process easy and giving much better dye uptake.

C. Bleaching:
When bleaching cotton, a lot of chemicals, energy and water are part of the process. The company Huntsman has developed a wetter/stabilizer that maximizes the wetting and detergency of the bleaching process and a one-bath caustic neutralizer and peroxide remover in order to shorten the bleaching cycle, reduce energy and water required and deliver more consistent bleaching results. They have developed surfactants that are environmentally friendly (in that they do not contain Alkylphenol ethoxylates), and the system is both Oeko-Tex and GOTS approved. After fabric or yarn bleaching, residues of hydrogen peroxide are left in the bath, and need to be completely removed prior to the dyeing process, using a step called bleach cleanup. The traditional method is to neutralize the bleach with a reducing agent, but the dose has to be controlled precisely. Incomplete peroxide removal results in poor dyeing with distinct change of color shade and intensity, as well as patchy, inconsistent dye distribution. Enzymes used for bleach clean-up ensure that residual hydrogen peroxide from the bleaching process is removed efficiently – a small dose of catalase breaks hydrogen peroxide into water and oxygen. This results in cleaner waste water and reduced water consumption.

Bleaching with glucose, sulphinic acid derivatives and recently with laccase (enzyme) is being developed as an alternative. Laccase enzyme belongs to the oxidoreductase group. Laccase’s oxidative effect is complex and it does not work independently. A mediator is necessary and a chemical mediator is employed between the enzyme and indigo.

D. Garment Washing:
Enzymes have been used increasingly in the textile washing industry since the late 1980s. Many of the enzymes developed in the last 20 years are able to replace chemicals used by mills. Different types of washing such as enzyme wash, stone enzyme wash etc enzyme are used largely. The first major breakthrough was when enzymes were introduced for stone washing jeans in 1987 – because more than one billion pairs of denim jeans require some sort of pre-wash treatment every year. Within a few years, the majority of denim finishing laundries had switched from pumice stones to enzymes.

Enzyme wash is used to get the old or used appearance on garments. Garments are washed inside a washing machine with enzymes. Enzyme wash is performed with a kind of live cell, which can break some of the fibers of fabric and can give the fabric a special effect, desired on the garment. Enzyme wash provides the fabric a soft, sanded or ‘peached’ effect that is very desirable on many garments. Enzyme wash is also useful for indigo denims.

E. Dyeing:
Today, enzymes are used to treat and modify fibers, particularly during textile processing and in caring for textiles afterwards. They are used to enhance the preparation of cotton for weaving, reduce impurities, minimize “pulls” in fabric, or as pre-treatment before dying to reduce rinsing time and improve color quality.

F. Finishing:
Uses of enzyme in finishing section are classified in

  1. Bio-finishing
  2. Denim finishing

1. Enzymatic finishing/Biofinishing: Biofinishing or biopolishing (removing fiber fuzz and pills from fabric surface) – enzymatic biofinishing yields a cleaner surface, softer handfeel, reduces pilling and increases luster.

Biopolishing is a process of treatment of cotton and other cellulosic textiles with cellulases enzymes to remove protruding fibers from textile fabrics and produce a softer and smoother hand-feel. Bio-polishing also reduces fabric pilling tendency and improves fabric luster, brightness and drape. Bio-polishing can also be used as a replacement or as a supplementary process for denim stone-washing. In bio-polishing, the celluases enzymes are used to break down the cellulose polymer chains of the surface fibers by hydrolysis, which are then easily removed during washing due to increased water solubility. Important parameters of cellulases bio-polishing process include concentration of the enzyme, pH, temperature, any surfactant used, process time and agitation / mechanical action during the process.

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On the contrary to other finishing procedures that can be organized with regard to a distinct functionality that is intended, the term biofinishing includes a number of different processes. The common characteristic of these processes is the application of enzymes as an active system to develop the desired textile property. Different enzymes are in use, and their name indicates the catalytical function of the protein (Table).

Table: Important types of enzymes used in biofinishing operations.

Enzyme Function Application
Amylase Hydrolysis of starch Desizing
Pectinase Hydrolysis of pectins Pretreatment of natural cellulose fibres (cotton, flax and hemp)
Catalase Decomposes hydrogen peroxide Removal of residual peroxide in advance to dyeing/printing operations
Cellulase Hydrolyse cellulose Anti-pilling, anti-fibrillation of regenerated cellulosics, biofinishing of denim, in detergents (laundry)
Protease Hydrolysis of proteins Anti-felt treatment of wool, household detergents (stain removal)
Lipases Hydrolyse lipids Removal of lipids (household detergents)
Peroxidase Oxidative splitting of reactive dyes Rinsing of reactive dyeing for higher fastness

2. Denim finishing: A characteristic of denim products (jeans) is their used-look appearance. After the production of the garment, a wide range of procedures is applied to widen the coloristic potential of a product, which mainly is available in blue or black color. In the traditional stone washing process, the blue denim was faded by the abrasive action of pumice stones on the garment surface. Nowadays, denim finishers are using a special cellulase. Cellulase works by loosening the indigo dye on the denim in a process known as Bio-Stone Wash / Stone Enzyme Wash. A small dose of enzyme can replace several kilograms of pumice stones. The use of less pumice stones results in less damage to garment, machine and less pumice dust in the laundry environment; in addition, it’s possible to fade denim without risk of damaging the garment.

References:

  1. Textile Chemistry by Thomas Bechtold, Tung Pham
  2. Textile Engineering-An Introduction Edited by Yasir Nawab
  3. Textile Processing with Enzymes Edited by A. Cavaco-Paulo and G. M. Gübitz
  4. Bioprocessing of Textiles by Dr. C. Vigneswaran, Dr. M. Ananthasubramanian and Dr. P. Kandhavadivu
  5. https://textilelearner.net/enzymes-in-textile-wet-processing/
  6. https://textilelearner.net/application-of-enzymes-in-textile-processing/

You may also like:

  1. Enzymes and Its Applications in Textile Wet Processing Industry
  2. Application of Enzymes in Textile Processing
  3. Effects of Various Enzymes on Denim Garment Washing
  4. Enzyme Stone Wash Process of Garments
  5. Biopolishing in Textile: Process, Advantages and Disadvantages
  6. Bioscouring of Cotton Fabrics
  7. Bio-Stone Washing with Celluloses for Denim
  8. Sustainable Finishing Techniques in Textile Industry

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