Enzymes in the Textile Industry:
Enzymes were discovered in the second half of the nineteenth century, and since then have been extensively used in several industrial processes. Enzymes are macromolecular biocatalysts that mediate virtually all of the biochemical reactions that constitute metabolism in living systems. Enzymes are generally globular proteins and like other proteins consist of long linear chains of amino acids that fold to produce a three-dimensional product. Enzymes have been broadly accepted by various industrial applications because of their green chemistry and ecological benefits.
Nowadays, enzymes are commercially used in many applications such as textiles, detergents, leather, and paper industries. Currently, enzymes are becoming an important element in the textile industry, specifically in wet processing, because of their unique characteristics to replace conventionally used harsh chemicals. Different types of enzymes are being used on a variety of textile substrates and at different processing stages. Enzymes are environment-friendly, save precious water and energy and work under mild conditions.
Enzymes have traditionally been used for stone washing and bio-polishing of cotton fabrics and garments. Also enzymes have been incorporated in detergents to remove fiber fuzz and brighten the color of the fabric.
Different Types of Enzymes for Textile Application:
a) Amylase: Amylases are widely used as desizing agents to remove starch from fabrics after weaving. It is used in desizing of jeans. (AQUAZYM) makes denim streak-free, softer and more uniformly faded.
b) Cellulases and Hemicellulases: Cellulases are used in textile processing mainly for depilling and to obtain stone washing effects. Cellulases are high molecular colloidal protein catalysts in metabolic form and are commonly produced by soil-dwelling fungi and bacteria. Desizing of CMC, stylish effects on cellulosic fibres, Non-stone treatment for jeans.
c) Pectinolytic enzymes:
Pectin-degrading enzymes have received much interest for their use in the pretreatment of textile fabrics (‘bioscouring’) prior to dyeing.The removal of pectin components from the cotton cell wall is claimed to improve fibre hydrophilicity, to facilitate dye penetration and to contribute to substantial water savings when compared to the traditional alkaline scouring process. Specially, scouring of vegetable or bast fibres like jute, hemp, flax, remie etc.
d) Proteases: Proteases are important components of detergent formulations for removing protein stains (egg, blood etc.) from textiles. Additionally, proteases have a useful potential in silk and wool processing. Specially, scouring of animal fibres, or degumming of silk, modification of wool properties.
e) Esterases: Esterases have been suggested as useful components of detergent formulations to remove lipid-based stains from textiles while some esterases have been claimed to hydrolyse polyester. Esterases hydrolyse ester bonds and their classification is based on the type of ester bond hydrolysed.
f) Nitrile-hydrolysing enzymes: Nitrilases have been shown to improve dye uptake and hydrophilicity of acrylic fibres. These improved properties are achieved by enzymatic conversion of nitrile groups into carboxylic acid groups at the surface of acrylic fibers.
g) Laccases: Laccases in combination with redox mediators are used in textile processing to bleach denim fabrics, decolourising indigo. Research efforts have been made to use laccase as a bleaching and/or oxidative coupling agent for dyeing animal fibres and human hair.
h) Lipases: Elimination of fats and waxes.
i) Catalases: Catalases can be used in textile processing for the removal of residual hydrogen peroxide after bleaching while peroxidases have a potential for dye decolourisation after dyeing. Catalases convert hydrogen peroxide into water and oxygen showing first order kinetics.
Role of Enzymes in the Textile Industry:
The introduction of enzymes in textile processing has great potential to reduce environmental issues associated with chemicals. The enzymes in the textile industry were used for a long time; however, the researchers are focusing on the modified and new enzymes to enhance the process efficiency.
Although enzymes have been employed in textile processing for many years, there is currently renewed interest in the possible benefits offered by enzyme processing, and not just for the traditional desizing of cotton. Enzymes are becoming a relatively cost-effective, pollution-free means of treating cellulosic fabrics for dehairing, pill-preventing or biopolishing, as well as the well-known stonewashing applications. For wool fabrics, somewhat different enzymes can be used to dehair processed fabrics, and even to render wool shrinkproof. For the consumer, there are the ‘biological’ laundry powders and liquids which rely, in part, on the action of enzymes for their effectiveness.
Firstly, in the preparatory finishing area amylases are commonly used for desizing process and secondly, in the finishing area cellulases are used for softening, biostoning and reducing of pilling propensity for cotton goods. At present, applications of pectinases, lipases, proteases, catalases, xylanases, etc., are used in textile processing. There are various applications which entail enzymes included fading of denim and non-denim, bioscouring, biopolishing, wool finishing, peroxide removal, decolourisation of dyestuff, etc.
Bio-desizing of cotton is the classic example of an application of enzyme in textile processing. In the early 1950s, amylase was the first microbial enzyme introduced by Novo Nordisk. Since then, various enzymes based systems have been well-established in the textile industry, like amylases for the desizing of cotton, cellulases for the bio-finishing of cellulosic textile, catalases for the peroxide neutralisation, and proteases for the degumming of silk as well as anti-pilling and softening of wool. The enzymes like xylanase, pectinase or hemicellulases are extensively used for the retting of bast fibres (jute, flax, ramie). In addition to that, hydrolases class of enzymes are reported on modification of synthetics textile material to impart antistatic properties and hydrophilicity. Moreover, enzymes are used with detergents in garment laundering, which can remove a variety of stains from the garment.
Recently, researchers have been investigating the utilisation of enzymes in a combined desizing, scouring and bleaching of textile, which can eliminate the separate processes and also save precious water and energy. Furthermore, the textile chemical processing unit is a highly chemical-intensive unit in the textile industry. The effluent discharged from the unit is highly toxic, non-biodegradable, coloured, and contains heavy metals, inorganic salts, acids, alkalis and other components. Therefore, researchers are investigating the novel enzymes which can be used for the textile effluent treatment.
In textile finishing process different chemicals have been used which cause environmental hazards. As per increasing awareness on eco-toxic effects, enzymatic treatment has been introduced in textile finishing process.
For example, bio-polishing of cotton knit fabrics are done by enzymes. Bio-polishing not only improves appearance, color brightness, water absorbance property of fibers, and hand feel, but also minimizes the tendency for pill formation. Besides, anti-felting of wool fiber, denim washing, hydrophilic finishing are done by various enzymes.
Conclusion:
Already we know that enzymes are normally biodegradable proteins; for some specific chemical reactions, it can act as biological catalysts and work in relatively mild conditions. An enzyme’s exact reaction specificity can be used for precise or targeted textile finishing without inflicting undesirable effects. The enzyme usage in the textile industry has become an example of green chemistry, which allows improving the final product quality by the development and application of eco-friendly technologies in fiber processing and strategies.
References:
- Sustainable Textile Chemical Processing Edited by Dr. Javed N. Sheikh Prof. (Dr.) M. D. Teli
- Textile Processing with Enzymes Edited by A. Cavaco-Paulo and G. M. Gübitz
- Pollution Control in Textile Industry By S. C. Bhatia
- Chemistry of the Textile Industry By C. Carr
- Textiles and Clothing: Environmental Concerns and Solutions Edited by Mohd Shabbir
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