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Enzyme application in Textile Industry[edit]
The use of enzymes in textile manufacturing has been a long tradition. It has now become one of the most rapidly growing field in industrial enzymology. Examples include degumming of silk with sericinases, finishing of wool with proteases, softening of jute with cellulases, etc. [1] Enzymes are now considered a vital part of White biotechnology. The global market potential of enzymes for textile application is estimated to be around 150 million USD.
Approximately 75 enzymes are commercially used in textile industry. Commercially used enzymes require selected microbial strains to be produced in sufficient quantity. Thus advances in biotechnology and its applications in the textile industry has helped the industry grow tremendously over the past few years. [2]
Applications of biotechnology, specifically enzymes, in textile wet processing has also paved the path to environmentally friendly technology. This is because enzymes used are biodegradable in nature. [3] Reduced process time, energy and water savings, better quality product are other reasons which have made enzymes a preferred choice over chemicals in textile manufacturing. [4]
Various enzymes used in Textile industry[edit]
Pectinase[edit]
Pectinase are used in preparation of textile fibres like hemp and flax produced by dew retting which requires the action of pectolytic enzymes. This allows rapid and controlled process and also inhibits bacterial or fungal contamination. [3] It is also used in cotton preparation. [5] They act by destroying the cutinized structure by digesting the inner layer of pectins in the cuticle of cotton. It is also used in carbonization of wool.[6]
Catalase[edit]
Catalase is used in removal of hydrogen peroxide prior to dyeing. This is important because reactive dyes are very sensitive to peroxides and therefore require use of a chemical scavenger. [3] They are also used in bioscouring. They work at an optimum pH 8.5. [7]
Amylase[edit]
Amylase breaks down starch into simple sugars. It catalyses breakdown of α 1,4-D-glycosidic linkages in polysaccharides. It acts on starch, glycogen, oligosaccharides in a random manner thereby liberating reducing groups. [6] They are stable over a pH range of 4-11. [2]
It is used for desizing of woven cotton as well as man-made fabric. It has several advantages like it is thermostable, improves speed, helps in characterization and consistency of the process, etc. [3]
Lipase[edit]
Lipase are known to split fats into glycerol and fatty acids. [6] It is also used for desizing of fabrics. It is specifically used to remove triglyceride based lubricants from the fabrics. [3] It is also used for washing as a detergent due to this property. [5] It is also used to improve the removal of fat/oil even at temperature at which the fatty material is in a solid on fabric. [6]
Xylanase[edit]
Xylanase is used for scouring and bleaching. It has replaced the age old caustic soda for the purpose. It removes substances like pectin, waxes residual seed coating, colour which inhibit natural absorbancy of the fibre and prevents dyeing, printing or other finishing of the fabric. [3] It is used for processing jute and improves its bleaching ability. [6]
Cellulase[edit]
Cellulase is a hydrolytic enzyme [2] which breaks down cellulose. Fungi such as Trichoderma reesei and Humicola insolens mainly produce commercial cellulases. [6] Cellulase accounts for 14% of the world's industrial market. [2] It is used for biostoning. This has replaced the age old pumic stone used for the same purpose. This is used by Denim garment processors and allows quality and uniform finishing of fabrics. It is also used for Biopolishing. [3]
Laccase[edit]
Laccase is used for Denim finishing. Laccase decolourizes the indigo dyestuff and also enhances the apparent abrasion effect with little impact on cellulosic fibre strength. [3]
Protease[edit]
Protease are enzymes which breakdown protein. [6] It is used for wool finishing to increase comfort. It also allows degumming of silk which helps produce sand washed effects on silk garments. [3] It is also used for stone washing of denim since cellulose causes the problem of back staining. [6]
Peroxidases[edit]
Peroxidases are used as an enzymatic rinse after reactive dyeing. Oxidative splitting of hydrolysed reactive dyes on the fibre occur in this process. [5]
Processes part of Textile Industry which use enzymes[edit]
Usage of ezymes in the textile industry has become a very important and common phenomenon. Important processes of textile manufacturing which depend on enzymes are discussed further.
Bio-polishing[edit]
Bio-polishing is a finishing process that improves fabric quality by reducing fuzziness. [1] It is a process which can be carried out during any stage of wet processing is usually carried out after bleaching since the fabric, at this stage, is clean, hydrophilic and more accessible to cellulase. The main principle is to hydrolyse cellulose into glucose which modifies the surface and properties of cellulosic fibres and fabrics in order for an enzymatic removal of the fuzz. [3]
Commercial cellulase contains three enzymes : exo-β-(1,4) glucanase, endo-β-(1,4) glucanase which contributes the maximum in degrading cellulose fibre and β-glucanase. Their action forms cellobiose which splits further. Weakend fabric can be separated by mechanical stress. [6]
Enzymatic biopolishing is permanent and keeps the fabric in good condition after repeated washing. It also enhances the colour, feel of products hence increases their economic value. Usage of cellulase thus helps in increased smoothness and softness, prevention of the pills formation, increased lusture and colour brightness, etc. [3]
Enzymatic desizing[edit]
Desizing is important for complete removal of starch-containing size without fibre damage. This also helps in uniform wet processing. [1] Desizing helps in preparing the fabric for dyeing and finishing. [2] Enzymatic desizing can be done in 3 major steps :
1.Impregnation : Fabric absorbs the enzyme solution. During this stage, gelatinization or starch/size is possible to the highest extent.
2. Incubation : Here, size is broken down by the enzyme. Long incubation time help in requirement of low enzyme concentration.
3. After-wash : Here, the breakdown products are removed. This involves a subsequent detergent wash with NaOH at the highest possible temperature.
Years ago, desizing was done using acid, alkali or oxidizing agent at high temperature which has now been replaced by enzymatic treatment. [2] Formerly, amylase derived from malt or pancrease was used which has now been replaced by liquid bacterial amylase. [3] The advantage of amylase is that it is specific to starch, thus it removes it without damaging the support fibre. Amylase are usually used at 30-60 degree celcius temperature. [1]
Enzymatic Scouring/ Bioscoring[edit]
This refers to scouring of textile material with enzymes. [1] It is necessary for pastel or light shade textile. [6] Scouring is removal of non-cellulosic material present on the surface of cotton. [1] It can be applied on any type of cotton. The bio-scoured material can further then be used for dyeing, bleaching, etc. Usually for this process, enzymes like protease, pectinase, lipase are used. [3] Pectinase destorys the cotton cuticle and body of cotton fibre. [1]
The process involves pretreatment with water at 100 degree celcius to melt wax and lipid compounds to redistribute them over the fiber surface. One bath enzymatic scouring is feasible when sufficient amyloglucosidase for glucose production is present.
This process allows less water usage and lower costs. [3] Biological Oxygen Demand and Chemical Oxygen Demand of bioscouring is 20-45% as compared to alkaline scouring. [1] Conventional scouring also required high temperature and high consumption of chemicals. [8]
Bleaching[edit]
Textile beaching is usually done with hydrogen peroxide. But replacement of hydrogen peroxide with an enzymatic bleaching system leads to better product quality due to less fibre damage as well as leads to substantial savings on washing water needed for removal of hydrogen peroxide. This also removes an additional process of peroxide neutralization.
Combination of amyloglucosidases, pectinase sand glucose oxidases can be used for bleaching . Low concetrations of Laccases can also be used alternatively. [1]
Peroxide Neutralization[edit]
This process is essential after bleaching because if residual peroxide on the fabric is not neutralized, it results in patchy dyeing. Catalases are eco-friendly options for this process as each molecule of catalase can neutralize five million molecules of hydrogen peroxide. It also doesn't interfere with dyeing.
This can be done in batch process. Upon draining after peroxide bleaching, the fabric is rinsed with cold water, set in fresh bath and catalase is added to it. After running the bath for 10-15 minutes, it is drained and dyeing can be continued in the same path. [3]
Wool processing[edit]
Enzymatic treatment of wool helps in removal of protruding fibres, which are responsible for the fuzzy appearance. Thus a silky sheen is obtained which improves lusture of the wool. Traditionally, for this process chemicals like silicones, dichloroisocyanuric acid, triscarin were used. Now enzymatic treatment with amylase is done. [3]
Wool also requires treatment for felt-shrinkage. Earlier chlorine based compounds were used for this which released toxic wastewater and produced bad quality wool. Felt-shrinkage treatment with keratin degrading enzymes now has made it possible to find solution of these problems. [9]
Polyester Processing[edit]
Polyester enzymes are used to produce surface modification which increases the hydrophilicity of a polyester which thus improves fabric characteristics like stain resistance, dyeability and wettability. [1]
Treatment of Denim[edit]
Denim is a heavy grade cotton. It's washing is done to give it a worn out look. [2] Earlier, sodium hypochlorite or potassium permanganate were used for fading on denim, called pumice stones. But they were required in large quantity, caused wear and tear of machine, etc. This led to the necessity of using enzymes for the process.[1]
Acid, hybrid or neutral cellulase is now used for Denim washing. [6] Acid cellulose has a pH range of 4.5-6 and neutral pH have a range of pH 6-8. [2] Cellulase loosens the indigo on denim in a process called Bio-stonewashing. Small quanity of cellulase is sufficient for the process. Laccase has also found to be useful for Bio-stonewashing. [1]
Bio-stoning has now made it possible to fade denim to a greater degree without the risk of damaging the garment. [6]
Degumming[edit]
Degumming refers to the process of eliminating sericin from silk. For this process, proteases are used. they make silk white by decreasing its yellowness, decreases its stiffness, improves its crease recovery and makes it lustrous and absorbent.
Years back, alkaline soultion containing soap was used for this process but it had to be discontinued since it was a harsh treatment for the fibre. Proteolytic enzymes can act without damaging fibrin even in higher concentrations. [6]
Industrial enzymes[edit]
For different process, specific enzymes from the wide category of enzymes are used. Some of them are :
- Biopolishing : SEBriteBP+, SEBriteBP, Denibrade, SEBrite Prime, Ezysoft XCL
- Desizing : Rapindenz, Spersize, Ezysize Ultima
- Wool scouring and gunwash : SEBrite WSC
- Bio-washing : Coldfade 3535, Denibrade N 30, Fadex500, Denicell, Neurastone NC, Enzitone, Denibrade 10 C
- Jute softening and upgrading : Goldenaz
- Silk Degumming : Degummase P. [6]
- Stone wash effect : Chromolase THN [8]
Advantages of using enzymes in textile industry[edit]
Usage of enzymes allow textile manufacturers to reduce pollution in textile production since bio-enzymes used in chemical processing of fibers and textiles are non-toxic and eco-friendly. This is advantageous in textile production keeping in mind the increasing environmental concerns and legistation on eco-toxicological issues. [3] Enzymes also accelerate the reaction by lowering the activation energy, thus reducing the process time. They are highly specific in nature, therefore for example, this allows desizing to be done for cotton without its loss of strength. [4]
There is also promising future for the reuse of enzyme, which will decrease the processing cost drastically as well as allow wide renovation in textile wet processing. [3] They are economially beneficial again as they allow less water and energy consumption as they shorten the process cycle. [1] Water usage is reduced by almost 19000 litres per ton of textile bleach. [10] Enzymes can also be used at catalytic concentrations at a low temperature which serves as an added advantage. These can also be used at near to neutral pH. [1]
Enzymes are safe to handle and non-corrosive in their application which serves as an added advantage. [5] They can catalyze broad spectrum of reactions as well. [6]
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