By:Aravin Prince .P
B.Tech (Final Year)
DEPARTMENT OF TEXTILE TECHNOLOGY,
RVS COLLEGE OF ENGG & TECH,
► GREEN ALTERNATIVE
► HISTORY OF ENZYMES
► CHARACTERISTICS OF ENZYMES
► MECHANISM OF ENZYMES
► ENZYMES IN TEXTILES
► APPLICATION OF ENZYME IN TEXTILE PROCESS
► CURRENT APPLICATION OF ENZYMES IN INDUSTRY
The bulk part of textile production migrates to the developing world, partially because of stricter environmental regulations in the industrialized countries. The developing world has the possibility to create a unique competitive advantage by promoting environmentally sustainable production process based on Biotechnology.
Biotechnological solutions enable not only such cleaner processes but can also create cost and time-saving as well as other fabric quality advantages to textile manufacturers.
This paper is focused on the use of enzymes to prepare, bleach, and finish cotton materials. So far it has been revealed that cotton material can be prepared for dyeing and other processes by the uses of enzymes. Since use of the gentle enzyme process replace the need for hard processing with sodium hydroxide and other harmful chemicals, there is less contribution to the textile effluent and a softer textile product.
One of the most negative environment impacts from textile production is the traditional process used to prepare cotton fiber, yarn, and fabric. Before cotton fabric or yarn can be dyed, it goes through a number of processes in a textile mill.
One important step is scoring is the complete or partial removal of the non-cellulosic components found in native cotton as well as impurities such as machinery and size lubricants. Traditionally it is achieved through a series of chemical treatments and subsequently rinsing in water. This treatment generates large amounts of salts, acids, and alkali and requires huge amount of water.
With advent of genetic engineering, technology has reached a stage where synthetic polymers i.e. polyester fibers can be etched with the help of enzymes. We even have exciting discoveries wherein synthetic analogues of functional groups in enzymes are prepared to act in similar manner as natural enzymes, a technology appropriately termed as �bio-mimick
Enzyme system is built on pH buffers, sequesterents, surfactants and basic enzymes. The choice of these chemicals is governed largely by their effect on enzyme activity. The basic enzymes are stabilized by immobilization to improve their working characteristics, handling safety and stability.
The result of bio preparation with enzymes is that the cellulose is not degraded, resulting in less weight or strength loss than occurs with either caustic scouring or cellulose treatment. In addition, the amount of wax removed is not as high as that which occurs with the other processes, resulting in an improved hand.
I. Technology of Textile Bleaching and Mercerizing by Dr VA Shenai
II. Chemical Preparatory Process for Textiles by Dr G.Nalangilli & A. Edwin Sundar
About the author:
Aravin Prince .P
B.Tech (Final Year)
DEPARTMENT OF TEXTILE TECHNOLOGY,
RVS COLLEGE OF ENGG & TECH,
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THE GREEN ALTERNATIVE:
With bio-preparation using the enzyme the cotton fibers can be treated under very mild condition. The environmental impact is reduced since there is less chemical waste and a lower volume of water is needed for the procedure. The bio preparation process decreases both effluent load and water usage to the extent that the new technology becomes an economically viable alternative. Instead of using hot sodium hydroxide to remove the impurities and damaging parts of the fiber enzymes do the same job leaving the cotton fiber intact. It is believed that the replacement of caustic scouring of cotton substrates by bio preparation with selected enzymes will result in the following quantifiable improvements: lower, BOD, COD, TDS, and Alkalinity. Process time, Cotton weight loss, and harshness of hand.
An extremely powerful alkaline pectinase recently has been isolated. This new enzyme is now being produced in volume and is being reduced to commercial use in bio preparation on a worldwide basis. The major benefit of this enzyme in bio preparation is that the enzyme does not destroy the cellulose of the cotton fiber. The enzyme is a pectate lyase, and as such very rapidly catalyses hydrolysis of salts of polygalacturonic acids (pectin�s) in the primary wall matrix. The term alkaline pectinase is used to describe the enzyme because the biological catalyst is used under mildly alkaline conditions which are very beneficial in preparation process.
Enzyme is a Greek word �Enzymos� meaning �in the cell� or �from the cell�. They are the protein substances made up of more than 250 amino acids. Based on the medium for their preparation, they are classified as bacterial, pancreatic (blood, lever etc) malt (germinated barely) etc. their major functions are fails on hydrolysis, oxidation, reduction coagulation and decomposition. Grouped under the following groups:
� Oxidoreductases � Oxidation, reduction reaction.
� Transferases � Transfer of functional groups.
� Hydrolases � Hydrolysis reaction
� Lyases � Addition to double bond or its reverse
� Isomerases � Isomerisation
� Ligases � Formation of bonds with ATP clevages.
� Hydrolases type of enzyme is mostly used in textiles. Enzymes are preferred in textiles due to the following reasons :
� Accelerate the rate of the reaction
� Specific in action
� Low temperature operation
� Safe and control is easy
� Replace harsh chemicals
� No pollution
� Biologically degradable
THE HISTORY OF ENZYMES:
� Amylase Desizing (1952)
� Protease Wool ( 1984)
� Cellulase Bio-stoning (1987)
� Catalase Bleach clean up (1993)
� Laccase Denim Bleaching (1996)
� Peroxidase Enzymatic Rinse (1999)
� Pectate Lyase Bio-scouring (2003)
CHARACTERISTICS OF ENZYMES:
A characteristic feature of the enzyme is that it is not used by itself during the process and can be recovered at the end of the reaction.
Enzymes are advantageous because of their low activation energy requirement, since the reaction conditions are close to the ambient.
Sharp control over process conditions is essential because the enzymes are very sensitive to pH and temperature variation
Enzymes only accelerate the rate of the reaction. The active centres in the enzyme such as fissures, holes, pockets, cavities or hollows form complex with the substrate in lock and key fashion. The bio-reaction takes place in this complex and its destruction leads to the release of original enzyme and the product.
ENZYME IN TEXTILES:
Enzymes are successfully used in various textile process like pretreatment, dyeing and finishing. E enzymes are more eco-friendly & being natural products and are completely bio-degradable and accomplish their work quickly and efficiently with out leaving any pollutants behind. Enzymes find their application in the following areas.
Biodegradable polymers and polyesters can be synthesized using common commercial soil bacteria.
Enzyme-based retting processes used on hemp and flax produce a finer, cleaner fiber, allowing novel processing techniques such as rotor. Wrap, friction or jet spinning technology. Enzymes are also used to enhance the natural bacterial action in jute processing, allowing a significant reduction in processing time and fewer process stages.
Enzymes are used to remove lubricants and sizes. Enzymatic desizing has achieved industry-wide adoption as a particularly cost-effective treatment, with savings in both processing costs and wastewater treatments.
DEGUMMING OF SILK:
Sticky insect secretions from silk fibres can be removed using enzymes.
Wool and Cotton can be scoured effectively using enzyme rather than harsh chemicals.
Enzymes rather than caustic chemicals can be used to fade fabrics without the wastewater treatment cost of ordinary bleaches.
Bio-stoning has been widely adopted as the standard method of achieving �stone �washed� denim. Enzymes are used to fade the denim rather than the abrasive action of pumice stones. Substantial savings result from reduced water usage and less damage to the fabric
WOOL SOFTENING /SHRINK PROOFING:
Enzymes has been used effectively in shrink proofing of wool, giving improved quality and significantly reduced effluent costs as opposed to using chemical treatments.
Bio polishing involves the use of enzymes to shear off the micro fibres of cotton and other cellulose materials to produce fabrics with superior softness, drape and resistance to pilling.
Medical textiles biological elements are being incorporated into medical textiles, such as wound dressings and surgical gowns, to give them anti-bacterial properties.
This mode has been specially developed to achieve a cleaner pile on terry towels. A treatment with �ultrazyme LF conc.�- A powerful composition gives a clear look to the pile, improved softness and absorbency.
Fabrics containing regenerated cellulosic fiber often show fuzzy surface due to chafing during wet processing. A smooth and clear finish can be achieved by bio singing.
APPLIFCATION OF ENZYMES IN TEXTILE PROCESS:
Biotechnology has been used in textile industry for over 100 years. Amylase enzymes from malt extract were first used to degrade starch-based sizes for cheap and effective desizing. Since the action of enzymes on starch is highly selective, and cellulose remains totally unaffected by the nature of the enzyme reaction, enzymes are used for desizing.
Enzymes differ from simple catalysts another very important way. Enzymes are much more specific. Sulphuric acid as a source of H+ will catalyse the formation of any ester from the appropriate alcohol and carboxylic acid, but many enzymes are so specialized that they will catalyse a reaction of one molecule, but will leave untouched a very similar molecule. Amylase a digestive enzyme will hydrolyze starch, but not cellulose. Both molecules are polymers of glucose. They differ in the orientation of one bond at the junction of glucose units. Other enzymes can work effectively on a broader range of substrates (the molecule whose reaction is being catalyzed).
Enzymes like DIASTAFOR, which is made from malt extract, do not act in presence of zinc chloride, which is usually used in the sizing composition as an anti mildew agent.
Bio-desizing enzyme systems are based on amylase that solubilises starch in sizing preparations. Conventional bio desizing systems operate at temp 55-65 degree centigrade. �Unodesize� is a high temperature stable amylase having stability up to 80-90 degree centigrade.
Traditionally, cotton scouring has required the use of harsh alkaline chemicals (caustic), extreme temperatures water. Expenses include not only the cost of the caustic and energy, but also the cost of treating wastewater to caustic and by-products.
Today, textile producers have a new, effective alternative to chemical scouring with the advent of the Cottonas novel enzyme not only cleans better than chemical scouring. But also greatly reduces the need for extensive and energy consumption. The Cottonase T enzyme is a versatile, economically viable and environmentally friendly chemical scouring in cotton preparation. Noncellulosic impurities, such as fats, waxes, proteins, pectins, natural and water-soluble compounds, are found to a large extent in the primary wall and to a lesser extent in the secondary 3) and strongly limit the water absorbency and whiteness of the cotton fiber. Quantity and composition varies v present serious problems as they are basically undyeable.
The bio scouring process is built on
Lipase enzymes act on proteins & natural waxes to effect scouring of cotton.
Advantages of bio scouring:
Milder conditions of processing, low consumption of utilities, yet excellent absorbency in goods.
No oxy-cellulose formation and less strength loss because of absence of heavy alkali in bath.
Uniform removal of waxes results in better levelness in dyeing
Highly suitable for scouring of blends containing fibres like silk, wool, viscose, modal, lyocell, lycra etc.
Low TDS in discharge.
Fabric is softer and fluffier than conventional scouring. Ideal for terry towel/ knitted goods.
SINGLE STAGE BIO SCOURING AND BIO DESIZING:
The unified bio desizing and scouring process is based on amylase, proteas, pectinase and lipase enzymes. This combination acts on starch, proteins and natural waxes to effect desizing and scouring
REMOVAL OF NEPS AND SEED COAT FRAGMENTS:
With conventional alkaline scouring and bleaching seed coat fragments are removed. However, undyeable neps remain a problem. Neps generally consist of flat immature cotton fibers.
Laccases from different sources were incorporated into the bioscouring process as well as after bleaching and impact during the treatment was increased. With this treatment it is possible to break up seed coat fragments as numbers drastically. Neps, after dyeing the fabric with a red direct dye and evaluated by image analysis, however challenge.
In bleaching, especially in hydrogen peroxide, the reactive dyes are very much sensitive to residual peroxide. So treatment of fabric with enzyme and then catalyst is added after oxidative bleaching and allow reacting for 15 min at 30-40 degree centigrade. It degrades residual peroxide into water and oxygen. The result found out, that enzyme treated fabric shows best results than untreated fabric.
The best suitable conditions
Temp range 20-60 degree
Time 10-15 mins
� Glucose oxidases
Have been explored for use in bleaching cotton. It is possible that these enzymes either separately or in combination may result in sufficient bleaching of cotton fiber without the associated damage that occurs with harsh processes. Indeed �Glycosyl hydrolases� may offer a key for successful enzymatic bleaching.
Cotton and cotton blend fabrics contain small cellulosic micro fibrils. Cellulase enzymes are used to remove these fuzz/pills, imparting softness/smoothness to the fabric, imparting gloss/luster to the fabric. Cellulase enzymes are usually classified by the ph range in which they are most effective. Acid- stable, neutral stable and alkaline stable are the three catagories. Cellulase enzymes consists of a complex mixture of exo-glucanases and beta glucosidases and endo glucanases. The endo glucnases hydrolyses long polymers into smaller ones; the exo-glucanase splits glucose from the non-reducing end of cellulose and the beta- glucosidase hydrolysis cellobiose to glucose. Cellulase enzymes are capable of degrading cellulose by performing a specific catalytic action on the 1, 4-linkage of two beta-glucose residues of the cellulose molecules.
Dyed or printed polyester-cellulosic blends often treated with a strong solution of sulphuric acid to dissolve the cellulosic component. The treated goods have a soft and fluffy feel. The process is risky due to highly corrosive acids that are also difficult to treat in effluent treatment plant.
In the bio carbonizing process the goods are treated with a cellulose enzyme based formulation �chemizyme UZ� to achieve dissolution of cellulosic component. The goods are padded in a warm solution of this product and patched on a roll under normal conditions and are washed off after 12-16 hours. This process offers an eco friendly option to the obnoxious use of strong acids.
SHRINK PROOFING TREATMENT FOR WOOL:
The surface of wool and other animal fibers is covered with a scaly cuticle. This cuticle is responsible for shrinkage problems that occur when wool is laundered. Treatment to avoid felt shrinkage has involved treating wool with either chlorine-based chemical in order to remove the cuticle or synthetic resins to cover the surface of the fiber. In these methods, the waste water from the processing can contain AOX (absorbable organic halogens), which are harmful to the environment. Furthermore, wool has been treated with resins usually has a poor hand and reduced water absorption and desorption abilities. Due to this factor, the dyeing industry has been calling for the development of shrink-proofing technology free from chlorine-based chemicals.
Extraction of new keratin- degrading enzyme suitable for use in shrink-proofing treatment for wool was isolated from mold.
Mold capable of effectively degrading keratin extracted from soil samples taken from different locations.
Because this enzyme acts preferentially on the cuticle that is responsible for felt shrinkage, it gives woolen fabric an excellent resistance to shrinkage without weakening the fiber or damaging the hand.
Furthermore use of this enzyme can lead to the elimination of environmental problems associated with chemicals used in other treatment methods.
DEGUMMASE ENZYMES IN THE PROCESSING OF SILK:
The desizing of silk by enzyme is a well known process which requires previous swelling of silk sericin by a selected surfactant. Application of serine protease in this context has been reported. However all the parameters of the process must be carefully controlled so that silk itself is not attacked.
Finishing is a value addition process, which hides the fabric defects and improves the aesthetic value. The areas where the enzymes are used in finishing process are bio-washing/bio-polishing.
The fashionable stone wash look of denim garment and other processes that improve fabric appearance by removing fuzz fibres and pills and delivering softening benefits are all well known in the area of cellulose finishing.
Denim washing is the removal of surface dyes and fibres to give the garment a use appearance. With the fast developing finishing technology in past decades, the various denim washing techniques have been devised. to produce a variety of trendy garments. One such recent washing is bio-washing.
The enzyme used for bio-washing is neutral stable cellulase. These enzymes are produced from humicola isolans which cause controlled super ficial attack on the fiber leading to decolourisation without bringing about excessive loss in fabric strength
Here natural stable (bacrosol JN) enzymes are mostly used, which acts at the pH of 6 and some of the cellulases where multicomponent are represented as the whole cellulose complex.
When indigo is released to wash liquid during washing, sometimes the indigo redeposit on the white washing on the white part of the denim fabric, giving lighter blue shade which is most visible on white weft yarn end white pocket woven. This phenomenon is back staining. To avoid back staining, denim processors are adding anti-redeposition chemical (Sandoclear IDS, an effective DA) during enzyme washing. Recently, it was discovered that many of the proteins present in the conventional acid stable cellulose promote the redepositon of indigo dye by adding protease (0.01% to 0.1%) during this cellulose wash. A dramatic reducing of back staining and visible increase in the contrast can be obtained.
Bio-polishing is a finishing process for cellulosic fabrics and garments. It is the process of improving surface of the material. It is also an �Enzymatic singeing�.Bio-polishing with acid cellulose effectively reduces fabric fuzz and the pilling on denim materials. A cellulosic treatment gives the fabric a durable improvement of:
� Resistance to pilling
� A clear lint and fuzz free surface structure
� Bio-polished garment looks new even after repeated wear
� Bio-polishing permanently enhances fabric look without any chemical coating bio-polishing improves drapebility and softness.
� The fabric surface obtains a silky sheen similar to that resulting from traditional mercerisation.
LIPASE ENZYMES IN IMPROVING ABSORBENCY AND WETTING OF PET FABRICS:
Biodegradation of polyesters and ester-containing copolymers and blends by lipases has been reported. All these studies have focused on how the chemical compositions of the polymers affect lipase assisted degradation. The above studies have not used, however, lipases to modify polyester surface. In principle, hydrolysis of the ester linkage in polyesters should produce polar-hydrophilic hydroxyl and carboxylic groups, thus improving fiber surface wettability. This hypothesis has been tested recently by evaluating the effects of five lipases or hydrolysing enzymes on water wetting and absorbent properties of several polyester fabrics. It has been shown that the enzyme reaction time are effective under even more moderate conditions, including relatively shorter reaction time at ambient temperature and without a buffer.
DEGRADATION OF TKP BASED GUMS:
Gums based on Tamarind Kernel Powder are a cheaper substitute for starch as a sizing base and for guar gum as a Printing thickener. TKP base gums are difficult to remove by desizing. Product �Degumase PGR� is very effective in enzymatic degradation of TKP polymers.
CURRENT TEXTILE ENZYME APPLICATION IN INDUSTRY:
� Desizing (amylase)
� Bleach cleanup (catalases)
� Bio-polishing (cellulases)
� Scouring (pectate lyase)
� Enzymatic rinse (ERP)
� Proteases for wool and silk
� Peroxidases for decolorisation
ADVANTAGE OF ENZYMES IN TEXTILE:
� Enzymes can often replace chemicals or processes that present safety or environmental issues.
� Replacing acids in the starch processing industry;
� Replacing acids, alkalis or oxidizing agents in fabric desizing;
� Use of enzymes in the tanneries to reduce the use of sulfied ;
� Enzymes replace pumice stones for �stone washing� jeans. This reduces pumice and waste;
� Enzymes are consumer friendly when used in detergent formulations allowing the use of less aggressive for reduce clothing damage during washing.