It has been predicted that future development and progress of textile industry in India would be driven by the demands from garment manufacturing industry which in turn would be influenced by export markets. Under these circumstances processing of garments also assumes an unprecedented importance. Qualitatively speaking, finishing enzymes find major application in textile processing, next only to desizing enzymes. The garment processing industry is almost exclusive consumer of these enzymes for producing novel effects. The denim sector of garment industry is very peculiar and articles made from denim have been popular over longer period than any other type of garment. The denim culture is likely to grow in future. Denims are warp faced twill fabrics, made from 6s-12s warp dyed yarns and undyed weft. Warp yarns are ring dyed, using indigo colour. The denim garments were subjected to abrasive action of pumice stones to achieve “vintage”, “worn out “ effects as a fashion. This process had many drawbacks such as damage to machinery, residual deposit of stone powder on garments, lack of uniformity etc. This was fully or partly replaced by use of cellulase enzymes that have degrading action on fibre surface to give faded effect. Faded effects are also achieved by treatment with Sodium Hypochlorite or Potassium Permanganate. Bleaching effects on indigo are also achieved by Laccase, an oxidase type of enzyme, to give characteristic effects of fading. Today fashion conscious denim markets constantly receive innovative products. These are produced by combination of processes involving mechanically or chemically abrasive techniques with bleaching chemicals which are popularly known as stonewash, ice wash, acid wash, frosted wash, moon wash etc.

In garment processing, apart from desizing with Amylase enzymes, Cellulase enzymes are widely used to impart:

a) Fading by surface degradation of cotton fibers in indigo dyed denims.

b) Clear finish by removing protruding fibers in cotton or blended garments in denim or non-denim category.

c) To achieve soft, smooth feel with combination of a variety of exhaustible softeners.

The finishing system based on cellulase enzymes can be divided into two basic categories.

1) Neutral Enzymes (Operative pH band of 6.5-7.0)

2) Acid Enzymes (Operative pH band of 4.0-4.5)

Neutral Enzymes include systems operating around neutral pH range, which give characteristic softness with minimal back staining in case of denims, with better contrast between dyed and undyed yarns.

Acid Enzyme systems are more economical in application, but give lesser clarity of denim pattern due to back staining. In case of other cotton garments dyed with reactive colours, hydrolysis of dye-cellulose linkages in acidic pH cannot be ruled out with the result, there is likely colour bleeding in enzyme bath. An anti-staining/anti-re-deposition specialty, CLEAROL DX can be added to bath to minimize this drawback of back staining. A number of formulations have been developed in our laboratories, and are being successfully used in denim processing industries, for certain consumer preferred fashions. The enzyme treated goods are more receptive to action of other finishing specialties due to opening of fiber structures and creation of more active sites. Judicious use of softeners in separate bath is recommended. Drum washers are the preferred machinery for garment processing. As the conditions require comparatively milder temperatures, mechanical agitation must be carefully controlled. The drums diameter should be around 100 cm, with baffles to give adequate agitation and uniform action. Drums should have rotation of around 30 rpm for woven garments and 10 rpm for knitted garments.

Finishing of Cotton Knits:

Cellulase enzyme treatments increasingly find applications in cotton hosiery sector to enhance aesthetic feel as well as surface clarity. ULTRAZYME SUPER is an enzyme-based formulation, well suited for use in winches or high turbulence soft flow machines. Adequate caution must be exercised to deactivate residual enzyme by elevating temperatures to around 80-85deg C., otherwise the reaction would continue to take place resulting in loss of physical strength of goods.

Post-Enzymatic Treatment of Dyed Goods:

Cellulase enzymes are highly substrate specific – any structural change of the substrate can have an adverse effect on the reactivity of the enzymes. Direct dyes are captured inside the fiber by relatively weak secondary forces as well as by physical entrapment through dye aggregation. We found that the hydrolysis rate, except for very small direct dyes, decreased to a certain extent when dyes were incorporated into the fiber structure. Fiber-reactive dyes, on the other hand, form true chemical bonds to the functional groups of cellulose, so the type, number and position of the reactive group had a decisive effect on hydrolysis. Color brightness was strongly dependent on the dye class and on the structure of the specific dye, fiber reactive dyes being generally the brightest.

Special type of Enzymes:

Bioscouring Enzymes:

Before cotton yarn or fabric can be dyed, it goes through a number of processes in a textile mill. One important step is scouring — the complete or partial removal of the non-cellulosic components of native cotton such as waxes, pectins, hemicelluloses and mineral salts as well as impurities such as machinery and size lubricants. Scouring gives a fabric with a high and even wettability that can be bleached and dyed successfully. Today, highly alkaline chemicals such as sodium hydroxide are used for scouring. These chemicals not only remove the impurities but also attack the cellulose, leading to a reduction in strength and loss of weight of the fabric. Furthermore, the resulting wastewater has a high COD (chemical oxygen demand), BOD (biological oxygen demand) and salt content.

In 2004, AETL introduced Addscour that reduces environmental impact and, in most cases, works out more economical to use. Unlike other commercial bioscouring enzymes available based on alkaline pectinase, Addscour is effective for batch and continuous process and can be used for scouring of knit and woven fabrics and garments.The effectively comes because of right enzymes blended in Addscour over years of research. The new process is called Bio-Preparation. It has been welcomed because rinsing water can be reduced by more than half compared with traditional processes. This is especially advantageous since hot rinsing water is used, meaning that considerable amounts of energy can be saved. Quality improves too. The enzymatic treatment leaves the cellulose structure almost intact, so it reduces weight loss and strength loss. Bio-Scouring has a number of potential advantages over traditionally prepared textiles. It reduces total water consumption by around 25%, the treated yarn/fabrics retain their strength properties, and the weight loss is much less than for processing in traditional ways. Bio-Scouring also gives softer cotton textiles.

 Bio-washing Enzyme:

Abrasion Yarn the abrasive action of lightweight pumice stones on the garment surface, which removes some of the dye. However, too much abrasion can damage the fabric, particularly hems and waistbands. This is why denim finishers today use acid, hybrid or neutral cellulases to accelerate the abrasion by loosening the indigo dye on the denim. Since a small dose of enzyme can replace several kilograms of stones, the use of fewer stones results in less damage to garments, less wear on machines, and less pumice dust in the working environment. Productivity can also be increased through laundry machines containing fewer stones but more garments. With a stone-free process, the need for the removal of dust and small stones from the finished garment is reduced. There is also no sediment in the wastewater, which can otherwise block drains. Denim garments are dyed with indigo, which adheres to the surface of the yarn. The cellulase molecule binds to an exposed fibril (bundles of fibrils make up a fibre) on the surface of the yarn and hydrolyses it, but leaving the interior part of the cotton fibre intact. When the cellulases partly hydrolyse the surface of the fibre, the indigo is partly removed and light areas are created.

Neutral cellulases or Neutrastone Series designed by AETL acting at pH 6-8, acid cellulases (Denicell Series) acting at pH 4-6  and hybrid cellulases (Addcool Series) acting at pH 5 – 6.5 are used for the abrasion of denim. There are a number of cellulases available, each with its own special properties. These can be used either alone or in combination in order to obtain a specific look. Application research in this area is focused on preventing or enhancing backstaining depending on the style required. Backstaining is defined as the redeposition of released indigo onto the garments. This effect is very important in denim finishing. Backstaining at low pH values (pH 4-6) is relatively high, whereas it is significantly lower in the towards neutral pH range. Neutral cellulases are therefore often used when the objective is minimal backstaining. Hybrid cellulases are effective tool to save energy cost as processing can be done at ambient or room temperature conditions.

Desizing Enzyme:

Enzymes like heat stable amylase, fungal amylase are used for desizing woven fabrics because of their highly efficient and specific way of desizing without harming the yarn. As an example, desizing on a jigger is a simple method where the fabric from one roll is processed in a bath and re-wound on another roll. First, the sized fabric is washed in hot water (80-95°C) to gelatinize the starch. The desizing liquor is then adjusted to pH 5.5-7.5 and a temperature of 60-80°C depending on the enzyme. The fabric then goes through an impregnation stage before the amylase is added. Degraded starch in the form of dextrin is then removed by washing at 90-95°C for two minutes. The jigger process is a batch process. By contrast, in modern continuous high-speed processes, the reaction time for the enzyme may be as short as 15 seconds. Desizing on pad rolls is continuous in terms of the passage of the fabric. However, a holding time of 2-16 hours at 20-60°C is required using low-temperature alpha-amylases before the size is removed in washing chambers. With high-temperature amylases, desizing reactions can be performed in steam chambers at 95-100°C or even higher temperatures to allow a fully continuous process.

 Dehairing Enzyme:

Enzymatic Dehairing in tanneries has been envisaged as an alternative to Sulfides. Tanneries are constantly concerned about the obnoxious odor and pollution caused by the extremely toxic sodium sulfide used in the Dehairing process step. Deaths due to this toxic chemical process have even been reported. Worldwide, it is estimated that 315 million bovine leathers are produced per year. Considering a waste treatment cost of $0.30 per m2 of leather produced, more than $1 million is spent per day to treat the waste from tanneries around the world. We report here a novel keratinase from Bacillus subtilis that has the potential to replace sodium sulfide in the Dehairing process.
Hides and skins have hair attached to them that must be removed for their use as leather. The conventional way to remove hair from hides is to use harsh chemicals such as lime and sodium sulfide. These chemicals completely dissolve the hair and open up the fiber structure. With enzyme-assisted Dehairing, it is possible to reduce the chemical requirements and obtain a cleaner product and a higher area yield with fewer chemicals in the wastewater. Since the enzyme does not dissolve the hair as the chemicals do, it is possible to filter out the hair, thus reducing the chemical and biological oxygen demand of the wastewater.

Biopolishing Enzyme:

Abrasion Yarn the abrasive action of lightweight pumice stones on the garment surface, which removes some of the dye. However, too much abrasion can damage the fabric, particularly hems and waistbands. This is why denim finishers today use acid, hybrid or neutral cellulases to accelerate the abrasion by loosening the indigo dye on the denim. Since a small dose of enzyme can replace several kilograms of stones, the use of fewer stones results in less damage to garments, less wear on machines, and less pumice dust in the working environment. Productivity can also be increased through laundry machines containing fewer stones but more garments. With a stone-free process, the need for the removal of dust and small stones from the finished garment is reduced. There is also no sediment in the wastewater, which can otherwise block drains. Denim garments are dyed with indigo, which adheres to the surface of the yarn. The cellulase molecule binds to an exposed fibril (bundles of fibrils make up a fiber) on the surface of the yarn and hydrolyses it, but leaving the interior part of the cotton fiber intact. When the cellulases partly hydrolyse the surface of the fiber, the indigo is partly removed and light areas are created.

Neutral cellulases or Neutrastone Series designed by AETL acting at pH 6-8, acid cellulases (Denicell Series) acting at pH 4-6  and hybrid cellulases (Addcool Series) acting at pH 5 – 6.5 are used for the abrasion of denim. There are a number of cellulases available, each with its own special properties. These can be used either alone or in combination in order to obtain a specific look. Application research in this area is focused on preventing or enhancing backstaining depending on the style required. Backstaining is defined as the redeposition of released indigo onto the garments. This effect is very important in denim finishing. Backstaining at low pH values (pH 4-6) is relatively high, whereas it is significantly lower in the towards neutral pH range. Neutral cellulases are therefore often used when the objective is minimal backstaining. Hybrid cellulases are effective tool to save energy cost as processing can be done at ambient or room temperature conditions.

Bio-carbonizing:

Polyester / cellulosic blends after dyeing and/ or printing are occasionally treated with strong solution of sulphuric acid to dissolve cellulosic component. The resultant goods are soft and have a peculiar fluffy feel. This process is risky due to highly corrosive acid that is also difficult to treat in an ET plant.

The process developed at UNO, has none of the above drawbacks. It offers a safe and eco-friendly to the obnoxious practice of using sulphuric acid. The goods are treated with cellulose enzyme based formulation to achieve dissolution of cellulosic fibers.

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