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H O M E
SECTION 1 SECTION 2
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NEW TRENDS IN ENZYMATIC PROCESSING Owing to the specific nature, enzymes have become an important class of bio-chemicals in textile processing. Being bio-catalysts, enzymes were not consumed in the reaction. They were also used in the processing from a standing bath. Illustrating a schematic diagram for working of an enzyme, he indicated the active and secondary sites and how the enzyme was larger than the substrate as it attached itself to cellulose forming a complex in which the concentration of the reactants increased thousands times due to which the reaction proceeded. The substrate was broken into degradation products making the enzyme available to attach itself again to another substrate and the cycle was repeated and thereby the enzyme became a biocatalyst. BIO-SINGEING This mode of finishing has been specifically developed to achieve clearer pile on terry towel goods. A treatment with an enzyme, which is a powerful cellulase composition, gives clearer look to the pile, improves absorbency and softness. Earlier, desizing was carried out by steeping the fabric with mineral acid, which affected the cellulose as well as the colour. Use of enzymes here led to reaction with the starch only and thus they assumed considerable significance. Explaining the action of enzymes, the food consumed by human body was digested due to secretion of the enzyme. At the enzyme-substrate complex level, the concentration of the reactants became large and accelerated the reaction while reducing the activation energy barrier. Thus, the reaction which took place at higher temperature and severe conditions could be carried out at relatively lower temperatures and milder conditions. BIO-SCOURING Bio scouring did not involve any colour, yet after scouring the fabric was dyed with colours. Cotton could be treated with bioscouring enzyme although the techno-economical parameters were not conductive. But, it had a bright future due to rigorous effluent treatment since disposal of both caustic soda and soda ash was causing environmental concern. The enzymes helped removal of waxes, pectins, sizes and other impurities on the surface of the fabric. Combination of pectinase and lipase gave best results, but cost of the latter was a deterrent. Advantages of bioscouring were lower BOD, COD, TDS, and the alkaline media of water, extent of cotton weight loss, which was a boon to the knitting industry, lower alteration of cotton morphology i.e. less damage since it was specific to pectin and waxes and not cellulose besides increased softness. The lone disadvantage was that the cotton motes were not removed, which warranted peroxide bleaching. Bio-Scouring Process Details... BIO-BLEACHING: It was applicable for all kinds of colours and a single enzyme could be used in the textile industry. Bio-bleaching had been adapted for denim. Indigo specific lipases were used to bleach indigo. Earlier denim was bleached with chlorine to get lighter denim or wash down effect. Lipase combination was used successfully and if this could be extended to other colours, this would become an important enzyme in future. The advantages were environment friendly application, non AOX generation and cellulose was not affected. A bio-bleaching or lipase treatment on denim gave an authentic wash resulting in an excellent look, which was better than a neutral wash and a grey cast, which was used in bleaching. Amylase and lipase were used for desizing and cellulase for aberration. Lactase was introduced for bleaching of indigo. It ensured shade quality particularly with reactive dyes, reduced the complexity of treatment after peroxide bleaching and conserved water. In case of reactive dyeing, after bleaching it was vital that the peroxide residues must be cleared out of the system and as such there were no fool proof ways of such clearance, which entailed several rinsing operations or reduction treatments. Empirically, it was difficult to know how much quantity of reducing agent was required to react with the peroxide left in the bath. In the event either of them happened to be excess, it might affect the dyeing. Therefore, after bleaching, the bath should be neutralized with peroxide killers like peroxidase or catalase followed dyeing with reactive dyes. They did not affect reactive dyes and only react with the peroxide. These catalysts were fastest acting type as 1 molecule of catalyst destroyed 5 million molecules of peroxide or 700 times its own weight of peroxide. |