Enzymology

1. Enzymology Lecture 6 by RumezaHanif

2. Properties of enzymes In the textile industry • accelerate the reaction • Operates under mild conditions • Alternative for polluting chemicals • Acts only on a specific substrate • Easy to control • biodegradable

3. Enzymatic Desizing • In the textile industry amylases are used to remove starch-based size for improved and uniform wet processing. • Amylase is a hydrolytic enzyme which catalyses the breakdown of dietary starch to short chain sugars, dextrin and maltose. • The advantage of these enzymes is that they are specific for starch, removing it without damaging to the support fabric. • An amylase enzyme can be used for desizing processes at low-temperature (30-60ºC) and optimum pH is 5,5-6,5.

4. Enzymatic Scoring • Scouring is removal of non-cellulosic material present on the surface of the cotton. • In generally cellulase and pectinase are combined and used for Bioscouring. • In this pectinasedestroy the cotton cuticle structure by digesting the pectin and removing the connection between the cuticle and the body of cotton fibre whereas cellulase can destroy cuticle structure by digesting the primary wall cellulose immediately under the cuticle of cotton.

5. fibres, yarns or fabrics have various kinds of impuri-ties like motes, seed coat fragments, pesticides, dirt, chemical residues, metallic salts of various kinds, and immature fibres. External impurities are removed in the blow room processing while internal impurities of cotton fibres removed by scouring processes. Cotton fibre is constituted with different layers in its body.

6. Constituents of cotton fibre • Cellulose (90%-94%), waxes (0.6%-1.3%), pectic substances (0.9%-1.2%), protein (0.6%-1.3%), ash (upto 1.2%), organic acids (upto 0.8%) and others (1.2%). • The main target of scouring is to remove waxes, pectins, hemi-celluloses and minerals from the raw cotton fibres during the early stage of textile wet processing to make the fibres highly absorbent, which is necessary for the subsequent processes such as bleaching, dyeing, printing and finishing. For this purpose, Caustic soda (NaOH) treatment is used in conventional scouring, whereas, Enzymes(Cutinases, Pectinases etc.) treatment is applied in bioscouringprocess.

7. Enzymatic Bleaching • The purpose of cotton bleaching is to decolourise natural pigments. • Mainly flavonoids are responsible for the colour of cotton. • The most common industrial bleaching agent is hydrogen peroxide. • Conventional preparation of cotton requires high amounts of alkaline chemicals and consequently, huge quantities of rinse water are generated. • However, radical reactions of bleaching agents with the fibre can lead to a decrease in the degree of polymerisation and, thus, to severe damage. • Therefore, replacement of hydrogen peroxide by an enzymatic bleaching system would not only lead to better product quality due to less fibre damage but also to substantial savings on washing water needed for the removal of hydrogen peroxide.

8. Bleaching enzymes • Amyloglucosidases, pectinases, and glucose oxidases, laccases

9. Enzyme biopolishing • Biopolishing is a finishing process that improves fabric quality by mainly reducing fuzziness and pilling property of cellulosic fibre by using cellulase enzyme. • Cleaner surface is obtained conferring a cooler feel • Lustreis obtained as a side effect • Fabric obtains softer feel. • Tendency of the fabric to pill ends.

10. Treatment of denim with enzymes • Denim is heavy grade cotton. In this dye is mainly adsorbed on the surface of the fibre. That is why fading can be achieved without considerable loss of strength. • Cellulase and Laccase

11. Enzyme applications in textile preparatory process • degumming of silk with sericinases • the felt-free-finishing of wool with proteases • the softening of jute with cellulases and xylanases • synthetic fibers such as polyester or polyacrylonitrile are modified by an enzymatic treatment.