The wet processing of textiles is energy and water intensive, as well as requiring the use of numerous chemicals. Wet processing steps, depending on the textile product, can include sizing, desizing, scouring, bleaching, mercerisation, printing, and finishing. Many of these steps require high temperatures, mechanical agitation, and different chemicals to be added, whilst thorough rinsing with large volumes of water to remove excess chemicals is needed between steps. The use of enzymes in textile manufacture is an increasingly important way to lower the energy, water and chemical footprint of many of these processes.

Enzymes are generally non-toxic, environmentally-friendly biological catalysts that lower the energy required in chemical processes, as well as the efficiency of reactions. To meet the needs of the global textile industry, new development in enzymatic treatments makes it now possible to customise and tailor these compounds to suit specific end uses. This means less energy for heat, fewer chemicals requiring removal from effluents, and less water for rinsing. 

Benefits

The benefits of enzymatic treament versus conventional chemicals need to be weighed against their typically higher cost, and their compatibility with other processing steps needs to be checked. However, some examples of when enzymes are used in the wet processing of textiles are listed below [1]:

• Desizing: Amylases degrade the starch used to size cotton for weaving into glucose. These enzymes are more specific than the conventionally dilute acids, meaning there is less fibre degradation and lower effluent load.
• Removing glucose from sizing effluent: Glucose oxidase breaks the glucose down into hydrogen peroxide, reducing the organic pollution levels, as measured by the biological oxygen demand (BOD), of the effluent
• Scouring: Can be carried out by enzymes such as proteases, pectinases and cellulases instead of the typical energy- and water-intensive sodium hydroxide method [2]
• Bleaching: Laccases are used for bleaching denim to get a ‘stone washed’ effect, both reducing the potential damage to the garment and providing a greater degree of wanted ‘fade’
• Washing: Catalases remove the residual hydrogen peroxide left over from bleaching and improve the uniformity and uptake of dyes in the fabric
• Finishing: Cellulases are used in ‘polishing’ cotton textiles, removing loose fibres adhered to the fabric. This is a bio-polishing process which gives cotton a soft feel and reduces the pilling property of the cellulosic fibre. Similarly, esterases, lipases, and cutinases can replace sodium hydroxide in improving the softness and moisture absorption characteristics of polyethylene terephthalate (PET) fabrics