Enzymes have been around mankind since thousands of years. They are living organisms and have been used to carry out chemical reactions to make items like cheese, beer and wine. As it has become crucial to reduce pollution in textile processing, the textile manufacturers have increased the use of enzymes in various textile processes. Today, enzymes are widely used and well known for their non-toxic and environment friendly nature.
Enzymes are obtained naturally from animal tissues and plant resources but most of them are obtained from microorganisms. Using enzymes gives deep insight of all the aspects of textile processing, basic biochemistry, enzymology and how it is used for industrial application. The use of enzyme is widely recognized in textile industry as each enzyme is used to create specific effect in each textile process.
Moreover, it works in moderate situations and speeds up the reactions. The commonly used enzymes in textile processes are amylases, catalase and laccase. These are used to remove the starch and scale down the effectiveness of hydrogen peroxide, lignin and bleaching textiles.
Enzymes are safely used in the textile processes like de-sizing, scouring, bleaching, dyeing and finishing. Moreover, enzymes are used as substitute of harmful chemicals which pose environmental risks and hence are biodegradable. The latest development in enzyme application is using cellulases for denim finishing and lactases to remove the color from textile waste matter and textile bleaching.
Uses of Enzymes
Some important processes of textile wet processing which use enzymes have been discussed below:
Desizing: Earlier, fabrics were treated with acid, alkali or oxidizing agents to remove the size. Sometimes they were soaked in water for many days which naturally gave rise to microorganisms that would cut down the starch. But both these methods were hard to manage, time consuming and sometimes damaged or discolored the fabrics. However, this problem was solved by using enzymes as they removed starch without harming the fibres.
Scouring: In this process, dirt on the surface of the fibres like wax, pectins, fats and other impurities are removed. This gives the fabric better wetting ability, which in return helps the fabric to get bleached and dyed properly. Chemicals like caustic soda are used for this process. Thus, not only it removes impurities but also decreases the strength and weight of the fabric. Also, it releases harmful chemicals in the waste water.
By using enzymes in the new scouring process known as Bio-Scouring, all impurities are removed and it keeps the cellulose structure of the fabric unharmed. Therefore, the fabric has higher wetting and infiltration abilities.
Bleaching: This process requires lot of water, energy and chemicals. A new bleaching process is developed which not only reduces the length of the bleaching cycle but also saves water and energy. Moreover, after the fabric is bleached the remains of hydrogen peroxide is left in the wash which needs to be completely cleaned before dyeing. This is done by a process called bleach cleanup.
If traditional method is applied, one has to be careful with the dosage of the reducing agent. If hydrogen peroxide is not removed completely, it will result into poor dyeing. Now enzymes are used in this step which ensures that peroxide is completely removed and little amount of catalase breaks hydrogen into water and oxygen. This reduces the usage of water in the whole process and the waste water is cleaner.
Garment Washing: Enzymes are widely used in textile washing and have replaced the usage of chemicals in the past 20 years. Enzymes are used for different types of washing like enzyme wash, stone enzyme wash etc.
Dyeing: Scientists have developed enzymes which are extracted from fungi. These enzymes are used to make colorants for dyeing textiles and leather. The colorants have chemical features that allow them to stick to the fibers and eliminate the addition of chemicals that can pollute water while dyeing.
Finishing: The uses of enzyme in finishing processes are classified into two as given below.
The first one is Bio-finishing. It removes fibre hair and strands from the surface of the fabric. Using enzymes in bio-finishing gives dirt free and softer surface. It also adds luster to the fabric and decreases pilling.
Secondly, enzymes are used for Denim finishing. The standard method of stonewashing used harsh pumice stones to fade the denim. But now it has been replaced by using special cellulose enzyme to fade the denim. This process is known as Bio- stonewashing. As a result, less damage is done to the denim, machine and the environment.
Textile industry has been turning to eco-friendly methods as it gives rise to major environmental problems. Hence, microbial enzymes have taken an important place in the textile processes. Going by facts, enzymes have been used in the textile processes since 1857. Today, a range of enzymes like cellulase, lipase, catalase and protease are used in many textile applications such as degumming, silk or wool finishing and others discussed above.
The cellulase enzyme is used as it gives great finish to rayon, linen, cotton knits and woven fabrics. At present, cellulases are included in many detergents for removing surface hair, depilling and maintaining the lucidity of the color.
Benefits of enzymes in textile wet processes:
Firstly, the finishing agents and fibers that are produced using enzymes are eco-friendly. It is an economical technology that saves water and energy. They have low emissions and make use of renewable resources. The textile effluents have high level of BOD (Biochemical oxygen demand)/COD (Chemical oxygen demand). However, using enzymes in textile processes considerably changes the quality of effluents.
The main reason of using enzymes in textile applications are the growing environmental threats due to disposal of polluted waste water or releasing harmful chemicals in air and water. Enzymatic processes effectively reduce BOD/COD and remove or decolorize dyes in the waste water.
Moreover, microbial enzymes have the ability of degrading azo dyes which will be very useful to the textile industry. The use of enzymes in textile industry is a sign of promoting eco-friendly technology. Besides, it enhances the quality of the final product.
To conclude, one can affirm that the use of enzymes has largely benefited textile processing and is eco-friendly. There are 7000 known enzymes but only around 75 are usually used in the textile industry. Therefore, further research is required for the development of commercial enzymes and for finding new enzyme producing micro organisms.