Diversified use of Enzymes in Bio-technology for Textile Wet Processing

What are enzymes?

Enzymes are macromolecular biological catalysts. They are responsible for thousands of metabolic processes that sustain life.Enzymes are highly selective catalysts, both greatly accelerating the rate and greatly enhancing the specificity of metabolic chemical reactions. Most enzymes are proteins, although some catalytic RNA molecules have been identified. Enzymes adopt a specific three-dimensional structure, and may employ organic (e.g. biotin) and inorganic (e.g. magnesium ion) cofactors to assist in catalysis.

Role of enzymes in Bio-technology for textile wet processing:

Among the all micro-organisms enzymes are widely used in textile sectors. They are so suitable that replace the uses of toxic chemicals, reduce activation energy, maximum result with minimum cost as well as environment friendly. So they are widely used in singeing, scouring, bleaching, mercerizing, ETP plant, bio-polishing, finishing etc and play an important role in textile sectors.

Enzymes and their classifications:

Enzymes, the micro-organism which is considered as the heart of the bio-technology, are consists of proteins, having a high molecular weight, consist of long chain of amino acids held together by peptide bonds. They are present in all living cells and acts as a catalyst in bio-chemical reactions.

According their protein size (may be tubular or round) and capability to attack substrate they are classified into two major groups. They are:

1. Hydrolase enzymes.

2. Oxidoreductase enzymes

Applications of hydrolase enzymes in textile wet processing:

Enzyme name	Substrate attack	Textile application
1.Amylase	Starch	Starch de-sizing.
2.Cellulase	Cellulose	1.bio –polishing
3.Pectinase	Pectin	Bio–scouring replace caustic soda
4.Catalase	Peroxides	Use as peroxide killer.
5.Protease	Protein molecules	Use in silk & wool processing.

Applications of oxidoreductase enzymes in textile wet processing:

Enzyme name	Substrate attack	Textile application
1.Laccase	Color-chromophore and pigments.	1. Discoloration of colored effluent.
2. Azo reductase.	Azo Color-chromophore and pigments.	Discoloration of azo dyes effluent.
3.peroxidase	Color-chromophore and pigments.	Discoloration of ramazol of basic dye effluent.
4. Glucose oxidases	Pigments	1.Bio bleaching of cotton

Condition for maximum efficiency of enzymes:

The maximum efficiency of any enzyme depends on some criterion. They are:

Temperature of the processing bath.

P^H of the bath.

Concentration of enzymes.

Inhibitors.

A short list of different condition for de-sizing enzymes to get maximum efficiency is given below:

Types of enzymes	Temperature (0C)	PH	Concentration
1.Pancreatic	50-55	7-7.5	1-5 mg/l
2.Malt extractor	55-60	5.5-6.5	3-20mg/l
3.Bacterial	65-70	5.5-7.5	.5-3gm/l

Application of different bio -technology in textile wet processing:

Bio-desizing:

De-sizing is a mandatory process in textile wet processing to remove size materials from warp yarns in order to increase dye absorbency. Traditionally two methods are applied. They are-

Hydrolytic method

Oxidative method

In Hydrolytic method desizing is carried out by using high concentrate Caustic Soda (Na0H) (.4%-.5%) at a temperature 60-70^oC and at a P^H = (9.5-10.5) or, highly concentrate Hydrochloric acid (HCl) (.5%-1%) at a temperature 40-50⁰C and P^H= (4-5) is used at a liquor ratio 1:10.

In oxidative method toxic Chlorite and Bromite is used. But this process can be easily carried by using analyze Enzymes replacing the use of toxic chemicals such as NaOH, HCl, Chlorite, Bromite, at a low temperature and less liquor ratio(1:10) to reduce production cost. Since the amylase just hydrolyzes (1-4,∞) glucosidic linkage of amylase and emylopectins of starch to convert into soluble dextrin

The advantages of using Amylase enzyme in de -sizing:-

Replace using harsh chemical like NaOH, HCl

Reduce Vaporization of toxic Chlorine and Bromine

Reduce BOD value of starch in waste water to save aquatic animals and plants.

Low temperature, low liquor ratio that is by using amylase the liquor ratio reduce to 1:6 that indicates 

To process 10 tonne fabric it will reduce 40 m³ water to be wastage. So, it is a huge amount of water to be saved as well as to reduce cost for only one industry. Think about all industries, the quantity will cut a huge figure.

Bio-scouring:-

The step after de-sizing is scouring and it is also mandatory step in wet processing. Traditionally, alkaline chemicals such as Caustic Soda (NaOH) are used to remove the non-cellulosic components from fiber to increase dye-absorbency. But the process is very concern to environment. Because-

NaOH causes the raise of P^H in surface water

It requires high temperature (100-110⁰C) which causes emission of huge amount of CO & CO₂.

It not only removes the non-cellulosic components but also attack cellulosic components which degrade fabric strength.

4. The alarming result is that, these hazardous chemicals have high BOD&, COD value in waste water and also increase the overall production cost.

But simply using Bio- Technology we can replace excess NaOH and reduce environment pollution,

The commonly used enzymes in Bio-scouring are-

Pectinase – to decompose pectin substance

Protease- to decompose protein

Lipases- for fats and waxes.

Their synchronizing combination give best result at low temperature, 65^OC, low energy level without using environmental hazardous chemicals like

Bio-bleaching:-

To achieve high degree of whiteness, as well as to increase dye absorbency power, we have to remove natural color from the fiber. Universally H₂O₂ (Hydrogen Peroxide) is used as bleaching agent. But the process has some considerable drawback. They are:

The process consumes large quality of chemicals, water and energy because environmental pollution and increase production cost.

The residual H₂0₂ should be killed to get best result in dyeing and finishing by repeated washing causes water pollution.

Although there is no such enzyme which is capable of imparting full satisfactory bleaching condition .The advantage of use Peroxidases enzymes is that the process get dynamicity since it activate oxidizing agent like H ₂O₂.

The third one is the most promising movement of glucose oxidases as like Peroxidases enzymes capable of producing hydrogen Peroxide and gluconic acid from glucose and oxygen. The most significance is that the

1. Re -use of sugar contaminated effluent from other wet processing steps.

2. Moreover by using enzymes scouring and bleaching can be done in the single stage since their functions are fixed.

Peroxide killing:-

After bleaching the residual H₂O₂ must be killed and traditionally repeated washing is done which causes wastage of huge water. But by simply using hydrolase type enzymes H₂O₂ can easily decomposed into H₂0 + 0₂. Beside, dyeing can be done in the same bath since the hydrolase enzymes don’t attack the reactive dyes.

If we done dyeing and peroxide killing in the same bath, to process 1000kg fabric (cotton) it will reduce 10 m³ (10 tonne) water to be wastage. When it is considered for all industries, the figure will cut a good one.

Bio-polishing:-

The process can be applied before dyeing or after dyeing or both. The main principle is to reduce floating fibers from the fabric surface to make a smooth and high degree of levelness.

Conventionally it is done by fire-flame and heated beam at a temperature (100-120^oC) which causes high power consumption as well as emission of large volume of CO₂ causes increasing of surface temperature. But by simply using cellulose enzymes we can do it easily without polluting the environment at a fix temperature 65⁰C only. Their other contribution is that, they replace the use of volcano lava stone to achieve a high degree of color fading in denim processing to save cost as well as air pollution.

Bio-Washing:

Finishing is mandatory since it increase the lusturous appearance to attract the customers. Conventionally they are done by repeated washing with chemicals, stone wash, dry cleaning agent, soap, detergent etc. But now by using enzymes this process is done without using these toxic chemicals with a liquor ratio 1:5 in garments washing.

Enzymes use in garments washing.

Enzymes	Effective for
1.cellulases	Color brightening, softening, soil remover.
2.Proteases	Grass, blood, egg stains.
3.Lipases	Butter, salad oil.