Enzyme
WHAT ARE ENZYMES?
The enzymes are large protein molecules made up of long chain amino acids , which are produced by living cells in plants , animals and microorganisms , such as bacteria and fungi.
Advantages of enzymes over conventional chemicals
Enzyme technology is fast growing and emerging field of science , which has found innumerable applications in the textile wet processing. Since enzymes are natural products , they are easily biodegradable , non polluting , cleaner, gentle , non aggressive with minimum damage to substrate and environment. Enzymes promised a cleaner and environment friendly future by having the capacity and potential to enable us to live harmoniously with the nature.
ENZYMES IN TEXTILES PROCESSING
The processing of textiles is being done chemically, whether it is pretreatment dyeing , after treatment or finishing . The chemicals and conditions used often harsh and harmful to the substrate and some times degrade it also. These chemicals increase the pollution load in air and water, thus creating problems in the treatment and disposal of effluents as well as sludgedisposal. Enzymes in textile industry are used due to following reasons,
a. They accelerate the reaction rates
Enzymes acts as catalysts and speed up a particular chemical reaction by lowering activation energy for a reaction. The reaction rates are very fast when takes place in the presence of suitable enzymes.
b. They are specific
one particular enzyme will only catalyze a specific reaction under standard conditions such as time ,temperature, and pH and on only one or few substrates.
c. They operate under milder conditions
most enzymes have a maximum activity at an optimum temperature and pH conditions and most of the enzyme assisted reaction takes place under milder reaction conditions such as temperature ,pH and pressure.
d. They are safe and easy to control
enzymes perform well in the normal pH and temperature conditions , that too in the milder conditions such as concentration. When no longer required these are deactivated by changing the conditions such as pH and temperature. Most of the enzymes , being natural products are biodegradable and converted into natural products after disposal.
e. They replace harsher chemicals
when used , enzymes catalyze the reaction rates at milder conditions , they replace the excessively used harsher , toxic and non biodegradable chemicals. The reaction conditions are also milder instead of extreme concentrations, temperature and pressure.
f. They are eco friendly and biodegradable
Since enzymes are protein molecules , they are degraded by other proteolyses enzymes secreted by micro organisms to amino acids , which are natural products and re enter the food chain.
Types of enzymes
All the enzymes used in textile industry can be classified into 6 basic enzyme classes, based on the type of chemical reaction they catalyze, these are
1.Hydrolases
These are the enzymes that catalyse a hydrolysis reaction .Examples of hydrolases are cellulase ,proteases, amylases and lipases. They target substrate and physically modify the fiber itself, and degrade textile auxiliary and impurities.
2.Lyases
These are enzymes that catalyse the separation of two parts of molecules with the formation of double bond with one or the other. Lysase make additional textile impurities susceptible to enzyme attack.
3.Oxidoreductases
These are the enzymes which catalyze the oxidation of the one compound with the reduction of the other. Examples are dehydrogenases, oxidases,laccases ,peroxidases and catalases.
4.Transferases
These enzymes catalyse the transfer of a functional group from one (donor) molecule to another (acceptor) molecule.
5.Isomerases
Isomerases are enzymes that catalyse the structural rearrangements of isomers .
6.Ligases
These are the enzymes that catalyse the reactions which make bonds to join together smaller molecules into bigger molecules.
New classes of enzymes that under research , for the application into textile processing are
Polyesterases
For the application on polyester to improve the undesirable properties of polyester textiles under mild conditions, such as pilling, hydrophilicity, cationic dye absorption and binding, removal of polyester size , delusturing and improving oil stain resistance.
Nitralase,nytrile hydratase and amidase
These are the nitrile degrading enzymes for the degradation of nitrile groups for modification of acrylic fiber, to improve its undesirable properties .
Use of enzymes in different textile processing applications
1. Bio singeing
2. Desizing.
3.enzymatic back stain clean up.
4.denim washing
5.non denim fabric finishing
6. biopolishing
7.bio scouring
8.bio bleaching.
9.peroxide killing.
10.degumming of silk
11.modification of wool fiber.
12.print washing
13.after treatment ( washing off ) of dyed goods.
14.waste water and effluent decolrisation and treatment.
15.wool and silk scouring.
16.wool bio carbonizing
17.shrink resist treatment of wool fiber.
18.to improve undesirable properties of polyester.
19.to improve undesirable properties of acrylic.
Description of common enzymatic treatment in textiles
Amylases :-
Thermo stable amylase 70-1100C
pH 6.0-6.8
Conventional amylase 50-700C pH 6.0-6.8
Low temperature amylase 30-700C pH 6.0-6.8
To remove starch based sizes , these are specific to starches without affecting the substrate.
Cellulases :-
acid cellulases 30-600C
pH 3.8-5.8
Neutral cellulase 40-550C
pH 6.0-7.0
These are used to modify the surface properties of cellulosic fibers and fabrics in order to achieve the desired handle and surface effect.
Hemicellulases and pectinases :-
Mixture of enzymes 45-550C
pH 4.8-5
Pectinases are used to separate fibers and eliminate pectins in jute,ramie and flax. Pectinases when used with cellulases , remove impurities of raw cotton and vegetable impurities of raw wool.
Proteases:-
There are many protease ,each with different specificity towards different protein fibers.
These are used in leather and wool, for shrink proofing of wool, to give wool a soft and supple hand. Alkaline protease are used in leather industry to remove hair form hides.
Catalase
for bleach clean-up i.e. removal residual hydrogen peroxide after the bleaching of cotton.
Conclusion
Use of enzyme based technology in natural as well as synthetic textiles is already established. It is technology of future , by which we can replace the harmful and harsher chemicals and processes , with cleaner , biodegradable and mild processes.
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