Bio-Polishing
Bio-Polishing
■ The application of cellulases in wet textile processes has been, like enzymatic desizing, successfully
introduced and accepted in the textile industry. Cellulase enzymes are a class of hydrolytic enzymes
that are used for different cotton finishing processes: cellulases can be utilised to give indigo-dyed
cotton fabrics (denim) an aged appearance (also known as biostoning) and to give cotton fabrics a
renewed appearance by colour brightening and softening of the material through the removal of
microfibres (depilling, also known as biopolishing).
■ Bio-polishing is also called Bio-finishing, which is a process applied to cellulose textiles that produces
permanent effects by the use of enzymes. Bio-polishing removes protruding fibres and slubs from
fabrics, significantly reduces pilling, softens fabric hand and provides a smooth fabric appearance,
especially for knitwear and as a pretreatment for printing. Second rate articles can obtain the high
value eye appeal of first rate ones.
■ The bio-polishing process targets the removal of the small fiber ends protruding from the yarn
surface and thereby reduces the hairiness or fuzz of the fabrics. The hydrolysis action of the enzyme
weakens the protruding fibers to the extent that a small physical abrasion force is sufficient to break
and remove them. Bio polishing can be accomplished at any time during wet processing but is most
convenient performed after bleaching.
Enzyme Based Process in Textile Wet Finishing
Offer Following Advantages
■ Ecological friendly production of fibers and finishing agents.
■ Reduction in BOD / COD in the effluents treatment plant (ETP).
■ Saving of water and energy.
■ Alternative for polluting chemicals.
■ Enzymes act as catalysts and remain the same after the reaction. It speeds up the reaction by
increasing the rate of particular reaction.
■ Enzymes are very specific and they catalyze only on some specific substrates. Substrate is the
material upon which an enzyme acts. It will react only to a specific substance.
■ Every specific enzyme has a specific temperature and pH value in which they perform their best in
speeding the chemical reaction but any temperature or pH beyond the specified one would only
degrade the enzymes performance.
■ Enzymes can be easily reused.
Enzymes
■ Enzymes are high molecular weight proteins produced
by living organisms to catalyze the chemical reaction
essential for the organism’s survival. They have complex
three - dimensional structures composed of long chains
of amino acids held together by peptide bonds.
Molecular weights ranging from 10,000 to about
150,000 and occasionally to more than 10,00,000.
■ Enzymes are basically biocatalysts capable of notably
accelerating the chemical reactions which occur in living
organisms. Enzymes are capable of performing these
tasks, because unlike food proteins such as egg albumin,
gelatine or soya protein, they help to catalyze reactions.
This means that by their more presence, and without
being consumed in the process, enzymes can speed up
chemicals process that would otherwise run very slowly.
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Figure: Structure of Enzyme
The History Of Enzymes
and uses in Textile
Types of
enzymes
Textile use and effects.
Cellulases
Bio – finishing, bio – polishing, anti-pilling, softness, smoothness, luster
improvement and stone washed effect on denim
Cutinase
Bio-polishing of polyester fabrics and can be
Combined with a compatible cellulase to treat P/C fabrics.
Amylases
Standard procedure for the removal of starch warps size.
Proteases
In household washing agents’ better removal of protein containing soil
or stains. Anti-felting (shrink resist) of wool, degumming of silk with the
problem of silk fibroin damage.
Lipases
In detergents for the hydrolysis of lipids.
Catalase- Bleach cleanup (1993).
Pectinases
Hydrolysis of pectins, for example in cotton preparation and retting of
flex and hemp.
Laccase- Denim Bleaching (1996).
Catalases
Catalyse the decomposition of hydrogen peroxide, important
Before reaction dying or printing of peroxide bleached fabrics and yarns.
Peroxidases
Used as an enzymatic rinse process after reactive dying, oxidative
Splitting of hydrolyzed reactive dyes on the fibre and in the liquor,
Providing better wet fastness decolorized waste water and potentially
toxic decomposition compound.
Ligninases
Removal of burns and other plant compound from raw wool.
Collagenases
Removal of residual skin parts in wool.
Esterases
In development polyester finish removal of oligomers
Nitrilases
In development polyacrylonitrile preparation for better coloration.
Amylase- Desizing (1952).
Protease - Wool Scouring (1984).
Cellulase- Bio-stoning (1987).
Peroxidase- Enzymatic Rinse (1999).
Pectinase, Lipase- Bio-scouring (2003).
Table - Types of enzyme for textile use and their effect
Properties of Enzyme
1. Enzymes are specific: Contrary to inorganic catalysts such as acids, bases, metals, and metal
oxides, enzymes are very specific. In other words, each enzyme can breakdown or synthesized
one particular compound. In some cases, they limited their actions to specific both in the
compound with which they react. Most proteases, for instance, can breakdown several types of
protein, but in each protein molecule only certain bonds will be cleaned depending on the
which enzyme is used.
2. Enzymes are very efficient catalysts: The enzymes catalase, which is found abundantly in the
liver and in the red blood cells, is so efficient that in one minute, one enzyme molecule can
catalyze the breakdown of five million molecules of hydrogen peroxide to water and oxygen.
3. Origin – natural source: Enzymes are present in all biological systems. They come from
natural system and when they are degraded the amino acid of which they are made of can be
readily absorber back into nature.
4. Enzymes work only on renewable raw material: Fruits, cereals, milk, fats, meat, cotton
leather and wood are some typical candidates for enzymatic conversion in industry. Both the
usable products and the waste of most enzymatic reaction are non – toxic and readily broken
down.
Cellulase Enzyme
Cellulases are high molecular colloidal protein bio-catalyst. Industrial cellulases represent complex of a
number of cellulases, cellobiose and related enzymes of completely non uniform composition in a
molecular weight range of 10,000 to 4 million.
Cellulases can be derived from a variety of microorganisms, especially fungi, such as Trichoderma reesei,
Humicola insolens, Aspergilus niger and Bacillus subtilus. They may be produced both in powdered forms
(often adsorbed on a support medium) and as concentrated liquids. These organisms can all be used to
produce acid-stable as well as neutral- and alkaline-stable cellulase mixtures. Cellulases are capable of
breaking the 1, 4-β-glucoside bond ofcellulose randomly. As a result of which the fabric surface becomes
smooth with the loss of surface fibresand the hand becomes soft. There is also loss in strength
proportional to the amount of weight reduction.
There are mainly three types of cellulases:
Acid stable (more effective in pH range of 4.5 - 5)
Neutral stable (effective at pH 7)
Alkaline stable (not used widely)
Action Of Cellulase Enzymes On Cellulose
Enzymes are large molecular complex and can’t penetrate interior of the fabric. Hence
enzyme action takes place preferentially on the surface. Where cleavage of cellulose chain
occurs. Microfibrils, which are loose fibres break off under the influence of bio-catalytic
degradation and modify the surface of the fabric.
Industrial production of cellulose involved large scale growth of fungal populations,
followed by extraction of the enzyme. The extracted enzymes contain multiple compound
that work together to yield glucose from a cellulose polymer chain. At least four
compounds have been identified being important in providing efficient glucose
production.

Endocellulases cleave the long cellulose chains randomly to produce two shorter
chains
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Exocellulases attack one end of the cellulose chain, cleaving one glucose unit at a
time
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Cellobiohydrolases similarly act on one end of the cellulose chain, producing a
cellobiose molecule

Cellobioases degrade cellobiose molecules to the simplest glucose unit.
These actions are illustrated in Figure.
The mechanisms of cellulase degradation of cotton are still not fully elucidated, but it appears that the first step involves attack by an
endocellulase, which attaches itself to the cellulose surface, forming a complex. After cleaving a glucose unit the enzyme molecule
may detach itself and move to another site, or may remain to degrade the same site further.
Process Variables/Factors affecting Bio-polishing
■
Concentration
■
Temperature
■
pH
■
Time
■
M : L Ratio
■
Mechanical Agitation
Concentration
Concentration of enzyme is a major factor, which affects the performance of the bio-polishing of the knitted fabric.
There are different types of enzymes available in the market. Each enzyme has an optimum concentration, pH and
temperature range.
From this Table, it can be concluded that as the concentration of cellulase increases from 0.5% to 3.5%, weight loss
increases significantly. Optimum percentage weight loss is obtained at 3% concentration. Increase in concentration
of enzyme causes an increase in strength loss. Fabric thickness is reduced with increase in concentration of
enzyme. Hence 3% concentration of enzyme is the optimum dose.
Temperature
Temperature affects the performance of cellulase. Each enzyme has
an optimum temperature range where enzyme activity is maximum.
Hence it is essential to determine the optimal temperature. Increase
in temperature decreases the enzyme activity rapidly and the enzyme
action comes to almost zero and the enzymes are permanently
deactivated at 70ᵒC almost for all enzumes. Low temperature shows
reduction in reaction speed but does not deactivate the enzyme. It is
therefore possible to use a lower temperature by a longer cycle.
pH
pH is also a critical factor affecting the efficiency of bio-polishing. A particular type of cellulase is most effective and can
be operated at a certain specific pH range.
Time
Duration of enzyme treatment on bio-polishing depends on the type of enzymes and fibres, optimum temperature, pH,
concentrations and amount of hairiness need to remove from the fabric. Study shows that 30-50 minutes are sufficient
for proper bio-polishing.
M:L Ratio
M:L Ratio has a substantial effect on bio-polishing. As the liquor ratio increases the bath concentarion of cellulase
decreases, and the fabric weight loss decreases. It is found that as the liquor ratio increases the pilling rating of
treatment sample decreases and best result is obtained at 1 : 10 M:L Ratio.
Bio-polishing Of 100% Cotton Knitted Fabric With Cellulase Enzyme
Bio-polishing can be carried out before or after scouring and bleaching or dyeing.
Now-a-days it single stage bio-polishing and dyeing is performed at industries for cost
minimization, energy and time saving.
Recipe of bio-polishing
Cellulase Enzyme
Wetting agent
Acetic acid
Peroxide killer
M:L
Temperature
pH
Time
1 gm/L
1gm/L
1 cc/L
0.1 gm/L
1:10
550C-600C
4.5 - 5.5
40-50 minutes
One bath Bio-polishing and Dyeing
Enzymatic cellulose degradation is also possible during reactive dyeing. Here the dyeing
process as well as bio-polishing will be affected. Number of washes, time, cost and energy
can be saved by this one bath method. However, it should be noted that there is some
reduction in colour yield of reactive dyeing. This is because reactive dyeing is carried out in
acidic pH during bio-polishing. But precaution is taken during addition of soda-ash as
reactive dyes require alkaline condition for its fixation as ceullase enzymes could not
withstand higher alkaline pH. If the soda-ash is added before the accomplishment of biopolishing it will be completely deactivate the enzyme.
Enzyme inactivation
To prevent any damage of the fabric after the finishing operation it is very essential that the reaction be terminated at the end of
treatment by enzyme inactivation. If the enzyme is not inactivated entirely then at the end of the reaction fibres get damaged and even
extreme cases total destruction of the material may result. The enzyme inactivation is therefore of great importance from the technical
point of view.
There are two distinct process of termination of enzyme:
1) Heat treatment at 80°C for 10-15 minutes.
2) By raising the pH to 11-12.
■ Difference Between Enzyme Wash and Bio Wash/Polishing:
S/L
No.
Subject
Enzyme Wash
Bio Wash/ Polishing
01
Definition
To minimize the adverse effect of stone wash, the garments
are washed by using enzyme to bring the effect of stone or
sand wash on dyed denim fabric.
02
Removing
equipment from
the garments
During enzyme wash, certain amount of indigo dye and
cellulose fibers from the surface of the fabric are removed.
03
Size of enzyme
molecule
The appearance of natural cellulosic material such as
cotton can be improved through an enzymatic
treatment. This is known as bio wash or bio polishing.
The bio polishing treatment remove the fuzz and pilling
from the fabric surface and gives the fabric a softer and
smoother handle, superior color brightness and glossier
appearance.
The cellulase enzyme molecule is too large to penetrate
the interior of a cotton fiber.
04
Fading of color
05
Abrasion process
06
Applying stage or
process
The cellulase enzyme molecule is not so large than bio
polishing enzyme molecule.
Fading due to removal of color with the fibers due to
mechanical abrasion takes place.
For enzyme wash, mechanical abrasion process is required.
Enzyme wash can be applied on the particular stage.
For bio polishing wash, no color fading is formed.
For bio polishing wash, no abrasion process is required.
Bio polishing can be carried out on cotton as well as
viscose, jute, flax, ramie etc. it can be applied at any wet
processing stages or in other processes.
Evaluation of Bio–polishing
Enzyme suppliers determine the activity of their products by measuring the extent of the catalysed reaction under carefully
controlled condition. A standard test exists for analysis (AATCC Test method 103), but the evaluation of cellulases more complex and
can vary from supplier to supplier. One common method is to measure the degradation of carboxymethyl cellulose solution. Some
others are to determine pilling tendency, weight or strength loss of standard cotton fabrics under laboratory conditions. For
example, the hydrolysis degree HD, is determined by
HD = (Mₒ – M)/ Mₒ
Where, Mₒ and M are the weight of the test material before and after bio –finishing respectively.
Advantages of Using Enzymes For Bio-polishing
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Hairiness fluffs and pills are removed.
Material soilimg tendency is prevented.
Improved handle.
Achievement of surface smoothness and a clear structural appearance.
Improved luster.
Material texture relaxation.
Levelness of dyeing and sharp outlines of print.
Improved sew ability.
Fast to washing, low pilling tendency, no napping in use, or during care operation.
Stone wash effect without pumice stone and dyestuff destroying chemicals.
Poor quality, uneven, napped, knoppy material surface (i.e.) typical second quality goods are
converted into elegant, lustrous, soft, top quality with a fine, high quality surface appearance.
Disadvantages
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Loss in weight.
Formation of fiber dust.
The reproducibility of the effect (which is dependent upon many parameters).
Loss in tear strength.
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