Biopolishing

Course name: Wet preparatory process

Course Code: WPE 201

Course Teacher:
Tabassum Ferdous Jenny
Assistant Professor,
Department of Wet Process Engineering
Bangladesh University of Textiles.
Biopolishing
• Biopolishing is a finishing process carried out before, during, or after dyeing.

• It increases fabric superiority by reducing hairiness and pilling of cellulose fabric and
leading to velvety, slicker feel, and brighter color.

• The purpose of the process is to eliminate protruding micro hairs of cotton by an

interaction of cellulase enzyme.

So the features of biopolishing can be summarized as below:

• Removal of fibrils and fuzz fibers from cotton fabrics.

• De-pilling effect (improvement of pill resistance)

• Desirable touch properties are achieved.

• Brighter luminosity of colors.

Fig : Cotton fabric surface before (A) and after (B) biopolishing
treatment using cellulase enzyme.
Enzyme:
• Enzymes are biological catalysts. They are naturally occurring proteins capable of
catalyzing specific chemical reactions, and facilitate the reaction without being consumed.

• Enzymes have complex three dimensional structures composed of long chain amino acids
with molecular weight ranging from 10,000 to about 150,000 and occasionally to more than
10,00,000.

• They are present in almost all life forms and play important role in many aspects of life.
i.e., in the production of our food, facilitating digestion and various industrial applications,
on our clothes, in producing fuel for our automobiles, and reducing energy consumption as
well as environmental pollution.
Advantages of enzymatic processing:
1. Enzyme catalysed reactions are several orders of magnitude faster than chemically
catalysed reactions.

2. Enzymes are highly specific in chemical reactions and they rarely form by-products.

3. Enzymes catalyze reactions under comparatively milder conditions of temperature (below

100ºC), pressure (atmospheric) and pH (around neutral).

4. Consequently, enzymatic treatments offer savings in chemicals and energy and have less
or no impact on the environment.

5. The enzymes are fully biodegradable.

Activity of enzyme on substrate

Fig. 1 : Lock-and-key mechanism of enzyme

Activity of enzyme on substrate (cont..)

• Most enzymes are much larger than the substrates they act on, and only a small portion
of the enzyme (around 3–4 amino acids) is directly involved in catalysis.

• The region that contains these catalytic residues, binds the substrate, and then carries
out the reaction is known as the active site.

• It has been suggested that the enzymes show specific catalytic action because both
the enzyme and the substrate possess specific complementary geometric shapes that
fit exactly into one another .

• This is often referred to as the ‘lock and key’ model (Fig: 1), where the reactive
substrate acts as a key which precisely fit into the enzymatic lock.
Types of enzyme

Some common types of enzymes and their specific activities are as follow:

• Lipases: Split fats into glycerol and fatty acids.

• Amylases: Split starch into dextrin and sugars.

• Proteases: Split proteins into soluble polypeptides and amino acids.

• Pectinolytic or pectinases: Degrade pectin.

• Zymases: Convert glucose into alcohol and carbon dioxide.

• Cellulases: Degrade cellulose to soluble products (Used for Biopolishing).

• Catalases: Convert hydrogen peroxide into water and oxygen.

• Saccharidases: Convert polysaccharides to glucose.

Applications of enzyme in textile processing:

The application of enzymes in various stages of textile processing may be summarized as

follows :

• Desizing: Amylase, lipase.

• Scouring: Pectinase, cellulase.

• Bleaching: Oxidoreductase, xylanase.

• Dyeing: Oxidoreductase.

• Finishing: Cellulase, oxidoreductase, lipase.

• Composting (biodegradation of textile wastes): Cellulase, protease, nylonase,

polyesterase.
Cellulase

• Biopolishing involves the use of cellulase enzymes, due to their capability of hydrolyzing
cellulosic micro-fibrils (hairs or fuzz) protruding from yarn surface.

• There are two types of cellulase, namely acid cellulase (effective in pH 4.5-5) and neutral
cellulase (effective at pH 7). Among them acid cellulase is largely used in bio polishing.

• Cellulases are produced by a wide variety of bacteria (e.g- clostridum, cellulomonas) and
fungi (e.g- Humicola, Trichoderma, Penicillium). Among these the more important
commercially is the one from Trichoderma reesei .

• Cellulase derived from Trichoderma reesei contains a group of enzymes namely

1.endoglucanases (EG), 2. cellobiohydrolases (CBH) or exoglucanases and 3. cellobiases or
β.glucocidases. They act synergistically to hydrolyse cellulose.
The mechanism of cellulase action on cellulose

1. Cellulase catalyzes the hydrolysis of cellulose by deteriorating or lowering β(1→4) glycosidic

links.

2. Cellulases available in the market for biopolishing are a combination of endoglucanases,

exoglucanases, and β. glucosidases ; they are capable of modifying cellulosic fibers in a
required fashion.

3. The endoglucanases (EG) degrades cellulose by selectively cleaving through the amorphous
sites and breaking long polymer chain into shorter chains.

4. Cellobiohydrolases (CBH) or exoglucanases degrades cellulose sequentially from the ends of

glucose chains, thus producing cellobiose as the major product and it plays a mediator role in
degrading cellulose.

5. Cellobiases or β. glucosidases complete the hydrolysis reaction by converting cellobiose into

glucose.
The mechanism of cellulase action on cellulose (cont..)

Fig. structure of cellulose (showing β(1→4) glycosidic links)

Fig. Action of cellulase on cotton

The mechanism of cellulase action on cellulose (cont..)

Fig. Action of cellulase on cotton

Enzyme Inactivation

• To prevent any damage of the fabric after the end of treatment, it is very essential
that the reaction be terminated by enzyme inactivation.

• If the enzyme is not inactivated entirely then at the end of the reaction, fibers 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. Hot treatment at 80°C for 20 min.

2. By raising the pH to 11–12.

Factors affecting enzyme finishing

1. pH: The optimal pH for a particular cellulase depends upon it’s origin. Trichoderma based
products work best at pH 4.5-6, whereas cellulase from Humicola are more effective at pH 6-
6.5.

2. Temperature: The reaction temperature is also critical since at low temperatures the reaction
rate is slower than desired but very high temperature can deactivate the enzyme by providing
enough energy to alter it’s molecular alignments and thereby destroy it’s catalytic ability.

3. Time: Since enzymes are true catalysts and are not consumed during reaction, the hydrolysis
reaction will continue until either the reaction condition change or the cellulase is physically
removed from the reaction mixture.

4. Mechanical agitation: The kinetics of the reaction are controlled by mass transfer effects.
The absorption-desorption mechanism of enzyme action depends on agitation to remove
hydrolysis byproducts and expose new fiber area to attack.
Typical examples

Recipe:

Concentration of enzyme- 3%

M:L- 1: 10

Temperature- 55°C

pH- 4-5

Time- 55 minutes
Advantages of bio-polishing
• Protruding short fibers and pills are removed and thus material sticking (the burr effect) is
prevented.

• Improved handle ( surface smoothness) and luster.

• Increased flexibility and sew ability.

• Ease to wash, low pilling tendency, no napping in use, or during care operation.

• Stone wash effect without pumice stone and dyestuff destroying chemicals.

• Poor quality goods can be converted into top quality goods with a fine, high quality surface
appearance.

Disadvantages of bio-polishing
• Loss in weight

• Loss in strength
Any Question?
Thank You