Bio-processing of textiles

Abstract:

Textiles have undergone wet chemical processing since time immemorial. Human ingenuity and imagination, craftsmanship and resourcefulness are evident in textile products through out the ages; we are to this day awed by beauty and sophistication of textiles sometimes found in archeological excavations. The paper mainly focuses on various enzymes, bio- friendly processes, and discusses some integrated Eco balancing aspects.

INTRODUCTION

Bioprocessing can simply be defined as the application of living organisms and their components to industrial products and processes. It is not an industry in itself, but an important technology that will have a large impact on many industrial sectors in the future. Bioprocessing is the application of biological organisms, systems or processes to manufacturing industries. Bioprocessing firms will rely mainly on inexpensive substrates for biosynthesis, processes that will function at low temperatures, and will consume little energy.

In Textile Processing the Enzymatic removal of starch sizes from woven fabrics has been in use for most of this century and the fermentation vat is probably the oldest known dyeing process. What has given Bioprocessing a new impetus in the last few years has been the very rapid developments in genetic manipulation techniques which introduces the possibility of ‘tailoring’ organisms in order to optimize the production of established or novel metabolites of commercial importance and of transferring genetic material from one organism to another. Bioprocessing also offers the potential for new industrial processes that require less energy and are based on renewable raw materials.

Various applications which entail enzyme and colors broadly included fading of denim and non-denim, bio-scouring, bio-polishing, silk degumming, carbonsing of wool, peroxide removal, washing of reactive dyes, etc. incidentally enzymes were consumed to the tune of about 70%in detergents than in textile industry.

Role of BIOTECHNOLOGY in Textile Processing

The major areas of applications of biotechnology in textile industry are,
•Improvement of plant varieties used in production of textile fibres and in fibres and in fibre properties
•Improvement of fibres derived from animals and health care of animals
•Novel fibres from biopolymers and genetically modified microorganisms
•Replacement of harsh and energy demanding chemical treatments by
Environment friendly routes to textile auxiliaries such as dyestuffs
•Novel uses for enzymes in textile finishing
•Development of low energy enzyme based detergents
•New diagnostic tools for detection for adulteration and quality control of textiles
•Waste managements

Role of Enzymes in Textile Processing

Enzymes are large protein molecules made up of long chain amino acids which are produced by living cells in plants, animals and microorganism such as bacteria of fungi.

Enzymes are secretions of living organisms, which catalyze biochemical reactions. Enzymes are biocatalysts without which no life in plant or animal kingdom can be sustained.

Today enzymes have become an integral part of the textile processing. Though enzyme in desizing application was established decades ago, only in recent years the application has widened with new products introduced. With the increase in awareness and regulation about environment concerns, enzymes are the obvious choice because enzymes are biodegradable and they work under mild conditions saving the precious energy. Enzymes being biocatalysts and very specific are used in small amounts and have a direct consequence of lesser packing material used, the transportation impact is lower. In an overall consideration enzymes are the wonder products.

Salient features of enzyme application in textile process are

•Extremely specific nature of reactions involved, with practically no side effects.
•Low energy requirements, mild conditions of use, safe to handle, non- corrosive in their applications.
•On account of lesser quantities of chemicals used in process as well as ease of biodegradability of enzymes results in reduced loads on ETP plants.
•Enzymes under unfavorable conditions of pH or temperatures chemically remain in same form but their physical configuration may get altered i.e. they get “denatured” and lose their activity. For this reason live steam must never be injected in a bath containing enzymes and any addition of chemicals to the enzymes bath must be done in pre-diluted form.
•Compatibility with ionic surfactants is limited and must be checked before use. Nonionic wetting agents with appropriate cloud points must be selected for high working efficiency as well as for uniformity of end results.
•High sensitivity to pH, heavy metal contaminations and also to effective temperature range. Intense cautions are required in use.

Enzymes for cellulosic textiles

Amalyses

Amylases are hydrolase class of enzymes, which hydrolyse 1-4 α glucosidic linkage of amylase and amylopectin of starch to convert them into soluble dextrins. Among the different classes of commercially available amylases. Some important industrial enzymes for textile and their sources

The following types find major application in textiles.

Thermostable amylases

Amylases which catalyse starch hydrolysis in the temperature range of 70-110oC and at pH 6.0-6.8.

Conventional anylases

Amylases which catalyse starch hydrolysis in the temperature range of 50-70oC and at pH 6.0-6.8.

Low temperature amylases

Majority of fungal amylases which catalyse starch hydrolysis in the temperature range of 30-70oC and at pH 6.0-6.8.

Cellulases

Cellulases are hydrolase class of enzymes which cleavage 1-4β glucosidic linkage of cellobiose chain or cellulose. The commercially available cellulases are a mixture of enzymes viz., Endogluconases, Exogluconases and Cellobiases, Endogluconases are subclass of celluase enzymes which randomly attack the cellulose enzymes and hyudrolyze the 1-4 β glucosidic linkage of cellobiose chain. Exoglucanases of cello-biohydrolases are again subclass of cellulose enzyme which hydrolyses 1-4 β glucosidic linkage of cellulose to release cellotiose from the cellulose chain and Cellobiases are enzymes whichhydrolyse cellobiose into soluble glucose units. All these three enzymes act synergistically on cellulose to hydrolse them. Among the different classes of commercially available cellulases, following types find major application in textiles.

Acid Cellulases:

Acid cellulases are class of enzymes that act at pH 3.8-5.8 (-optimum 4.5-6) and in the tempereature range of 30-60oC. The low temperature range of 30-60oC and conventional acid cellulases act in the temperature range of 45-60oC.

Neutral Cellulases:

Cellulase enzymes which actr at pH 6.0-7.0 and in the temperature range of 40-55oC are termed as neutral Cellulases.

Pectinases

Pectinases are a mixture of enzymes, which along with other such as cellulose, are widely used in the fruit juice industry. Enzymes in this pectinase group include polygalacturonases, pectin methyl esterase and pectin lyases. These pectinase enzymes act in defferent ways on the pecans, which are found in the primary cell walls of cotton and jute. Pectins are large polysaccharide molecules, made up of chains of galacturonic acid residues.

Proteases

Proteases are Hydlolase class of enzymes, classified based on the source from which it is extracted, optimum temperature of activity. Proteases precisely act on peptide bonds formed by specific amino acids to hydrolyze them. Commercial proteases are available, which can work in different range of pH and temperature. Trypsin (pancreatic), Papain based and alkaline proteases find industrial applications in textiles.

Peroxidases

Peroxidases or Catalases are Oxidoreductase class of enzymes. The perosidase enzyme catalyse the decomposition of hydrogen peroxide in to water and molecular oxygen as illustrate.
2H₂O₂→2H₂O O₂

Catalase is a heam-contaioning enzyme. Thus, in addition to the protein part of the molecule the enzyme contains a non-protein part, which is a derivative of heam and includes the metal iron. Peroxidases effectively degrade the hydrogen peroxide at varied pH between 3 to 9 and in the temperature range 30 -80 �C.

Laccase

Laccases are Oxidoreductase class of enzymes, belonging to bluoxidase- copper metalloenzymes. Lassases are generally active at pH 3-5 and in the optimal temperature range of 30-50oC. They oxidize using molecular oxygen as electron acceptor from the substrate. Their special property of oxidation of indigo pigments is made use of in textile industries.

TRENDS IN BIOPROCESSING

BIOCATALYSIS

Owing to the specific nature, enzymes have become an important class of bio-chemicals in textile processing. Being bio-catalysts, enzymes were not consumed in the reaction. They were also used in the processing from a standing bath. Illustrating a schematic diagram for working of an enzyme, he indicated the active and secondary sites and how the enzyme was larger than the substrate as it attached itself to cellulose forming a complex in which the concentration of the reactants increased thousands times due to which the reaction proceeded. The substrate was broken into degradation products making the enzyme available to attach itself again to another substrate and the cycle was repeated and thereby the enzyme became a biocatalyst.

BIO-SINGEING

This mode of finishing has been specifically developed to achieve clearer pile on terry towel goods. A treatment with an enzyme, which is a powerful cellulase composition, gives clearer look to the pile, improves absorbency and softness.

Earlier, desizing was carried out by steeping the fabric with mineral acid, which affected the cellulose as well as the colour. Use of enzymes here led to reaction with the starch only and thus they assumed considerable significance. Explaining the action of enzymes, the food consumed by human body was digested due to secretion of the enzyme. At the enzyme-substrate complex level, the concentration of the reactants became large and accelerated the reaction while reducing the activation energy barrier. Thus, the reaction which took place at higher temperature and severe conditions could be carried out at relatively lower temperatures and milder conditions.

BIO-SCOURING

Bio scouring did not involve any colour, yet after scouring the fabric was dyed with colours. Cotton could be treated with bioscouring enzyme although the techno-economical parameters were not conductive. But, it had a bright future due to rigorous effluent treatment since disposal of both caustic soda and soda ash was causing environmental concern. The enzymes helped removal of waxes, pectins, sizes and other impurities on the surface of the fabric. Combination of pectinase and lipase gave best results, but cost of the latter was a deterrent.

Advantages of bioscouring were lower BOD, COD, TDS, and the alkaline media of water, extent of cotton weight loss, which was a boon to the knitting industry, lower alteration of cotton morphology i.e. less damage since it was specific to pectin and waxes and not cellulose besides increased softness. The lone disadvantage was that the cotton motes were not removed, which warranted peroxide bleaching.

INTEGRATED BIO-DESIZING AND BIO-SCOURING:

The integrated Bio-desizing and Bio-scouring system uses an empirically developed enzyme formulation, based on amylase, pectinase, protease and lipase that act synergistically, resulting in desizing and scouring of cotton goods, under mild conditions.

BIO-BLEACHING:

It was applicable for all kinds of colours and a single enzyme could be used in the textile industry. Bio-bleaching had been adapted for denim. Indigo specific lipases were used to bleach indigo. Earlier denim was bleached with chlorine to get lighter denim or wash down effect. Lipase combination was used successfully and if this could be extended to other colours, this would become an important enzyme in future. The advantages were environment friendly application, non AOX generation and cellulose was not affected. A bio-bleaching or lipase treatment on denim gave an authentic wash resulting in an excellent look, which was better than a neutral wash and a grey cast, which was used in bleaching.

Amylase and lipase were used for desizing and cellulase for aberration. Lactase was introduced for bleaching of indigo.

PEROXIDE KILLERS:

It ensured shade quality particularly with reactive dyes, reduced the complexity of treatment after peroxide bleaching and conserved water. In case of reactive dyeing, after bleaching it was vital that the peroxide residues must be cleared out of the system and as such there were no fool proof ways of such clearance, which entailed several rinsing operations or reduction treatments.

Empirically, it was difficult to know how much quantity of reducing agent was required to react with the peroxide left in the bath. In the event either of them happened to be excess, it might affect the dyeing. Therefore, after bleaching, the bath should be neutralized with peroxide killers like peroxidase or catalase followed dyeing with reactive dyes. They did not affect reactive dyes and only react with the peroxide. These catalysts were fastest acting type as 1 molecule of catalyst destroyed 5 million molecules of peroxide or 700 times its own weight of peroxide.

ENZYMES EFFECT ON COLOUR

Hydrolases and oxireductases constituted important class of enzymes which dealt with colour in textile application. Speaking about how the enzymes affected these applications one said that when looked at fading, especially of denim, one came across the three classes of cellulase viz. acid, neutral and engineering. The affect of cellulase on denim and the wash down effect was attributed to the yarn, which was ring dyed i.e. yarn dyed with indigo was present only on the outer ring of the denim. Due to affect of enzyme and physical aberration of cellulose, the exposed areas became white as well as indigo dyed. If it was non denim, it was ring dyed non denim containing vat, sulphur or pigments. This kind of effect on denim was called salt and pepper effect. The more contrast, better was the denim wash. Some of the denims had blue or greyer cast because they were woven with one up or two down and one of the yarn was coloured while the other wasn’t. thus, the effect was created with the combination of the hydrolysis of 1-4 glucose linkage in cellulose and the abrasion e.g. turbulence of friction of metal to metal or fiber to fiber led to denim appearance.

Combination of enzyme, sand blasting and bleach evolved a fashion recently. Sand blasting was enzyme treatments which subject the denim fabric to sand at high pressure with consequent exposure of white area while blowing off surface colour followed by a treatment of the fabric again with enzyme, leading to a salt and pepper effect and bleached to reduce the colour value. Furthermore, after sand blasting, treatment with enzyme followed by over dyeing of the abraded areas produced typical effects on denim.

BIO-POLISHING

It was perceived that bio-polishing and fading or bio-polishing and wash down were two different operations. But both of them basically employed the same action. They degraded the cellulose due to abrasion or friction between fiber to fiber or fiber to metal resulting in removal first from cellulose and then surface bleeding. It was reported in literature that bio-polishing before dyeing cloud increase depth apparently due to clarity of shade. Bio-polishing or cellulase enzyme treatment of lyocell type of regenerated cellulose could produce peach like effect.

Bio-polishing give cleaner appearance to the garment besides wash down effect. If it was sulphur or pigment dyed goods or ring dyed fabric, wash down effect as well as cleaning of fabric surface could be obtained. The result surface hair was removed, reduced pilling, better print registration and colour brightness. Size of cellulase enzyme was about 8nm as also the size of cellulose monomer, which was in similar region.

BIO-CARBONISING

Polyester / cellulosic blends after dyeing and/ or printing are occasionally treated with strong solution of sulphuric acid to dissolve cellulosic component. The resultant goods are soft and have a peculiar fluffy feel. This process is risky due to highly corrosive acid that is also difficult to treat in an ET plant.

The process developed at UNO, has none of the above drawbacks. It offers a safe and eco-friendly to the obnoxious practice of using sulphuric acid. The goods are treated with cellulose enzyme based formulation to achieve dissolution of cellulosic fibers.

DEGUMMING OF SILK

Silk is made up of two types of proteins like fibrin and ceresin. In the case of enzymatic treatment, a ceresin specific protein was used to degum the silk with out causing damage, impart softness and increase dye uptake of about 30%. If silk was degummed by alkaline treatment, there was damage to fibrin and heavy weight loss.

Enzymes used in Detergents

Protease: Remove stains caused by proteins such as blood, grass, egg and human sweat.

Amylase: Remove starch-based stains such as those made by potatoes, pasta, rice and custard.

Lipase: Break down fats, oils and greases removing stains based on salad oils, butter, fat-based sauces and soups, and certain cosmetics such as lipstick

Cellulase: Brighten and soften the fabric, and release particles of dirt trapped in the fibres.

Textile Auxiliaries

Textile auxiliaries such as dyes could be produced by fermentation or from plants in the future (before invention of synthetic dyes in the nineteenth century many of the colours used to dye textiles came from plants e.g. woad, indigi and madder). Many microorganisms produce pigments during their growth, which are substantive as indicated by the permanent staining that is often associated with mildew growth on textiles and plastics. It is not unusual for some species to produce up to 30% of their dry weight as pigment. Several fo these microbial pigments have been shown to be benzoquinone, naphthoquinone, anthraquinone, perinaphthenone and benzofluoranthenequinone derivatives, resembling in some instances the important group of vat dyes. Microorganisms would therefore seem to offer great potential for the direct production of novel textile dyes of dye intermediates by controlled fermentation techniques replacing chemical syntheses, which have inherent waste disposal problems (e.g. toxic heavy metal compounds). The production and evaluation of microbial pigments as textile colourants is currently being investigated.

Another biotechnological route for producing pigments for use in the food, cosmetics of textile industries is from plant cell culture. One of the major success stories of plant biotechnology so far has been the commercial production since 1983 in Japan of the red pigment shikonin, which has been incorporated into new range of cosmetics. Traditionally, shikonin was extracted from the roots of five year old plants of the species Lithosperum erythrorhiz where it makes up about 1 to 2 per cent of the dry weight of the root,. Din tissue culture, pigment, yields of about 15 per cent of the dry weight of the roof cells has been achieved.

ENZYMATIC DECOLORIZATION

In textile dyeing as well as other industrial applications, large amounts of dyestuffs are used. As a characteristic of the textile processing industry, a wide range of structurally diverse dyes can be used in a single factory, and therefore effluents from the industry are extremely variable in composition. This underlines the need for a largely unspecific process for treating textile waster water. It is known that 90% of reactive dyes entering activated sludge sewage treatment plants will through unchanged and be discharged in to rivers.

High COD and BOD, suspended solids and intense colour due to the extensive use of dyes characterize wastewater from textile industry, especially process houses. This type of water must be treated before discharging it into the environment. The water must be decolorized; harmful chemicals must be converted into harmless chemicals.

Biological treatments have been used to reduce the COD of textile effluents. Physical and chemical treatments are effective for colour removal but use more energy and chemicals than biological processes. They also concentrate the pollution into solid or liquid side streams that require additional treatments or disposal, on the contrary biological processes completely mineralize pollutants and are cheaper. Instead of using the chemical treatments, various biological methods can be used to treat the water from the textile industry. These methods include, Biosorption, use of Enzymes, Aerobic and anaerobic treatments etc. Only biotechnological solutions can offer complete destruction of the dyestuff, with a co-reduction in BOD and COD. In addition, the biotechnological approach makes efficient use of the limited development space available in many traditional dye house sites.

Decolorization of dyes by using biotechnology

The synthetic dyes are designed in such a way that they become resistant to microbial degradation under the aerobic conditions. Also the water solubility and the high molecular weight inhibit the permeation through biological cell membranes. Anaerobic processes convert the organic contaminants principally occupy less space; treat wastes containing up to 30,000 mg/l of COD, have lower running costs and produce less sludge. Azo dyes are susceptible to anaerobic biodegradation but reduction of azo compounds can result in odor problems. Biological systems, such as biofilters and bioscrubbers, are now available for the removal of odor and other volatile compounds.

The dyes can be removed by biosorption on apple pomace and wheat straw. The experimental results showed that 1 gm of apple pomace and 1 gm of wheat straw, with a particle size of 600 m, where suitable adsorbents for the removal of dyes from effluents. Apple pomace had a greater capacity to adsorb the reactive dyes taken for the study compared to wheat straw.

Decolorization of the dye house effluent using enzymes

The use of lignin degrading white-rot fungi has attracted increasing scienrific attention as these organisms are able to degrade a wide range of recalcitrant organic compounds such as polycyclic aromatic hydrocarbons, chlorophenol, and various azo, heterocyclic and polymeric dyes. The major enzymes associated with the lignin degradation are laccase, lignin peroxidase, and manganese peroxidase. The lacasses are the multicopper enzymes which catalyzes the oxidation of phenolic and non-phenolic compounds. However, the substrate of the laccases can be extended by using mediators such as 2,2-azoinobis-(3-ethylthiazoline-6-sulfonate)m 1-hydroxy benzotriazole. The following fungi have been used for laccase production and for the decolorization of synthetic dyes. Trametes modesta, trametes versicolor, trametes Hirsuta, and Sclerotium Rolfsii

From the results obtained it was clear that Trametes Modesta laccase showed the highest potential to transform the textile dyes into colorless products. The rate of the laccase catalyzed decolorization of the dyes increase with the increase in temperature up to certain degree above which the dye decolorization decreases or does not take place at all. The optimum pH for laccase-catalyzed decolorization depends on the type of the dye used. Dyes with different structures were decolorized at different rates. From these results it can be concluded that the structure of the dye as well as the enzymes play major role in the decolorization of dyes and it is evident that the laccase of trametes modesta, may be used for decolorization of textile dyestuffs, effluent treatments, and bioremediation or as a bleaching agent.

Activated sludge systems can also be used to treat the dye house effluents. But the main difficulty with activated sludge systems is the lack of true contact time between the bacteria of the system and the suspended and dissolved waste present. Immobilized microbe bioreactors (IMBRs) address the need of increased microbial/waste contact, without concomitant production of excessive biosolids, through the use of solid but porous matrix to which a tailored microbial consortium of organisms has been attached. This allowed greater number of organisms to be available for waste degradation without the need of a suspended population and greater increased contact between the organisms and the waste in question.

Finishing of cotton knits

Cellulase enzyme treatments increasingly find applications in cotton hosiery sector to enhance aesthetic feel as well as surface clarity. Ultrazyme Super is an enzyme –based formulation, well suited for use in winches or high turbulence soft flow machines. Adequate caution must be exercised to deactivate residual enzyme by elevating temperatures to around 80-85oC, otherwise the reaction would continue to take place resulting in loss of physical strength of goods.

Enzyme catalyzed synthesis of polyester

It has been known for many years that enzymes can carry out though synthesis of polymers with useful properties. One well-known example, first described in 1926, is the fact that certain polyesters are synthesized and intea-cellularly deposited in granules by many microorganisms. Among the attractive properties of enzymatically-produced polyesters are their high biodegradability and their immunological compatibility with human tissue. In addition, a number of these materials have been formed into fibres.

Biotechnology is being used to produce novel polypeptide structures. Initial work has concentrated on a polypeptide modeled after the natural material elastin. The first material investigated is poly(GVGVP), where G is glycine, V is valine, and P is proline. Previously, methods were developed to extrude this polymer into fibre via wet extrusion from water solution. Subsequently the fibre was cross linked with ionizing radiation to produce an insoluble structure having a reversible thermal contraction (in water) as temperature is raised above a critical temperature in the range of 30oC. Poly (GVGVP), produced by fermentation using genetically engineered E. Coli has been spun into fibre and the fibres exhibit similar properties to the chemically synthesized material. The extrusion process worked well and allowed the collection of tens of meters of fibres without breakage. Drafting of the filament during extrusion allowed the production of fibre as fine as 30 microns. Baxenden Chemicals, UK based company has studied the enzymatic synthesis of polyester. The biocatalyst used in this process was a lipase from the thermophilic bacterium Camdoda Antarctica that is cloned in E. coli bacteria for the mass production. The advantages of this process are that it does not utilize the organic solvents, inorganic acids and it is more energy efficient.

Previously, enzymatic polymer production has most often been carried out using intact microbial cells. K. L. Houmiel et al. inserted the genes for the polyester-forming enzymes into two different green plant species, and a polyester copolymer with desirable properties was produced within the plant leaves and seeds. However, producing plant-derived plastics increases emissions of greenhouse gases (e.g. CO2), due to high fossil fuel consumption in crop tarming and processing. Accordingly, polyester production within plants was recently abandoned by Monsanto. Three cloned D. coli strains, which, respectively, over-express the ketothiolase, reductase and synthase (the latter is also called polymerase) enzymes, whose sequential action produces the polyester, poly-(R)-hydroxybutyrate (PHB).

INTEGRATED Eco- BALANCING APPROACHES

•Raw material uses should be zero residues.
•Rigid procedures, requiring the use of only specific chemicals and specific methods should be converted into flexible ones to facilitate substitution of non-eco friendly chemicals by their safe counterparts from time to time.
•Green Technology or Clean Technology should be practiced so that the Gross National Product (GNP) of a nation should be increased by substantially reducing the quantities of inputs.
•Eco friendly index of product must include its shelf life period and extend of ecofriendliness of degradation products.
•Eco friendly Machinery should be used e.g. Kyungwon Enterprise Co. of South Korea has developed a washing machine that does not required detergents to clean cloths. In this machine water is transformed into an electronically charged liquid that cleans goods with same power as that of a conventional synthetic detergent powder. These make washing easier, cheaper and environment friendly7.

Conclusion

It can be seen from what has been discussed that the field of the biotechnology remains one of the most promising for textile industry to seek out high quality, high added value finishes. Collaboration with biotechnology field to make the research product for the textile industry into the commercial reality in the textile finishing plant will be needed to decrease the lead time environment problem and minimize the profitability innovation and novelty in the enzyme will be necessary to stimulate the more discerning the consumer market and to develop specialty and niche market for textile fabric industry.

Bioprocessing with its pervasive field of application surely going to conquer the world of textiles and will make it to rich the pinnacle of its performance. There are few to enunciate, however many such potentials are yet to explore. Bio-processing in textiles provides to be a boon to the ever changing conditions of the ecology as well as economy.

References

1.Shenai V.A., Technology of bleaching and mercerizing, Sevak publication
2.www.fibre2fashion.com
3.www.textileinfo.com
4.Mehra R.H., Mehra Anil R., Mehra Arun R and Mehra Sanjay R., ‘Enzymatic Softening of Textiles’, Indian Textile Annual and Directory, 1992-93, pp.77-84.
5.Edward Menezes “A lecture on Enzymes and Colour” oct2004 UICT
6.Hee-Jung K. Times of India, (Bombay Edition), 10 September 1998,10