Indian Journal of Fibre & Textile Research Vol. 26, March-June 200 1 , pp. 206-2 1 3

B iotechnology applications in textile industry

Deepti Gupta"

Department of Textile Technology, Indian Institute of Technology, Hauz Khas, New Delhi 1 10 0 1 6, India

The applications of biotechnology to textiles are discussed with reference to improvements in natural fibres, novel new biodegradable fibres and polymers, biofabrics, intermediates and dyes from micro-organisms, and treatment of textile waste water. Majority of the techniques are not yet commercialized. However, wherever a clear economic justification and market for a particular product or process exists, progress has been rapid. It is thus expected that in future, many of the biotechnological processes would help in solving the environmental problems posed by textile industry.

Keywords: Biodegradable fibre, Biofabric, Biotechnology, Dye, Natural fibres

1 Introduction Biotechnology encompasses a range of scientific

and engineering techniques for applying biological systems to the manufacture or transformation of materials in order to develop novel processes and products. It is not an industry in itself but is expected to have a large impact on many different industrial sectors in the future. Techniques have been developed which directly modify and harness the power of the DNA molecule, the engine house of any biological system. Consciousness and expectations for better quality fabric and awareness about environmental issues are two important drivers for textile industry to adopt biotechnology in its various areas.

With the increased realization of the immense potential of biotechnology applications in textile industry, major initiatives have been launched world­wide to encourage research and development activity in this field. The UK Department of Trade and Industry launched a 1 3 million pound Bio-Wise Program in January 1 999. The first Symposium on Biotechnology in Textile Industry was held at Minho, Portugal, in May 2000. It was widely attended by scientists as well as the representatives of enzyme manufacturers.

This paper discusses biotechnology to textiles following emerging areas :

the applications of with reference to the

• Improvements in natural fibres • Novel fibres and polymers • Biofabrics

UPhone : 659 1 4 17; Fax: 658 1 103; E-mail : dbg33 @ hotmail.comJdeepti @ textile.iitd.ernet.in

• Dyes and intermediates from micro-organisms • Treatment of wastes of textile manufacturers and

processors

2 Improvements in Natural Fibres Biotechnology can play a crucial role in production

of natural fibres with highly improved and modified properties besides providing opportunItIes for development of absolutely new polymeric materials. The natural fibres under study are cotton, wool and silk.

2.1 Cotton Cotton continues to dominate the market of natural

fibres. It has the greatest technical and economic potential for transformation by technological means. Genetic engineering research I on the cotton plant is currently directed by a two- pronged approach : • Solving the major problems associated with the

cultivation of cotton crop, namely the improved resistance to insects, diseases and herbicides, leading to improved quality and higher yield.

• The long- term approach of developing cotton fibre with modified properties, such as improved strength, length, appearance , maturity and colour.

2.1.1 Transgenic Cotton Each year, thousands of research hours and

hundreds of thousands of dollars are spent to prevent cotton from caterpillars that love to eat cotton. Cotton growers fight to produce a salable product using chemical sprays, natural controls, cultural practices, pheromones (insect mating hormones) and monitoring. Use of excessive pesticides is posing a serious threat to the green image of cotton2•

GUPTA: BIOTECHNOLOGY APPLICATIONS IN TEXTILE INDUSTRY 207

After years of research, a completely new kind of tool is available for cotton growers to ward off the pink bollworm, one of the major cotton pests. About ten years ago, Monsanto scientists obtained a toxin gene from the soil bacterium called Bt (which is the nickname for Bacillus thuringiensis) and inserted it into cotton plants to create a caterpillar-resistant variety. The gene is DNA that carries the instructions for producing a toxic protein. The toxin kills caterpillars by paralyzing their guts when they eat it. Plants with the Bt toxin gene produce their own toxin and thus can kill caterpillars throughout the season without being sprayed with insecticide. Because the toxin is lethal to caterpillars but harmless to other organisms, it i s safe for the public and the environment. Monsanto registered their Bt gene technology for transgenic cotton under the trademark Bollgard® and authorized selected seed companies to develop cotton varieties carrying the patented gene3.

More stable, long lasting and more active Bts are now being developed for the suppression of loopers and other worms in cotton. Insect resistance is also being developed using a 'wound- inducible promoter' gene capable of delivering a large but highly localized dose of toxin within 30-40s of an insect biting. Introduction of the controversial terminator gene i n cotton renders the second generation of cotton impotent and the farmer has to depend on fresh supply of seed.

Development of fibres containing desirable shades in deep and fast colours would change the face of the entire processing industry. Coloured cottons are also being produced not only by conventional genetic selection but also by direct DNA engineering. Although several naturally coloured cotton varieties have been obtained by traditional breeding methods, no blue variety exists. As blue is in great demand in Lhe textile industry, particularly for jeans production, synthetic fabric dyes are used. However, the ingredients of these synthetic dyes are often hazardous and their wastes are polluting. Additionally, they take time and energy to work into the cloth. Natural blue cotton does not have these disadvantages and, therefore, has great market potential. The genetic engineers plan to insert into cotton plants the genes that are responsible for the production of blue colour i n the i ndigo plant, formerly the source of blue dye, until a cheaper synthetic method is discovered. By 2005, Monsanto hopes to have this blue-coloured cotton commercially available.

Another major breakthrough has been the ability to produce cotton containing natural polyester, such as polyhydroxybutyrate (PHB), inside their hollow core, thereby creating a natural polyester/cotton fibre. About 1 % polyester content has been achieved and it has led to 8-9% increase in the heat retention of fabrics woven from these fibres. Other biopolymers, including proteins, may also be i ntroduced into cotton core i n a similar manner4•

A US biotechnology company, Agracetus, has already been awarded a patent covering the entire cotton 'genome' and is setting up a company FibreOne to create, produce and market these speciality products. With its genetically engineered cotton, Agracetus wants to develop and market speciality fibres that will combine the preferred appearance and texture of cotton with enhanced fibre properties. These customized fibres will be tailored to the needs of the textile industry. New properties may include greater fibre strength, enhanced dyeability, improved dimensional stability, reduced tendency for shrinking and wrinkling and altered absorbency. Greater strength will allow higher spinning speeds and improved strength after wrinkle- free treatments. Improved reactivity will allow more efficient use of dyes, thus reducing the amount of colour in effluents. To reduce the waste generated during scouring and bleaching processes, it would be interesting to have fibres with less of pectins , waxy materials and undesirable colour. Another example is the fibres contammg enzymes that can biodegrade environmental contaminants. These fibres would be pklced in filters. through which contaminated water i s passed5•

2.2 Wool6

Developments are also taking place for other natural fibres. Maximum work i s being carried out on animal hair fibres, the most prominent among them being wool.

Studies are underway in New Zealand and Australi a to make use of biotechnological methods for enhancing the quality and yield of wool fibres. One of these techniques is the ,use of DNA markers to identify useful genes . This will allow breeders to more accurately select rams for improved production and wool quality . The other technique is the use of genetic engineering to modify the genetic makeup of animals to provide them with specific properties that would be hard to introduce by conventional breeding procedures. Modem reproductive technologies

208 INDIAN J. FIBRE TEXT. RES., MARCH-JUNE 200 1

including artificial insemination, semen freezing, embryo transfer and embryo micromanipulation have been applied to produce animals with new genes. Merino sheep that grow (about l 3%) faster and larger than normal have been produced. This has been achieved by genetic modification of the sheep using a unique gene that alters the amount of growth hormone circulating in the bloodstream. Genetic technologies are being employed to reduce costs and improve production efficiency by increasing the parasite resistance among animals.

In 1 998, a revolutionary biowool harvesting process (Bioclip) became available. The technique relies on an artificial epidermal growth factor which when injected into sheep interrupts hair growth. A month later, breaks appear in the wool fibre and the fleece can be pulled off whole, without the use of a mechanical hand piece, in half the normal shearing time. Wool harvested using it will be free of second cuts and skin pieces contaminating the fleece.

Trends in apparel continue to be for lighter, softer and more comfortable products. To meet these requirements, fine diameter fibres are needed. OPTIMTM is the transformed wool fibre developed by CSIRO Wool Technology and The Woolmark Company. This newly developed fibre is thinner, longer and stronger. The diameter of wool is reduced typically by 3-4)lm and the knitwear produced is 20-30% lighter than the normal.

2.3 DNA Profiling of Animal Hair Fibres709

Identification of both raw and processed speciality animal fibres is important to help combat adulteration or false declaration and to ensure adherence to the international trading agreements. Cashmere, in particular, is frequently adulterated with much cheaper fibres such as wool or yak hair. Thus, there is a clear need for a quick and objective method of fibre analysis.

British Textile Technology Group has developed a novel technique based on DNA hybridization analysis to objectively confirm the type of animal fibres present in an unknown sample or blend. This technique can be used to demonstrate the presence of adulterants in commercial samples of exotic cashm�re fibres and other speciality fibres. Further research is being conducted to make possible the quantitative analysis of blends using DNA profiling methods.

Similar probes are now being identified to disti nguish between cotton , ramie, kapok, coir, flax,

jute and hemp fibres. The technique can also be used to establish the degree of pre-processing of the fibre (from its pattern of DNA degradation) and thereby distinguish virgin from recycled fibres.

Research is being conducted in China and elsewhere to overcome the dependence of silkworms on mulberry leaves, improve the strength and fineness of silk, increase the viral resistance , and even produce coloured fibres.

3 Novel Fibres

The use of biotechnology has the potential of control and specificity in polymer synthesis which is difficult, if not impossible, to achieve in chemical systems. New materials produced using advanced biologically - based approaches represent the textiles of the future. Two of the tools of molecular biology, namely recombinant DNA and genetic engineering techniques, now make it possible to construct highly specific polymers. For example, both polyamides (i.e.protein polymers) and polyesters have been produced in this manner.

3.1 Protein Polymers

Biological systems are able to synthesize protein chains in which molecular weight, stereochemistry, amino acid composition and sequence are genetically determined at the DNA level. A current area of investigation is to understand those features of protein polymers that confer high tensile strength, high modulus and other advantageous properties. Once those features are understood, the tools of biotechnology will make possible entirely new paradigms for the synthesis and production of engineered protein polymers. If they can be made economically viable, these new approaches will help to reduce the dependence on petroleum and furthermore will enable the production of materials that are biodegradable. Use of transgenic plants for large-scale production of these and other synthetic

. . b

. I dlo• 1 1 protems IS emg exp ore

Efforts in biosynthesis have been directed towards the preparation of precisely defined polymers of three kinds : (i) natural proteins such as silks, eiastins, col lagens and marine bioadhesives, (ii) modified versions of these biopc.lymers, such as s implified repetitive sequences of the native protein, and (ii i ) synthetic proteins designed de novo that have no close natural analogues. Althol.gh such syntheses pose significant technical problems, these difficulties have

GUPTA: BIOTECHNOLOGY APPLICATIONS IN TEXTILE INDUSTRY 209

all been successfully overcome in recent years. Using this technology, a whole new class of synthetic proteins with advanced properties, known as bioengineered materials, is being created.

3.2 Spider Silk

Spider dragline silk is a versatile engineering material that performs several demanding functions. The mechanical properties of dragline silk exceed those of many synthetic fibers. Dragline silk is at least five times as strong as steel, twice as elastic as nylon, waterproof and stretchable . Moreover, it exhibits the unusual behaviour that the strain required to cause failure actually increases with increasing deformation 12 .

Spiders extrude an aqueous solution of silk protein to spin the molecules into oriented fibres. The female garden cross spider can use seven different glands, each containing silk with a unique amino acid sequence, to produce fibres with different properties. Work is under way to fully characterize the molecular weight and sequence distribution; the nature of the in vivo solution (speculated by some to be liquid crystalline); and the structure, size and orientation of the crystalline regions and their interconnection to the amorphous regions in such materials.

Active research is going on at the University of Massachusetts to try and synthesize spider silk in the laboratory. This material comprises two amino acids (glycine and alanine) and it has been shown that it is the alignment of these amino acids which is responsible for spider silk' s incredible strength. Having established the alignment, the specific gene is cloned and inserted into bacteria such as E. coli. The bacteria reproduce and eventually form a cloned colony that produces the synthetic polymer by way of protein synthesis 1 3•

Another approach, being tried out, is to produce spider silk in the milk of transgenic goats. Researchers at Nexia Biotechnologies, Montreal, have successfully produced high quality spider silk by splicing the spider silk gene into the mammary glands of milk animals 14.

3.3 Other New Fibre Sources There are many more biopolymers, of particular

interest in sanitary and wound healing applications, which include bacterial cellulose and the polysaccharides such as chitin, alginate, dextran and hyaluronic acid. Some of these are discussed below :

3.3.1 Chitins and Chitosans

Chitins and chitosans both can form strong fibres. Chitin is found in the shells of crustaceans, such as crab, lobster, shrimp, etc. Resembling cellulose, the chitin consists of long, linear polymeric molecules of beta- ( 1 -4) linked glycans. The carbon atom at position 2, however, is aminated and acetylated. Fabrics woven from them are antimicrobial and serve as wound dressing products and as anti-fungal stockings. Chitosan also has promising applications in the field of fabric finishing, including dyeing and shrink proofing of wool. It is also useful in filtering and recovering heavy and precious metals and dyestuffs from the waste streamsl5•

Wound dressings based on calcium alginate fibres are marketed by Courtaulds under the trade name 'Sorbsan'. Present supplies of this polysaccharide rely on its extraction from brown seaweeds. However, a polymer of similar structure can also be produced by fermentation from certain species of bacteria. Dextran, which is manufactured by the fermentation of sucrose by Leuconostoc mesenteroides or related species of bacteria is also being developed as a fibrous nonwoven for speciality end uses such as wound dressings. Additional biopolymers, not previously available on a large scale, are now coming onto the market, thanks to biotechnology. Another example is hyaluronic acid, a poly disaccharide of D­

glucuronic acid and N-acetyl glucosamine. This acid is found in the connective tissue matrices of vertebrates and is also present in the capsules of some bacteria. Fermentech, a British biotechnology company, is now producing hyaluronic acid by fermentation 16.

3.3.2 Bacterial Cellulose17,18

Cellulose produced for industrial purposes is usually obtained from plant sources or it can be produced by bacterial action. Acetobacter xylinium is one of the most important bacteria for cellulose production as sufficient amounts can be produced which makes it industrially viable. Cellulose produced by Acetobacter, which has the ability to synthesize cellulose from a wide variety of substrates, is chemically pure and free of lignin and hemicellulose. Cellulose is produced as an extra cellular polysacaccharide in the form of ribbon like microfibrils. It has high crystallinity, high degree of polymerization, high tensile strength and tear resistance, and high hydrophilicity that distinguishes it from other forms of cellulose. This bacterial

2 10 INDIAN J . FIBRE TEXT. RES., MARCH-JUNE 2001

cellulose is being used by Sony Corporation of Japan in acoustic diaphragms for audio speakers. They are also being used in the production of activated carbon fibre sheets for absorption of toxic gas and as thickeners for niche cosmetic applications. In medical field, because of the hydrophilic and mechanical properties of bacterial cellulose, it is used temporarily as a skin substitute and in wound healing bandages.

A second biotechnological route being explored for the production of cellulose is the in vitro cultivation of plant cells. It has been possible to produce cotton fibres in vitro by culturing cells of various strains of Gossipium. Plant tissue culture provides an exciting opportunity for producing cotton all the year round, of a consistent quality and free from the contamination from pests.

3.4 Corn Fibrel9.20

An entirely new type of synthetic fibre derived from a plant is Lactron. This environment- friendly corn fibre was jointly developed by Kanebo Spinning and Kanebo Gohsen of Japan. Lactron, the polylactic acid fibre, is produced from the lactic acid obtained through the fermentation of corn starch. Strength, stretchability and other properties of Lactron are comparable to those of petrochemical fibres such as nylon and polyester (Table 1 ). As the material is compatible with human body, it is being used for sanitary and household applications. In addition to clothing, the company is also promoting its non­clothing applications, e.g. construction, agricultural, paper making, auto seat covers and household use2 1 •

The energy required for production of corn fibre is low and the fibre is biodegradable. Moreover, no hazardous gases are created when it is incinerated and the required calories for combustion are only one­third or half of those required by polyethylene or polypropylene. It safely decomposes into carbon dioxide, hydrogen and oxygen when disposed of in soil . Lactron is being marketed in various forms s'!,ch as woven cloth, thread and non-woven cloth. Shinwa and Unichika companies of Japan have launched

spun bonded nonwovens, films and sheets made from this new fibre. Developments for thermal-bonded and spun-lace nonwoven types are also underway22.

3.5 Polyester Fibres

It has been known since 1 926 that certain polyesters are synthesized and intra-cellularly deposited in granules by many micro-organisms. Some of these materials have been formed into fibres. Polyhydroxybutyrate (PHB) is an energy storage material produced by a variety of bacteria in response to environmental stress and is a homopolymer of D-(­

)-3-hydroxybutyrate which has properties comparable to polypropylene . It is being commercially produced from Alcaligenes eutrophus by Zeneca Bioproducts and sold under the trade name Biopo124,25. As the cost of production of Biopol was very high, new methods for more efficient production of PHB have been developed by using transformed E.coli strains. This process gives higher yields of PHB . The cost of production is greatly lowered as the expensive glucose- based substrate is substituted by whey which is a much cheaper substitute26.

As PHB is biodegradable, there is considerable interest in using it for packaging purposes to reduce the environmental impact of human garbage. Thus, it is already finding commercial application in speciality packaging uses. Because of it's immunological compatibility with human tissue, PHB also has utility in antibiotics, drug delivery, medical suture and bone replacement applications.

4 Biofabrics The development of biocidal fabrics was based on

the idea of activating textiles with reactive chemicals to impart desirable properties. The latest research, however, is aimed at producing fabrics containing genetically engineered bacteria and cell strains to manufacture the chemicals within the textiles , thereby making the chemical stores within the fabrics the self-replenishing materials.

A collaborative project is on between the textile

Table I--Comparative properties of Lactron and polyester fibre23

Property Lactron Polyester Multifi lamt>nt Monofilament

Tenacity,g/den 4.5-5.5 4.5-5 4.5-5 Alignment, % 30-40 25-35 30-40

Young's modulus,kg/mm� 400-600 400-600 1 1 00- 1 300

Crystallinity, % 70 70 50-60

Melting point, °C 1 75 1 75 26)

GUPTA: BIOTECHNOLOGY APPLICATIONS IN TEXTILE INDUSTRY 21 1

science research team at University of Massachusetts, Dartmouth and the bio-engineers at Harvard Medical to carry out research leading to the production of a class of fabrics with special properties called biofabrics27. Biofabrics will contain micro-fabricated bio-environments and biologically activated fibres. These fabrics will have genetically engineered bacteria and cells incorporated into them, that will enable them to generate and replenish chemical coatings and chemically active components.

Niche applications for bio-active fabrics exist in the medical and defense industries, e.g. drug producing bandages or protective clothing with highly sensitive cellular sensors, but biofabrics may form the basis of a whole new line of commercial products as well, e.g. fabrics that literally eat odours with genetically engineered bacteria, self -cleaning fabrics, and fabrics that continually regenerate water and dust repellants.

For such an approach to be successful, technologies will have to be developed to micro-fabricate devices able to sustain cellular or bacterial life for extended periods, exhibit tolerance to extremes of temperature, humidity and exposure to washing agents, as well as tolerance to physical stress on the fabrics such as tension, crumpling and pressure.

5 Dyes and Intermediates from Micro-organisms Textile auxiliaries, such as dyes, can be produced

from the plants or by the fermentation in future. It is known that some microbial species can produce, up to 30% of their dry weight, pigment or a mixture of pigments. Several of these (benzoquinone, naphthoquinone, anthraquinone , perinaphthenone and benzofluoranthenequinone derivative), in some instances, have been shown to resemble the vat dyes.

5.1 Naphthoquinone Dye

One of the major breakthroughs in the biotechnological production of dyes is the commercial production of shikonin using plant cell culture methods. The red pigment traditionally extracted from Lithospermum species gave an yield of about 1 -2%. The new method yields about 1 5% of the dry weight of root cells as pure pigment. The method IS successfully being used in Japan since 1 983.

5.2 Anthraquinones

Several attempts are being made fungal synthesis of anthraquinones cheap and environment-friendly

to exploit the for producing anthraquinone

dyestuff intermediates. Anthraquinones have been isolated from a number of fungi including Drechslera, Trichoderma, Aspergillus and Curvularia strains. Most of these fungi produce a mixture of anthraquinones. A strain of Curvularia lunata produces cynodontin of up to 70% purity. This has been successfully converted into two anthraquinone biodyes- CI Disperse Blue 7 and CI Acid Green 28. The properties of these dyes are similar to those of their synthetic counterparts28.

The advantages of such a process are that the medium of fungal culture requires no expensive chemicals and the fermentation is carried out at room temperature and neutral pH so that the expensive fuel consuming high temperatures and non-environment friendly strong acids and alkalis for the chemical synthesis are not required. Further, work is directed towards identifying and manipulating the genes required for anthraquinone synthesis so that the anthraquinone produced by the fungi could be specifically designed. Yields could be increased by genetically promoting the production of the anthraquinone synthase enzyme system which is responsible for producing the required chemical.

5.3 Indigo

The commercial chemical processes for manufacturing indigo result in the generation of significant quantities of toxic waste products. Thus, a method whereby indigo may be produced without the generation of toxic byproducts has always been desired. The production of microbial indigo was first reported in 1 928. However, it was not until the early 1 980s when scientists seeking a greener alternative method of indigo production looked at the · micro­organisms more seriously. Now, through the commercial application of recombinant DNA technology, it has been possible to develop a novel and environmentally sound biosynthetic indigo production method. In this system, a precursor for indigo production (indole) is produced intra-cellularly at high levels from glucose by microbes. Indole produced in this manner can then be converted to indigo through the action of another enzymatic system followed by exposure to air29. High purity indigo has been obtained from the strains of the microbe Pseudomonas putida3o•

6 Treatment of Textile Waste Water Biotechnological techniques are also being

employed for the elimination of toxic wastes from

2 1 2 INDIAN 1 . FIBRE TEXT. RES., MARCH-JUNE 2001

textile effluents. Some major environmental problems faced by the textile industry include the removal of colour from dye bath effluent and handling of toxic wastes such as PCPs, insecticides and heavy metals. Some of these wastes are toxic enough to poison the systems used to treat them.

The dyes are capable of forming toxic aromatic amines . The majority of colour removal techniques work either by concentrating the colour into a sludge or by the partial / complete breakdown of the colour molecule. While disperse, direct and basic dyes get removed from the waste water via adsorption onto activated sludge, the acid dyes and reactive dyes exhibit low adsorption values and thus pass through the activated sludge processes largely unaffected.

Waste water originating from reactive dye processes create a particular problem as the dyes can exhibit low levels of fixation with the fibre. The unfixed dyes are highly water soluble and are not removed by conventional treatment systems. This is particularly noticeable as the human eye can detect reactive dyes at concentrations as low as 0.005 mglL in clear river water. In response to this, several waste treatment systems based upon aerobic and anaerobic bacterial action have been developed. It has been found that only biotechnological solutions can offer complete destruction of the dyestuff with a reduction in biological oxygen demand (BOD) and chemical oxygen demand (�OD).

Biological systems, such as biofilters and bioscrubbers, are also now available for the removal of odour and other volatile compounds. BAF systems (biological aerated filters or biofilters) comprise a submerged packed bed with fixed biofilm which is continually aerated.

6.1 Fungi for Decolouration

Azo dyes constitute the largest group of synthetic dyes being used by the textile industry. They do not occur in nature and are resistant to aerobic bacterial degradation. However, the azo linkage is susceptible to reduction and the anaerobic bacteria can readily reduce the azo l inkage to yield potentially carcinogenic aromatic amines. It is believed that in many cases, decolouration of reactive azo dyes under anaerobic conditions is due to the action of azo reductase enzymes.

Azo-reductase R) -N=N-R2 + 4e- + 4H+ � R)-NH2 + R2NH2

where R) and R2 are the aromatic substituents in dye molecules.

More recent research shows that the wood degrading white rot fungus P. chrysosporium is the only known organism that can completely degrade a number of azo dyes. The laccase produced by P. chrysosporium is capable of oxidizing the phenolic azo dyes. Laccase oxidation might detoxify azo dyes because this reaction releases azo linkages as molecular nitrogen which prevents amine formation3 )

. This new approach involving direct microbial attack on the azo linkage of organic dyestuffs is already being tested in some pilot units in a couple of major UK dye houses.

In another study, a new peroxidase enzyme produced by white rot fungus P.ostreatus has been shown to successfully decolorize Remazol Brilliant Blue R and the triphenyl methane dye Crystal Violet by an oxidative mechanism32.33. Other researchers have shown that the oxidation of azo dyes -Methyl Orange and Eriochrome Blue Black--by lignin peroxidases is enhanced by the inclusion of additives such as tryptophan or indole in the system34.

Alternatively, it is known that many gut organisms produce extracellular flavanoid compounds which reduce azo bonds in food grade dyes. The gram negative bacteria shewanella species isolated from an industrial effluent stream was shown to degrade a range of reactive dyestuffs, including the commercially important dye Remazol Black B. The decolorization mechanism involving the bacteria appears to function with the aid of an extracellular flavin35•

6.2 Metal and Toxin Removal

Fungi are also being employed to absorb heavy metals from effluent streams. The ligninase producing white wood rot fungus have been used in the paper and pulp industry for removing lignin bound chlorine. They are also effective against biphenyls, aromatic hydrocarbons and chlorinated compounds such as PCP and DDT.

7 Conclusion

Biotechnology has already led to the development of new products, opened new markets, speeded up production of pure products and helped reduce the pollution load . Textile industry is a key sector where immense possibilities exist for biotechnological applications but the current awareness of biotechnology is less. Therefore, the applications are as yet limited. Experience has shown (as in case of

GUPTA: BIOTECHNOLOGY APPLICATIONS IN TEXTILE INDUSTRY 2 1 3

enzyme applications) that wherever a clear economic justification and market for a particular product or process exists, progress has been rapid. So, it can be predicted that in the long term, more and more of the cumbersome and polluting chemical procedures employed by the textile industry will be substituted or supported by the biotechnological processes.

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