In an ever more competitive global market which representsclose to $700 billion, the textile industry is seeking new sources of innovation,one of which is biotechnology. In 1996, the global enzyme market for textiles amounted tojust $178 million. However, textile and Apparel companies are now spending moretime and money on environmentally relevant issues. Regulatory pressure isexpected to intensify for both textiles and leather as less pollutingtechnologies become available and it becomes possible to generate less waste.
Enzymes have been used in textile processing since the earlypart of the last century to remove starch-based sizing, but only in the pastdecade has serious attention been given to using enzymes for
Producing new fibers through biotechnology
Biotechnology makes it possible to produce cotton withimproved fiber features. Agricetus has produced a genetically engineered cottonwhich contains a bacterial gene that produces a polyester-like substance thatis reported to have the texture of cotton but to be much warmer. Zeneca usesmicrobes to produce a naturally occurring polyhydroxybutyrate (PHB) bybacterial fermentation. Monsanto is now investigating genetically engineeredplants to be used to produce PHB. Weyerhaeuser has already commercializedbacterially derived cellulose which is finer, more uniform, and more resilient.Sony has developed stereo speaker cones and diaphragms from bacterialcellulose.
DuPont has developed a microbe-based fermentation processfor the manufacture of 1, 3-propanediol, a key ingredient in pclytrimethyleneterephthalate, a polyester that is superior to the widely used polyethyleneterephthalate (PET), but which was previously too expensive to make in largeamounts.
Cellulases are also gaining widespread use in the productionof the relatively new fiber, Iyocell, the generic name for solvent-spuncellulosic fibers. Lyocell is spun from wood pulp in a closed amine oxidesolvent system. The solution is then filtered and extruded to form thefilament. Compared to other man made fibers (such as rayon), Iyocell hasgreater strength and a more environmentally favorable manufacturing process.However, the fiber tends to fibrillate during processing. This fibrillation isunique to Iyocell and can be controlled by cellulase treatment to achieve asoft, luxurious fabric and laundering fastness. In one case, Iyocell wastreated with Primafast(r) SGL cellulase from Genencor International, which isan engineered cellulase composition designed specifically to achieve thedesired performance.
Cellulose-based fabrics such as cotton and linen, but alsosynthetic cellulosics such as rayon, can form unsightly little "bobbles"on the surface. Courtaulds Chemicals has recently developed a new cellulosicfabric from Iyocell fiber, called Tencel, which has better strength andhandling properties but is subject to this defect. Coats Viyella ClothingStevensons, a UK company, in conjunction with Courtaulds, has shown that enzymetreatment prevents this problem. "Once this process has been carried out,the fabric is stable for the rest of its life", says Dr. John Scotney ofCoats Viyella Clothing Stevensons.
Biostoning of denim
Jeans, manufactured from denim, are one of the world's mostpopular clothing items. The "stonewash look" has been traditionallyachieved by locally removing the indigo dye using a process in which pumice stoneis added to the washing drum to abrade the garment. Enzymes can be used tofacilitate removal of the indigo from the yarn surface. In practice, threewashing methods can be used:
- stone washing with pumice only;
- stone-free washing with enzymes only ("biostoning");
- washing with a combination of pumice and enzymes.
Today, biostoning is the main process used in the denim finishing industry, a shift promoted by process economics, fashion and, to a lesser extent, environmental impact.
A life cycle assessment was performed on the three methods of reducing the indigo content and the three process steps specifically related to the production of stonewashed jeans: stone washing, wash off (removal of the stones), and wash (clean-up of the garment). Only these three steps were covered by the LCA.
The biostoning washing method scored best on eight out of ten environmental parameters. The "combined" washing method scored best for water toxicity because of higher emissions of phosphorus compounds into water from the biostoning washing method. The pumice washing process scored better under the heading "odor" mainly because of the ammonia, emissions from agriculture and from the production of ammonia for fertilizers used in the raw material production for cellulase fermentation.
A cost comparison based on environmental regulations or needs was also made for the three washing methods. The highest costs arise from wastewater treatment and were for the pumice method, the lowest were for biostoning. These cost differentials will increase if potential future standards for sustainable development are to be met.
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