Wednesday, 12 July 2000

BRINGING THE BENEFITS OF BIOTECHNOLOGY TO TEXTILES AND CLOTHING

Portugal, 3-7 May 2000

Reported by Paul Hamlyn

Some 129 participants from 28 countries attended the first Symposium on Biotechnology in the Textile Industry, held in Portugal during the first week of May. Most of the participants were from Universities and, not surprisingly, several enzyme companies also sent representatives. The meeting was organised jointly by the Working Party on Textile Biotechnology and the University of Minho. Four main areas were covered: cellulases and cellulose, use of enzymes in cotton preparation, protein fibres and decolourisation of dyes in textile wastewater.

Cellulases and cellulose

Cellulases have had the most impact on textile processing in recent years. Current commercial applications include "biostoning", "biopolishing" and as laundering "brightners" of cotton fabrics. However, there is a fine balance between producing the desired effect and causing excessive damage to the fibres leading to an unacceptable loss in strength. Experimental evidence was presented from several research groups indicating that the use of mono-component endoglucanase or endoglucanase-enriched cellulase complexes together with a high level of mechanical agitation can achieve the desired performance with only a limited loss of tensile strength. Most of this work had been done using woven cotton fabrics. Jaakko Pere presented details of work carried out in Finland on the treatment of cotton yarns with mono-component cellulases. Steaming increased the accessibility of the yarns to the enzymes. The resulting decrease in hairiness and tendency towards pilling was mainly attributed to endoglucanase activity.

The presentation by Chris Jones from Unilever Research introduced an extremely novel application for cellulase enzymes based on their ability to bind selectively and strongly to cellulose molecules. This property can be exploited for the targeted delivery of substrates (e.g. softening agents) to cotton and is highly specific giving minimal delivery to synthetic fibres. Unilever have patented the process and demonstrated its feasibility when included in a laundry detergent product.

Cotton preparation

The papers in this section were mainly concerned with replacing conventional chemical treatments used in the preparation of cotton with enzymes. This could potentially lead to considerable savings in water usage, energy and effluent treatment costs. Enzymatic desizing using amylases is an established process that has been in use for many years. More recently, pectinases have shown promise in replacing the traditional alkaline scouring treatment. Novo Nordisk have introduced ‘BioPrep’, an enzymatic process to remove hydrophobic and other non-cellulosic components from cotton. The new process operates at mild pH conditions over a broad temperature range and can be applied using existing equipment such as Jet Dyers. Price and performance is claimed to be economical when considering the total process costs. There was general agreement that uptake of biotechnology by the textile industry would depend on the ability to use existing equipment and work procedures. Bioscouring has had a slow start but is expected to become a valid alternative to chemical scouring.

Workers at the University of Auburn (USA) have developed a combined process for desizing, scouring and bleaching using a mixture of amyloglucosidase, pectinase and glucose oxidase. Glucose generated enzymatically from the desizing and scouring stages is converted into hydrogen peroxide by glucose oxidase for the final biobleaching stage. However, currently glucose oxidase is far too expensive for use in textile processing.

Removal of the seed coat fragments is the most difficult part of a cotton biopreparation process. Ian Harding from the University of Georgia (Athens, USA) claimed that progress was being made and put forward the view that a total enzymatic process would be the definite part of the operations in a number of mills in the United States within the next 5 to 10 years.

Protein fibres

Elisabeth Heine presented work carried out at DWI (Aachen, Germany) looking at the potential application of enzyme treatments in wool finishing. The use of sulphuric acid to remove vegetable matter from wool (carbonisation) has a number of drawbacks. A combined cellulase, pectinase and xylanase treatment degraded up to 7% of the vegetable matter but there was no improvement on this after combing. Protease treatments had also been assessed. A more even dyeing (based on examination of wool fibre cross-sections) was achieved in semi-industrial trials following the enzyme treatment.

Rudi Breier (Dr Petry Gmbh, Reutlingen, Germany) introduced a new, purely enzymatic process based on the use of a protease to impart shrink-resistance to wool. Lanazym can replace traditional chemical antifelt treatments and so far 35 tons of wool have been commercially processed.

George Roberts (Nottingham Trent University, UK) had examined the effectiveness of different chitosans (differing in molecular weight, degree of deacetylation etc.) as an anti-felting treatment for wool. He claimed that it should be possible to tailor specific chitosans for wool that do not effect fabric handle. However, some washing treatments can remove chitosan so a care label would have to be included on the finished garments.

Paul Kiekens (Gent University, Belgium) reviewed progress on spider silk. Because of the unique properties of spider silk the possibilities for commercial exploitation had been researched for many years. Bioproduction of the silk protein in mammals (e.g. from the milk of transgenic goats) seemed to offer the most potential. However, a commercial process is still several years away.

Decolourisation of dyes in textile wastewater

Although textile dyes generally have low toxicity compared with other chemicals used in textile processing evidence of their presence in the environment is very high and they cannot be effectively degraded in conventional waste treatment plants. Therefore, decolourisation of dyes in textile wastewater is seen as a priority area for biotechnology. Even the humble rhubarb plant (Rheum palmatum) is under investigation because of its ability to accumulate and biotransform sulphonated anthraquinones. However, most papers in this section focussed on the white rot fungi.

Ian Hardin and co-workers (University of Georgia, Athens, USA) are carrying out a three year intensive study on the potential application of white rot fungi to decolorise dyes in textile effluent. Whole organisms were being used to overcome the need for isolated enzymes and co-factors but glucose is required as a carbon source to maintain metabolic activity. In a scaled-up process it is envisaged that the effluent from desizing, a major component of the BOD, could supply the glucose. In laboratory trials effectiveness was found to vary with dye structure and the species of fungus. Clearly, much more research is required in this area before a commercial process can be developed. It is also very important to monitor the toxicity of any breakdown products. One advantage of using fungi is that they don’t produce amine groups (highly toxic to aquatic life) which can be generated during bacterial breakdown.

General papers

Sonja Salmon from Novo Nordisk pointed out that although most of the enzymes currently in commercial use are hydrolases, oxidoreductase enzymes hold much promise for improved textile process technology, especially within dyeing and bleaching operations. Catalase is already used for bleach clean-up prior to dyeing saving the need for three rinses when using dyes that are attacked by peroxide. Laccase has been shown to give enhanced denim abrasion with reduced back staining in biostoning and peroxidase has potential for the decolourisation of dyes as part of an effluent treatment process.

Paul Hamlyn (BTTG, Manchester, UK) outlined the use of DNA analysis to objectively confirm the types of animal fibres present in an unknown sample or blend. This technique has been used to demonstrate the presence of adulterants in commercial samples ranging from raw fibres to finished garments.