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Enzymatic up-grading of wool fibres

Final Report Summary - ENZUP (Enzymatic Up-grading of Wool Fibres)

The market value of wool is limited by the fact that consumers place increasingly high demands on machine wash-ability and soft feeling. Felting shrinkage, which is a typical property of wool due to the configuration of the scales of the wool fibre, is a serious problem, especially during washing. Chlorination, followed by polymer deposition, is commonly used to modify the scales of wool fibres in order to confer shrink-resistance, but this involves major drawbacks such as contaminating the wastewater with absorbable organic chlorides (AOX) and the environment.

Enzymatic treatment represents a very interesting alternative to chlorination. Recent studies suggest a reasonable possibility for improving wool shrink-resistance. There is, however, no commercial application so far, due to difficulty in controlling enzyme reactions on protein fibres.

Proteolytic enzymes are known to penetrate and degrade the internal wool structure during processing, causing fibre damage. The ENZUP project targeted this problem. The proteases are being genetically engineered and modified to have large molecular sizes which will limit the enzyme penetration into the fibres. The degradation by proteases will only take place on the outer layers of wool fibres.

The project has developed chemically modified proteases with three different levels of molecular sizes. Production of the modified proteases has been optimised at the large scale in order to reduce cost and improve the efficiency of production. Furthermore, fundamental studies have been undertaken to understand the effect of the enlarged molecular size of proteases on the treatment of wool and their surface modification. As a result the knowledge and data for controlling enzymatic reactions on protein fibres has been obtained from the project to support the application of modified proteases in the bioprocesses including wool scouring and bio-finishing processes for wool fibres.

The technology for enlarging molecular size of proteases (subtilisin) has been further developed through a genetic engineering approach by the ENZUP project. The high molecular weight subtilisin is constructed based on the fusion of prosubtilisin E DNA sequence, from Bacillus subtilis, with a DNA sequence that codifies to an elastin-like polymer.

From the application of chemically and genetic modified proteases with high molecular weights on wool fibres, the results showed that these enzymes can be used for specific surface modification of protein materials including wool anti-felting treatment, reduction of pilling and low temperature dyeing without damaging wool fibres.

In addition, the chemical modification of proteases with the Eudragit polymer can make the enzyme more stable and compatible with most detergent formulations. Therefore, the modification of proteases can lead to applications of proteases in washing detergent formulations for cleaning wool stains.

A new process for genetic modification of proteases was developed. The high molecular weight protease was constructed based on the fusion of prosubtilisin E DNA sequence, from Bacillus subtilis, with a DNA sequence that codifies to an elastin-like polymer. Engineered proteases show increased molecular weight which prevents their diffusion into protein materials. Thus, these enzymes can be used for specific surface modification of protein materials including anti-felting treatment of wool without damaging the wool fibres. In addition, these proteases will find application in detergents for wool based textiles where the enzyme degrades protein stains without damaging wool fibres. These results are of high interest for applications in the textile industry.

Wool yarns were treated with both commercial and chimeric subtilisins. It was found that the commercial subtilisin is able to penetrate inside the wool cortex, but fibre damage was expected due to its small size. But using the chimeric subtilisin, there was a significant reduction of felting, pilling and tensile strength loss of wool yarns since the hydrolysis was restricted to the cuticle layer of wool.

These results are of great importance. This novel process of enzymatic-controlled hydrolysis overcomes the unrestrained diffusion of enzymes and extended fibre damage which are the major obstacle on the use of enzymes for wool finishing applications.

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