Chemical Modification Of The Protease And The Application In Anti-Felting Finishing Of Wool

Enzymatic process is the most promising technology which will replace chlorine-Hercoset treatment for improving shrink resistance of wool fabrics. The use of proteases to hydrolyse the cuticles at the surface of wool fibres, always results in high strength and weight losses. This suggests that restriction of the enzyme activity to the wool surface is required. The research on restraining the range of action of enzyme to the the cuticles by chemical modification attracts much attention. But there are no reports on improving shrink resistance of wool fabrics by chemical modification of enzyme in our country now.Firstly, Glutaraldehyde, Microbial Transglutaminase(MTG) and 1-ethyl-3-(3-dimethyl -aminopropyl) carbodiimide hydrochloride(EDC) were employed to modify the protease. The molecular weight distribution of the modified protease were characterized by size exclusion chromatography and SDS-PAGE. The structural changes were analysed by UV absorption spectrum, circular dichroism spectra and fluorescence emission spectra. Then the appropriate and effective methods were applied in the anti-felting finishing of wool fabrics. The anti-felting effect of the modified proteases was evalued according to shrinkage, tensile strength, the alkaline solub -ility and dye ability of wool fibers. Finally, SEM was carried out to observe the surface of wool fibers treated by the native and modified proteases.The chemical modification results showed that glutaraldehyde was not an efficient crosslinker for the protease. When MTG was used for the modification of the protease, it could be hydrolysed by the protease and lost cross-linking function. EDC can be used to modify the protease.The protease was covalently coupled to chitosan with EDC. It was found that the secondary and the whole structures of the modified protease were much more regular and compact than the native one. The conjugated protease presented a lower affinity towards casein with an increase in Km. There was no change in optimum temperature, but the modified protease displayed higher stability above 70℃, compared to the native enzyme.In terms of shrinkage, tensile strength and elongation of the samples, wool fabrics treated by the native protease showed the best anti-felting effect with a high decrease in strength and elongation. EDC modified protease had a slight effect on the strength and elongation of wool, though had a worse benefit effect on the wool fibers felting behaviours than the native one. In the solution of pH 8.5, the midified protease was in the form of immobilization on chitosan which worked differently from the above proteases. In a short treatment time, the anti-felting effect of the immobilized protease was not an well as the native one. But in the condition of long treatment time and high activity, the effect was better with less damage to tensile strength and elongation of wool. It was found that the dyeing rates of wool fabrics were higher after being treated by the modified proteases than by the native one. SEM images of wool fibers conformed that modifications of the protease enabled the reaction of the protease to be controlled, so that less degradation of the wool occurs than in similar treatments with the native protease. In the system of pH 6, the anti-felting effect of the native protease was still the best, but with the maximum damage to wool fibers.