Surface Modification of Cellulose Acetate with Cutinase and ...

Enzymatic Modification of Wool Surface - Introduction
surface specific because the reaction with the cuticle takes place in less than 10 seconds.
Chlorination results in the oxidation of cystine residues to cysteic acid residues in the
surface of the fiber and allows the Hercosett 125 polymer, applied afterwards, to spread
and adhere evenly along the fibre surface (Heine, 2002). This polymer, which is
normally used to improve the wet strength of paper products, swells to 10x its normal
thickness in water thus preventing the scale edges of adjacent fibres from interacting
and causing felting during washing.
The chlorine-Hercosett process has been employed in the industry for the last 30 years,
and about of 75% of the world's treated wool is processed by this route in one of its
forms (Holme, 2003). As previously mentioned (Chapter 1) this process has excellent
advantages (antifelt effect, low damage and low weight loss) but it also shows a number
of drawbacks like limited durability, poor handle, yellowing of wool, difficulties in
dyeing and the most important today, release of absorbable organic halogens (AOX) to
the effluents (Heine, 2002; Schlink and Greeff, 2001). There is therefore an increasing
demand for environmentally friendly alternatives.
4. Enzymatic Finishing Processes for Wool
Enzymes can be used in order to develop environmentally friendly alternative
processes. Since wool mainly consists of proteins and lipids especially proteases and
lipases have been investigated for wool fibre modification. However, the complex
structure of natural fibres, especially of wool, brings complexicity to enzymatic fibre
modification. Proteases and lipases can catalyse the degradation of different fibre
components of wool preventing an accurate control of the reaction. If not controlled,
this diffusion leads to a strong damage of the wool fibre, being crucial to restrict the
enzymatic action to the wool fibre surface. The following subchapters describe the
approaches developed in the scope of this thesis aiming to restrict subtilisin E
hydrolysis to the surface of wool.
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