Page 196 - Advances in Textile Biotechnology

Enzymatic treatment of wool and silk fi bres 177

Smith et al. (unpublished work) investigated the use of proteases and a

protease enlarged by chemical modification in the raw wool scouring
process, which led to improved dyeing and shrink resistance. It was shown

that protease improved the scouring process and modified the cuticlar layer.
A reduction of lipid content was found and this led to an improvement in
the dyeability.
Wool fabrics may contain vegetable matter such as burrs, seeds and shives

which may attach themselves to the fibre and can pass through to the fi nal
stage of weaving or knitting. To remove vegetable matter from wool fabrics,
the wool may need to undergo an additional chemical carbonizing process.
Alternatives using enzymes such as cellulases, pectinases, hemicellulases
and xylanases to remove vegetable matter from wool have been investi-
gated in the scouring process (Sedelnik, 2003; Das and Ramaswamy, 2006;
Gouveia et al., 2008; Kholiya et al., 2008). The enzyme treatments may
promote the degradation of vegetable matter, resulting in its easier removal.
It was reported that enzymatic treatment might be able to lower the con-
centration of sulfuric acid needed for the carbonizing process (Sedelnik,

2003). Cleaning raw wool fibres using enzymes needs to be further studied
and developed. A process combining a mixture of different enzymes might
make scouring more efficient: saving water and energy.

8.3.3 Enzymatic fi nishing
The application of enzymes in wool-finishing processes to achieve soft

handle, shrink-resistance and improved dyeability has been extensively
studied and developed in last decade, and has been recently reviewed by
Heine and Höcker (1995 and 2001) and Shen (2009).
Early studies and more recent work (Bishop et al., 1998; Moncrieff, 1953;

Shen et al., 1999) have confirmed that the action of proteases on undamaged
wool is slow. This is because of the protective nature of the hydrophobic
epicuticle surface containing fatty acid molecules and highly crosslinked
cuticle cell components. However, once some of the cystine disulfi de cross-
links in the cuticle cells are broken, the rate of enzyme reaction is greatly
increased. It was found that during treatment with proteolytic enzymes,
enzyme attack occurred preferentially at the highly swellable cell mem-
brane complex by the enzyme penetrating between cuticlar cells and then
between cortical cells. Once the enzyme has diffused into the membranes
between the cells, it can rapidly disrupt the cell membrane complex, and

damage the fibre if the reaction is prolonged. A fl uorescence microscopy
study demonstrated the diffusion of fluorescently labelled enzymes between

the cuticle scales, through the cell membrane complex and into the cortical
cells (Heine, 1991; Fogorasi and Heine, 2006). Therefore, it is diffi cult to
limit enzymatic degradation to the cuticle scales and to achieve machine-

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