Page 197 - Advances in Textile Biotechnology

178 Advances in textile biotechnology

washable wool without signifi cant fibre damage (Heine et al., 2000). Recently,
scanning electron microscopy (SEM) has been used to observe the degrada-

tion of wool fibre cross-sections caused by proteases digestion. The SEM

images confirmed that the proteases preferentially digest the cystine-poor
endocuticle, cell membranes, nuclear remnants, and intermacrofi brillar
materials on the wool cross-sections (Okada et al., 2008).
During enzymatic treatment of wool using proteases on their own, an
early study (Moncrieff, 1953) showed that the attack on wool fi bres is vari-

able. The enzymes appear to attack weathered fibres more rapidly and

therefore attack the tips of fibres more than the root ends. Irregularity of

damage of fibres by enzymes was clearly shown by SEM.
Bishop et al. (1998) reported that carefully controlled treatments with
proteolytic enzymes can reduce the buckling load and collapse energy of
wool yarns. These treatments were shown to improve the softness and
reduce the subjectively perceived prickle of wool fabric knitted from the
treated yarns. The combination of chlorination and treatments with proteo-
lytic enzyme was also reported to improve handle properties, especially for

coarse wool and mohair fibres, as well as improving fibre whiteness, without

causing any significant damage to the wool (Holme, 2006).

Enzymatic treatments for lipid removal have been studied to make the
wool fibre more hydrophilic, in order to make subsequent enzymatic treat-

ment more efficient. Triacylglycerol lipase (EC 3.1.1.3) and lipoprotein

lipase (EC 3.1.1.34) have been used. Heine (Heine, 1991; Nolte et al., 1996)
investigated the removal of lipids from the outer surface layer of the wool

fibre by treating grease-free wool with a lipoprotein lipase. It was found
that the aliphatic hydrocarbon content of the cuticle surface was reduced

by 20%. Mall et al. (2002) used ToF-SIMS (time-of-flight secondary ion
mass spectrometry) surface analysis to monitor the loss of surface lipids
caused by treatment of scoured wool with lipases. It was found that the
anionic surfactants left on the surface of wool fibre from the scouring

process might inhibit the enzyme. No change in the fibre wettability was

observed, probably because the integrity of the hydrophobic surface layer

was not sufficiently attacked by the enzymes. Recently, Wang et al. (2010)

investigated the effect of lipase treatment on the fibre surface of wool
fabrics cleaned by soxhlet extraction with chloroform/methanol 87 : 13(v/v).
It was reported that the lipase treatment hardly affects the cuticle surface
of the wool, resulting in no noticeable improvement of wettability.
The use of cutinase to hydrolyse the outermost bound lipids in the wool
surface has recently been investigated. Cutinase has hydrolytic activity
towards a broad variety of aliphatic esters. Wang et al. (2009) reported that
treatment by cutinase can improve the wettability of wool fabrics from a
contact angle of 135° to 92° after 4 h incubation with cutinase activity at
−1
10 U g fabric. However, cutinase can not achieve the complete removal

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