Page 220 - Advances in Textile Biotechnology

Functionalisation of wool and silk fi bres using enzymes 201

confers on the device the desired functionality at specifi ed addresses. This
enzymatic assembly approach provides an alternative to existing chemical
coupling methods. It positively responds to technological requirements,
including spatial selectivity, orientational control, and mild treatment condi-
tions, which allow the biological activity of proteins to be maintained during
the multi-step assembling procedures because the enzymatic approach does
not require reactive chemical agents or activated polymers.

Leather processing

Leather processing includes filling, i.e. the introduction of materials into the

voids that exist between the fibres of the leather to smoothen any irregular-
ity on the leather surface. Protein by-products such as gelatine and casein

can be used as filling materials during leather processing. For example,
glutaraldehyde crosslinked gelatines resulted in highly polymerised fi lling
polymers that were able to fill the leather and, more importantly, also

remained bound to the leather during washing steps (Taylor et al., 2006a).
As a further development of this approach to leather fi lling, microbial
TGase was used as crosslinking agent for various proteinaceous industrial

by-products, specifically gelatine, whey, and whey protein isolate (Taylor et
al., 2006b). The crosslinked biopolymers showed values of melting point,
viscosity, and molecular weight distribution suitable for their use as fi llers,
suggesting that there is potential for these relatively inexpensive and sus-
tainable resources to be recycled in leather processing. Filling experiments

demonstrated that the enzymatically prepared filling materials could be

effectively used as fillers, which were bound to the leather and could not
easily be removed during further processing (Taylor et al., 2007).

9.3 Functionalisation of protein fi bres using
transglutaminases

Among protein-based textile fibres, wool has become an eligible substrate
for the application of TGase enzymes. The content of Gln+Glu in wool is
−1
1098 μmol g , corresponding to ∼12 mol% (Lindley, 1977), 40% of which
can be attributed to Gln alone (Maclaren and Milligan, 1981). The amino
acid analysis of the individual histological components of the wool fi bre, i.e.
cuticle, CMC, and cortex, has shown that Gln+Glu residues are present in
−1
roughly the same amount, i.e. 894 μmol g in the cuticle (∼9 mol%),
−1
−1
968 μmol g in the CMC (∼10 mol%), and 1081 μmol g in the cortex
(∼12 mol%) (Lindley, 1977). Considering that the relative amount of each

histological component in fine wool fibres is about 10, 5, and 85 wt% for

cuticle, CMC, and cortex, respectively (Bradbury and King, 1967), the
content of Gln+Glu in the different morphological compartments of intact

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