Page 140 - Advances in Textile Biotechnology

Enzymatic modifi cation of polyacrylonitrile and cellulose acetate fi bres 121

0.36% of the acetyl groups from CDA and CTA, respectively. These results
agreed with studies that describe a higher level of acetic acid released for
CDA than for CTA, a more substituted cellulose acetate. Studies reported
on the biodegradation of cellulose acetate, using micro-organisms or cell-
free enzymes, provide evidence that the degree of substitution is inversely
correlated with the degree of deacetylation (Altaner et al., 2001, 2003;
Moriyoshi et al., 1999, 2002; Puls et al., 2004; Samios et al., 1997). It was
proposed that steric hindrance and crystallinity are important factors in the
effectiveness of the adsorbed enzyme to promote hydrolysis, thus favouring
CDA over CTA (Lee and Fan, 1982).
Altaner et al. (2001) reported that acetyl esterases from 13 different com-

mercial origins could significantly use cellulose acetates with DS ≤ 1.4 as
substrates. Among them only one enzyme from Humicola insolens was able
to release a small number (10%) of acetyl groups from a cellulose acetate
DS 1.8, after 220 h. Another report described the application of an acetyl
esterase from Aspergillus niger that was able to hydrolyze 5% of acetyl
groups on a cellulose acetate DS 1.8 after 140 h, but was unable to release
acetic acid for a DS 2.3 (Altaner et al., 2003). Comparing these values with
those obtained for an assay carried out for only 8 h, it was demonstrated
that recombinant cutinase had an activity with as great a potential as acetyl
esterase for CDA and CTA materials.
Evidence of hydroxyl-group formation on the surface CDA and CTA
fibres was also obtained by the improvement in the chemically specifi c

coloration of the fabrics with a reactive dye (Remazol Brilliant Blue R, C.I.
61200) (Matamá et al., 2010). Increases in K/S of 25 and 317% were obtained
for diacetate and triacetate, respectively, after treatment with cutinase for
24 h. The results showed that cutinase was able to modify the surface of the
cellulose acetate fabrics, increasing the number of hydroxyl groups (both
in CDA and CTA), and lowering the carbonyl groups (detected only in CTA
by DRIFT). Cross-sections of fibres treated with cutinase conjugated with

FITC were observed by fluorescence microscopy. The fl uorescence signal

was located mainly at the surface, the core of the fibres did not emit fl uo-

rescence indicating that the labelled protein did not penetrate inside the

fibres, therefore confirming the superficial action of cutinase on CDA and
CTA fi bres.
Matamá et al. (2010) presented a novel approach to increase cutinase

adsorption on cellulose acetate fibres. Using molecular genetic tools, they
constructed chimeric cutinases by fusing the catalytic domain with a carbo-
hydrate-binding module (CBM). Four constructions were obtained using
two distinct CBMs, fused independently to the C-terminal of cutinase, and
varying the linker DNA sequence (Fig. 5.9). CBMs were selected on the

basis of ligand affinity, because the two cellulose acetate fibres are structur-
ally distinct from cellulose (the native ligand) and each other, with different

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