Page 105 - Advances in Textile Biotechnology

86 Advances in textile biotechnology

the covalent attachment of bioactive compounds to functionalize polymer
surfaces including relevant techniques in polymer surface modifi cation such
as wet chemical, organosilanization, ionized gas treatments and UV radia-
tion were described (Shearer et al., 2000; Goddard and Hotchki, 2007).
Synthetic polymers coated with bioactive compounds include applications
in textile manufacturing, microelectronics, bioprocessing and medical and
food packaging (Shalaby et al., 2006).
In order to reduce the use of chemicals and their environmental impact,
new technologies have been developed to replace classical methodologies.
Glow discharge (plasma) techniques are particularly useful for function-

alization of surfaces. The surface modification of polyamide fibres and fi lms
by atmospheric plasmas has been described (Foerch and Hunter, 1992;
Oktem et al., 2000; McCord et al., 2002; Pappas et al., 2006) and this tech-
nique has also been a valuable tool to improve the biocompatibility of fi bres
(Shmack et al., 2000).

Surface modification with enzymes is considered to be a valuable tool to
improve the quality and the processing properties of synthetic fi bres. A
biocatalytic method has the advantage of being performed under mild and
environmentally friendly process conditions. Moreover, no complicated
machinery is required, in contrast to plasma treatments, and few or no
additional chemicals are needed. Furthermore, the direct control of the

relative amount of specific groups formed is difficult to achieve by using

physical techniques. Owing to the selectivity of enzyme reactions and their
occurrence only at the surface of the fibres, enzymatic hydrolysis is desir-

able when compared with traditional chemical methods.
Biocatalytic processes have been developed to modify polyamide sur-
faces enhancing hydrophilicity (Guebitz and Cavaco-Paulo, 2007). Enzymes
that are able to hydrolyse polyamide surfaces are proteases, amidases and
cutinases. Figure 4.2 shows the mechanism of action of these enzymes
through polyamide structures.
Heumann and co-workers have demonstrated that polyamide substrates
can be effi ciently functionalized by esterase, cutinase or protease action. A
model substrate (adipic acid bishexylamide) was developed for screening
polyamidase activity of a given enzyme. A protease from Beauveria sp., an
amidase from Nocardia sp. and a cutinase from Fusarium solani were used
to hydrolyze this model substrate (Heumann et al., 2006). The enzymatic

hydrolysis of polyamide 6.6 fibres was extensively studied by Silva et al.,
and several process parameters were defined. For the first time, the action

of a cutinase from Fusarium solani pisi towards polyamide fabrics was
reported. The hydrolysis of nylon fabrics is based on the breakage of the
amide linkages of the polymer surface resulting on amino and carboxylic
groups yielding (Cavaco-Paulo et al., 2005; Silva and Cavaco-Paulo, 2004;
Silva et al., 2005a).

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