Page 118 - Advances in Textile Biotechnology

Enzymatic modifi cation of polyacrylonitrile and cellulose acetate fi bres 99

Koeller and Wong, 2001). Enzymes are environmental friendly catalysts not
just because they are biodegradable themselves but also because of their
mild operating conditions. They can result in processes that generate fewer
waste disposal problems and that require lower energy input, leading to
lower costs and lower emissions of greenhouse gases to the environment
(Rozzell, 1999). The enzyme can be used as the sole catalyst in a reaction,
in combination with other enzymes, or with inorganic reagents. Moreover,
many enzymes accept unnatural substrates, and genetic, pathway and
medium engineering can improve further their stability and specifi c activity

as well as modulate their substrate specificity (Koeller and Wong, 2001).
These qualities make enzymes remarkable catalysts. It is now widely rec-
ognized that enzyme-catalysed chemical transformations are convenient
alternatives to traditional (non-biological) transformations. Biocatalysis is
a tool of increasing importance for industries that aim at sustainable devel-
opment (Schäfer et al., 2007; van Beilen and Li, 2002).

Textile materials made from synthetic fibres are, in general, uncomfort-
able to wear because they are hydrophobic. This means that these materials
can not absorb perspiration and water vapour can not easily be transported
away from the body. The hydrophobic nature also leads to their character-
istic static cling and stain retention during laundering (Gübitz and Cavaco-
Paulo, 2008).

Textile finishing is the final stage in the fabric manufacturing process and

includes all the processes that modify the surface of fibres to add useful
qualities to the fabric, ranging from interesting appearance and fashion
aspects to high-performance properties for industrial needs (Schindler and
Hauser, 2004). As the use of high performance textiles grows, the need for

chemical finishes to provide the fabric properties required in these special
applications has grown accordingly. Currently, more than 20 different types

of chemical finishers exist for both natural and man-made fibres (Fig. 5.1)

(Schindler and Hauser, 2004). There are several methods for the surface
modifi cation of synthetic polymers to increase hydrophilicity. The methods
currently used are plasma treatments and chemical finishers, including alka-

line and acid hydrolysis. In addition to the environmental issues, these

methods are difficult to control, sometimes they are of reduced technical

lifetime and in some instances severe fibre weight losses and yellowing
occur (Gübitz and Cavaco-Paulo, 2003, 2008). On the other hand, enzymes
are well-suited for targeted surface functionalization of polymers. In addi-
tion to the advantages referred to above, enzymes are macromolecules and
for that reason their action is normally restricted to the most superfi cial
layers of polymer fi bres.
The broad substrate specificity and catalytic promiscuity, exhibited by

some enzymes, uncover a new range of possible biocatalytic transforma-
tions (Bornscheuer and Kazlauskas, 2004). The ability of enzymes to use

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