Surface Modification of Cellulose Acetate with Cutinase and ...

Chapter 4
quality of the fibres causing losts of fibre material during the process (Shukla et al.,
1997; Zeronian and Collins, 1989).
Nowadays, due to environmental concerns and especially due to more strict
legislation and regulations on the wastewater discharges that were established and
implemented, there is an incresed interest in the replacing of the chemical traditional
textile processing for enzymatic processes. Enzymes can offer to the textile industry
the ability to reduce costs, protect the environment, address health and safety and
improve quality and functionality. Genetic engineering allowed the developement of
many automated protocols for screening proteins with desirable properties and then
provides the tools for amplification, cloning, expression of genes and purification of
the recombinant selected proteins. However, in some cases, the technological
application of enzymes under the demanding industrial conditions is not possible. In
fact, among all the enzymes known, only a few are recognized as commercial
products.
Molecular geneticsa associated with techniques of site-directed mutagenesis and/or
random mutagenesis led to newer enzymes with altered functions that are desired for
their application like improvement of catalytic efficiency, higher substrate specificity
and increased stability.
For instance, the structure and function of cutinases are well studied, and genetic
engineering was previously used to improve their properties for several applications
as for example, fat stain removal in detergents (Carvalho et al. 1999; Longhi and
Cambillau 1999).
In the first part f this work the potential of molecular genetics tools to modify
cutinase from Fusarium solani pisi was demonstrated. Site-directed mutagenesis of
cutinase was carried out to enlarge the active site, which could then better
accommodate polymeric synthetic substrates like polyamide (PA) or polyethylene
terephthalate (PET). Several cutinase mutants, all of which exhibited an enlarged
active site were expressed. A single amino acid replacement, L182A, was shown to
better stabilise the PET model substrate 1,2-ethanodiol dibenzoate tetrahedral
intermediate at the enzyme active site (Subchapter 2.2- Araújo et al., 2007). This
mutant also showed increased PA-hydrolysing activity and up to five-fold higher
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