Surface Modification of Cellulose Acetate with Cutinase and ...
Surface Modification of Cellulose Acetate with Cutinase and ...
Surface Modification of Cellulose Acetate with Cutinase and ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
General Discussion <strong>and</strong> Future Perspectives<br />
activity on PET when compared <strong>with</strong> the native enzyme (Subchapter 2.3- Silva et al.,<br />
2007 <strong>and</strong> Subchapter 2.4- O’Neill et al., 2007).<br />
Similarly the activity <strong>of</strong> a nylon-oligomer hydrolysing enzyme EII’ from<br />
Flavobactererium sp. was increased 200-fold by genetic engineering (Negoro, 2000).<br />
In addition to genetic engineering, reaction engineering (temperature <strong>and</strong> additives)<br />
seems to be an important factor <strong>and</strong> enzymatic hydrolysis <strong>of</strong> PA can be increased in<br />
the presence <strong>of</strong> solvents (Silva et al., 2005a).<br />
Not only the structural design <strong>of</strong> the active site <strong>of</strong> the enzymes but also the regions<br />
required for sorption <strong>and</strong> for guiding the enzyme along the substrate, might be<br />
important for polymer hydrolysis. <strong>Cellulose</strong>-binding modules (CBM) accomplish this<br />
role in cellulases. For this reason, the biomodification <strong>of</strong> the surface <strong>of</strong> cellulose<br />
acetate was performed <strong>with</strong> cutinase fused <strong>with</strong> either the carbohydrate-binding<br />
module <strong>of</strong> Cellobiohydrolase I, from the fungi Trichoderma reesei, or the<br />
carbohydrate-binding module <strong>of</strong> Endoglucanase C, from the bacteria Cellulomonas<br />
fimi. The knew recombinant cutinase fused to the fungal CBM presented better<br />
performance hydrolysing cellulose diacetate <strong>and</strong> improving the colour levels <strong>of</strong><br />
treated fabrics (Subchapter 2.5- Matamá et al., 2008).<br />
The second part <strong>of</strong> this thesis relates to the biomodification <strong>of</strong> wool, to accomplish<br />
total easy care wool i.e. machine washability plus tumble dryability, to compete <strong>with</strong><br />
other fibres.<br />
The traditional method to confer dimensional stability to wool articles uses chlorine<br />
which has various drawbacks. Several enzymatic methods have been attempted to<br />
replace this hazardous chemical finishing treatment, <strong>with</strong>out great success mainly<br />
due to diffusion <strong>of</strong> enzyme into wool cortex (Shen et al., 1999). Chemical<br />
modification <strong>of</strong> proteases proved to be effective for wool finishing, however the<br />
presence <strong>of</strong> small amounts <strong>of</strong> free enzyme still representes a drawback (Silva et al.,<br />
2004; Silva et al., 2005b). In our work we used subtilisin E from Bacillus subtilis,<br />
genetically modified, in order to avoid its penetration inside the fibre.<br />
The first attempt was to create a chimeric poly-subtilisinE composed <strong>of</strong> 2, 3 <strong>and</strong> 4<br />
subtilisin units. Chimeric subtilisins were overexpressed but no active <strong>and</strong> soluble<br />
recombinant proteins were recovered (Subchapter 3.2- Araújo et al., 2008a). The<br />
221