Surface Modification of Cellulose Acetate with Cutinase and ...

Surface Modification of Cellulose Acetate with Cutinase and Cutinase Fused to Carbohydrate-binding Modules
cutinase per fabric weight, at pH 8 and 30º C, for 15 hours. Both images were acquired
with a total magnification of 1000x.
The protein was found at the fibre surface of both fabrics and it was also possible to see
some lack of uniformity as for the reactive dye staining. Scanning electronic
microscopy images were also obtained for both fabrics treated for 18 hours with
50 U mL -1 cutinase (results not shown). The surface of CDA was not apparently altered
by the enzymatic treatment while a slight fibrillation of the triacetate surface was visible
after the cutinase treatment. The impact of the hydrolysis of acetyl groups should be
more drastic on the highly ordered structure of CTA than on the more disordered CDA.
From the mathematical fitting of X-ray diffraction patterns, crystallinity indexes were
determined for CDA and CTA, samples and respective controls (table II). There was a
small decrease in the crystallinity index after the enzymatic treatment, for both fibres.
CTA was most affected, with a decrease of 12% while CDA had a decrease of 8%.
Table II. Crystallinity indexes for CDA and CTA. The samples (2% w/v) were treated
with 25 U mL -1 of cutinase, at pH 8 and 30º C, for 24 hours.
CDA CTA
Control 0.38 0.68
treated sample 0.35 0.60
Cutinase was able to modify the surface of the cellulose acetate fabrics, increasing the
number of hydroxyl groups and consequently the hydrophilic character and the dye
affinity. Since there were changes on the crystallinity index, other physical properties
should be tested for a better evaluation of the impact of such surface modifications on
the textile performance of these fibres.
3.4. Cellulose di- and triacetate treatment with cutinase fused to cellulose-binding
modules
For further improvement of cutinase catalysis, several fusion proteins with known and
well characterized CBMs were produced. The inclusion of spacers between the cutinase
and the CBMs was performed in three of the fusion proteins. The importance of these
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