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