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 />
After 18 hours, the relative difference in colour strength between treated samples <strong>and</strong><br />
controls was around 50% for CDA <strong>and</strong> 450% for CTA. For both fabrics, the relative<br />
K/S increased rapidly in the first hours <strong>of</strong> treatment <strong>and</strong> slowed down as the protein<br />
adsorption equilibrium was being settled. In the particular case <strong>of</strong> these modifications, a<br />
very slow enzymatic reaction occurs. We believe that the fast initial increases in colour<br />
are an artefact created by an incomplete protein removal during the washing procedure<br />
at the end <strong>of</strong> each treatment. It seems that the dye is also able to react <strong>with</strong> hydroxyl<br />
groups present in the protein molecules not removed from the fabric. If this argument is<br />
correct the actual relative K/S increase is bellow the observed values.<br />
3.3. <strong>Surface</strong> modification <strong>of</strong> cellulose di- <strong>and</strong> triacetate fabrics <strong>with</strong> cutinase<br />
Samples <strong>of</strong> CDA <strong>and</strong> CTA fabric (2% w/v) were treated <strong>with</strong> 25 U mL -1 <strong>of</strong> cutinase for<br />
24 hours. Table I shows the values <strong>of</strong> increase in colour strength <strong>and</strong> acetic acid<br />
liberated to the reaction medium for both cellulose acetates (the control values were<br />
subtracted).<br />
Table I. Hydrolysis <strong>of</strong> CDA <strong>and</strong> CTA fabrics by cutinase. The parameters evaluated<br />
were the amount <strong>of</strong> hydroxyl groups at the fibre surface, measured as relative increase<br />
<strong>of</strong> K/S values at 590 nm, <strong>and</strong> the acetic acid release to the liquor. The samples (2% w/v)<br />
were treated <strong>with</strong> 25 U mL -1 <strong>of</strong> cutinase, at pH 8 <strong>and</strong> 30º C, for 24 hours. The controls<br />
were subjected to the same conditions except the for enzyme. Samples <strong>and</strong> controls<br />
were competitively dyed at 50º C.<br />
CDA CTA<br />
K/S 590nm (%) 25 ± 9 317 ± 32<br />
Acetic acid (mg L -1 ) 1.9 ± 0.2 Nd<br />
nd – non detected<br />
Evidence <strong>of</strong> hydrolysis was obtained by the increase in K/S for both fabrics <strong>and</strong> by the<br />
formation <strong>of</strong> acetic acid for CDA. It was not possible to detect this product in the<br />
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