Surface Modification of Cellulose Acetate with Cutinase and ...

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