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 />
1. Introduction<br />
<strong>Cellulose</strong> is the most abundant natural polymer <strong>and</strong> it is a valuable renewable resource<br />
(Steinmann, 1998; Kamide, 2005). However, it presents major drawbacks in its<br />
applicability due to its insolubility in most solvents <strong>and</strong> its decomposition prior to<br />
melting (Braun <strong>and</strong> Kadia, 2005). Since the end <strong>of</strong> the 19 th century, the attained<br />
development on cellulose chemistry allowed new processes <strong>and</strong> a continuous expansion<br />
<strong>of</strong> the applications <strong>of</strong> cellulose derivatives, particular the cellulose esters. <strong>Cellulose</strong><br />
acetate is used as a raw material for plastics, textiles, filter tows, films or membranes<br />
(Rustemeyer, 2004). In the textile field, cellulose acetates are characterised by a<br />
combination <strong>of</strong> desirable <strong>and</strong> unusual properties like s<strong>of</strong>t <strong>and</strong> silk-like h<strong>and</strong>, good textile<br />
processing performance <strong>and</strong> higher hydrophilicity than synthetic fibres, thus being more<br />
comfortable to use (Steinmann, 1998; Law, 2004). The native cellulose properties <strong>of</strong><br />
cellulose esters can be partially recovered by chemical hydrolysis <strong>of</strong> the acyl groups<br />
(Braun <strong>and</strong> Kadia, 2005). The surface hydrolysis is also considered an important tool to<br />
improve the surface reactivity <strong>and</strong> hydrophilic character <strong>with</strong>out radically change the<br />
tensile properties <strong>of</strong> the fibres <strong>and</strong> films (Braun <strong>and</strong> Kadia, 2005). Traditional processes<br />
used to modify polymer surfaces are based on the addition <strong>of</strong> strong chemical agents.<br />
The major advantages <strong>of</strong> using enzymes in polymer modification compared to<br />
chemicals are milder reaction conditions <strong>and</strong> easier control. In addition, they are<br />
environmental friendly <strong>and</strong> perform specific non-destructive transformations on<br />
polymer surfaces (Guebitz <strong>and</strong> Cavaco-Paulo, 2003, 2007).<br />
Work on the modification <strong>of</strong> cellulose acetate <strong>with</strong> enzymes has been mostly done in<br />
the context <strong>of</strong> its biodegradation (Puls et al., 2004). The degradation <strong>of</strong> cellulose <strong>and</strong><br />
hemicellulose is naturally carried out by microorganisms <strong>and</strong> requires the concerted<br />
action <strong>of</strong> many enzymes. Among these carbohydrate-active enzymes, there is the group<br />
<strong>of</strong> carbohydrate esterases which hydrolyse the ester linkage <strong>of</strong> polysaccharides<br />
substitutents, allowing the exo- <strong>and</strong> endoglycoside hydrolases to cleave the polymer<br />
chains. <strong>Cellulose</strong> acetate was found to be a carbon source for several microorganisms<br />
<strong>and</strong> a substrate <strong>of</strong> several acetyl esterases in cell-free systems (Gardner et al., 1994;<br />
Samios, 1997; Sakai et al., 1996; Altaner et al., 2003a, 2003b). A negative correlation<br />
between the degree <strong>of</strong> substitution <strong>and</strong> the biodegradability <strong>of</strong> cellulose acetates was<br />
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