Surface Modification of Cellulose Acetate with Cutinase and ...

Surface Modification of Cellulose Acetate with Cutinase and Cutinase Fused to Carbohydrate-binding Modules
1. Introduction
Cellulose is the most abundant natural polymer and it is a valuable renewable resource
(Steinmann, 1998; Kamide, 2005). However, it presents major drawbacks in its
applicability due to its insolubility in most solvents and its decomposition prior to
melting (Braun and Kadia, 2005). Since the end of the 19 th century, the attained
development on cellulose chemistry allowed new processes and a continuous expansion
of the applications of cellulose derivatives, particular the cellulose esters. Cellulose
acetate is used as a raw material for plastics, textiles, filter tows, films or membranes
(Rustemeyer, 2004). In the textile field, cellulose acetates are characterised by a
combination of desirable and unusual properties like soft and silk-like hand, good textile
processing performance and higher hydrophilicity than synthetic fibres, thus being more
comfortable to use (Steinmann, 1998; Law, 2004). The native cellulose properties of
cellulose esters can be partially recovered by chemical hydrolysis of the acyl groups
(Braun and Kadia, 2005). The surface hydrolysis is also considered an important tool to
improve the surface reactivity and hydrophilic character without radically change the
tensile properties of the fibres and films (Braun and Kadia, 2005). Traditional processes
used to modify polymer surfaces are based on the addition of strong chemical agents.
The major advantages of using enzymes in polymer modification compared to
chemicals are milder reaction conditions and easier control. In addition, they are
environmental friendly and perform specific non-destructive transformations on
polymer surfaces (Guebitz and Cavaco-Paulo, 2003, 2007).
Work on the modification of cellulose acetate with enzymes has been mostly done in
the context of its biodegradation (Puls et al., 2004). The degradation of cellulose and
hemicellulose is naturally carried out by microorganisms and requires the concerted
action of many enzymes. Among these carbohydrate-active enzymes, there is the group
of carbohydrate esterases which hydrolyse the ester linkage of polysaccharides
substitutents, allowing the exo- and endoglycoside hydrolases to cleave the polymer
chains. Cellulose acetate was found to be a carbon source for several microorganisms
and a substrate of several acetyl esterases in cell-free systems (Gardner et al., 1994;
Samios, 1997; Sakai et al., 1996; Altaner et al., 2003a, 2003b). A negative correlation
between the degree of substitution and the biodegradability of cellulose acetates was
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