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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General Introduction: Application <strong>of</strong> Enzymes for Textile Fibres Processing<br />
have been tested at the scale <strong>of</strong> industrial process (Shen et al., 2007). Pre-treatment <strong>of</strong><br />
wool fibres <strong>with</strong> hydrogen peroxide, at alkaline pH in the presence <strong>of</strong> high<br />
concentrations <strong>of</strong> salts, also targets enzymatic activity on the outer surface <strong>of</strong> wool, by<br />
improving the susceptibility <strong>of</strong> cuticle for proteolytic degradation (Lenting et al., 2006).<br />
Some authors describe methods to improve the shrink resistance <strong>of</strong> wool by treating<br />
wool previously <strong>with</strong> a smoother oxidizing agent, like H2O2, instead <strong>of</strong> the traditional<br />
oxidizers, NaClO or KMnO4 <strong>and</strong> then <strong>with</strong> a protease (Yu et al., 2005). The strong<br />
oxidation power <strong>of</strong> NaClO or KMnO4 is always difficult to control. Besides, reaction <strong>of</strong><br />
NaClO <strong>with</strong> wool produces halogenide. On the other h<strong>and</strong>, H2O2 seemed to provide a<br />
more controlled, cleaner <strong>and</strong> moderate oxidation. Zhang <strong>and</strong> collaborators used an<br />
anionic surfactant to promote the activities <strong>of</strong> proteases on wool (Zhang et al., 2006).<br />
Other authors refer processes to achieve shrink-resistance by treating wool <strong>with</strong> a<br />
protease followed by a heat treatment (Ciampi et al., 1996). The screening for new<br />
protease producing microorganisms <strong>with</strong> high specificity to cuticles is being<br />
investigated as an alternative for the existing proteases (Erlacher et al., 2006).<br />
8. Cysteine proteases: papain<br />
Cysteine proteases (CP´s) catalyse the hydrolysis <strong>of</strong> peptide, amide, ester, thiol ester<br />
<strong>and</strong> thiono ester bonds. More than twenty families <strong>of</strong> cysteine proteases have been<br />
described (Barrett, 1994). The CP family can be subdivided into exopeptidases (e.g.<br />
cathepsin X, carboxypeptidase B) <strong>and</strong> endopeptidases (papain, bromelain, ficain,<br />
cathepsins). Exopeptidases cleave the peptide bond proximal to the amino or carboxy<br />
termini <strong>of</strong> the substrate, whereas endopeptidases cleave peptide bonds distant from the<br />
N- or C-termini (Barrett, 1994).<br />
CPs are proteins <strong>of</strong> molecular mass in the range <strong>of</strong> 21 - 30 kDa. They are synthesized as<br />
inactive precursors <strong>with</strong> an N-terminal propeptide <strong>and</strong> a signal peptide. Activation<br />
requires proteolytic cleavage <strong>of</strong> the N-terminal propeptide that also functions as an<br />
inhibitor <strong>of</strong> the enzyme (Otto <strong>and</strong> Schirmeister, 1997; Grzonka et al., 2001).<br />
Papain is the best known cysteine protease. It was isolated in 1879 from the fruits <strong>of</strong><br />
Carica papaya <strong>and</strong> was the first protease <strong>with</strong> the crystallographic structure determined<br />
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