Page 296 - Advances in Textile Biotechnology

Enzymatic functionalization of cellulosic fi bres for textiles 277

onto cellulosic fibres in water results in gentle, surface-specifi c chemical
functionalization (Fig. 11.3, Step b). The incorporation of XGO-R into XG
by the enzyme is essential since, as discussed above, short XG oligosaccha-

rides do not have a signifi cant affinity for cellulose. Thus, the extended
polysaccharide chain of the XG-R product functions as a molecular anchor,
the length of which can be adjusted by the molar ratio of XG to XGO-R.
The functional group density on the cellulosic surface can therefore be
controlled either by adjusting the length of the XG-R anchoring tail, or
varying the loading amount of XG-R with respect to the cellulose. Depend-
ing upon the nature of the R group, further elaboration of the surface
chemistry is possible (Fig. 11.3, step c).
Our initial proof-of-concept work (Brumer et al., 2004) focused on the

well-known fl uorophore fluorescein, which was conjugated to aminated
XGOs (XGO-NH 2 ) by reaction with fl uorescein isothiocyanate (FITC) to
yield XGO–FITC. XET-catalyzed incorporation of XGO–FITC into XG,
following the scheme shown in Fig. 11.3, produced XG–FITC. Both the
enzyme-catalyzed production and binding of XG–FITC to the model cotton

cellulose substrate Whatman No. 1 filter paper were extensively character-
ized. To demonstrate the substrate versatility of the method, XG–FITC was

adsorbed onto regenerated cellulose films and a XG–sulforhodamine con-
jugate (XG–SR) was bound to regenerated cellulose fi bres (Brumer et al.,
2004).

Functionalized xyloglucan (XG-R) for the activation of cellulosic surfaces

Although the production of yellow paper and pink fibres is somewhat

trivial, the established methodology has a certain industrial relevance. The

attachment of dyes and fluorophoric optical brightening agents (OBA) is
widespread in both the paper and textile industries, whereas retention of

these small organic molecules on cellulosic fibres is sometimes poor. Indeed,
our laboratory collaborated with a large industrial wood pulp producer to
test the potential of the XET/XG system to increase the efficiency of OBA

retention. To this end, we generated a sulfated aminostilbene derivative of
XG (XG–OBA) using XET, and demonstrated that it was quantitatively
bound to pulp fibres, producing a dosage-dependent UV brightening effect

(Fig. 11.5). Notably, the XG–OBA was retained on the pulp even after harsh
mechanical refi ning (Zhou et al., 2006b and Brumer et al., unpublished
results).
Although inclusion of the final functionality on XG before cellulose

binding may be preferred in some applications, in many cases it is desirable
to produce activated (or activatible) cellulose surfaces that are capable of
further reactions. As mentioned above, the amino group provides such a

chemical handle for further elaboration, and cellulosic fibres activated with

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