Page 337 - Advances in Textile Biotechnology

318 Advances in textile biotechnology

Glucose Cellobiose and small
chain oligomers

b-Glucosidase
CBH

EG

Amorphous regions
Crystalline regions
13.2 Reaction scheme of enzymes on insoluble cellulose substrates.

three-dimensional structure of a fabric and the accessibility of the yarn

used, the fibre structure and porosity will determine the ability of the cel-
lulose binding domain to couple to the surface of the material. Fibre struc-
ture on the molecular scale and polymer organisation in the material thus
directly influences the observed activity of EG and CBH on a given

substrate.
For textile processing, the strength loss that correlates with weight loss
occurring during the hydrolysis process is most critical (Kumar and Purtell,
1994). Although fabric construction, yarn twist, type of enzyme and process
conditions can be controlled easily, every preceding step applied during
textile processing has to be considered carefully with regard to possible

modification in fibre properties. Any change in fibre reactivity will also

modify hydrolysis rate and thus overall weight loss.
Carrillo et al. studied the cellulose hydrolysis rate of various viscose,

modal and lyocell fibres by analysis of the formation of reducing sugars in
the treatment baths. The highest concentration of reducing sugars was

found by hydrolysis of viscose fibres, followed by modal fi bres, whereas

lyocell fibres showed the lowest rate of hydrolysis. Fibrillated lyocell fi bres
showed a higher degradation rate, most probably because of the higher
accessibility and surface area available in the fi brillated fi bre (Carrillo et al.,

2003a). Lyocell fibres which had been defibrillated by cellulase treatments

also exhibited a higher rate of dye uptake, which was explained by the

increased accessibility of the fibre structure owing to morphological and
structural changes (Carrillo et al., 2003b).

Study of the protein sorption on the fibres showed the highest sorption
for viscose, followed by modal and lyocell. Although the protein sorption

on modal fibres is only slightly lower than on viscose fibres, a much lower

hydrolysis rate was observed for modal fibres. Thus, in addition to the avail-
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