Page 162 - Advances in Textile Biotechnology

Enzymatic versus chemical processing of cotton 143

effective removal of seed coat fragments, a treatment with a combination
of cellulases and pectinases, followed by hydrogen peroxide, was needed
(Tavcer, 2008). A unique approach was the application of a hydrolytic and
oxidative enzyme mixture produced by solid-state fermentation on seed
coat fragments (Csiszar et al., 2007). The seed coat fragments were used as
a carbon source for the production of the enzymes, which were then applied
to seed coat fragments in fabrics, with promising results. At present, despite
the advances that have been made, a completely enzymatic process for
removing and decolorizing seed coat fragments in woven fabric has not
been achieved, though the solid state fermentation approach seems to gen-

erate the specific enzymes that will be needed for success.

6.5.4 Application of mechanical and sonic power to
increase mass transfer

The biggest drawback to the use of bioscouring in the textile industry is
that enzyme actions are relatively slow, and though bioscouring lends itself
to use in batch processing, its diffusion-controlled process means that using
it in continuous processes is diffi cult. Yachmenev et al. (2001, 2003, 2007)
described the use of ultrasonic energy to increase the rate of mass transfer
of enzyme molecules to the fiber surface. Moholkar et al. (2003) looked in

detail at the mechanisms involved in these processes and concluded that
optimizing cavitation intensity is of paramount importance to achieve an

efficient ultrasonic wet textile process.

Another approach to improving the efficiency of the enzyme processes
on cotton was that reported by Agrawal et al. (2008), where, in addition to
creating a cutinase–pectinase mixture to remove wax and then pectin, they
applied mechanical action using a wedge apparatus to flex the fabric. The

net result was a significant improvement in both the time needed for the
desired increase in hydrophilicity, and a dramatic decrease in the tempera-
ture at which the process could be operated, down to 30 °C (Agrawal et al.,
2008).

6.5.5 Effects of bioscouring on cotton properties
Alkaline scouring is done to improve the water absorbance of the cotton
fiber. It accomplishes this by removing a mixture of materials from the

surface of the cotton fibers. It is non-specific and works by hydrolyzing both

the materials themselves and/or excising connecting compounds that are
attached to the pectins, proteins and waxy compounds. Bioscouring done
with enzymes is very much the opposite, with enzymes by nature being quite
specific in how they act on various molecular entities. Bioscouring can

create the needed hydrophilicity in the cotton fabric, but at the same time

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