Page 205 - Advances in Textile Biotechnology

186 Advances in textile biotechnology

(Krasowski et al., 1999; Mahmoodi et al., 2010). It was shown that the use
of ultrasound in the degumming of raw silk with proteases can lead to a
slight increase in the degumming effect. That might be due to the improve-

ment in the movement of enzymes to the fibre surface, the increase in the
swelling of sericin and/or the dispersion of the enzyme-degraded sericin.
Degumming has also been attempted after pre-treatment of the silk with

sodium thiosulfate or sodium hydrosulfite solution. The pre-treatment
accelerates the removal of sericin by proteases. The fabric whiteness is also
significantly improved. Novozymes recommend the pre-treatment of plain

and crepe silk fabrics with sodium hydrosulfite at 95 °C for 5 min and
30–60 min, respectively, before to enzymatic treatment. Owing to the high
temperature, some sericin is removed at this stage. The pre-treatment
reduces the enzyme dosage and the reaction time needed. Subsequent
enzyme treatment using alkaline protease (Alcalase from Novozymes)
under mild conditions is able to remove the remaining sericin completely

so that damage to the fibroin can be avoided (Novozymes technical sheet
on Alcalase).
Protease enzymes are also used in washing and finishing processes of silk.

A biofinishing process, called ‘sand washing’, modifies the protein fi broin
of degummed silk. It can achieve the effect of ‘peach skin’, a velvety look
imparting a ‘worn’, ‘aged’, or ‘washed many-times’ look.
8.5 Future trends

Environmental issues have been an ongoing concern for the textile industry
and will necessarily become of increasing importance. As a natural fi bre,
wool is perceived by consumers to be renewable and sustainable. Within
the wool industry, a great effort has been made to develop green technology
in order to replace the harmful chemicals traditionally used in wool process-
ing. Biotechnology through the use of enzymes provides environmentally
preferable methods in wet processing to produce wool products with
improved softness, antipilling and easy-care properties, especially machine-
washability. However, the reaction of conventional protease formulations
on wool is difficult to control and may cause unacceptable damage owing

to the unique surface structure of the wool fi bre. Modification of enzymes

or alteration of the absorption and penetration pattern of enzymes during
treatment can confer specifi c finishing to wool including soft handle, shrink-

resistance and low temperature dyeing without significant damage to the
fibres. Integration of the use of enzymes with other modern technology

might be able to expand the finishing process to enhance the wool perfor-
mance for specific end uses.

Natural silk has remained a luxury fibre. In the future silk materials will

not only be widely used for textile fabrics, garments and bedding materials

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