Page 195 - Advances in Textile Biotechnology

176 Advances in textile biotechnology

wool scouring industry because of the tightening of environmental legisla-
tion. The use of enzymes in wool scouring might improve the effi ciency of
the removal of grease and natural impurities from raw wool and reduce
water consumption and scouring effl uents. However, in the literature there
are only a few reports relating to the bioscouring of wool fi bres (Christoe,
1984; Das and Ramaswamy, 2006; Gouveia et al., 2008; Kholiya et al., 2008;
Sedelnik, 2003).
As well as grease, a proteinaceous residue is found on the surface of raw

wool fibres. The water-insoluble and water-soluble components of this

protein have amino acid compositions similar to skin flakes and suint pep-
tides, respectively; they can be present in significant quantities in raw wool

(Anderson and Christoe, 1984; Christoe, 1984). Christoe (1984) studied the
effect of adding a proteolytic enzyme in single-bowl scouring experiments.
The enzyme caused a change in the distribution of grease between the
emulsion, sludge, and middle phases in centrifuging. The results also varied
with pH when a protease (Esperase from Novozymes) was used in the
scouring experiments. Under alkaline conditions scouring effectiveness was

improved marginally, but there were significant changes in terms of the
characteristics of the scoured wool.
Interference between enzymes, surfactants and buffer needs to be con-
sidered in the wool-scouring process. The presence of buffer and surfactants
may affect the activities of enzymes. It is well known that proteolytic
enzymes are compatible with non-ionic surfactants that are widely recom-
mended to be used in enzymatic treatments. A recent study (Zhang et al.,
2006) has shown that the activity of the protease Esperase towards wool
can be promoted by an ethoxylated alkyl phosphate anionic surfactant.
Therefore, this anionic surfactant can provide additional benefits if chosen

instead of the widely used non-ionic surfactants. This could lead to the

development of a more efficient enzymatic scouring process. Buffers are
used to maintain the optimum pH for protease activity during enzyme
treatment, but it is found that different buffer systems and their ionic
strengths have different effects on the activity of proteolytic enzymes. This
is because of the interference of buffer cations and anions with the confor-
mation of enzymes and their biological reactions.
Wool scouring can be divided into three stages. The first stage is to

remove a substantial amount of the water-soluble contaminants and dirt.
The second stage involves scouring in hot detergent solution to remove the
easy-to-remove contaminants, which include the bulk of the wool wax and
most of the remaining dirt and water-soluble matter. The third stage removes
the remaining hard-to-remove contaminants such as oxidised wool wax, fi ne
particulate dirt and strongly-adhering non-wool proteins (Christoe et al.,
1994). The scouring process and surface modification of wool fi bres could

be integrated by adding enzymes to the later stage of wool scouring line.

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