Journal of Biomaterials and Nanobiotechnology, 2011, 2, 65-70
doi:10.4236/jbnb.2011.21009 Published Online January 2011 (
Copyright © 2011 SciRes. JBNB
Enzyme Assisted Ultrasound Scouring of Raw
Wool Fibres
Betcheva Rositza, Yordanov Dancho*, Yotova Lubov
Department of Textile Chemistry, University of Chemical Technology and Metallurgy, Sofia, Bulgaria.
Received September 10th, 2010; revised September 24th, 2010; accepted September 30th, 2010.
Scouring of raw wool is a chemical treatmen t that needs a high amount of detergents, a lkalis and water. Effluents pro-
duced by this treatment are extremely polluted with chemicals and impurities washed out from the fibers. It is well
known that the ultrasound washing can remove effectively different substances from the textile surfaces even without
surfactants due to the cavitations occurring at certain parameters of the ultrasound field. On the other side water
treatments of woo l comb in ed with mecha n ical ag ita tio n p rovo k ed felting which can impa ir the quality of wool materials.
Felting itself depends not only on the parameters of water treatments but also on the structure of wool cuticle. Partial
hydrolysis of the cuticle with some proteases can decrease considerably the wool felting. The aim of this work is to
study the possibility of applying the ultrasound at the process of raw wool scouring and the influence of proteases on
the felting properties of wool at these conditions. It has been found out that ultrasound environment applied does not
impair the specific activity of enzyme auxiliaries used and leads to increasing of their effect on the surface of wool fi-
bers. Thus the scouring process studied could be used for developing of a technology producing lower amount and less
polluted effluents.
Keywords: Enzyme, Felting, Scouring, Ultrasound, Wool
1. Introduction
The tendency of wool to felt and shrink is mainly due to
its scaly structure. Wool shrinkage occurs when the fi-
bers are subjected to mechanical treatments combined
with higher temperatures and use of different detergents.
It is well known that the scouring of raw wool fibers is a
textile chemical processing that needs a lot of detergents
and water due to the high amount of impurities [1]. On
the other side there are many data that ultrasound (US)
could destroy and remove the pollutants on textile sur-
faces even without any additional auxiliaries in the
washing bath [2] Logically it can be expected that US
will increase wool fiber felting occurring at the condi-
tions of scouring. The chlorine-Hercosett is the most
widespread process used to modify the surface of wool
fibers in order to provide resistance to felting and
shrinkage [3,17,18]. Currently a wide range of enzymatic
treatments are being studied as an alternative of chemical
treatments [4,20].The corresponding technologies of tex-
tile processing usually combine the enzyme application
with an intensive mass transfer (for example by stirring)
[1,14,16]. There is no available data if US scouring of
raw wool fibers is equally effective to the classical de-
tergent washing and if it can cause higher wool felting
and shrinkage. It is of a practical interest if the applica-
tion of protease auxiliaries originally formulated for use
as detergent additives can influence the process of US
wool scouring.
Bearing in mind the above mentioned the aim of this
work is to study the possibility of applying the ultrasound
at the process of raw wool scouring and the influence of
proteases on the felting properties of wool at these condi-
2. Experimental
2.1. Fibers and Chemicals
Raw wool treated were Bulgarian merino fibers, quality
64 (22-25μm). The auxiliaries used were the enzyme
containing Bioprot Multi and Bioprot Gentle (Biocon
2.2. Enzyme Activity and Protein Concentration
The activity of proteases in Bioprot Multi and Bioprot
Gentle was measured by incubating 1ml of these prod-
Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres
Copyright © 2011 SciRes. JBNB
ucts with 1ml of 2% casein solution and 2ml 0,1 M bo-
rate buffer, for 20 min at temperature 37˚C. After incu-
bating the reaction was stopped by adding 4 ml 6% tri-
cloroacetic acid solution, and then the precipitate was
removed by centrifugation at 5000rpm, at room tem-
perature for 10 min. The absorbance due to the amino
acids produced was analysed at 280 nm.
Temperature and pH dependences of enzyme activity
were investigated as follows:
- at different pH-values and 37˚C,
- at pH 7.8, and different temperatures.
The concentration of protein was determined by
Lowry method [5], using bovine serum albumin as a
2.3. Characterization of Wool Fibers
Wool fibers (treated with enzyme and combined en-
zyme/ultrasonic) were characterized by their felting
properties and by the weight lost after treatment.
The felting ability of wool fibers was evaluated by
Blankenburg method. Diameters of wool spheres formed
during the agitation test were measured and the changes
of felting ability were calculated from them.
The weight lost of pre-treatment wool fiber was calcu-
lated in the following way. Wool fabrics were condi-
tioned at 100˚C for 2 h, desiccated and weighed until
constant weight was reached.
2.4. Determination of Tyrosine
Tyrosine is a mino acid produced from the reaction of
protein with enzyme [5]. Its concentration was measured
in the following way. A sample of 6ml solution was
taken from the enzyme reactor and added to 5ml of
0.11M tricloroacetic acid solution. The precipitate was
removed by filtration and centrifugation. Then, 2ml of
filtrate were mixed with 5ml of 0.05M Na2CO3 solution
and 1ml of two-fold diluted Folin’s reagent. After mixing,
the colour was allowed to develop for 30 min at 37˚C.
The light absorbance related proportionally to the con-
centration of amino acid produced was analyzed at 660
nm, based on dl-tyrosine as standard.
2.5. Experimental Design
The experimental equipment designed for this study is
shown on Figure 1. The enzymatic treatment (with and
without US) of wool fibers was performed in a glass bot-
tle with total volume of 300ml. Wool fiber samples of 3
g each were treated with enzymes in phosphate buffer
solution (pH 7.8, 0.01M) in a water bath at 37˚C for 5
hours and 80 rpm.
In the present study, the cavitations experiment (US
irradiation treatment) were carried out by using an ultra-
sonic bath form VWR-China with capacity 3,7L, HF-45
Figure 1. 3D plan view of the experimental equipment.
kHz and 117V. The actual intensity of US was calculated
according to the method introduced by Lorimer et al.
(1991) [6]. The field intensity in the glass bottle of ultra-
sonic vessel used for our study was 95 W/cm2.
3. Results and Discussion
The proteolytic activity of auxiliaries used was calculated
in order to give a more precise qualitative evaluation of
the influence of US treatment. Proteolytic activity was
defined according to Equation 1, pH7.8 and temperature
of 37˚C on casein as substrate.
U /mg(A1000)/(ta)
- A is the adsorption of reaction media at 280nm,
- a is the quantity enzyme in test chub,
- t is the incubation time.
The results of these measurements are given in Table
1. They show that the US applied generally increases the
enzyme activity most probably by intensifying the mass
transfer of reaction products. It is well know that the agi-
tation increases the rate of enzymatic hydrolysis and the
US in our case play the same role [7,14].
It is well known that every enzyme product has a spe-
cific pH and temperature of application for having the
highest effectiveness of application. That is why our first
task in the presented study was to evaluate the activity of
enzyme auxiliaries used. The influence of pH on this
parameter can be seen at Figure 2.
The results obtained showed that the application of US
did not change the position of the maximum of pH de-
pendence. For Bioprot Multy these maximums are in pH
Table 1. Enzyme activity of the Bioprot Multi and Bioprot
Gentle at pH 7.8 and 37˚C on casein as substrate.
Enzyme Bioprot Multi, U /mg Bioprot Gentle,U/mg
With ultrasound 89672 87570
Without ultrasound 81159 81125
Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres
Copyright © 2011 SciRes. JBNB
Figure 2. Effects of pH on the relative activity of enzyme
auxiliaries: (() enzymatic treatment without US, () enzy-
matic treatment with US).
range of 7.5 – 8.5. For the other product studied – Bio-
prot Gentlе - the maximum is at pH 6.5. The tendency of
increasing the relative intensity of proteolytic effect with
US is well pronounced in all pH range studied for both
enzymatic auxiliaries
Temperature of application is the other important fac-
tor for the effectiveness of enzymatic treatments. De-
pendences given at Figure 3 showed again that the ap-
plication of US does not change the position of enzyme
activity maximum. The ultrasound applied increases the
intensity of casein degradation in the range of 20-70˚C.
For both auxiliaries studied the temperature of maximum
enzyme activity remains 60˚C with and without US ap-
3.1. Effect of Ultrasound Treatment on Raw
Wool Fibers.
The effect of scouring conditions (enzymatic and com-
bined enzymatic/ultrasound) on the fiber shrinkage prop-
erties was studied in order to show the possible changes
of quality of scoured wool fibers.
Wool active proteases hydrolyzing some protein com-
pounds at the enzymatic treatment may degrade the cuti-
cle scales of wool fiber, which are responsible for the
wool textile tendency to undergo felting and shrinkage.
The proteolytic attack, however, is not only limited to the
fiber surface, since proteases can easily penetrate inside
Figure 3. Influence of temperature on the relative activity of
enzyme auxiliaries: (() enzymatic treatment without US, ()
enzymatic treatment with US).
the wool fiber, causing to wool fibers significant weight
and tensile strength loss [4,19].
The used auxiliaries containing proteases (Bioprot
Multi and Bioprot Glenle) are originally formulated as
detergent additives [8]. Data obtained from our experi-
ments showed a significant decrease of shrinkage ofwool
fibers treated with enzymes compared to the fibers
treated only with a buffer solution Figure 4. For both
studied auxiliaries the increase of their concentration in
the scouring bath produces wool fibers with a lower
shrinkage. The best results obtained at our experimental
conditions are with Bioprot Gelntle - 6.5mg/ml and Bio-
prot Multi - 6.5mg/ml with sonication. Taking into con-
sideration the enzyme concentration in the products
studied, we can make a conclusion that Bioprot Milti has
a higher level of affinity to the wool fibers. These results
were also confirmed by the determination of the shrink
age using a Blankenburg method presented on Figure 4.
These results were also confirmed by SEM micropho-
tographs of the scoured wool fibres shown on Figure 5.
The fibers were treated with enzyme with concentration
6.5mg/ml at 37˚C, pH 7.8 for 300min with and without
ultrasound. On Figure 5 picture (a) and (c) show that
US/enzymatic treatment significantly changed the wool
surface, while after the classical enzymatic treatment
picture (b) and (d) it remains with well pronounced scaly
Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres
Copyright © 2011 SciRes. JBNB
Figure 4. Shrinkage (g/cm3) of merino raw wool of 100%,
treated with different enzyme concentration ET = [0.5; 1;
1.5; 2; 2.5; 3; 3.5; 4; 4.5; 5; 5.5; 6; 6.5mg/ml] at 37˚C, pH7.8
for 300min, ((a)-Bioprot Multi and (b)-Bioprot Gelntle).
Figure 5. SEM microphotographs of the raw wool fibres
after treatments with total enzyme concentration ET:
6,5(mg/ml): (a / c) US combined Bioprot Multi / Bioprot
Gentle, (b / d) Bioprot Multi / Bioprot Gentle.
structure. The reasons behind can be found in the prote-
ase nature and morphological characteristics of wool
fiber. It has been proved that the proteolytic attack is not
only limited to the fibre surface, since proteases can eas-
ily penetrate inside the wool fiber, causing significant
weight and tensile strength loss to wool fibers [4,9]. Pic-
-ture (a) and (c) could be considered as proves that the
combination of US with some proteases would be a
promising option for an effective anti-felting processing
in wool industry.
In order to explain the results obtained from the ex-
periments with a combined enzymatic/US processing, the
adsorption of Bioprot Gentle and Bioprot Multi on wool
was studied. As it can be seen at Figure 6 the ultrasound
assisted adsorption shows a lower level of saturation
compared to the case of enzymatic treatment where no
saturation is observed. The lack of saturation could be
explained with the constant diffusion of the proteolytic
enzyme into the wool fiber that has been proved in sev-
eral investigations [4,10,21].
Together with the wool surface saturation with enzyme
registered in presence of ultrasound, a higher level of Ty-
rosine formation was found out in our experiments Fig-
ure 7. That was considered as an indicator for keratin
destruction caused by proteases [4]. Definitely the con-
centration of Tyrosine at enzymatic-ultrasound treatment
is higher than that concentration at the classical enzymatic
treatment, suggesting a higher level of surface hy-
drolysis when the combined treatment is applied. There
could be two main reasons for this phenomenon. The first
one could be the change of mass transfer conditions (ad-
sorption - desorption equilibrium of the enzyme and the
Figure 6. Enzyme adsorbed on wool fibre, (open symbols-)
enzymatic treatment with US and (close symbols-) enzy-
matic treatment without US, (a) Bioprot Multi and (b) Bio-
prot Gelntle: treated with different enzyme concentration,
at 37˚C, pH 7.8 for 300 (min).
Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres
Copyright © 2011 SciRes. JBNB
Figure 7. Formation of Tyrosine form enzymatic hydrolysis
on wool fibre (mM), (open symbols-) enzymatic treatment
with US and (close symbols-) enzymatic treatment without
US, (a) Bioprod Multi and (b) Bioprod Gelntle: treated with
different enzyme concentration, at 37˚C, pH 7.8 for 300min.
products of hydrolysis) stimulated by the sonification.
The other hypotheses can be connected to the irradiation
of water caused by the US waves. This irradiation leads
to a breakdown, or sonolysis, of the liquid resulting in
the formation hydroxyl and hydrogen radicals [11].
These molecules have a higher lever of reaction ability
and could combine between themselves as to form H2O2.
[4] It is reported that H2O2 is likely to promote a partial
removal of the bounded fatty acid barrier of the epicuti-
cle, probably more effective than the enzyme treatment.
On the other hand sonication has acceleration effect on
the enzyme-catalyzed reactions [12-16]. This corre-
sponds to Figure 8, where weight loss is presented at the
both studied scenarios. It can be noticed that at a higher
enzyme concentration the weight loss is also increased,
but not at such degree as tyrosine formation.
4. Conclusion
Ultrasound applied together with proteases increases the
enzyme activity up to 10%. This effect can be applied in
combined enzymatic-ultrasound scouring of raw wool
fibers. Wool treated in this way shows lower shrinkage
which indicates a higher level of proteolysis on the fi-
bersurface. The surface wool proteolysis at enzy
Figure 8. Weight loss (%) of merino raw wool of 100%,
treated with different enzyme concentration ET = [0.5; 1;
1.5; 2; 2.5; 3; 3.5; 4; 4.5; 5; 5.5; 6; 6.5]mg/ml at 37˚C, pH7.8
for 300min, [(a) - Bioprot Multi and (b) - Bioprot Gelntle].
matic/ultrasound treatment is partly proved by the ad-
sorption model for the enzyme which is characterized
with a saturation which differs from the model in the
classical enzymatic treatment. Ultrasound/enzymatic
scouring could be applied for producing of wool fibers
with less felting ability. An additional advantage of this
treatment is avoiding of detergent use that could be con-
sidered more positive from the point of view of washing
effluents pollution and purification resulting in energy
consumption and overall processing costs.
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