*3.3.3. Whiteness and whiteness after bleaching with H2O2*

The synergistic action of protease-lipase improved the whiteness of the silk fabrics (Figure 5a). Increasing enzyme concentration and treatment time resulted in increased whiteness values. The highest whiteness values for each combination were observed at highest enzyme loading and after 90 min of treatment. Those values were 55.2 and 59.8 Berger degree for papain+ Lipolase® Ultra 50T and Esperase® 8.0L+ Lipolase® Ultra 50T, respectively. It should be noted that the conventional degumming resulted in a lower whiteness value (58.8 Berger degree) (Figure 5a). The addition of lipase improved the whiteness of the silk fabrics com‐ pared to results obtained by the use of protease only. For example the whiteness of the silk fabrics treated with 75 U. g-1 fabric Esperase® 8.0L for 60 min was found 52.2 Berger degree, while the corresponding value of the fabrics treated at the same conditions adding 50 U. g-1 fabric Lipolase® Ultra 50T was 57.3 Berger degree.

min (Table 8). Addition of 50 U.

50 Ug-1 Papain + 50 Ug-1 Lipolase® Ultra 50T

75 Ug-1 Papain + 50 Ug-1 Lipolase® Ultra 50T

8.0L + 50 Ug-1 Lipolase® Ultra 50T

8.0L + 50 Ug-1 Lipolase® Ultra 50T

(0.0291, gf.

**Type of treatment**

50 Ug-1 Esperase®

75 Ug-1 Esperase®

Papain and Esperase®

degummed materials

*3.3.5. Shear property*

rics treated with 75 U.

(1.24, gf.

g-1

**(gf.**

**Bending rigidity (***B***)**

**cm2.cm-1)**

cm2.cm-1). The same pattern was observed for all conditions tested.

No enzyme 0.0205±0.0005 0.0117±0.0001 *0.0161* 1.80±0.02 1.60±0.01 *1.70*

30 min 0.0300±0.0003 0.0200±0.0004 *0.0250* 1.50±0.02 1.34±0.01 *1.42* 60 min 0.0250±0.0005 0.0170±0.0002 *0.0210* 1.44±0.03 1.30±0.03 *1.37* 90 min 0.0200±0.0002 0.0160±0.0002 *0.0180* 1.28±0.02 1.22±0.02 *1.25*

30 min 0.0220±0.0002 0.0180±0.0001 *0.0200* 1.34±0.02 1.30±0.01 *1.32* 60 min 0.0170±0.0003 0.0140±0.0002 *0.0155* 1.29±0.03 1.25±0.01 *1.27* 90 min 0.0160±0.0002 0.0130±0.0003 *0.0145* 1.26±0.01 1.23±0.02 *1.25*

30 min 0.0424±0.0009 0.0233±0.0002 *0.0329* 1.85±0.04 1.50±0.05 *1.68* 60 min 0.0341±0.0005 0.0200±0.0001 *0.0271* 1.80±0.04 1.45±0.05 *1.63* 90 min 0.0330±0.0007 0.0187±0.0003 *0.0259* 1.60±0.06 1.40±0.05 *1.50*

30 min 0.0491±0.0005 0.0231±0.0002 *0.0361* 1.90±0.06 1.20±0.04 *1.55* 60 min 0.0242±0.0003 0.0195±0.0005 *0.0219* 1.58±0.03 0.90±0.03 *1.24* 90 min 0.0214±0.0007 0.0170±0.0003 *0.0192* 1.53±0.02 0.10±0.02 *0.81* Marseille soap 0.0537±0.0006 0.0264±0.0003 *0.0401* 1.80±0.03 1.60±0.01 *1.70*

**Table 11.** Comparison of micromechanical properties of silk fabrics treated at varying durations with various levels of

Combined action of proteases with Lipolase resulted in silk fabrics with lower *G* values compared to untreated and conventional treated silk fabrics (Table 11). Increasing protease concentration and treatment time resulted in silk fabrics less rigid with better drape (lower

Shear rigidity was also affected by the addition of Lipolase® Ultra 50T. For example, silk fab‐

60 min (Table 8). Addition of 50 U/g Lipolase® Ultra 50T resulted in 65% increase in *G* value

cm-1.degree-1). The same pattern was observed for all conditions tested.

fabric Esperase® 8.0L exhibited a *G* value of 0.43 (gf.

8.0L combined with constant level of Lipolase®

*G* values) compared to those treated with Marseille soap.

g-1

fabric Lipolase® Ultra 50T resulted in 43% decrease in *B* value

**warp weft** *mean* **warp weft** *mean*

Physichochemical and Low Stress Mechanical Properties of Silk Fabrics Degummed by Enzymes

**Shear stiffness (***G***)**

**cm-1.degree-1)**

http://dx.doi.org/10.5772/53730

253

**(gf.**

Ultra 50T, with reference and conventionally

cm-1.degree-1) after

**Figure 5.** a) Whiteness Index and (b) Whiteness Index after bleaching with Η2Ο2 of degummed silk fabrics using Mar‐ seille soap (conventional treatment) or mixture of papain and Esperase® 8.0L with Lipolase® Ultra 50T at different load‐ ings and treatment times.

The synergistic action of protease-lipase improved the bleaching effect of the silk fabrics (Figure 5b). Increasing enzyme concentration and treatment time resulted in increased whiteness values after bleaching. The whiteness after bleaching of the silk fabrics treated with papain and Lipolase® Ultra 50T ranged between 78.0-89.0 Berger degree, while the cor‐ responding values for the fabrics treated only with papain were found between 68.4-76.0 Berger degree. Higher whiteness values were observed for the fabrics treated with the mix‐ ture of Esperase® 8.0L with Lipolase® Ultra 50T. The whiteness ranged between 95.23-108 Berger degree. The silk fabrics treated with Esperase® 8.0L + Lipolase® Ultra 50T exhibited 40% increase in whiteness in comparison with those treated with the conventional method with Marseille soap, while the corresponding increase in whiteness for the fabrics treated with papain and Lipolase® Ultra 50T was 15%.

#### *3.3.4. Bending property*

Enzymatically and soap treated silk fabrics exhibited higher *B* values compared to untreated silk fabrics. Bending rigidity of the enzymatically treated silk fabrics was affected by en‐ zyme concentration and treatment time. Increasing enzyme concentration and treatment time resulted in lower *B* values, namely in less rigid fabrics compared to conventionally treated ones (Table 11).

One interesting aspect is that addition of Lipolase® Ultra 50T caused further decrease in *B* values compared to those obtained when silk fabrics were treated only with protease. For example, silk fabrics treated with 75 U. g-1 fabric Esperase® 8.0L exhibited a *B* value of 0.0381 (gf. cm2.cm-1) after 60


min (Table 8). Addition of 50 U. g-1 fabric Lipolase® Ultra 50T resulted in 43% decrease in *B* value (0.0291, gf. cm2.cm-1). The same pattern was observed for all conditions tested.

**Table 11.** Comparison of micromechanical properties of silk fabrics treated at varying durations with various levels of Papain and Esperase® 8.0L combined with constant level of Lipolase® Ultra 50T, with reference and conventionally degummed materials

#### *3.3.5. Shear property*

be noted that the conventional degumming resulted in a lower whiteness value (58.8 Berger degree) (Figure 5a). The addition of lipase improved the whiteness of the silk fabrics com‐ pared to results obtained by the use of protease only. For example the whiteness of the silk

while the corresponding value of the fabrics treated at the same conditions adding 50

**Witeness Index after bleaching (Berger** 

**Figure 5.** a) Whiteness Index and (b) Whiteness Index after bleaching with Η2Ο2 of degummed silk fabrics using Mar‐

The synergistic action of protease-lipase improved the bleaching effect of the silk fabrics (Figure 5b). Increasing enzyme concentration and treatment time resulted in increased whiteness values after bleaching. The whiteness after bleaching of the silk fabrics treated with papain and Lipolase® Ultra 50T ranged between 78.0-89.0 Berger degree, while the cor‐ responding values for the fabrics treated only with papain were found between 68.4-76.0 Berger degree. Higher whiteness values were observed for the fabrics treated with the mix‐ ture of Esperase® 8.0L with Lipolase® Ultra 50T. The whiteness ranged between 95.23-108 Berger degree. The silk fabrics treated with Esperase® 8.0L + Lipolase® Ultra 50T exhibited 40% increase in whiteness in comparison with those treated with the conventional method with Marseille soap, while the corresponding increase in whiteness for the fabrics treated

Enzymatically and soap treated silk fabrics exhibited higher *B* values compared to untreated silk fabrics. Bending rigidity of the enzymatically treated silk fabrics was affected by en‐ zyme concentration and treatment time. Increasing enzyme concentration and treatment time resulted in lower *B* values, namely in less rigid fabrics compared to conventionally

One interesting aspect is that addition of Lipolase® Ultra 50T caused further decrease in *B* values compared to those obtained when silk fabrics were treated only with protease. For example, silk

fabric Esperase® 8.0L exhibited a *B* value of 0.0381 (gf.

**degree)**

fabric Esperase® 8.0L for 60 min was found 52.2 Berger degree,

30 60 90 Marseille

50 Ug-1 Papain+50 Ug-1 Lipolase 75 Ug-1 Papain+50 Ug-1 Lipolase 50 Ug-1 Esperase® 8.0L + 50 Ug-1 Lipolase 75 U.g-1 Esperase® 8.0L + 50 Ug-1 Lipolase

Marseille soap No enzyme

**Treatment time (min)**

soap

No enzyme

cm2.cm-1) after 60

8.0L with Lipolase® Ultra 50T at different load‐

**(b)**

fabrics treated with 75 U.

252 Eco-Friendly Textile Dyeing and Finishing

ings and treatment times.

*3.3.4. Bending property*

treated ones (Table 11).

fabrics treated with 75 U.

**Whiteness Index (Berger degree)**

U. g-1 g-1

fabric Lipolase® Ultra 50T was 57.3 Berger degree.

50 Ug-1 Papain+50 Ug-1 Lipolase 75 Ug-1 Papain+50 Ug-1 Lipolase 50 Ug-1 Esperase® 8.0L + 50 Ug-1 Lipolase 75 U.g-1 Esperase® 8.0L + 50 Ug-1 Lipolase

Marseille soap No enzyme

30 60 90 Marseille

**Treatment time (min)**

seille soap (conventional treatment) or mixture of papain and Esperase®

with papain and Lipolase® Ultra 50T was 15%.

g-1

soap

No enzyme

**(a)**

Combined action of proteases with Lipolase resulted in silk fabrics with lower *G* values compared to untreated and conventional treated silk fabrics (Table 11). Increasing protease concentration and treatment time resulted in silk fabrics less rigid with better drape (lower *G* values) compared to those treated with Marseille soap.

Shear rigidity was also affected by the addition of Lipolase® Ultra 50T. For example, silk fab‐ rics treated with 75 U. g-1 fabric Esperase® 8.0L exhibited a *G* value of 0.43 (gf. cm-1.degree-1) after 60 min (Table 8). Addition of 50 U/g Lipolase® Ultra 50T resulted in 65% increase in *G* value (1.24, gf. cm-1.degree-1). The same pattern was observed for all conditions tested.

## *3.3.6. Tensile property*

The elasticity, (tensile strength) of the silk fabrics treated with papain and Lipolase® Ultra 50T was higher than the elasticity of the untreated and soap treated silk fabrics and seemed to be dependent on protease dosage and treatment time (Table 12). Increasing papain dos‐ age and treatment time resulted in an increase elasticity of the enzymatically treated of silk fabrics. At highest papain dosage and for treatment times 60 min and more, the elasticity was superior to that of Marseille soap treated silk.

Addition of Lipolase® Ultra 50T in papain degumming mixture produces more elastic fabrics compared to those obtained by single papain treatement. For example silk fabrics treated with

Enzymatic degumming of silk fabric using proteolytic enzymes (papain, Esperase® 8.0L) and mixtures of thereof with a lipolytic (Lipolase® Ultra 50T) enzyme under mild conditions was investigated. The results obtained are encouraging in comparison with those of the conven‐

Silk fabrics treated with Esperase® 8.0L (an alkaline protease) at high concentration (75 U/g fabric) for 60 min exhibited degumming efficiency nearly 99%, which indicate almost com‐ plete removal of sericin from the surface of the fabric. Esperase® 8.0L treatment resulted in fabrics with adequate wettability, higher CrI and whitenees after bleaching compared to

On the other hand papain was not so effective in the degumming process. This could probably be attributed to the different substrate specificity of the proteases, that is, the chemical struc‐ ture of the target cleavage site. The silk fabrics treated with both proteolytic enzymes exhibited low bending and shear rigidity and higher elasticity compared to Marseille soap treated silk fabrics. This means that the silk fabrics after enzymatic degumming were softer, less rigid, with

Since the silk of *Bombyx mori* apart of the proteins fibroin and sericin, also contains fats, wax etc., the combined effect of proteolytic enzymes with a lipolytic one was investigated. Com‐ bined action of protease with lipase (Lipolase® Ultra 50T) resulted in lower degumming effi‐ ciency compared (under the same conditions) with protease treatment only, but generated silk fabrics with significant improvement in whiteness after bleaching. As far as the proper‐ ties measured in the Kawabata evaluation system the combination of proteolytic with lipo‐ lytic enzymes resulted in silk fabrics with extremely low bending rigidity, reduced shear stiffness and with higher elasticity compared to Marseille soap treated. This means that the fabrics were softer, less rigid with better drape compared to conventionally treated. Addi‐ tion of lipolase caused decrease in bending and increase in shear rigidity and elasticity of the

Silk degumming is a high resource consuming process as far as water and energy are con‐ cerned. Moreover, it is ecologically questionable for the high environmental impact of efflu‐ ents. The development of an effective degumming process based on enzymes as active agents would entail savings in terms of water, energy, chemicals, and effluent treatment. This could be made possible by the milder treatment conditions, the recycling of processing water, the recovery of valuable by-products such as sericin peptides, and the lower environ‐

better drape and higher elasticity compared to those treated with Marseille soap.

8.0L + Lipolase® Ultra 50T mixture causes a decrease in the fabric's elasticity.

fabric Lipolase® Ultra 50T increases this value at 3.80%. On the other hand the use of Esperase®

fabric fabric for 60 min exhibited a tensile strength value of 2.93%. Addition of 50

Physichochemical and Low Stress Mechanical Properties of Silk Fabrics Degummed by Enzymes

http://dx.doi.org/10.5772/53730

255

papain at 75 U.

**4. Conclusions**

U. g-1 g-1

tional method of degumming (Marseille soap).

those treated conventionally (Marseille soap).

silk fabrics compared to those treated only with protease.

mental impact of effluents.

Opposite trend was observed for the fabrics treated with Esperase® 8.0L + Lipolase® Ultra 50T combination. Increasing protease dosage and treatment time the silk fabrics became more anelastic (Table 12).


**Table 12.** Comparison of micromechanical properties of silk fabrics treated for different times with various levels of papain and Esperase® 8.0L combined with constant level of Lipolase® Ultra 50T, with reference and conventionally degummed materials

Addition of Lipolase® Ultra 50T in papain degumming mixture produces more elastic fabrics compared to those obtained by single papain treatement. For example silk fabrics treated with papain at 75 U. g-1 fabric fabric for 60 min exhibited a tensile strength value of 2.93%. Addition of 50 U. g-1 fabric Lipolase® Ultra 50T increases this value at 3.80%. On the other hand the use of Esperase® 8.0L + Lipolase® Ultra 50T mixture causes a decrease in the fabric's elasticity.
