**4. Conclusions**

*3.3.6. Tensile property*

254 Eco-Friendly Textile Dyeing and Finishing

more anelastic (Table 12).

**Type of treatment**

g-1 fabric Papain + 50 U.

g-1 fabric Papain + 50 U.

g-1 fabric Esperase®

g-1 fabric Esperase®

papain and Esperase®

degummed materials

8.0L + 50 U.

8.0L + U.

50 U.

75 U.

50 U.

75 U.

was superior to that of Marseille soap treated silk.

g-1 fabric Lipolase® Ultra 50T

g-1 fabric Lipolase® Ultra 50T

g-1 fabric Lipolase® Ultra 50T

g-1 fabric Lipolase® Ultra 50T

8.0L combined with constant level of Lipolase®

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

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

No enzyme 5.15 ± 0.2 1.63 ± 0.07 *3.39*

30 min 3.30 ± 0.10 2.70 ± 0.20 *3.00* 60 min 3.60 ± 0.10 3.00 ± 0.10 *3.30* 90 min 3.90 ± 0.20 3.10 ± 0.10 *3.50*

30 min 4.10 ± 0.20 3.30 ± 0.20 *3.70* 60 min 4.20 ± 0.20 3.40 ± 0.30 *3.80* 90 min 4.40 ± 0.40 3.50 ± 0.20 *3.95*

30 min 4.85 ± 0.10 1.74 ± 0.05 *3.30* 60 min 4.75 ± 0.20 1.65 ± 0.02 *3.20* 90 min 4.60 ± 0.20 1.50 ± 0.03 *3.05*

30 min 4.96 ± 0.10 1.87 ± 0.09 *3.42* 60 min 4.62 ± 0.40 1.55 ± 0.05 *3.09* 90 min 4.51 ± 0.30 1.36 ± 0.04 *2.94* Marseille soap 4.29 ± 0.20 1.42 ± 0.02 *2.86*

**Table 12.** Comparison of micromechanical properties of silk fabrics treated for different times with various levels of

Ultra 50T, with reference and conventionally

**Tensile (%) warp weft** *mean* 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‐ tional method of degumming (Marseille soap).

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 those treated conventionally (Marseille soap).

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

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 fabrics compared to those treated only with protease.

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‐ mental impact of effluents.
