*3.3.1. Weight loss*

The results are depicted in Figure 4 both as weight loss (Figure 4a) and degumming efficien‐ cy (Figure 4b). Without enzymes, the weight loss was negligible.

**Figure 4.** a) weight loss of silk fabrics treated with mixtures of proteases/lipase for 30, 60 and 90 min and (b) degum‐ ming efficiency of the enzymatic process

The degree of fabric's degradation was found to be affected by both enzyme concentration and treatment time. Increasing enzyme concentration and treatment time resulted in in‐ creased weight loss values. The combination of Esperase® 8.0L with Lipolase® Ultra 50T was found superior to that of papain. The highest weight loss (15.9%, w/w) was achieved when fabrics were treated with 75 U. g-1 fabric Esperase® 8.0L + 50 U. g-1 fabric Lipolase® Ultra 50T for 90min, while weight loss during conventional degumming was higher (20.4 %, w/w).

Degumming efficiency did not exceed 78% (Figure 4b). The proteases and lipase combina‐ tion did not improve the results obtained when the fabrics degummed only with proteases.

#### *3.3.2. Wettability and crystallinity index*

Wettability seemed to depend more on the enzymes used for degumming and less on treat‐ ment time. (Table 10). The most effective combination is that of Esperase® 8.0L with Lipo‐ lase® Ultra 50T. This combination at the highest enzyme loading used, exhibited adequate water absorbency (<1 sec) after 60 min of treatment. The mixture of papain with Lipolase® Ultra 50T did not improve the wettability of the silk fabrics compared to those treated only with papain, even at higher treatment times.

**3.3. Synergistic action of protease-lipase on silk degumming: Effect of treatment time**

and Esperase® 8.0L at an enzyme activity of 50 and 75 U.

treated and conventional degummed silk fabrics were used as controls.

cy (Figure 4b). Without enzymes, the weight loss was negligible.

30 60 90 Marseille soap

g-1

**Treatment time (min)**

lase® Ultra 50T) at a constant activity of 50 U.

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

*3.3.1. Weight loss*

0

ming efficiency of the enzymatic process

fabrics were treated with 75 U.

*3.3.2. Wettability and crystallinity index*

5

10

**Weight Loss (%)**

15

20

25

250 Eco-Friendly Textile Dyeing and Finishing

Proteases and lipases are normally used in combination for degumming and removing oth‐ ers impurities such as waxes, fats, mineral salts and pigments [49]. Waxes and fats as well as colorants and mineral components occur exclusively in silk gum layer (sericin) [66]. The combined effect of enzyme activity (expressed as Units of protease per g of silk fabric) and treatment time on physicochemical and low-stress mechanical properties of cotton fabric was investigated. Raw silk fabrics were treated with two different proteases namely papain

g-1

The results are depicted in Figure 4 both as weight loss (Figure 4a) and degumming efficien‐

**(a)**

**Figure 4.** a) weight loss of silk fabrics treated with mixtures of proteases/lipase for 30, 60 and 90 min and (b) degum‐

The degree of fabric's degradation was found to be affected by both enzyme concentration and treatment time. Increasing enzyme concentration and treatment time resulted in in‐ creased weight loss values. The combination of Esperase® 8.0L with Lipolase® Ultra 50T was found superior to that of papain. The highest weight loss (15.9%, w/w) was achieved when

fabric Esperase® 8.0L + 50 U.

Degumming efficiency did not exceed 78% (Figure 4b). The proteases and lipase combina‐ tion did not improve the results obtained when the fabrics degummed only with proteases.

Wettability seemed to depend more on the enzymes used for degumming and less on treat‐ ment time. (Table 10). The most effective combination is that of Esperase® 8.0L with Lipo‐

90min, while weight loss during conventional degumming was higher (20.4 %, w/w).

**Degumming Efficiency (%)**

g-1

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

fabric combined with a lipase (Lipo‐

**(b)**

fabric Lipolase® Ultra 50T for

fabric ic for 30, 60, 90 min. Furthermore, buffer

30 60 90 Marseille soap

**Treatment time (min)**

g-1

Crystallinity index increased with treatment time for all enzyme combination tested (Table 10). The combination of Esperase® 8.0L with lipase was more effective compared to that of papain. However, the addition of lipase did not seem to improve Crystallinity Index in any condition tested, compared to the action of single protease.


**Table 10.** Wetting time and Crystallinity Index of silk fabrics treated conventionally (Marseille soap) or enzymatically.
