Journal
SUSTAINABLE CHEMISTRY AND PHARMACY
Volume 27, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.scp.2022.100681
Keywords
Silk fibres; Degumming; Sericin; Enzyme; Thermophilic protease; Dyeing
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In this study, a green method for degumming natural silk using a thermophilic protease enzyme was adopted, which resulted in a high degree of whiteness of the silk fibers without compromising dyeability and mechanical properties. Additionally, the degumming process extracted sericin with a lower molecular weight compared to conventional methods.
Degumming of natural silk is energy and water-consuming process which is usually carried out at the boil for 3 h in three consecutive water baths or by using alkaline soapy solutions. Herein, we adopted an energy and water-saving green method for degumming of raw natural silk by the thermophilic protease enzyme (TPE) from Bacillus safensis FO-36bMZ836779 strain. Bio-degumming of natural silk was carried out using different enzyme concentrations, temperatures, duration and pH. The dyeability of the conventionally and bio-degummed natural silk towards acid dye was investigated. To save more energy and water, a one-bath degumming and dyeing of natural silk was conducted in two successive steps. The chemical, physical and mechanical properties of the bio-degummed silk fibers were studied using amino acid analysis, SDS-PAGE electrophoresis, scanning electron microscopy, X-ray diffraction pattern, whiteness index, and tensile strength. The chemical and biological oxygen demand as well as the total dissolved and suspended salts of the bio-degumming effluent were measured. Results of study show this that the amount of sericin obtained from bio-degumming of silk at the optimum conditions (50% v/v at 55 degrees C for 3 h) is very close to that obtained by the energy and time-consuming conventional degumming process. The degree of whiteness of the bio-degummed natural silk was highly improved without any negative impact on dyeability and mechanical properties. No severe deterioration of the bio-degummed fibre surface was detected by the SEM micrographs. The molecular weight of sericin extracted by degumming process is lower than that obtained by conventional degumming of natural silk.
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