Boosting sericin extraction through alternative silk sources

Silk sericin (SS) is a natural polymer widely studied in the design of biodegradable materials for cosmetic, biomedical, food, and chemical applications. This work was designed to explore the molecular and structural characteristics of SS extracted from different silk sources with different processing degrees: high-quality cocoons (NCs), defective cocoons (DCs), and raw silk yarn (Y). The last two sources have been less studied. SS solutions were obtained from each source using the high-temperature and high-pressure degumming method (HTHP). The molecular weight distribution and amino acid composition of SS extracts were determined using gel permeation chromatography (GPC) and reversed-phase chromatography (RP HPLC), respectively. SS films were formed from each solution and then characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance spectroscopy (NMR), and differential scanning calorimetry (DSC). Water uptake and degradation of SS films were also evaluated. The molecular characteristics of SS extracts were related to the processing degree of the silk source. Moreover, the properties of SS films seemed to be dominated by the primary structure and the presence of natural impurities in each extract. The results suggest that silk sources could be selected ad hoc to design SS materials with distinctive properties for specific applications.