Detailed investigation on new chemical-free methods for silk sericin extraction

Abstract

The degumming of silk and the recovery of sericin from wastewater can be performed in different ways. In this study, the quantity and quality of silk sericin from mulberry silkworms are evaluated through four degumming methods: the alkaline, the hot water, the high temperature and high pressure (HTHP) and the microwave methods. The sericin powders obtained were rigorously characterized through the elementary composition, Scanning Electron Microscopy (SEM), spectroscopy (UV, IR and fluorescence), secondary structure, thermal stability, molecular weight analysis, and compared to a commercial sericin. The results demonstrate that microwave is the most effective degumming method because all of the sericin contained in the cocoons is recovered. It was shown that sericin samples obtained by different extraction methods have similar composition. However, differences were observed in the chain length of sericin samples. The molecular weights of sericin are high for alkaline and microwave degumming and lower molecular weights are observed for sericin from hot water and HTHP degumming. The analysis of the secondary structure confirms that sericin is highly structured in aggregated or in β sheet conformation. The morphology and the structural organization of the sericin can be altered from one extraction to another, modifying sericin properties. • Four degumming methods of silk sericin from Bombyx Mori have been compared • Development of a new process for the sericin recovery with a laboratory microwave • Microwaves degumming is the most efficient extraction with 99.8% yield of sericin • Sericin extracts have the same composition and are similar to a commercial sericin • Extraction methods influence the molecular weight and solubility of sericin in water