Optimization of the Green Conventional Extraction Method of Sericin from Silkworm

In the silk production process, cocoons from <i>Bombyx mori</i> worm are degummed and separated from their components. This step generates large residual quantities of an aqueous solution containing various chemical substances, including sericin-a protein that, when discarded improperly, negatively impacts the environment. Sodium bicarbonate and coconut soap are commonly used in the degumming process. The phosphates in the soap and the sodium bicarbonate increase the biological oxygen demand (BOD) and chemical oxygen demand (COD), leading to water contamination. In this study, a Box-Behnken experimental design was used to maximize the extraction of sericin through a conventional extraction under chemical-free conditions. From a total of 45 experiments, the optimal extraction conditions were identified as a solid-to-liquid ratio of 1:20 <i>w</i>/<i>v</i>, a temperature of 120 °C, and 90 min of extraction time. Sericin yields ranged from 9% to 18%. Infrared spectroscopic characterization of the extracted sericin confirmed the presence of protein-specific functional groups and common interactions associated with β-sheet structures. Fractions of high molecular weight (50 kDa to 200 kDa), identified by means of Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, demonstrate the potential functionality of extracted sericin for the development of biopolymer films useful in biomedical and food industry applications. The optimized methodology is a good alternative to recycle the waste of sericulture chain for obtaining extracts enriched in sericin, as well as to promote the mechanization of artisanal production processes.