Mechanical Extraction from Silk Produces an Undegraded Sericin 3 Rich Hydrogel

Silk sericin, a hydrophilic protein traditionally discarded during silk degumming, holds significant potential for biomedical applications due to its antioxidant, antibacterial, and biocompatible properties. Conventional chemical degumming produces a high yield but degrades sericin, impacting its properties. Other extraction methods utilizing denaturants such as guanidine hydrochloride produce high-quality sericin but at an extremely low yield. This study introduces an innovative mechanical extraction method that combines cutter milling with shear homogenization in water to isolate sericin from Bombyx mori cocoons without the use of chemicals. Through careful control of shear intensity and thermal management, the process achieved a yield of 7.0 ± 1.4%, nearly 3-fold higher than guanidine hydrochloride extraction. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis of the extracted sericin revealed minimal degradation, with distinct bands ranging from ∼20 kDa to over 200 kDa. Unlike alkaline-degummed sericin, the extract produced a thick hydrogel. Proteomic analysis of the extract revealed a unique composition, with a high proportion of Sericin 3, whereas chemical extraction yielded more Sericin 1. The ability to selectively extract sericin fractions may deepen understanding of their functional roles and enable targeted strategies to precisely tune hydrogel properties.