ENZYMATIC HYDROLYSIS OF SILK SERICIN BY PROTEASES AND ANTIOXIDANT ACTIVITIES OF THE HYDROLYSATES

ABSTRACT This study was conducted to investigate the free radical-scavenging activity and antioxidant activity of silk sericin hydrolysates (SSH). SSH were obtained by hydrolysis of silk sericin with alcalase, trypsin, neutrase, bromelin, papain and flavourzyme. Its ability to scavenge 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonicacid) (ABTS) cation radicals and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals was determined by ultraviolet spectrophotometry. The antioxidant activities of the SSH, including lipid peroxidation in linoleic acid system, reducing power and ferrous ion chelating ability, were evaluated. The results showed that different protease hydrolysates possessed different ability to quench the ABTS cation radicals and DPPH radicals. Among those tested, alcalase hydrolysate exhibits the highest scavenging activity than other proteases (P < 0.05). Alcalase hydrolysate exerted the highest peroxidation inhibition than other proteases (P < 0.05). The reducing power and ferrous ion chelating ability of six SSH were significant. These results indicated that six SSH were natural antioxidants with potent antioxidative activity. PRACTICAL APPLICATIONS Most of silk sericin must be removed during raw silk production at the reeling mill and the other stages of silk processing. At present, silk sericin is mostly discarded in the silk processing wastewater. If silk sericin was recovered and recycled, it could represent a significant economic and social benefit. Silk sericin is a natural macromolecular protein derived from silkworm Bombyx mori. Silk sericin is useful because of its antioxidant activity. Silk sericin can be cross-linked, copolymerized and blended with other macromolecular materials, especially artificial polymers, to produce materials with improved properties. The protein is also used as an improving reagent or a coating material for natural and artificial fibers, fabrics and articles. The materials modified with silk sericin and sericin composites are useful as degradable biomaterials, biomedical materials and functional membranes.