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What silk is

The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori, which are reared in captivity. The protein fiber of silk is composed mainly of fibroin (75-80%) and a smaller coating of sericin (20-25%).

Fibroin and sericin

Fibroin is an insoluble protein present in silk. Fibroin combines stiffness and toughness, and has applications in several areas, including biomedicine and textile manufacture. Sericin is the gum that coats the fibres and lets them stick to each other. In raw silk, a glue-like layer of sericin coats two filaments of fibroin called brins. Sericin is composed of 18 different amino acids, of which 32% is serine.

The fibre

Silk fibers from the B. mori silkworm have a triangular cross section with rounded corners, 5-10 μm wide. The flat surfaces of the fibrils reflect light at many angles, giving silk a natural sheen.

Production

The process of silk production is known as sericulture. Extracting raw silk starts by cultivating the silkworms on mulberry leaves. To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms.

Uses

Sericin has also been used in medicine and cosmetics. When used in cosmetics, sericin has been found to improve skin elasticity. Since the 1990s, silk has been widely studied and used as a biomaterial.

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