Silk derived from silkworm
Bombyx mori
is a natural protein that is mainly made of sericin
and fibroin proteins. Sericin constitutes 25–30% of silk protein and it envelops the fibroin
fiber with successive sticky layers that help in the formation of a cocoon. Sericin ensures the
cohesion of the cocoon by gluing silk threads together. Most of the sericin must be removed
during raw silk production at the reeling mill and the other stages of silk processing. At
present, sericin is mostly discarded in silk processing wastewater. The cocoon production is
about 1 million tons (fresh weight) worldwide and this is equivalent to 400,000 tons of dry cocoon.