The enzymatic degumming of silk fibers

The silk fibers are obtained by the silkworm Bombyx mori is a composite material formed by two fibroin proteins surrounded by a sericin protein. Both fibroin and sericin, which account for about 75 and 25 wt.%, respectively, are proteins. Silk processing from cocoons to the finished clothing articles consists of a series of steps which include: reeling, weaving, degumming, dyeing or printing, and finishing. Degumming is a key process during which sericin is totally removed and silk fibers gain the typical shiny aspect, soft handle, and elegant drape highly appreciated by the consumers. Nowadays, batch degumming of silk is mostly carried out in alkaline baths containing soap and alkali. Soap is replaced by synthetic detergents in continuous degumming. In recent years, various studies have dealt with the removal of sericin by using proteolytic enzymes. Several acidic, neutral, and alkaline proteases have been used on silk yarn as degumming agents. Alkaline proteases performed better than acidic and neutral ones in terms of complete and uniform sericin removal, retention of tensile properties, and improvement of surface smoothness, handle, and lustre of silk. In this article, it has been tried to give information about enzymatic degumming of silk fibers.