Silk Protein Sericin Improves Mammalian Cell Culture

Abstract

Mammalian cell cultures generally require supplementation with fetal bovine serum (FBS), or its replacement, into the culture media. Sera contain various unidentified and unknown factors and the risk of infections, including bovine spongiform encephalopathy (BSE), is of serious concern. Therefore, the supplementation of sera into culture media is a major obstacle for purification to recover cell products and this limits pharmaceutical acceptance of products. In this study, we examined whether the sericin protein, derived from the silkworm cocoon, can be effectively used as a substitute for FBS in mammalian cell culture. Together with fibroin, sericin is a major component of raw-silk and is removed from raw-silk by a treatment called degumming to make the silk lustrous and semitransparent. In order to investigate the effect of sericin on the proliferation and the productivity of mammalian cells, sericin was added to cultures of various mammalian cell lines, such as murine hybridoma 2E3-O. Sericin successfully accelerated the proliferation of the cells. Moreover, the production of MoAb by the hybridoma cells was also improved in the presence of sericin. Although heat easily denatures and inactivates most proteins, sericin maintained mitogenic activity after conventional autoclaving (20 minutes) and longer (60 minutes) autoclaving.