In vitro production of Bombyx mori silk fibroin by organ culture of the posterior silk glands; isotope labeling and fluorination of the silk fibroin

An in vitro silk fibroin production system has been developed by culture of posterior silk glands from Bombyx mori. A large amount of the silk fibroin was produced continuously and effectively with a rotation culture procedure. Modified Grace's insect medium was used, and oxygen bubbling in the medium was performed. In addition, half of the medium was replaced with fresh medium every 6 h. The production yield of silk fibroin produced after 100 h culture was 81 mg/g wet weight of posterior silk gland. This culture system was used successfully for efficient 15 N isotope labeling of silk fibroin, which is required for 15 N solid state nuclear magnetic resonance (NMR) analysis of silk fibroin. Moreover, the introduction of fluorinated amino acids into silk fibroin was also carried out using this culture system. © 1993 John Wiley & Sons, Inc.