Appl Microbiol Biotechnol (2010) 85:459–470 DOI 10.1007/s00253-009-2267-2 MINI-REVIEW Silkworm expression system as a platform technology in life science Tatsuya Kato & Mizuho Kajikawa & Katsumi Maenaka & Enoch Y. Park Received: 24 July 2009 / Revised: 17 September 2009 / Accepted: 17 September 2009 / Published online: 15 October 2009 # The Author(s) 2009. This article is published with open access at Springerlink.com Abstract Many recombinant proteins have been success- fully produced in silkworm larvae or pupae and used for academic and industrial purposes. Several recombinant proteins produced by silkworms have already been com- mercialized. However, construction of a recombinant baculovirus containing a gene of interest requires tedious and troublesome steps and takes a long time (3–6 months). The recent development of a bacmid, Escherichia coli and Bombyx mori shuttle vector, has eliminated the conven- tional tedious procedures required to identify and isolate recombinant viruses. Several technical improvements, including a cysteine protease or chitinase deletion bacmid and chaperone-assisted expression and coexpression, have led to significantly increased protein yields and reduced costs for large-scale production. Terminal N-acetyl glucos- amine and galactose residues were found in the N-glycan structures produced by silkworms, which are different from those generated by insect cells. Genomic elucidation of silkworm has opened a new chapter in utilization of silkworm. Transgenic silkworm technology provides a stable production of recombinant protein. Baculovirus surface display expression is one of the low-cost approaches toward silkworm larvae-derived recombinant subunit vaccines. The expression of pharmaceutically relevant proteins, including cell/viral surface proteins, T. Kato : E. Y. Park (*) Faculty of Agriculture, Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan e-mail: acypark@ipc.shizuoka.ac.jp M. Kajikawa : K. Maenaka Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan membrane proteins, and guanine nucleotide-binding protein (G protein) coupled receptors, using silkworm larvae or cocoons has become very attractive. Silkworm biotechnol- ogy is an innovative and easy approach to achieve high protein expression levels and is a very promising platform technology in the field of life science. Like the “Silkroad,” we expect that the “Bioroad” from Asia to Europe will be established by the silkworm expression system. Keywords Silkworm . Bombyx mori nucleopolyhedrovirus (BmNPV) . Bacmid . Protein expression . Baculovirus display Introduction Various systems to produce recombinant proteins are available. Bacteria, especially Escherichia coli, are usually chosen first, due to the abundance of tools available for gene manipulations and the simple process for protein production. However, bacteria are severely limited because of their poor capacity to modify expressed proteins cotranslationally and posttranslationally, in spite of recent improvements of strains. Yeasts have some advantages over bacteria. Recombinant proteins expressed in yeast can be glycosylated, but certain modifications are not possible, especially in the case of complex form of N-glycosylation. Insect cell systems are now popular and used widely to produce proteins from higher eukaryotes because insect cells have a similar pattern and capacity of cotranslational and posttranslational modifications as mammalian cells, including glycosylation, phosphorylation, and protein pro- cessing. The insect cell systems include the baculovirus expression system and the stably transformed cell system. In the baculovirus expression system, not only cultured