Serum-free medium for recombinant protein expression in insect cells

The baculovirus expression vector system (BEVS) has been widely used to produce recombinant proteins because of several advantages, such as eukaryotic post-translational modifications similar to those in mammalian cells, high expression levels and safety, and large gene capacity. Usually, insect cell culture requires 5%‒10% fetal bovine serum, which has many adverse effects, including high cost, heterogeneity between batches, complex composition, and pollution risks. Therefore, serum-free medium (SFM) is indispensable for the production of recombinant proteins in insect cell culture. Here, the most commonly used insect cell lines and three insect cell media, namely basic medium, SFM, and chemically defined medium, are summarized. The basic components of insect cell SFM are similar to those of other cells but contain special components. The components, functions, and issues of different SFM used for insect cell culture are reviewed. In recent years, some special additives have been demonstrated to increase recombinant protein expression yield and quality in BEVS, and the functions and possible mechanisms of small-molecule additives are reviewed herein. Finally, future perspectives of SFM used in BEVS for recombinant protein production are discussed.