The department of Bioprocess Engineering at Fraunhofer IME has more than 20 years of experience in recombinant protein expression in various systems. Among the more than 100 different products there are model proteins such as GFP, pharma-relevant monoclonal antibodies and enzymes as well as challenging molecules such as membrane proteins, artificial fusion proteins (e.g. vaccine candidates), immunotoxins, regulatory proteins and effectors. In order to meet best the requirements of an individual protein, we test various expression systems for high product yield and quality. These systems include Escherichia coli, Pichia pastoris, Hansenula polymorpha, Schizosaccharomyces pombe, Saccharomyces cerevisiae, Nicotiana tabacum (different cultivars and cell lines), Nicotiana benthamiana (including cell lines), Oryza sativa (different cultivars), CHO cells, hybridoma cells, HeLa cells and HEK 293 cells.