Spirodela (duckweed) as an alternative production system for pharmaceuticals: a case study, aprotinin.

Aprotinin is a small serine protease inhibitor used in human health. Spirodela were transformed, via Agrobacterium, with a synthetic gene encoding the mature aprotinin sequence and a signal peptide for secretion which was driven by the CaMV 35S promoter. A total of 25 transgenic Spirodela lines were generated and aprotinin production was confirmed by northern and western blot analyses. Expression levels of up to 3.7% of water soluble proteins were detected in the plant and 0.65 mg/l in the growth medium. In addition, immunoaffinity purification of the protein followed by amino acid sequencing confirmed the correct splicing of the aprotinin produced in Spirodela and secreted into the growth medium.