Secondary metabolite production

Abstract

In the past it was frequently assumed that plant cells, mass produced in vitro, could serve as sources of valuable metabolites. It was envisaged that by strictly controlled manipulation of the physical environment and of the nutrient medium, cells in vitro could be induced to produce the desired products in large quantities. Particularly popular was the idea that the desired products could be manufactured by adding their precursors to the nutrient medium, but this approach has only rarely been successful (Robins et al. 1987, Berlin 1988). Mass production of cells in vitro is achieved by culturing cells in liquid medium in large fermentors. Such cultures generally consist of suspensions of relatively undifferentiated cells or small clumps of cells. However, production of valuable metabolites often depends on differentiated cells or structures (Yeoman 1987) such as glandular hairs, lactifers and resin ducts. Unfortunately, these can generally not be induced in cell suspension cultures. Use of callus cultures instead of cell suspensions of trees, will occasionally result in the formation of ducts or glands that produce such products as terpenes and volatile oils (Koch-Heitzmann and Schultze 1989). However, such callus cultures are an inefficient and expensive source of secondary products.