ABSTRACT
The omnipotency (omnis = all, potens = powerful) of the plant cell implies that all genetic information present in the plant is principally available in each cell. This means that genes encoding enzymes that belong to biosynthetic pathways can be brought to expression. Therefore, it seemed feasible to produce most plant secondary metabolites using in vitro grown cultures. The successful production of antibiotics by fungi and bacteria was the stimulus for researchers in the initial period of plant biotechnology in the 1960s. Meanwhile, it has become clear that plant cell cultures do not always accumulate either qualitatively or quantitatively the same compounds found in the parent plant from which they were established. For this reason only a very limited number of secondary metabolites can now be produced commercially by plant cells on a larger scale in bioreactors. To illustrate this, we have calculated the production rates in terms of mg product per litre culture per day (mg L−1d−1) for a number of plant cell cultures that have been described to accumulate secondary metabolites at varying levels (Table 10.1). With the exception of shikonin, used as a dye and an antiseptic agent, none of these secondary metabolites is produced on an industrial scale. Even at relatively high production rates, the manufacturing costs are too high for the realization of a profitable process. It seems that the highest production rates are found for compounds with a chemical structure that is not too complex, such as L-DOPA (an important anti-Parkinson drug) and coniferin (Fig. 10.1, A).
