PLANT-CELL BIOTECHNOLOGY FOR THE PRODUCTION OF ALKALOIDS - PRESENT STATUS AND PROSPECTS

The culture of plant cells on a large scale in bioreactors has been shown to be feasible. The price of a plant cell biotechnological product is mainly governed by the slow growth of plant cell cultures, making the depreciation costs of the bioreactor the major cost-determining factor. A review of the production of the economically important alkaloids in plant cell cultures shows that presently only berberine and sanguinarine are being produced. Important factors to be considered in connection with accumulation of alkaloids are biosynthetic rate, accumulation site, and catabolism. Recent studies in the field of the regulation of the biosynthesis of terpenoid indole alkaloids on the level of genes and enzymes are reviewed, showing that it is feasible to clone genes from secondary metabolism and express these in various other plants. Concerning storage, it seems that compartmentation also plays a role in the regulation of alkaloid biosynthesis. Furthermore, catabolism of terpenoid indole alkaloids in cell cultures is an important factor, at some point even equalling the rate of de novo biosynthesis. The ongoing studies on regulation of alkaloid biosynthesis might eventually lead to transgenic plants or plant cell cultures with an improved productivity of the desired compounds. This knowledge is also of interest in connection with studies on the role of secondary metabolism for plants, and may contribute to a better understanding of resistance of plants to diseases and various herbivores.