| Popis: |
At the end of the 70ties, plant tissue cultures were expected to become an alternative source to field grown plants for commercially important compounds (secondary metabolites). The idea was to grow suspension cultures of medicinal plants in huge bioreactors and to isolate from their biomass the desired compounds, for example morphinanes, quinine or cardiac glycosides. It was assumed that one would produce the compounds under better controlled conditions, independent of the climate and could react more flexible to changing demands of the market. For several reasons this ambitious goal has not yet been acchieved. The most serious problem is the fact that nearly all commercially attractive candidates for this technology are produced only in low amounts or are even lacking in biotechnologically relevant tissue cultures. Biotechnologically relevant means that product formation occurs or is stably inducable in rapidly growing cultures. Though all available conventional techniques (screening, selection, production media, biotic and abiotic elicitors) have been applied to these cultures, their productivity could not be improved distinctly. Presently, we have to accept that only some compounds of minor or no commercial impact can be produced by tissue cultures in high levels so that a commercial production could be envisaged (see for review1). It is more and more believed that the application of new, especially genetic techniques is required to express the really interesting pathways in cultured cells. |
