Fig. 2.

Methods for the production of bioactive secondary metabolites through plant in vitro culture. A Establishment of in vitro cultures after surface sterilization of plant material. Callus formation can also be induced on material from organ cultures. Reversely, organs like roots or shoots can be regenerated from callus. Hairy roots are obtained by infection of sterilized donor plant, or in vitro cultivated material, with Agrobacterium rhizogenes. B Multiplication of primary callus/organs/roots, first selection, and establishment of liquid cultures. C Selection of high yielding lines and optimization of culture conditions (nutrient medium composition, inoculum density, temperature, light, agitation and aeration). Strategies like elicitation, precursor feeding, or immobilization are pursued to further improve productivity. D The bioreactor design will depend on the culture type: stirred tanks, but also airlift and bubble column reactors for cell suspensions; mist or spray reactors and temporary immersion systems for organ cultures (including hairy roots)