Engineering of Secondary Metabolites in Tissue and Cell Culture of Medicinal Plants: An Alternative to Produce Beneficial Compounds Using Bioreactor Technologies

The plant kingdom encompasses a plethora of beneficial compounds which are the main source of chemicals needed for different industries and medicinal purposes. Slow growth rate, low yields, and difficulties to grow many of the medicinal plants in commercial scale are motivating factors for those searching for an efficient and alternative method. Tissue culture-mediated production of metabolites offers the advantages that are economically competitive over extraction from whole plant systems. Despite several solutions that have been proposed to overcome the potential problems of in vitro-mediated production of plant bioactive compounds, the success appears to require integration of a variety of tools. The quality, yield, stability, and the processing steps of a specific metabolite are subjected to change through metabolite engineering. Suppression of unwanted metabolite or introduction of new pathway for de novo synthesis of a dedicated metabolite are the other advantages of genetic engineering. Manipulation of secondary metabolites is a complicated process due to the fact that there are competing pathways with potential intervention for the same substrate or intermediates with the pathway of interest. Metabolic engineering using a single structural gene can stimulate a contest in accessibility of cofactors and development of feedback-inhibition mechanisms by accumulation of end products. It seems that successful engineering of plant secondary metabolites using a single structural gene should coincide with the manipulation of regulatory proteins and or targeting of a specific metabolite to subcellular compartments or even to the culture medium to reduce the total cost. This chapter highlights the recent strategies and achievements in metabolite engineering of medicinal plants for secondary metabolite production in cell or tissue culture systems.