Metabolic Burden Analysis in In Vitro Culture of Plants: A Bioprocess Strategy for Efficient Process Design

Plants serve as the source of a myriad of products owing to the therapeutic properties of their secondary metabolites. The increasing commercial importance but low yield of secondary metabolites has now raised interest in research focusing on increasing their yield. Alternatively, studies are conducted for mass propagation of plants. Although bioreactors are used extensively for microbial systems, they are now being considered as suitable alternatives for the production of secondary metabolites and mass propagation of plants. The successful design of a bioprocess strategy to culture different morphological forms of plants, viz. whole plant, callus, friable cell, and suspension culture, largely depend on the successful design of bioprocess parameters. The production of metabolites always imparts metabolic burden on the cell, a bioprocess parameter, scarcely explored for the production of metabolites in higher eukaryotes, especially plants. The metabolic burden is indicative of the ability of a cell to assimilate the resources (nutrients) and use the energy, thus derived, for growth and metabolite production. It is evident that metabolic burden is a parameter to assess the additional load on cells (or organism) in production, and understanding of the parameter will pave the way for designing an efficient bioprocess strategy. Previous studies have explored oxygen uptake rate, as an important parameter, indicative of metabolic burden. The importance of oxygen assimilation rate on plant cell culture and its possible impact on cell metabolism is being presented.