Gaseous metabolites and the ajmalicine production rate in high density cell cultures of Catharanthus roseus

Abstract

An important factor in the scale-up of plant cell processes for the production of secondary metabolites is the gas exchange between the gas and liquid phases. In aerobic fermentations, the gas exchange involves mainly two processes: the supply of oxygen and the removal of gaseous metabolites (CO,, ethylene, etc.). The concentrations of dissolved oxygen (DO) and dissolved gaseous metabolites (DGM) which are critical parameters in large-scale fermentations are dependent on mass transfer and mixing in the bioreactor as well as the biomass concentration. Since mass transfer and mixing are dependent on the size of the bioreactor, DO and DGM change during scale-up of the process. Consequently, it is essential for process design, optimization, operation, and scale-up to establish separate relationships between DO and DGM on the one hand and cell growth and secondary metabolite production on the other hand. In the present study, the relation between the DGM concentration and the specific ajmalicine production rate by Catharanthus roseus was investigated. DGM is a collective noun for the various gaseous compounds produced by plant cells. Carbon dioxide and ethylene are important representatives of this group. The effect of the individual compounds