Problems of optimisation of plant cell culture processes.

The adoption of plant cell cultures as an industrial process depends greatly on the economics of such a process. The multicycle or draw-fill culture technique is one method for improving the productivity and, hence, cost of a process. Mathematical models have been devised for the functional relationships between the nominal costs of biomass and secondary metabolites and the plant cell growth characteristics in a multicycle growth system. The models were used to evaluate the data obtained with cultures of Dioscorea deltoidea (which produces diosgenin) and Panax ginseng, grown in various types of bioreactors. The multicycle system gave an increase of 1.5-2 in biomass productivity compared with batch culture, but was probably only commercially viable if the cost of the process in the bioreactor was at least 30 times that of the medium and if an inoculum of about 30% of the culture of the previous cycle was left in the bioreactor. In the multicycle system incompletely utilised nutrient or metabolite accumulation can only reach 1.43 times or less that of the initial values. With the P. ginseng culture, about 75% of the calculated maximum cell packing density per fresh weight (approximately 530 g 1-1) in this regime was achieved. The possibility of growth in the standard bioreactor of a shear sensitive type culture was shown with a marine impeller speed up to 330 cm s-1.