Growth and immobilization of tripterygium wilfordii cultured cells.

The plant Tripterygium wilfordii produces di- and triterpenes of interest for male contraception and treatment of arthritis and skin disorders. Cell line TRP4a obtained form this plant in 1981 was reported to produce these valuable compounds at yields ( approximately 0.04% of the biomass dry weight) higher than found in the plant (0.001%). In order to improve this production, studies were carried out to determine the feasibility of eliminating the troublesome component of coconut milk originally used to culture this cell line. A defined formulation suitable for growth ad maintenance has been developed. This medium consisted of Gamborg's PRL4 or B5 medium supplemented with 2 mg L(-1) 2,4-dichlorophenoxyacetic acid and 20 g L(-1) sucrose. Furthermore, monitoring of carbohydrate uptake revealed that T. wilfordii cells, contrary to many plant cell species, did not hydrolyze sucrose extra-cellularly before uptake. Replacement of this disaccharide by glucose or fructose increased specific growth rate from 0.15 to 0.25 day(-1). As tripdiolide is reported to be present in broth extract in significant amounts, plant cell immobilization technology offers a promising alternative to suspension cultures, especially in view to on line harvesting of the product. Surface immobilized T. wilfordii cell cultures were successfully carried out in 2-L bioreactors. Their biomass production and carbohydrate uptake were comparable to those observed for shake flask grown suspension cultures. Higher nitrate and ammonium uptake were found in immobilized cultures.