Adventitious root culture of Lessertia frutescens for the production of triterpenoid saponins and polysaccharides

Lessertia frutescens is a perennial shrub of commercial importance in South Africa, but the scarcity of plant re-sources has limited current product production. In this study, to provide an alternative approach for obtaining L. frutescens material, adventitious roots (ARs) were induced from sterilized seedlings and cultured in a sus-pension culture system. During this process, selection tests were conducted to find a suitable auxin and its concentration for AR induction and a suitable basal medium for AR growth and metabolite accumulation; a kinetic study was then performed to constructure kinetic models. The results showed that compared to other auxins and concentrations, indole-3-butyric acid at 3 mg/L was suitable for increasing the number and length of ARs during AR induction. In AR suspension culture, Schenk and Hildebrandt (SH) was better than other basal media, and the maximum AR fresh (86.9 g/L) or dry weight (5.5 g/L), total triterpenoid saponin (92.6 mg/g DW), and polysaccharide (114.7 mg/g DW) contents were determined in the 1.5xSH medium. In addition, AR biomass and metabolite contents reached the maximum on day 42. The kinetic models for AR growth and triterpenoid and polysaccharide production were constructed, providing the basis for further optimization of culture condi-tions and large-scale culture.