Scale-up production of Rehmannia glutinosa adventitious root biomass in bioreactors and improvement of its acteoside content by elicitation

Rehmannia glutinosa is an important medicinal crop that has been widely used globally to treat various ailments such as hematinic deficiencies, diabetes, and adrenal disorders. To provide a sustainable supply to meet large demands, alternative cultivation methods, apart from conventional ones, are indispensable. This study developed an optimized condition for R. glutinosa adventitious root culture and a scale-up production system using a bioreactor. A woody plant medium enriched with vitamins, 30 g/L sucrose, and 2.0 mg/L 1-naphthaleneacetic acid (NAA) supported the optimum growth rate of adventitious roots (growth index of 25.67). The application of methyl jasmonate (MeJa) at a concentration of 200 μM showed the best enhancement of acteoside biosynthesis, with an approximately 2.53-fold increase (14.37 mg/g dry weight [DW]) compared with the control (5.67 mg/g DW). However, all treatments with MeJa and salicylic acid reduced the biomass of R. glutinosa adventitious roots compared with control. To validate the optimized protocol, the culture system was scaled up by comparing shake flask cultures with 2- and 20-L balloon type (air lift) bubble bioreactors (BTBB) along with elicitation using 200 μM MeJa. The 20-L BTBB cultures produced good-quality R. glutinosa roots with higher biomass (15.94 g DW), acteoside content (22.13 mg/g DW), and antioxidant activity (84.22 %) than shake flask cultures. In addition, fourier transform near-IR (FT-NIR) analysis showed no significant difference in the chemical composition of the in vitro adventitious roots and those that were commercially available. Thus, these findings will provide a basis for the development of large-scale R. glutinosa adventitious root production to meet the demands of pharmaceutical and oriental medicine industries without affecting its availability in nature.