A novel co-culture system of adventitious roots of Echinacea species in bioreactors for high production of bioactive compounds

To efficiently produce bioactive compounds of Echinacea via adventitious root (AR) culture, we established an AR co-culture system of Echinacea species. ARs of different combination of Echinacea species [E. pallida (Epa), E. purpurea (Epu), and E. angustifolia (Ean)] were inoculated into 5 L balloon-type airlift bioreactors to select a suitable combination group. The biomass of ARs increased in the Epa+Epu group but decreased in co-culture groups of Epa+Ean and Epa+Epu+Ean. In the Epa+Epu group, the content and productivity of total phenolics, flavonoids, and caffeic acid derivatives increased, a monomer of caffeic acid derivatives (caffeic acid) that is absent in single-species cultures (Epa or Epu) were synthesized; moreover, Epa+Epu also showed the highest antioxidant activity. The inoculum proportions in Epa+Epu significantly influenced the co-culture effect; among the proportion groups (Epa:Epu = 1:6, 2:5, 3:4, 1:1, 4:4, 5:2, and 6:1), the Epa:Epu proportion of 4:3 was the most favorable for AR biomass and bioactive compound accumulation, and the antioxidant activity also peaked at 4:3 proportion. In addition, the co-culture system is suitable for large bioreactors (10 and 20 L), wherein the AR biomass increased without a decrease in the amount of bioactive compounds. A co-culture system was thus successfully established in this study, and AR cultures are expected to be used as an alternative raw material for the production of Echinacea-derived products.