Optimizing elicitation strategy of salicylic acid for flavonoid and phenolic production of fed-batch cultured Oplopanax elatus adventitious roots.

Oplopanax elatus is a valuable medicinal plant, but its plant resource is lacking. Adventitious root (AR) culture of O. elatus is an effective way for the production of plant materials. Salicylic acid (SA) exerts enhancement effect on metabolite synthesis in some plant cell/organ culture systems. To clarify the elicitation effect of SA on fed-batch cultured O. elatus ARs, this study investigated the effects of SA concentration, and elicitation time and duration. Results showed that flavonoid and phenolic contents, and antioxidant enzyme activity obviously increased when the fed-batch cultured ARs were treated with 100 µM SA for 4 days starting on day 35. Under this elicitation condition, total flavonoid and phenolic contents reached 387 rutin mg/g DW and 128 gallic acid mg/g DW, respectively, which were significantly (p < 0.05) higher than those in the SA-untreated control. In addition, DPPH scavenging and ABTS+ scavenging rates, and Fe2+ chelating rate also greatly increased after SA treatment, and their EC50 values were 0.0117, 0.61, and 3.34 mg/L, respectively, indicating the high antioxidant activity. The findings of the present study revealed that SA could be used as an elicitor to improve the flavonoid and phenolic production in fed-batch O. elatus AR culture.

Selection of initial culture medium in fed-batch bioreactor culture of Rhodiola sachalinensis cells.

In fed-batch culture, numerous factors, such as initial culture conditions and feeding strategies, affect the culture efficiency. Among the factors, the effect of initial culture medium is rarely investigated. In this work, Rhodiola sachalinensis cells were cultured in the fed-batch bioreactor system and the effects of volume, medium strength, and sucrose concentration of initial culture medium on biomass and accumulation of salidroside, polysaccharides, flavonoids, and phenolics were investigated. The results showed that an initial medium volume of 3 L significantly (p < 0.05) increased biomass and the four bioactive compound contents. The maximum biomass and the highest contents of different bioactive compounds were determined at various MS medium strengths. Therefore, analytic hierarchy process (AHP) - technique for order preference by similarity to ideal solution (TOPSIS) was implemented and half-strength MS medium was selected. Furthermore, the effect of sucrose concentration was examined and 30 g/L sucrose in the initial medium was optimal, at which concentration, 39.45 mg/g DW of salidroside, 531.25 mg/g DW of total polysaccharides, 3.89 mg/g DW of total flavonoids, and 10.84 mg/g DW of total phenolics were produced. The findings of the present study provided a reference for further establishing the fed-batch culture system of R. sachalinensis cells.