Effect of nitrogen source on biomass and bioactive compound production in submerged cultures of Eleutherococcus koreanum nakai adventitious roots

Abstract

Ammonium to nitrate ratios of 0:30, 5:25, 10:20, 15:15, 20:10, 25:5, and 30:0 mM were tested to determine the optimal NH(4)(+) :NO(3)(-) ratio for improving biomass and bioactive compound production in Eleutherococcus koreanum Nakai adventitious roots using 3-L bulb-type bubble bioreactors. A high ammonium nitrogen ratio had a negative effect on root growth, and the highest fresh and dry weights were obtained when NH(4)(+):NO(3)(-) ratios were 5:25 and 10:20 (mM) after 5 weeks of culture. Although the total production of eleutherosides B and E was slightly higher at the 10:20 ratio than at the 5:25 ratio (NH(4)(+):NO(3)(-)), we proposed that the optimal NH(4)(+):NO(3)(-) ratio was 5:25 mM. This ratio achieved both the highest total production of five target bioactive compounds (eleutherosides B and E, chlorogenic acid, total phenolics, and flavonoids) and the highest root biomass. Furthermore, increasing NH(4)(+):NO(3)(-) ratios to 10:20 decreased pH in the medium, interrupted the absorption of essential minerals from the culture medium, and resulted in low biomass and increased relative oxidative stress levels, which were evaluated by determining 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Therefore, nitrate rather than ammonium nitrogen was more essential not for only biomass production but also for bioactive compound production in E. koreanum adventitious root cultures. The optimal nitrogen source ratio produced 5.63 g L(-1) of biomass and 24.41 mg of the five total bioactive compounds per gram of biomass (dry weight basis). The development of such in vitro culture technology will benefit the pilot-scale production of E. koreanum-based bioactive compounds for commercialization.