Effect of nitrogen concentration, source, and phosphate concentration on accumulation of biomass and calycosin-7-O-β-D-glucoside in Astragalus membranaceus adventitious roots

Abstract

Calycosin-7-O-β-D-glucoside (CG), a methoxylated isoflavonoid in Astragalus membranaceus Fisch. (Bunge), has a wide range of biological activities. Adventitious root culture is an alternative source to obtain active compounds. To improve CG production in A. membranaceus adventitious roots (AMARs), effect of nitrogen concentration, and phosphate concentration on accumulation of biomass, CG, and hydrogen peroxide were investigated. A low concentration of nitrogen promoted growth and CG accumulation in AMARs. Maximum biomass and CG productivity were obtained at a nitrogen concentration of 3 mM. Nitrate, rather than ammonium, was suitable for CG production. Phosphate concentration did not influence biomass accumulation; however, high concentration of phosphate (2.5 mM) was most favorable for CG accumulation. Furthermore, moderate levels of hydrogen peroxide promoted CG accumulation. Optimal concentrations of nitrogen and phosphate were used in scale-up culture of AMARs using a bioreactor. There was a 8- and 2- fold increase in the CG content and antioxidant activity, respectively, using a B5 medium containing 3 mM NO3− and 2.5 mM phosphate when compared to the standard B5 medium, which was equivalent to those observed in field-grown plants. Therefore, optimization of nitrogen and phosphate concentration in the medium is a simple and effective method to economically improve production of CG in AMARs.