Pathogenic fungal elicitors enhance ginsenoside biosynthesis of adventitious roots in Panax quinquefolius during bioreactor culture

Abstract

Fungi have been widely used as biotic elicitors to promote metabolite production of plant cell, tissue, and organ cultures. Alternaria panax Whetz. and Cylindrocarpon destructans (Zinss) Scholten are the main pathogenic fungi in ginseng cultivation. The present study used extracts of A. panax and C. destructans as elicitors to simulate adventitious roots (ARs) of Panax quinquefolius L. for improvement of ginsenoside accumulation during AR bioreactor culture. To select a suitable elicitation method, the effects of treatment duration and concentration of both fungal extracts were investigated. After 30 d of AR bioreactor culture, the addition of A. panax and C. destructans extracts for 8 d to the culture medium produced higher ginsenoside content and productivity than the other treatment periods. During the elicitation of both fungal extracts, the peak contents of nitric oxide (NO), putrescine (Put), and ginsenoside were observed at 2, 4, and 8 d, respectively. Therefore, NO and Put could be upstream signals to regulate ginsenoside synthesis. The optimal elicitor concentration varied between extracts of A. panax and C. destructans. The maximum total ginsenoside content and productivity were observed with 4mg/L and 20mg/L of the A. panax and C. destructans extracts, respectively. The ginsenoside monomers with the most increase were Rg3, Rh2, and Re for the A. panax extract and Rg3, Rh2, and Rf for the C. destructans extract. In addition, the AR biomass was more inhibited by the C. destructans (20mg/L) extract, although its ginsenoside content (34.1mg/g DW) was higher than that with the A. panax (4mg/L) extract. The maximum ginsenoside production (276.0mg/L) was achieved with the A. panax (4mg/L) extract. Therefore, the A. panax extract was more suitable as an elicitor for ginsenoside production during AR bioreactor culture. The present study confirmed that treating 30-d-old P. quinquefolius ARs with 4mg/L A. panax extract for 8 d during bioreactor culture is the optimal elicitation method; these ARs can be applied to the commercial production of P. quinquefolius products.