High production of ginsenosides by transformed root cultures of Panax ginseng: effect of basal medium and Agrobacterium rhizogenes strains.
Successful transformation of Panax ginseng was achieved when petiole segments were infected with Agrobacterium rhizogenes ATCC 15834 and MAFF 03-01724. Transformed roots were obtained after galls developed at infected sites. The root morphology, growth and ginsenoside productivity of roots transformed with different bacterial strains differed, and the roots from A. rhizogenes ATCC 15834 grew better and produced much more ginsenosides. Using the ATCC transformed root clone, various liquid culture media were tested to determine the optimum culture medium for ginsenoside production. The root growth was optimum in phytohormone-free Gamborg B5 liquid medium, however highest content of ginsenosides (a total of five ginsenosides 1.88% dry weight) was obtained when the roots were cultured in half-macro-salt strength Gamborg B5 liquid medium. Growth of the roots over a period of 8 weeks showed that their fresh and dry weight continued to increase. The ginsenoside Rb1 content was optimum after 5 weeks of culture. Ginsenoside Rc content began to decrease slightly after the third week of culture. Ginsenosides Rd and Rg1 contents fluctuated, while ginsenoside Re content continued to rise throughout the 8 weeks of culture. Ginsenoside production, however, did not peak within the 8 weeks of culture.