High conversion frequency of germinated somatic embryos of Siberian ginseng (Eleutherococcus senticosus Maxim) using a bubble column bioreactor

Embryogenic callus was obtained from young petiole, stem, and root explants of 4-year-old Siberian ginseng plants on medium supplemented with 2,4-dichlorophenoxyacetic acid. Embryogenic callus differentiated into somatic embryos (SEs), most of which could germinate but developed abnormally. Friable embryogenic callus was induced mainly from the root regions of germinated primary SEs or regenerated plantlets on plant growth regulator-free medium. Histological studies showed that the embryogenic callus initiated from the subepidermal cells of young roots. The bioreactor system was more efficient than suspension culture regarding the number and growth of SEs, although a similar amount of embryonic tissue was used. An average of 115,370 germinated SEs developed from an initial 400 mg of embryogenic callus, and 64.7 % of germinated SEs converted into plantlets after a 4-weeks culture on agar medium. During the bioreactor culture process, secondary SEs were induced directly from SEs at various stages, a phenomenon that rarely occurred in suspension culture. These secondary SEs developed quickly and germinated during the bioreactor culture process. Proline content and peroxidase and catalase activities of SEs cultured in bioreactors were higher than in SEs cultured in suspension culture.