Liquid Culture Systems for in vitro Plant Propagation

104 K. Y. Paek et al.
cosmetics, which are distributed around the world. Until now, ginseng has
been reported to contain saponins, antioxidants, peptides, polysaccharides,
fatty acids, alcohols and vitamins (Huang, 1993). The saponins, known as
ginsenosides, are widely believed to be the major bioactive compounds of
ginseng.
Generally, the ginseng roots on the market are from farms. Field
cultivation is a time-consuming and labour-intensive process, so the use of
the plant cell and tissue culture process has been investigated as an
alternative for the more efficient production of ginseng.
Ginseng tissue culture was first documented in 1964 (Luo et al., 1964);
since then numerous studies have been reported (as reviewed by Wu and
Zhong, 1999). The large-scale suspension culture of ginseng cells was first
reported by Yasuda et al. (1972). An industrial scale ginseng cell culture
process was initiated in the 1980s at the Nitto Denko Corporation (Ibaraki,
Osaka, Japan) using 2,000 and 20,000-litre STR bioreactors to produce
ginseng biomass. Two types of bioreactors are commonly used for these
plant cell suspension cultures: STR and air-lift types. Studies on ginseng
cells in STRs suggested that the agitator design and the agitation rate are
major factors affecting cell growth and saponin production (Furuya et al.,
1984). Up to now, the industrial application of ginseng cell culture has found
only a few commercial applications worldwide. The reasons are probably
due to the slow growth of ginseng cells and the higher water content of
cultured cells compared with field-grown plants. Transformed root (hairy
root) cultures offer a promising alternative method that can partially avoid
these problems (Yosikawa and Furuya, 1987; Yu, 2000), but hairy roots
usually produce opine-like substances which are lethal to mammalian cells.
Therefore, we started work on ginseng adventitious root culture, which
provides an efficient means of biomass production due to their fast growth
and stable metabolite production. A series of experiments was conducted to
establish efficient ginseng adventitious root growth and ginsenoside
production in liquid media (Yu et al., 2001a; Son and Paek, 2001) and
subsequently we established a pilot-scale culture of multiple adventitious
roots induced from callus using a BTBB bioreactor system (Figure 3 a, d and
e) (Yu et al., 2000a;Yu et al., 2001a, b; Choi et al., 2001). In the bioreactor,
roots were tangled and formed ball-like structures. Root interiors became
brown and their saponin content decreased sharply compared to actively
growing roots. Cutting root cultures during the culture period appears to be a
necessary procedure to promote root growth and prevent deterioration.
Therefore, multiple adventitious roots growing in bioreactors were sliced by
a blade connected to the top-driven motor. We measured a 150-fold growth
rate increase obtained at day 56 of culture when roots were cut during the
culture in a 500-litre BTBB: the total saponin content in harvested