Liquid Culture Systems for in vitro Plant Propagation

Application of bioreactor systems 101
3.3 pH
Changes in pH during culture have been reported by several authors
(Dussert et al., 1995; Hilton and Wilson, 1995; Yu, 2000; Lian et al., 2002b).
These changes appeared to be related to the balance between ammonium in
the medium - as shown by several authors (Hilton and Wilson, 1995;
Escalona et al., 1999; Lian et al., 2002b). Clear inhibitory effects of a culture
at pH 5.0 on embryogenesis were found by Lazzeri et al. (1987). Precise
recording of fluctuations in parameters, like pH in computer controlled
bioreactor cultures, will improve the repeatability of complex biological
process.
3.4 Nutrients
Nutrient availability is a major chemical factor involved in scaling up.
For large-scale culture in a bioreactor several aspects play an important role.
Periodic measurement of the individual nutrients at different times provides
information regarding nutrient uptake, biomass and metabolite production in
bioreactors. We investigated detailed analysis of the dynamics of various
nutrient compounds during Lilium bulblet growth in BTBB and it was found
that ammonium, nitrate and phosphate became exhausted from the medium.
After 16 weeks of culture considerable amounts of K + , Mg 2+ , Ca 2+ , Na + and
Cl - were still present in the medium, but the limiting growth factor was
sugar, rather than the main nutrient (Lian et al., 2002b). Similar
investigations were carried out with Begonia, rice suspension culture, carrot
somatic embryo, ginseng adventitious roots and potato microtuber growth
during bioreactor culture (Törmälä et al., 1987; Schmitz and Lörz, 1990;
Archambault et al., 1995; Yu, 2000; Yu et al., 2000). In spite of these
results, there is still a need for detailed investigation on hormonal
interactions and the dynamics of various nutritional compounds. Offline
analyses of changes in nutrient and hormone concentrations during
bioreactor culture will present new possibilities for the better manipulation
of embryogenesis and organogenesis.
4. Bioreactors in automated masspropagation
For production of cells, somatic embryos or organogenic propagules (e.g.
bulblets, corms, nodules, microtubers or shoot clusters), bioreactor culture is
one of the most promising ways for scaling up the system and there have
been several reports on large-scale propagation of horticultural and
medicinal plants by using bioreactors. However, inconsistencies in