Multiphase Bioreactor Design

CONCLUSIONS

Large-scale cultivation of plant cell suspensions for the production of valuable
phytochemicals is certainly feasible, although commercial application has been
comparatively limited. Under the current biological and processing conditions, plant cell-
based processes are commercially viable only for high value products. Analysis of
experience with plant cell suspensions, to date, suggests a framework for a rational
approach to the design and scale-up of bioreactors, based on conventional microbial
fermentation technology. However, a radical rethinking of conventional bioreactor design
may facilitate wider application of the technology, by reducing processing costs. There
are still significant gaps in our understanding of the interplay between the hydrodynamic
environment in any bioreactor and the cellular metabolism. Slow system growth rates,
coupled with the diversity and variability of plant cell Unes, have been real obstacles to
the accumulation of the same wealth of knowledge that exists for other, more
commercially significant biocatalysts.

ACKNOWLEDGEMENTS

The author is grateful for the co-operation of the following individuals in the preparation
of this chapter: Professor Wayne Curtis, Professor Pauline Doran, Dr. Ken Hibino, Dr.
Dermot Malone, Dr. Frank MacLoughlin, Dr. Kazuya Otsuji, Dr. Om Sahai, Dr. Yoseph
Shaaltiel, Dr. Shigeru Takahashi and Dr. Graham Wilson.

NOMENCLATURE

Symbols

Ad/Ar ratio of downcomer-to-riser cross sectional area (−)

ccrit critical dissolved oxygen concentration (% of air

saturation)

c* equilibrium dissolved oxygen concentration (mmol L−^1 )

Table 14.6 Choice of bioreactor operating strategy,

based on product formation and location patterns

(adapted from Payne et al., 1991)

Product formation Growth-

associated

Non-growth-associated

Operating strategy^ extracellular intracellular extracellular intracellular

Batch (^)
Fed-Batch (^)
Repeated (fed) batch/semi-
Bioreactor design for plant cell suspension cultures 443