Cryopreservation of Dedifferentiated Cell Cultures

When Gottlieb Haberlandt made the first efforts to cultivate single isolated plant cells in salt solutions his goal was to prove the totipotency of single cells (Haberlandt 1902). The cultivation of isolated plant cells in a chemically defined culture medium became possible only after the discovery and application of auxins (Gautheret 1939). Today plant cells as well as tissues can be cultivated in vitro for many applications in plant breeding, plant propagation, germplasm preservation and molecular biology.

The idea to produce valuable plant metabolites by large-scale fermentation of cell cultures was soon born (Routien and Nickel 1952). Scientists were fascinated by the idea of using dedifferentiated cell cultures as a replacement for intact plants in research and biotechnology. Tulecke and Nickell (1959) wrote: “…in essence these cell cultures represent a new kind of microorganisms…” The formation of a number of secondary metabolites was detected in the new material and in some cases the concentration of these compounds in the cell cultures exceeded even that in intact plants (for review see Carew and Staba 1965). The concept to produce such valuable compounds by growing cell cultures in fermentation vessels offers many advantages: the production is independent from specific climatic conditions and it can be carried out under defined and sterile conditions. Furthermore, the production of extractable raw material from plant cell cultures can be quicker than with intact plants, especially for plants like ginseng where harvest starts many years after planting and destroys the plants. Other candidates for cell mass production by cell culture are plants growing extremely slowly or where the content of a certain compound is extremely low like for the drug paclitaxel in Taxus plants.

Although in many cases high concentrations of certain compounds were obtained in plant cell cultures, like rosmarinic acid in Coleus blumei cell lines (see Berlin 1997), ginsenosides in Panax ginseng cell cultures (Thanh et al. 2005) or Raucaffricine in cell lines of Rauvolfia serpentina (Schuebel and Stoeckigt 1984), examples for the economic application of large scale fermentation of dedifferentiated plant cell cultures remain rare. The first process was established by the Mitsui Petrochemical Company for the production of Shikonin, a red-colored antimicrobial compound traditionally used in Japan (Fujita et al. 1982). Presently the best known example is the production of paclitaxel by Phyton in a large scale fermentation facility specific for plant cell cultures close to the city of Hamburg (Venkat 1998).