Bioreactors for Plant Cell Culture

Abstract

Plant cells are unique biocatalysts that have characters different from microorganisms or animal cells. The features of plant cells and cell cultures are described from an engineering point of view with the aim of secondary metabolite production and micropropagation to supply seedlings. The effects on cell proliferation and productivity of secondary metabolites by culture media and phytohormones are described. Plants contain secondary metabolites such as alkaloids, terpenoids, quinones, and phenylpropanoids that are useful for pigments, fragrances, and pharmaceuticals. Recombinant proteins produced by plant cells are considered safer from virus infection. Several types of bioreactors using plant cells, such as stirred tanks, bubble beds, rotary bioreactors, membrane bioreactors, and reactors for hairy root culture, are also described. Operation procedures are given to realize the effective use of plant cells. In particular, the effects of two-stage culture, initially for proliferation and then for the production of secondary metabolites, are discussed. Fluid dynamic stress affects the viability and activity of plant cells in a large-scale operation. Plant cells are deactivated by dynamic stress imposed by shear stress and turbulence of vortex flow. This negative effect of fluid dynamics is physiologically caused by metabolic inactivation of the cultured cells. Here, the nature of the fluid dynamic stress and some devices to eliminate the effect of dynamic stress are introduced. Optimization procedures for production efficiency are described with respect to signal regulation and the use of elicitors, such as methyl jasmonate. Bioreactors for immobilized plant cells are also described. Immobilized cells are protected from fluid dynamic stresses and stable in metabolic activities, although there is a possibility of mass transfer limitations regarding oxygen, substrate, and product transports. Finally, researches on the industrial application of plant cells are described with future aspects. Plant cell culture is expected to be applied further to the production of useful secondary materials and the somatic embryo production for agricultural application through micropropagation.