Development of a bioreactor suitable for embryogenic rice callus culture

Embryogenic rice calli induced from mature rice (Oryza sativa L., Sasanishiki) were cultured in a jarfermentor with disk turbine impellers, an air-lift reactor, and a turbine-blade reactor (TBR(R)), and the effects of agitation were investigated. In all cases, the growth inhibition was observed, though a slightly improved regeneration frequency was obtained in the TBR. To overcome the growth inhibition, small cubes of polyurethane foam were used as immobilization supports in the TBR culture. Supports accumulated around the cylindrical stainless-steel mesh in the reactor and rice calli were observed growing in them. Polyurethane foam with an average pore size of 1.3 mm gave the maximum ratio of immobilized cells during 1-week culture. When 5- or 10-mm cubes were used, supports were observed floating on the medium surface, but 3-mm cube supports accumulated uniformly around the stainless-steel mesh and were found to be suitable for the immobilized culture of rice calli. Three-millimeter cube supports corresponding to 5% by volume were added to 600 ml medium in the TBR and the effects of the agitation speed on the cell growth and regeneration frequency were investigated. At all the agitation speeds examined, no significant decrease in either the cell growth or the regeneration frequency occurred. From these results, it was concluded that the TBR is a suitable reactor for the propagation of embryogenic rice calli and that immobilization supports with 1.3 mm of average pore size are effective in preventing hydrodynamic stress as well as in supplying nutrients to the immobilized calli.