46 Fermentation and Biochemical Engineering Handbook tissue culture nurseries throughout the world. Most of these tissue culture nurseries are using flasks or bottles containing agar medium for commercial propagation, but the efficiency is also low. In order to improve the efficiency, use of a bioreactor is desirable. Using a small bioreactor (4 to 10 liters), the author has produced over 4, 000 to 10, 000 plantlets within I to 2 months. The bioreactor system allows the induction of somatic embryos from vegetative cells which then leads to the production of artificial seeds(Rodenbaugh et al 1987).2 3. 4 Bioreactors-Hardware Configuration The configuration of bioreactors most frequently used for plant cell tissue, and organ cultures is fundamentally the sameas that used for microbial or animal cell cultures. However, in plants, the cells, tissues, and organs are all susceptible to mechanical stresses by medium aeration and agitation. At times, the production of both cells mass and metabolites is repressed severely and the bioreactor must therefore have the characteristics of low shear stresses and efficient oxygen supply. For these reasons, different bioreactors (Fig. 18)have been investigated in order to select the most suitable design Wagner and Vogelmann( 1977)3 have studied the comparison of different types of bioreactors for the yield and productivity of cell mass and anthraqui- none(Fig. 19). Among different types of bioreactors, the yield of anthraqui- nones in the air-lift bioreactor was about double that found in those bioreactors with flat blade turbine impellers, perforated disk impellers, or draft tube bioreactors with Kaplan turbine impellers. It was also about 30% higher than that of a shake flask culture. Thus, the configuration of the bioreactor is very important and development efforts are underway for both bench scale and pilot scale bioreactors Aeration-Agitation Bioreactor. This type of bioreactor(Fig. 20)is popular and is fundamentally the same as that used with microbial cultures For small scale experiments, the aeration-agitation type bioreactors is widely used. However, when the culture volume is increased, many problems arise The following are some of the scale-up problems in large aeration-agitation bioreactors: (i)increasing mechanical stresses by impeller agitation and (ii) increasing foaming and adhesion of cells on the inner surface of the bioreactor. Despite these problems, a large scale pilot bioreactor(volume 20 kl)was constructed. It successfully produced both cell mass and metabolites This bioreactor is therefore the most important type for bioreactor systems46 Fermentation and Biochemical Engineering Handbook tissue culture nurseries throughout the world. Most of these tissue culture nurseries are using flasks or bottles containing agar medium for commercial propagation, but the efficiency is also low. In order to improve the efficiency, use of a bioreactor is desirable. Using a small bioreactor (4 to 10 liters), the author has produced over 4,000 to 10,000 plantlets within 1 to 2 months. The bioreactor system allows the induction of somatic embryos from vegetative cells which then leads to the production of artificial seeds (Redenbaugh et al., 1987).['*] 3.4 Bioreactors-Hardware Configuration The configuration of bioreactors most frequently used for plant cell, tissue, and organ cultures is hndamentally the same as that used for microbial or animal cell cultures. However, in plants, the cells, tissues, and organs are all susceptible to mechanical stresses by medium aeration and agitation. At times, the production of both cells mass and metabolites is repressed severely and the bioreactor must therefore have the characteristics of low shear stresses and efficient oxygen supply. For these reasons, different bioreactors (Fig. 18) have been investigated in order to select the most suitable design. Wagner and Vogelmann ( 1977)[131 have studied the comparison of different types of bioreactors for the yield and productivity ofcell mass and anthraqui￾none (Fig. 19). Among different types of bioreactors, the yield of anthraqui￾nones in the air-lift bioreactor was about double that found in those bioreactors with flat blade turbine impellers, perforated disk impellers, or draft tube bioreactors with Kaplan turbine impellers. It was also about 30% higher than that of a shake flask culture. Thus, the configuration of the bioreactor is very important and development efforts are underway for both bench scale and pilot scale bioreactors. Aeration-Agitation Bioreactor. This type of bioreactor (Fig. 20) is popular and is fundamentally the same as that used with microbial cultures. For small scale experiments, the aeration-agitation type bioreactors is widely used. However, when the culture volume is increased, many problems arise. The following are some of the scale-up problems in large aeration-agitation bioreactors: (i) increasing mechanical stresses by impeller agitation and (ii) increasing foaming and adhesion of cells on the inner surface of the bioreactor. Despite these problems, a large scale pilot bioreactor (volume 20 kl) was constructed. It successfully produced both cell mass and metabolites. This bioreactor is therefore the most important type for bioreactor systems