Prospects and problems in the large scale production of metabolites from plant cell tissue cultures

A wide range of plant products can be made directly by using plant cell tissue cultures. However, the economic production of even highvalue products from such cultures has not been conclusively demonstrated. One problem is that rapid growth and high product yields often appear to be mutually exclusive with plant cell tissue cultures. Some level of cellular differentiation often is required for the expression of genes associated with product formation; only unorganized cells grow rapidly. Another problem results from the tendency of plant cells to form aggregates, which leads to a mixture of cell types in culture. The biological response is a function not only of the chemical environment but also the physical (e.g. hydrodynamic) environment which makes scale‐up of suspension processes difficult. In addition, cell lysis due to high liquid shear is a significant design constraint. Some of these problems can be circumvented by using multi‐stage continuous culture devices or with immobilized cell reactors. Emphasis will be on membrane entrapped cultures.