Abstract
Cell growth and reaction characteristics within cell-immobilizing particles were investigated using the ethanol production system by Zymomonas mobilis to clarify the effect of mass-transfer resistance caused by cell growth on the overall reactivity of the immobilizing particles. For the immobilization of growing cells, the cell concentration at each position in the immobilizing particle increases monotonously with time, and after a certain period of cultivation the cell distribution and overall production rate reached steady state. However, the non-monotonous change with a peak of the production rate was observed with the elapse of time in the transient state. A novel method is proposed to restrict the overgrowth and consequently to enhance overall productivity in the steady state of the immobilized-cell biocatalyst, i.e., co-immobilization of microporous solid particles with growing cells. Also, a method to estimate the extent of the influence of co-immobilization of microporous particles was demonstrated, using a mathematical model.
