On the basis of the optimized substrate feeding rate of glucose acquired from an artificial neural network model of yeast fed-batch fermentation, an adaptive fuzzy neural network controller (FNNC) was developed, and on-line experiments were performed to examine the feasibility of the controller for actual use. The objective is to obtain a high concentration of cell mass in the shortest fed-batch culture time. Experimental results reveal that FNNC-controlled on-line feeding of substrate performs well.