An on-line feed rate control system for baker’s yeast production using the molasses uptake rate as a feeding index was developed. The optimal feed rate was obtained by maximising the feeding index. The experiments were performed to test this control system in fermenter of 30 m(3) total capacity. In baker’s yeast process 2760 kg M(50) was consumed and 2852 kg compressed yeast (D-c) was produced. Cell yield, final molasses dilution and final yeast concentration were 1.0 kg D-c/kg M(50), 1:6.5 and 52 g D-100/l, respectively. These results found that the developed feed rate control system is to be successful.