A rule based fuzzy controller (FLC) is developed for stabilization of
an unstable continuous stirred tank bioreactor (CSTBR) from various st
art-up conditions. The output variable is the reactor substrate concen
tration and the manipulated variable is the dilution rate. The perform
ance of the FLC is evaluated by simulating a mathematical model of an
unstable CSTBR. FLC is robust to perturbations in the specific growth
rate, specific consumption rate and also to a disturbance in the feed
substrate concentration. The performance of the FLC is superior to tha
t of a conventional proportional controller.