A robust adaptive control strategy for a class of continuous-flow bioreactor process where the intrinsic reaction rates are poorly know is provided. A numerical observer is used to obtain on-line discrete estimates of the main uncertainties (kinetics term, yield production, and biomass concentration) of a continuous bioreactor. With this estimate, a linearizing feedback control law is obtained which provides robust regulation against uncertainties, disturbances and additive noise on the substrate concentration measurements. The performance of the closed-loop system is illustrated via numerical simulations.