In this work, the key problem of estimation in bioprocesses when no structu
ral model is available is dealt with. A nonlinear observer-based algorithm
is developed in order to estimate kinetic rates in batch bioreactors. The a
lgorithm uses the measurements of biomass concentration and either substrat
e concentration or redox potential to perform the estimation of the respect
ive specific kinetic rates. For this purpose, a general mathematical model
description of the process is provided. The estimation algorithm design is
based on a nonlinear reduced-order observer. The observer performance is va
lidated with experimental results on a Thiobacillus ferrooxidans batch cult
ure. (C) 2000 Elsevier Science B.V. All rights reserved.