A four-dimensional model for the anaerobic fermentation process, developed and used earlier to simulate the oscillatory behavior of an experimental continuous stir-red tank fermentor is utilized in the present investigation to explore the static/dynamic bifurcation and chaotic behavior of this fermentor, which is shown to be quite rich. The present investigation is a prelude to the experimental exploration of bifurcation and chaos in a membrane fermentor. Dynamic bifurcation (periodic attractors) as well as period doubling sequences leading to different types of periodic and chaotic attractors have been uncovered. It is fundamentally and practically important to discover the fact that in some cases, periodic and chaotic attractors have higher ethanol yield and production rate than the corresponding steady states. (C) 2003 Elsevier Science Ltd. All rights reserved.