Design and optimal operation of an enzymatic process depend on the characteristics of the free- vs. immobilized-enzyme, purification problems, materials and operation costs. When the enzyme stabilization is not fully successful, the optimal choice of the reactor type and operation mode is depending on the process and enzyme deactivation characteristics. Quick simulation of operation modes based on the process kinetics and a library of reactor models can help in comparing alternatives for getting the final decision. The analysis is exemplified for two enzymatic processes, by determining the optimal operating policy for several tested reactors: classic batch, batch with intermittent addition of enzyme, semi-batch reactor, continuously operated packed-bed column, or a mechanically agitated reactor with immobilized enzyme in small beads. Prediction of reactor performances points out the best choice for the given enzyme characteristics, and also conditions allowing to switch the production from large-volume batches to the continuous operation mode. (C) 2011 Elsevier Ltd. All rights