In this paper, we have integrated process characterisation and reaction kinetic data for a transketolase catalysed carbon-carbon bond formation to build a comprehensive reaction model. Based on the synthesis of erythrulose from beta-hydroxypyruvate and glycolaldehyde, the model includes component degradation as a function of time and concentration as well as glycolaldehyde toxicity towards the enzyme. Using the ratio of initial substrate concentration as a process variable, simulations and analysis based on this model allowed process options to be evaluated. The model links bioconversion to upstream fermentation for enzyme production and downstream product purification and this could provide guidelines for process development. (c) 2007 Elsevier Ltd. All rights reserved.