A previously proposed model of a transketolase catalysed carbon-carbon bond formation reaction condensing beta-hydroxypyruvate and glycolaldehyde to synthesise L-erythrulose has been extended to describe various modes of operation as an alternative to a batch process. The alternative continuous and fed-batch operations, with each substrate being fed separately and together have been analysed using the extended model. The analysis was carried out simulating the product concentration after a given time under defined process conditions. Comparison of product concentration and yield on catalyst as two process metrics were used to identify promising cases for further process development. (C) 2009 Elsevier B.V. All rights reserved.