AbstractFive reactor systems (free cell batch, free cell continuous, entrapped cell immobilized, adsorbed cell packed bed, and cell recycle membrane reactors) were compared for ethanol production from xylose using Escherichia coli FBR5. In the free cell batch and free cell continuous reactors (continuous stirred tank reactor‐CSTR) productivities of 0.84 gL−1 h−1 and 1.77 gL−1 h−1 were achieved, respectively. A cell recycle membrane reactor resulted in the highest productivity of 55.56 gL−1 h−1, which is an increase of 66‐fold (e.g., 6614%) over the batch reactor. Calcium alginate gel CSTR resulted in a productivity of 2.04 gL−1 h−1 whereas adsorbed cell packed bed reactor resulted in a productivity of 4.39 gL−1 h−1. In the five reactor systems, ethanol concentrations ranged from 18.9 to 40.30 gL−1 with metabolic yields from 0.44 to 0.51. Published 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012