The extracellular invertase from Zymomonas mobilis (INVB) was used as a model protein to study the recombinant protein production by Escherichia coli. The effect of temperature, induction and post-induction time on expression of soluble INVB protein was studied in a bench-top fermenter. The maximum productivity of soluble protein (2.7 gl(-1) h(-1)) was obtained by decreasing the temperature (0.05 degrees C min(-1)) from 37 to 27 degrees C after induction with IPTG at the beginning of stationary phase. Under these conditions, the productivity of soluble INVB protein was increased by factor of 10, in relation to the process carried out overall at 37 degrees C. (c) 2006 Elsevier Inc. All rights reserved.