Effects of temperature shift strategies on human preproinsulin production in the fed-batch fermentation of recombinantEscherichia coli

Preproinsulin is a well-known precursor of human insulin for the regulation of blood glucose levels. In this study, fed-batch fermentations of recombinantEscherichia coli JM109/pPT-MRpi were carried out for the overexpression of human preproinsulin. The expression of human preproinsulin was controlled by the temperature inducibleP2 promoter. The time-course profiles of fed-batch fermentation and SDS-PAGE analysis showed that human insulin expression was triggered by a culture temperature change from 30 to 37°C. Fermentation shift strategies, including the multi-step increase of temperature and the modulation of initiation time, were optimized to obtain high titers of cell mass and preproinsulin. The optimized fed-batch fermentation, consisting of a three-step shift of culture temperature from 30 to 37°C for 2 h, gave the best results of 43.1 g/L of dry cell weight and 33.3% preproinsulin content, which corresponded to 2.0- and 1.2-fold increases, respectively, as compared to those of fed-batch culture at a constant temperature of 37°C.