The bacteriophage T7 expression system is one of the most popular methods used to produce recombinant proteins in prokaryotic cells. IPTG is generally used as the inducer. Without the reconstruction of expression vector or the use of different expression system, a novel induction strategy to enhance the level of protein expression is reported in this study. Our results show that the yield of purified glutamate mutase S component (MutS) protein is increased three-fold by reducing the induction temperature to 20 degrees C and using 0.2% lactose and 50 mg/L IPTG simultaneously as inducers. Similar results are also observed in the production of other recombinant proteins. This strategy proved to be more efficient and cheaper for high-level expression of a foreign gene under the control of the T7 expression system in Escherichia Coli, making it suitable for laboratory-scale preparation of recombinant proteins. (c) 2005 Elsevier Inc. All rights reserved.