Expression of human Insulin-like Growth Factor-1 in Escherichia coli induced by lactose

OBJECTIVE The optimal conditions for the expression of recombinant human insulin-like growth factor-1 fragment in Escherichia coli strain DH5α by using lactose as the inducer were studied.METHODS The recombined plasmid pET32a(+)/hIGF-1 was transformed into Escherichia coli strain DH5α.Lactose was used as an inducer instead of IPTG.The induction conditions in the Escherichia coli strain DH5α in different situations such as concentration of inducer,the time of culture before induction,the time and the temperature of induction culture were studied by SDS-PAGE e.g.and then optimized properly.RESULTS It was found that expression level of IGF-1 induced by lactose achieved the highest after Escherichia coli DH5α had been induced for 4h with 0.8% lactose beginning from strain density of OD600=0.7 at 37℃.The expression level of IGF-1 was about 40%-60% of the total cellular proteins,which is close to the level induced by IPTG.CONCLUSION Lactose could be used as a promising inducer in the production of recombined hIGF-1 in Escherichia coli.