Expression of Recombinant Gene in E.coli Using Lactose as Inducer

Objective To study the factor influencing the fermentation of recombinant E.coli strain using lactose as an inducer instead of IPTG.Methods Incubate the recombinant E.coli BL21(DE3)/S strain expressing the spike protein of SARS virus in spinner,using glucose and glycerol as carbon source and the lactose and isolactose at various concentrations as inducers.Verify the test result by the fermentation in a 40 L fermentor.Results In spinner,the lactose at a concentration of more than 0.5 mmol/L induced the expression of target protein,and the expression level was equivalent to that induced by IPTG.Glucose could inhibit the induction of lactose but could not inhibit the induction of isolactose.However,the glycerol as carbon source showed no inhibitory effect on the induction of lactose or isolactose.In fermentor,the existence of glucose at early stage inhibited the induction of lactose.Conclusion In the expression system of recombinant bacterial strain using lactose operon,lactose may be used as an inducer.However,non-glucose carbon source shall be used at the stage of induction.