The Influences of Lactose as an Inducer on Expression of Human β-defensin 3 in E.coli

The inductive conditions used lactose as inducer for the flask-shaking of E.coli BL21-pET-hBD_ 3 have been studied. The effect of three factors which were lactose concentration , induction time and temperature on growth of strains and on the yield of hBD_ 3 was analyzed in detail. The result indicated that high lactose concentration inhibit the growth of strains(P0.01) but had little effect on expression of target protein among 0.5%-5%(P0.05). Biomass would be improved as time passed(P0.01), but the yield of expressed protein didn′t increase obviously (P0.05). The greater expressed level of hBD_ 3 , as high as 28.1% of total strain protein, could be gained when strain was induced by 0.5% lactose at 37℃ for 4h. The effect using lactose as inducer is almost as same as using IPTG as inducer under control conditions.