Studies on Induction Conditions of Recombinant Escherichia coli Encoding β-Galactosidase

β-galactosidase can be used to hydrolyze lactose of milk into glucose and galactose. Athermostable β-galactosidase gene bgaB from Bacillus stearothermophilus was cloned and successfully expressed in E. coli T7 expression system. The optimum induction conditions, i.e. induction time, inducer concentration and induction length were studied on SOB media by IPTG and Lactose as inducers. The specific enzyme activity reached 11.5 and 7.7 U/mg protein, 90 and 60 times higher than that of original strain, respectively.