A synthetic lactose-inducible promoter was chosen; to study host cell responses to the over-expression of heterologous genes. Fermentations were conducted to compare the effect of induction strategies on the synthesis of beta-galactosidase versus the production of recombinant protein. The levels of lactose, IPTG and glucose during induction were manipulated to adjust the utilization of lactose as the inducer and/or the carbon source. In addition, the involvement of the gal operon in lactose metabolism was also explored in order to optimize lactose transport and utilization during induction.