High-level constitutive gene expression can result in cellular metabolic imbalance and limit production. To circumvent these problems, a P-alsSD-controlled auto-inducible 2-ketoisovalerate biosynthetic pathway and a P-spac-controlled IPTG-inducible Ehrlich pathway were constructed in Bacillus subtilis to modulate gene expression. Based on the precise gene expression characteristics of the two inducible pathways, the optimal IPTG induction time point and dose for 2-methyl-1-propanol biosynthesis were determined as 9.5 h and 300 mu M, respectively. Under the optimized conditions, strain BSU Delta L-03 with inducible pathways produced up to 3.83 +/- 0.46 g 2-methyl-1-propanol/l, which was about 60 % higher than BSUL04 with constitutive pathways.