T7 expression system in Bacillus subtilis utilizing the rhiL promoter responsive to pectin and glucose.

Abstract

We developed a T7 expression system in Bacillus subtilis, incorporating the rhiL promoter responsive to pectin and glucose to control the T7 RNA polymerase gene (T7 pol). Using the egfp reporter gene under the T7 promoter in a multicopy plasmid, we demonstrated that the EGFP expression was robustly induced by pectin and effectively repressed by glucose. These non-toxic and highly soluble effector compounds facilitate homogeneous expression control and large-scale protein production. The modified system, in which the Shine-Dalgarno sequence upstream of T7 pol was replaced with a highly efficient one from the ylbP gene, achieved a 6.1-fold increase in the maximum expression level upon induction while maintaining tight glucose-mediated repression. Moreover, the modified system's applicability to extracellular protein production was validated by the secretory production of B. subtilis cellulase EglS induced by pectin.