High-level Expression of Douchi Fibrinolytic Enzyme (DFE) in Bacillus subtilis WB800

A novel fibrinolytic enzyme gene was cloned from a Douchi producing strain, Bacillus subtilis DC 12. To efficiently expressed Douchi fibrinolytic enzyme (DFE) in B. subtilis, the overlapping promoter P43 sequence cloned from B. subtilis 168 and a B. subtilis terminator were fused by overlapping PCR, and inserted into pBE3 to yield a novel vector, pBEP43. Then the encoding DFE gene was cloned into pBEP43 and expressed in B. subtilis WB800 under the control of promoter P43. Results showed that DFE was efficiently expressed during the exponential growth and stationary time, and secreted into the medium. The maximum fibrinolytic activity level of 1270U/mL was 1. 87-fold to its expression mediated by its own promoter in B. subtilis WB800, 4. 1-fold to that of the wild-type strain B. subtilis DC 12.