High-level extracellular production of alkaline polygalacturonate lyase in Bacillus subtilis with optimized regulatory elements

The present work aims to construct a robust recombinant Bacillus subtilis to achieve secretory production of alkaline polygalacturonate lyase (PGL). First, 6 signal peptides (amyX, bpr, vpr, yvgO, wapA and nprE) were screened with a semi-rational approach and comparatively investigated their effects on the production of PGL. The signal peptide bpr directed efficient PGL secretory expression and increased PGL titer to 313.7 U mL−1. By optimizing and applying strong promoter P43 and Shine−Dalgarno sequence, higher titer of 446.3 U mL−1 PGL was achieved. Finally, the capacity of the recombinant B. subtilis WB43CB was evaluated with a fed-batch strategy in 3 L fermentor. The PGL titer reached 632.6 U mL−1 with a productivity of 17.6 U mL−1 h−1, which was the highest secretory production of PGL by the B. subtilis system. The recombinant B. subtilis strain WB43CB constructed in the present work has great potential in production of alkaline PGL.