Enhanced extracellular production of α-amylase in Bacillus subtilis by optimization of regulatory elements and over-expression of PrsA lipoprotein

α-Amylase was used as a heterologous model protein to investigate the effects of promoters, signal peptides and over-expression of an extra-cytoplasmic molecular chaperone, PrsA lipoprotein, on enhancing the secretion of α-amylase in Bacillus subtilis. Four promoters and six signal peptides were compared, successively, and the highest yield of α-amylase was achieved under the promotion mediated by PAₚᵣE, a strong constitutive promoter, and secretion by SPₙₚᵣE, a signal peptide from B. subtilis. Moreover, under conditions of overexpressed PrsA lipoprotein, the secretion production and activity of α-amylase increased to 2.5-fold. The performance of the recombinant B. subtilis 1A751PL31 was evaluated with a fed-batch fermentation in a 7.5 l fermentor. Optimization of regulatory elements and over-expression of PrsA lipoprotein had a significant effect on enhancing the production of α-amylase in B. subtilis.