Abstract:

In the present study, effects of different host strains of Bacillus licheniformis on the expression and secretion
of α-amylase were investigated. Firstly, the α-amylase expression vector, named pP43SAT, was constructed based on
the promoter P43 from Bacillus subtilis and the signal peptide, coding region and terminator of α-amylase gene from
B. licheniformis WX-02. The pP43SAT plasmids were then transformed into the B. licheniformis host strains WX-02
(ΔamyL), BL9 and BL10B, respectively, to obtain the α-amylase genetic engineering strains WX-02 (ΔamyL; pP43SAT),
BL9 (pP43SAT) and BL10 (pP43SAT), respectively. The α-amylase fermentation processes of these engineered strains
were compared. The α-amylase activities of strains BL9 (pP43SAT) and BL10 (pP43SAT) reached 94.01 and 101.94 U/mL,
respectively, which were increased by 21% and 31%, respectively, as compared with that of WX-02 (ΔamyL; pP43SAT).
These results showed that the novel host strains BL9 and BL10 contributed to the secretion and expression of α-amylase.
It was proved that the deletion of multiple proteases genes could enhance α-amylase expression obviously, and this study
provided the novel host strains and novel strategies for efficient expression of α-amylase.

Key words: α-amylase, Bacillus licheniformis, host strain, secretion and expression