High expression of Bacillus licheniformis alpha-amylase with a Bacillus secretion vector

A gene coding for the heat-stable alpha-amylase from Bacillus licheniformis ATCC14580 has been expressed with the aid of a B. amyloliquefaciens alpha-amylase-based expression/secretion vector by joining the structural part of the gene to a pool of vectors after the B. amyloliquefaciens alpha-amylase promoter and signal sequence. The recombinant plasmids obtained were stably maintained in B. subtilis and the heat-stable alpha-amylase activity rose several hundred times from the level of the donor. Eight different constructions were further analyzed. Each of them had an intact B. amyloliquefaciens signal sequence, the only difference being in a few nucleotides beyond the C terminus of the signal peptide. This, however, was enough to cause up to fourfold differences in protein yield. Possible reasons for the variation in the production level are discussed.