Enhanced alkaline protease production in addition to alpha-amylase via constructing a Bacillus subtilis strain

Bacillus subtilis Bios11 strain was previously isolated and identified. This strain naturally produces a high level of alpha-amylase. The multicopy (pS1) plasmid that carries the complete alkaline protease aprA gene was introduced to this host strain by transformation. The newly constructed strain was found to express the aprA gene and produces a high level of alkaline protease. The level of alpha-amylase production was not affected compared with the parent strain. The pS1 plasmid in the new host was proved to be segregationally and structurally stable, and the multicopy aprA gene was expressed at the stationary phase. This expression did not affect growth rate and sporulation frequency. Moreover, the level of alpha-amylase was maintained. Both alkaline protease and alpha-amylase enzymes were purified using a single-step affinity chromatography column. The use of the newly constructed strain would be valuable to the enzyme industry and would promote recycling of some food-processing wastes.