Construction and application of recombinant strain for the production of an alkaline protease from Bacillus licheniformis

The alkaline protease gene, Apr, from Bacillus licheniformis 2709 was cloned into an expression vector pET – 28b (+), to yield the recombinant plasmid pET-28b (+) – Apr. The pET-28b (+) – Apr was expressed in a high expression strain E. coli BL21. The amino acid sequence deduced from the DNA sequence analysis revealed a 98% identity to that of Bacillus licheniformis 2709. Sodium salt-Polyacrylamide gel electrophoresis (SDS-PAGE) was used to access the protein expression. SDS-PAGE analysis indicated a protein of Mr of 38.8 kDa. The medium components and condition of incubation were optimized for the growth state of a recombinant strain. The optimal composition of production medium was composed of glucose 8 g/L, peptone 8 g/L and salt solution 10 mL. The samples were incubated on a rotary shaker of 180 r/min at 37°C for 24 h.