Fusion expression of antibacterial peptide salmine from genetically engineered bacteria

To develop a genetically engineered Escherichia coli for potential mass production of antibacterial peptide salmine instead of extraction from fish sperm, three primers designed according to amino acid sequence of salmine were used to construct an oligonucleotide fragment (SAL) encoding salmine. SAL was inserted into a pEC vector and transformed into E. coli BL21 (DE3) to construct genetically engineered bacteria (E. coli BL21-pEC-SAL). Expression of the pEC vector in E. coli BL21-pEC-SAL was induced by addition of lactose and resulted in production of a fusion protein (20 KD) containing salmine peptides inside the E. coli cells. Expression of the fusion protein was significantly affected by growth media, time and temperature of incubation, and lactose induction time. A condition allowing the highest expression of the fusion protein (39.8%) was identified by growing E. coli BL21-pEC-SAL in tryptic soy broth at 43°C for 2-4 h followed by addition of lactose (0.2%) to the medium and incubating for additional 8-10 h. In conclusion, a recombinant vector containing gene encoding salmine peptide was constructed and expressed in E. coli BL21-pEC-SAL as a fusion protein.