Recombinant secretory expression, purification and antimicrobial activity of PR39 in Bacillus subtilis using a maltose-inducible vector

• Provided a safe and efficient protocol for large-scale production of antimicrobial peptides in B. subtilis.
• We establish a system for expressing PR39 as fusion protein in B. subtilis.
• Lower risks and toxicity than IPTG promoter depending on methanol induction during expression.
• Ideal antimicrobial activity and low haemolytic activity of recombinant PR39.

As a promising antibiotic candidate, it is necessary to find a safe method to produce the porcine cathelicidin antimicrobial peptide PR39. In this study, the antimicrobial peptide PR39 was successfully expressed with the maltose-inducible vector pGJ148 in the Bacillus subtilis WB800N. After induction with 3% maltose concentration, the fusion protein was successfully secreted onto the culture medium directly. After purification a Ni–NTA resin column, the fusion protein with a concentration of 17 mg/l was obtained from fermentation culture. Then, the purified fusion protein was cleaved using enterokinase, and tag-free PR39 was released. Approximately 2 mg of the recombinant PR39 with a purity of approximately 92.0% was obtained from a 1-l culture medium after purification with cation exchange column. The evaluation of antimicrobial and haemolytic activity demonstrated that the recombinant PR39 exhibited a high antimicrobial activity against several Gram-negative strains and a low haemolytic activity (256 μM) against human red blood cells. The synthetic PR39 produced similar results. This work expanded and provided a safe protocol for the large-scale production of antimicrobial peptides in B. subtilis.

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