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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