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NZ17074, a member of the arenicin family from Arenicola marina , exhibited potent antimicrobial activity against bacteria and fungi, but had some toxicity to human erythrocytes and porcine intestinal epithelial cells. To resolve this problem, one novel peptide N2 was designed based on NZ17074 by replacing Gly in position 1, 12 with Ala. N2 exhibited a typical β-sheet conformation in aqueous and almost had no hemolysis. N2 was expressed in Pichia pastoris using the small ubiquitin-like modifier fusion technology. The yield of N2 was approximately 6.5 mg/l, and its molecular weight was 2665.0 Da. The minimum inhibitory concentrations of N2 against Gram-negative bacteria ranged from 0.125 to 4 μg/ml. The antibacterial activity of N2 against Escherichia coli CVCC 195 and Salmonella enteritidis CVCC 3377 was enhanced up to 1–3-fold over parent NZ17074. This result provides some information that assists in the rational design of toxic antimicrobial peptides. [ABSTRACT FROM AUTHOR]

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 . [ABSTRACT FROM AUTHOR]