Antimicrobial peptides produced by Lactococcus lactis are natural and safe. The aim of this study was to investigate the physicochemical properties of antimicrobial peptides produced by L. lactis L-H410 and optimize the fermentation conditions for its production. The antimicrobial peptides exhibited broad-spectrum activity, and was stable against a broad pH range (2.0–9.5) and thermal treatment (at 80 ℃ for 30 min) and susceptible to proteases. The fermentation conditions (temperature, initial pH, and inoculum size) and medium components (carbon sources, nitrogen sources, stimulating factors, and divalent salt ions) were optimized by the combined use of one-factor-at-a-time method, Plackett-Burman design, path of steepest ascent, Box-Behnken design, and response surface methodology. The optimum fermentation conditions that provided maximum relative antibacterial potency of 378.7 AU/mL, which was 1.2 times of that before optimization (318.4 AU/mL), were determined as 3.32%, 2.5%, 0.2%, 0.02%, 29 ℃, 6.95, and 2.5% for sucrose, peptone, polyethylene glycol (PEG) 8000, manganese sulphate concentrations (m/m), temperature, initial pH, and initial inoculum, respectively.

The present study aimed to express soluble recombinant class Ⅱa bacteriocin in Escherichia coli. The plantaricin LPL-1 gene was cloned into an arabinose promoter, and the C-terminus was fused with the his-tag sequence for expression. The inhibitory activity of recombinant plantaricin LPL-1 against Listeria monocytogenes 54002 was used as the response variable. A novel cell factory, E. coil (ΔtrxB + Δgor + ahpC^M), suitable for class Ⅱa bacteriocin expression was established by CRISPR gene editing technology. It was derived from E. coil BW25331 by deleting the thioredoxin reductase (trxB) gene and glutathione reductase (gor) gene and mutating the gene encoding peroxidase (ahpC). The recombinant plantaricin LPL-1 was purified by affinity chromatography, and its physicochemical properties were analyzed. The purified plantaricin LPL-1 possessed wide pH stability (2–11), high thermal stability (60–100 ℃), and surfactant stability. The recombinant bacteriocin has wide potential for food industrial applications.