Whole-genome and transcriptome sequences of Lactiplantibacillus plantarum 163 are provided. There was one circular chromosome and four circular plasmids, with sizes of 3,131,367; 56,674; 49,140; 43,628; and 36,387 bp, respectively, in L. plantarum 163. The regulator Lp_2642 was selected from the genome data, the overexpression of which increased the transcriptional levels of related genes in plantaricin EF biosynthesis and enhanced plantaricin EF production. Its production was 17.30 mg/L in 163 (Lp_2642), which was 1.29-fold higher than that of the original strain. The regulation mechanism demonstrated that Lp_2642 can bind to three sites of plnA promoter, which enhances its transcription and expression, thereby increasing plantaricin EF production. Amino acids Asn-100, Asn-64, and Thr-69 may play a key role in the binding of Lp_2642. These results provide a novel strategy for mass production of plantaricin EF, which facilitates its large-scale production and application in the agriculture and food industries as a preservative.

Plantaricin EmF separated and identified from L. plantarum 163 was a novel class IIb bacteriocin. The molecular masses of plantaricin Em and F were 1638 and 3702 Da, respectively, with amino acid sequences FNRGGYNFGKSVRH and VFHAYSARGVRNNYKSAVGPADWVISAVRGFIHG, respectively. Plantaricin EmF not only exhibited broad-pH adaptability and thermostability but also showed high efficiency and broad-spectrum antibacterial activity. Its mode of action on L. monocytogenes damaged cell membrane integrity, resulting in the leakage of cytoplasm, changes in cell structure and morphology, and ultimately cell death. Additionally, plantaricin EmF inactivated L. monocytogenes in beef, effectively improving the quality indices of beef, thereby extending its shelf life, especially in combination with chitosan. Plantaricin EmF + 1.0% chitosan extended the shelf life of beef to 15 d, demonstrating its potential application value to replace chemical preservatives to control food-borne pathogenic microorganisms and extend the shelf life of meat and meat products in agriculture and the food industry.

Increasing cases of infections by S. aureus in food resulted in a great demand to utilize natural, safe, and effective antimicrobial agents which could inactivate foodborne pathogens in the food industry. A novel class IId bacteriocin, plantaricin 827, produced by Lactobacillus plantarum 163 was isolated and identified. Its molecular mass and amino acid sequence were determined to be 827 Da and N-His-Ser-Ser-Tyr-Gly-Tyr-Asp-OH, respectively. Plantaricin 827 not only possesses thermostable and pH adaptability but also shows a broader antibacterial spectrum. Its antibacterial mechanism against S. aureus increased the cell membrane permeability and integrity, resulting in the leakage of K+ and changes in cell morphology. Meanwhile, it inhibited the biofilm formation and interacted with genomic DNA minor groove in AT-rich regions. In addition, plantaricin 827 could significantly inactivate S. aureus in skim milk and extend the shelf life of milk. These results demonstrated that plantaricin 827 could effectively inhibit S. aureus and show the potential to replace chemical preservatives to control foodborne pathogens in dairy products.

Plantaricin EF, a kind of natural antibacterial substance, has shown inhibitory effect on most pathogen and spoilage microorganisms, which possessed great potential in food preservation. However, the lower production of plantaricin EF has limited its large-scale production and application. In this study, the effect of maltose on plantaricin EF production and its regulation mechanism in Lactobacillus plantarum 163 were investigated. Maltose significantly improved the biomass and plantaricin EF production, which increased by 3.35 and 3.99 times comparing to the control without maltose, respectively. The maximum production of plantaricin E and F in fed-batch fermentation were 10.55 mg/L and 22.94 mg/L, respectively. Besides, qPCR results showed that maltose remarkably improved transcription of plnA, plnB, plnD, plnE, plnF, plnG1 and plnH, and heighten transcription of lamR, lamK, hpk6 and rrp6. These results provided an effective method to enhance plantaricin EF production and revealed a possible regulatory mechanism from transcriptome results that hpk6, rrp6, lamK and lamR were relative to plantaricin EF production. Genes, hpk6 and rrp6, promote transcription of plnG1, whereas lamK and lamR enhance transcription of plnA, plnB and plnD, which increased plantaricin EF production. • Maltose was proved to be effective in promoting the biosynthesis of plantaricin EF. • Maltose promoted the transcription of biosynthesis and secretion genes of plantaricin EF. • Up-regulation of genes lamR, lamK, hpk6 and rrp6 heightened the plantaricin EF production.