Antimicrobial peptides of Lactobacillus plantarum UTNCys3.4 isolated from native fruits of Ecuadorian Amazonia inhibit the growth of foodborne pathogens

Lactic acid bacteria isolated from diverse ecosystems are known as the most versatile microorganisms used as probiotic or functional foods.  In the recent years, lactobacillus species were exploited for the selection of strains with antimicrobial molecules to be used in bio-preservation of food products. In this study we isolated and identify Lactobacillus plantarum UTNCys3.4 strain from Solanum stramonifolium fruits of Ecuadorian Amazon rainforest and evaluated the spectrum of inhibiting several foodborne pathogens commonly found in local food. However, using agar-well diffusion bioassay, the crude supernatant fluid (CFS) derived Cys3.4 strain showing elevated antimicrobial activity against E. coli ATCC 25922, Salmonella enterica subsp. enterica ATCC 51741, E. coli O157:H7 UTNEc1, Enterococcus aeruginosa UTNEn1, Salmonella Typhi UTNSm2 and Shigella UTNShg1 was further characterized for the presence of bacteriocin-like molecules. The antimicrobial activity of CFS was stable after heating at the ranking 60 to 121°C for 30 min, the activity was activated by exposure at acidic pH of 2.0 to 6.0 and decline at 10.0, suggesting that the inhibitory activity is related with the presence of either inhibitory peptides or organic acids.  Its active principle was proteinaceous in nature since the bacteriocin was inactivated by proteolytic enzymes, while resistance to lysozyme indicated their non-lipid and carbohydrate moiety form. These compounds were detected after 3 hours of bacterial growth indicating that the peptides were primary metabolites which might act as a barrier against pathogen growth and can be further exploited industrially to explore their biopreservante properties.