Production and Characterization of Antimicrobial Peptides and their Potential Applications

Abstract

A total of 120 bacterial strains were isolated from various fermented sources and screened for their antimicrobial activity. Among them, two bacterial isolates were selected based on their bactericidal activity against food-borne pathogens. Using 16s rRNA sequencing, they identified Enterococcus faecalis MSW5 and Enterococcus faecalis MSOL2. Bacteriocins production in TGME broth was initiated at the mid-log phase, reached a maximum within 24 h, and then declined. Both the bacteriocins remained stable at various physicochemical treatments but based on the results, E.faecalis MSW5 was selected. The crude bacteriocin was purified by cation-exchange chromatography and its molecular mass was 6.5 kDa. The amino acid sequencing of purified enterocin was determined by LC-MS/MS. The mode of action of enterocin was examined by measuring conductivity, and absorbance at 260 and 280 nm and by SEM and TEM analyses. Treated S. aureus cells showed pore formation and leakage of cytoplasmic content. Cytotoxicity analysis on vero cell lines showed only 8% inhibition. However, enterocin has shown anticancer activity (97.51±2.37 % of lung cancer cells), antibiofilm activity (70-98 %), and antioxidant activity (89.08 %) by DPPH assay. To determine in-vitro antimicrobial combinatorial therapy, five antibiotics (Oxacillin, tetracycline, vancomycin, doxycycline, and linezolid) and essential oils (Thyme, Oregano, Lemongrass, Cinnamon, Cymbopogon) were selected. A synergistic effect of antibiotics with bacteriocin was determined using a checkerboard assay and the FICI value was lt 0.5 for all food-borne pathogens. While for essential oils, the best synergism was observed between enterocin MSW5/O.vulgare with a FICI value of 0.372, 0.369, and 0.248 against S.aureus, S.Typhimurium, and L.monocytogenes, respectively. Additionally, the antibiofilm potential of enterocin MSW5 in combination with antibiotics and essential oils was also analyzed. newline