Functional Characterization of a Novel Heat-stable Recombinant LCI Bacteriocin

Background and Objective: Foodborne pathogens represent a substantial threat to living organisms. Therefore, techniques for prolonging food shelf life while ensuring food its quality are imperative practices that must be adopted. Bacteriocins are broadly addressed as preservatives. This study generally characterized LCI peptide as a β-structure antimicrobial peptide and a novel alternative for extending food shelf life.

Material and Methods: The antimicrobial activity of recombinant LCI was assessed against selected Gram-positive and Gram-negative bacterial strains. Temperature, pH and bile salt concentration stability of the antimicrobial peptide were studied. Furthermore, the effect of the peptide on the bacterial membrane was assessed.

Results and Conclusion: The study demonstrated that this novel LCI recombinant bacteriocin included antimicrobial characteristics with wide-spectrum activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MICs) were 50 µg.ml^-1 for Micrococcus (M.) luteus ATCC 6633, Staphylococcus (S.) aureus ATCC 6538 and Bacillus (B.) subtilis ATCC 6633 and 100 µg.ml^-1 for Gram-negative bacteria when assessed against Escherichia (E.) coli ATCC 8739, Salmonella (S.) typhimurium ATCC 13311 and Vibrio (V.) parahaemolyticus. Time-kill kinetics demonstrated a bactericidal mechanism of action, showing increased antimicrobial efficacy when reported with acetic acid. Membrane permeabilization assessments indicated that LCI created pores in bacterial membranes in a dose-dependent fashion. The peptide stability assessments revealed its heat resistance up to 100 °C for 15 min, while preserving activity in aqueous solutions within pH range of 3–11 and bile salt concentration of 0–2%. These characteristics indicate that LCI may be a viable candidate for antimicrobial uses, especially when used in combination with organic acids.