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Gallic acid liposomes (GA-LIP) and gallic acid liposomes decorated with lactoferrin (LF-GA-LIP) were fabricated, and their physiochemical, in vitro digestion and antibacterial activity were analysed. The average particle size of LF-GA-LIP was larger than that of GA-LIP, and the former had a higher encapsulation efficiency and storage stability. Electrostatic interaction existed between lactoferrin and the phospholipid bilayer. Spherical structures of both were observed by transmission electron microscopy and atomic force microscopy. Gallic acid existed in an amorphous form in both liposomes. Hydrogen bond was formed between the hydroxyl groups of gallic acid and the polar head of phospholipid in the liposomes. LF-GA-LIP displayed a delayed-release effect compared with GA-LIP in simulated digestion. It exerted higher antibacterial properties against Escherichia coli and Staphylococcus aureus than GA-LIP. The findings suggested that the liposomes decorated with lactoferrin could be developed as a favourable delivery system for a potential application in the food industry., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

With the aim of exploring a natural antilisterial peptide from food-derived origin, an antibacterial peptide named as Alpep7 was purified from the bromelain hydrolysate of rice bran protein (RBP) in this study. The resulting amino acid consequence was identified as KVDHFPL (Lys-Val-Asp-His-Phe-Pro-Leu) by ultraperformance liquid chromatography tandem matrix-assisted laser desorption/ionisation quadrupole time-of-flight mass spectrometry (MALDI Q-TOF MS). In addition, to assess the probability of the targeted delivery of liposome encapsulation of the peptide to Listeria biofilm, Alpep7-loaded liposomes were further prepared from a mixture of dipalmitoylphosphatidylcholine, stearylamine and cholesterol in a molar ratio of 10 : 3 : 2 and characterised by the analysis of particle size, zeta potential, microtopography and storage stability. The results showed that the liposomes exhibited a well-defined spherical shape, with an average diameter below 200 nm. The liposomes maintained favourable stability after storage at 4 °C for 4 weeks. Comparisons between the activities of free and liposomal Alpep7 via microbroth dilution, regrowth analysis and confocal scanning laser microscopy suggested that liposomal delivery was more effective during the initial exposure of the liposomes to the biofilms. The thermodynamic analysis indicated that the adsorption of liposomal Alpep7 to the listerial biofilm was a spontaneous, exothermic process. The results may provide a natural means for the treatment of listerial contamination and guide the potential application of liposomes for the targeted delivery of antimicrobials to pathogenic biofilms in the food industry.

Liposomes constructed from Escherichia coli membrane lipids were used as a pseudo-stationary phase in capillary electrophoresis and immobilised liposome chromatography to evaluate the interaction between antibacterial peptide (ABP) Apep10 and bacterial membrane lipids. The peptide mobility decreased as the concentration of liposomes increased, providing evidence for the existence of this interaction. The binding constant between Apep10 and the Escherichia coli membranes lipid liposome was higher than that of Apep10 with a mixed phospholipids liposome at the same temperature. The capillary electrophoresis results indicate that the binding ability of Apep10 with a liposome was dependent on the liposome's lipid compositions. Thermodynamic analysis by immobilised liposome chromatography indicated that hydrophobic and electrostatic effects contributed to the partitioning of Apep10 in the membrane lipids. The liposomes constructed from bacterial membrane lipid were more suitable as the model membranes used to study dynamic ABP/membrane interactions than those constructed from specific ratios of particular phospholipids, with its more biomimetic phospholipid composition and contents. This study provides an appropriate model for the evaluation of ABP-membrane interactions., Competing Interests: The authors have declared that no competing interests exist.

Anchovy (Engraulis japonicus) cooking wastewater (ACWW) is a by-product resulted from the production of boiled-dried anchovies in the seafood processing industry. In this study, the protein hydrolysate of ACWW (ACWWPH) was found to have antimicrobial activity after enzymatic hydrolysis with Protamex. For the targeted screening of antibacterial peptides, liposomes constructed from Staphylococcus aureus membrane lipids were used in an equilibrium dialysis system. The hydrolysate was further purified by liposome equilibrium dialysis combined with high performance liquid chromatography. The purified antimicrobial peptide (ACWWP1) was determined to be GLSRLFTALK, with a molecular weight of 1104.6622Da. The peptide exhibited no haemolytic activity up to a concentration of 512μg/ml. It displayed a dose-dependent bactericidal effect in reconstituted milk. The change in cell surface hydrophobicity and membrane-permeable action of the purified ACWWP1 may have contributed to the antibacterial effect. This study suggests that liposome equilibrium dialysis can be used for the targeted screening of antimicrobial peptides., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

An efficient immobilized bacterial membrane liposome chromatography method was used to screen potential antimicrobial peptides from boiled-dried anchovies. A novel cationic antimicrobial peptide (Apep10) was successfully isolated by one-step chromatography. The sequence of Apep10 was identified as GLARCLAGTL by matrix-assisted laser desorption/ionization quadrupole time-of-flight tandem mass spectrometry (MALDI-Q-TOF MS). The antimicrobial activity assessment indicated that Apep10 inhibited the growth of the reference bacteria (Escherichia coli, Shigella dysenteriae, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, Bacillus subtilis, and Streptococcus pneumoniae), with minimal inhibitory concentration (MIC) values ranging from 8 to 64 μg/mL. Almost no cytotoxicity against mouse erythrocytes was observed at concentrations below 20 μg/mL. Nucleotide leakage induced by Apep10 showed that the peptide exhibited permeable activity on the cytoplasmic membrane. Alterations in morphology were observed by scanning electronic microscopy (SEM). Membrane disruption was confirmed by confocal laser scanning microscopy (CLSM) with propidium iodide (PI). The results demonstrate that immobilized bacterial membrane liposome chromatography is a straightforward technique for screening unknown antimicrobial peptides with cell-membrane-interacting activities from boiled-dried anchovies.