Inhibition of Listeria monocytogenes in vitro and in goat milk by liposomal nanovesicles containing bacteriocins produced by Lactobacillus sakei subsp. sakei 2a

Abstract

Lactobacillus sakei subsp. sakei 2a is a bacteriocinogenic lactic acid bacteria isolated from a Brazilian meat product, capable to inhibit Listeria monocytogenes in vitro and in foods. In this study, bacteriocin produced by this strain were encapsulated in phosphatidylcholine (FC) and 1,2-dioleoyloxy-3-trimethylammonium-propane (DOTAP) liposomes, separately and in combination, were characterized and evaluated for activity against L. monocytogenes in vitro and in experimentally contaminated UHT goat milk, during storage at 7 °C for 14 days and 30 °C for 24 h. The FC and DOTAP/FC (3:1) nanovesicles containing bacteriocins (12.800 AU mL−1) presented zeta potential of −1.54 and + 38.13 mV, Entrapment Efficiency of 80.0% and 94.1%, and diameter of 91.19 and 81.49 nm, respectively. DOTAP/FC nanovesicle presented excellent stability, and maintained the same physicochemical characteristics over 28 days. Both free and encapsulated bacteriocins controlled L. monocytogenes growth in BHI medium and goat milk stored at 30 °C for at least 8 h, in a similar pattern. After 24 h in BHI medium, bacteriocins encapsulated in FC nanovesicles were more effective (p < 0.05) than free bacteriocins. However, in goat milk, no significant differences (p ≥ 0.05) were observed for the two types of nanovesicles. At 7 °C, both free and encapsulated bacteriocins retarded the L. monocytogenes growth, and after 5 days, counts were 5 log lower than in the controls, both in BHI and in goat milk. Encapsulation of bacteriocin in FC and DOTAP/FC nanovesicles did not affect the antimicrobial activity, but the advantages of their application for control of L. monocytogenes in goat milk based dairy products, when compared to free bacteriocins, remain unclear and more studies are needed.