Antilisterial activity and stability of nanovesicle-encapsulated antimicrobial peptide P34 in milk

Bacillus sp. P34, a strain isolated from aquatic environments of Brazilian Amazon basin, produces a bacteriocin-like substance (BLS) which was encapsulated in nanovesicles prepared from partially purified soy lecithin. The efficiency of free and encapsulated BLS P34 to control the development of L. monocytogenes and maintenance of antimicrobial activity was assessed over time in milk. The antimicrobial activity of free and encapsulated BLS P34 decreased approximately 50% after 4 days of storage (<4 °C) in skim and whole milk. After this period there was not significant loss of activity up to 21 days. The viable counts of Listeria monocytogenes in skim and whole milk containing 3200 AU/ml of free or encapsulated BLS P34 were always lower than those observed in controls without bacteriocin at both 30 °C and 7 °C. At 1600 AU/ml concentration, free and encapsulated BLS P34 were inhibitory to L. monocytogenes in skim milk, when compared with the control at 7 days. Nanovesicle-encapsulated and free BLS P34 shows potential use as biopreservative for application in milk-derived products.