title: Suppression of Listeria monocytogenes Scott A in Fluid Milk by Free and Liposome-Entrapped Nisin.
abstract: Nisin is an antimicrobial polypeptide inhibitory toward Gram-positive bacterial pathogens, including Listeria monocytogenes. Encapsulating nisin in lipid nanocapsules (i.e., liposomes) has been shown to protect antimicrobial functionality in complex food matrices. The capacity of liposomes to encapsulate a fluorescent reporter was determined via spectroscopy. Survival and growth of L. monocytogenes incubated in fluid milk containing 50 IU/ml free or liposome-entrapped nisin was assayed via periodic enumeration of survivors. Liposomes were formulated from phosphatidylcholine (PC) and phosphatidyl-DL-glycerol (PG) and prepared as PC, PC/PG 7/3 or PC/PG 6/4 (mol. fraction). Antilisterial activity of nisin-loaded liposomes was determined in ultra-high temperature processed fluid milk containing approximately 4.0 log10 CFU/ml L. monocytogenes Scott A plus liposomal or free nisin at 50 IU/mL. Samples were aerobically held at 5 or 20°C; L. monocytogenes were enumerated via plating after 0, 1, 3, 6, 12, 24, 48, and 72 incubation hours. Liposome entrapment did not enhance pathogen inhibition when compared to free nisin as a function of storage temperature or incubation duration.
authors.affiliation: Department of Animal Science, Texas Agri-Life Research, Texas A&M University, College Station, TX, 77843-2471, USA.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Schmidt
authors.affiliation: Department of Animal Science, Texas Agri-Life Research, Texas A&M University, College Station, TX, 77843-2471, USA.
authors.forename: Glenn
authors.initials: G
authors.lastname: Holub
authors.affiliation: Department of Nutrition and Food Science, Texas Agri-Life Research, Texas A&M University, College Station, TX, 77843-2253, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Sturino
authors.affiliation: Department of Animal Science, Texas Agri-Life Research, Texas A&M University, College Station, TX, 77843-2471, USA. matt_taylor@tamu.edu.
authors.forename: T
authors.initials: T
authors.lastname: Matthew Taylor
keywords: Encapsulation; Liposomes; Listeria monocytogenes; Milk safety; Nisin