29F-26
Stability and antimicrobial activity of liposomal nanocapsules containing nisin and lysozyme
L. M. WERE1, P. M. Davidson2, B. Bruce3, and J. Weiss2. (1) Department of Food Science and Technology, University of Tennessee, 2605 River Road, Knoxville, TN 37996-4500, (2) Dept. of Food Science & Technology, Univ. of Tennessee, 2509 River Dr., 201 Mcleod Food Tech Bldg., Knoxville, TN 37966-4539, (3) Dept. of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996
Addition of nisin or lysozyme to foods may reduce antimicrobial activity due to enzymatic degradation and/or interaction with interfering food components. Encapsulation of antimicrobials in liposomes could provide a protective microenvironment increasing antimicrobial activity and stability in foods.
The objective of this research was to determine the stability and antimicrobial efficacy of nisin and lysozyme encapsulated in phospholipid liposomes.
10mM phosphatidylcholine was dried under a stream of N2, rehydrated and ultrasonicated with 0.1x phosphate buffered saline containing 1mM EGTA, 50mM calcein and 0.1-5 mg/ml nisin, lysozyme or 1:1-nisin-lysozyme mixture to produce liposomes. Vesicles were separated from un-encapsulated antimicrobials by size exclusion chromatography (Bio-Gel A0.05M). Entrapment efficiency was determined fluorometrically using calcein as indicator. Antimicrobial activity of liposomes against Listeria monocytogenes (Scott A, 101, 310, V17) was determined using a microbroth dilution assay.
Entrapping calcein in liposomes caused fluorescence quenching of >65%, while co-encapsulating nisin and calcein decreased entrapment to >45%. At the same molar lipid/antimicrobial ratio, lysozyme induced more calcein release compared to nisin, and the nisin/lysozyme mixture had the lowest release, e.g. at a lipid/antimicrobial ratio of 4, 55% nisin, 50% lysozyme and 80% nisin-lysozyme was retained indicating that destabilization of liposomes depended on type of antimicrobial encapsulated. Encapsulated antimicrobials in PC-liposomes reduced growth of all strains of Listeria over a period of 48 hr (Figure 1). Growth inhibition was more pronounced for the nisin:lysozyme mixture which was explained in terms of absolute concentration of antimicrobials present.
The promising results of this research demonstrate that phospholipid liposomes may provide a novel carrier system capable of delivering antimicrobials in complex food systems to inhibit growth of pathogen
Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
2:00 PM - 5:30 PM, Sunday PM