89D-25 |
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D. W. CARNAHAN, Dept. of Food Science, Univ. of Massachusetts, Chenoweth Lab, Box 31410, Amherst, MA 01003, P. M. Davidson, Dept. of Food Science & Technology, Univ. of Tennessee, 2509 River Dr., Knoxville, TN 37996-4539, B. Bruce, Dept. of Biochemistry and Cellular and Molecular Biology, Univ. of Tennessee, Knoxville, TN 37996, and J. Weiss, Dept. of Food Science, Univ. of Massachusetts, Amherst, 234 Chenoweth Lab., Box 31410, Amherst, MA 01003-1410. Efficacy of many antimicrobials is greatly reduced when applied to a food system. This has been attributed to antimicrobials becoming sequestered in the hydrophobic regions of foods while bacteria are growing in areas containing water. This lack of activity may be overcome by using suitable delivery systems. The objective of this study was to evaluate the physicochemical and antimicrobial properties of carboxyl terminated silver nanoparticles as delivery systems for nisin and lysozyme. Growth and activity assays against four strains of Escherichia coli and Listeria monocytogenes were conducted at 32° C. Antimicrobial activity of loaded and unloaded silver nanoparticles was determined via a microbroth dilution assay. Nisin and lysozyme were attached to nanoparticles by incubating compounds and nanoparticles at specific concentration ratios (6:1 (nisin (2.5µg/ml) or lysozyme (2.0µg/ml) to silver), 4:1, 2:1, 1:1, and 1:2) for 16 h at 22° C. Particle size was determined via dynamic light scattering. All experiments were conducted at pH=7. Unloaded silver nanoparticles did not inhibit growth of strains. The size of the nanoparticles with nisin attached decreased as the ratio of nisin to silver decreased (420-455 nm at 6:1, 305-320 nm at 4:1, 275 to 325 nm at 2:1, 160-170 nm at 1:1, and 140-145 nm at 1:2). The size of the nanoparticles with attached lysozyme increased as the ratio of lysozyme to silver decreased, except at the 1:1 concentration (410 to 440 nm at 6:1, 545 to 715 nm at 4:1, 520 to 560 nm at 2:1, 420 to 545 nm at 1:1, and 620 to 680 nm at 1:2). Growth of two strains of E. coli and two strains of L. monocytogenes was inhibited at the highest concentrations of nanoparticles at all ratios of added nisin and lysozyme tested. Our results suggest that activity of lysozyme and nisin is maintained after adsorption to nanoparticles indicating the potential of nanoparticles to act as antimicrobial delivery devices.
Session 89D, Food Microbiology: Antimicrobial effects on foodborne microorganisms
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |