Date of Award
Master of Science
Food Science and Technology
Doris Helen D'Souza
Michael P. Davidson, Svetlana Zivanovic, Melissa Kennedy
Chitosan, a deacetylated chitin, is known to have a broad spectrum of antimicrobial activity. The objectives of this research were to determine the in vitro time and temperature dependent effects of chitosan with different molecular weights (53, 421 and ~1150 kDa) at two concentrations (35 percent and 0.7%) against the human noroviral surrogates, feline calicivirus (FCV-F9) and murine norovirus (MNV-1) at two temperatures (37oC and 18oC) over 2 hours. The virus titers were determined using standard plaque assays and compared to untreated virus controls. The tested chitosans were shown to decrease FCV-F9 titers, but had no observable effects on MNV- 1. Chitosan with molecular weight (M.W.) of 53 kDa at 0.35% decreased FCV-F9 titers by ~1.0 log PFU/ml, whereas at 0.7% decreased FCV-F9 titers by ~3.0 log PFU/ml after 2 h at 37oC and by ~1.0 log PFU/ml after both 1 and 2 h at 18oC. Chitosan with M.W. of 421 kDa at 0.35% decreased FCV-F9 titers by ~1.0 log PFU/ml whereas at 0.7% decreased FCV-F9 titers by ~2.0 at 37oC after 2 h. Chitosans with 421 and ~ 1150 kDa at 0.35% and 0.7% decreased FCV-F9 titers by ~1.0 log PFU/ml after 2 h at 18oC. Chitosan with ~ 1150 kDa at 0.35% decreased FCVF9 titers by ~1.0 log PFU/ml whereas at 0.7% decreased FCV-F9 titers by ~2.0 log PFU/ml at 37oC after 2 h. The results show that, in general, higher temperature and longer incubation cause greater inactivation of FCV-F9, with 53 kDa chitosan showing the greatest activity. Transmission electron microscopy did not show clear evidence of capsid damage of FCV-F9 treated chitosan and chitosan’s mode of action could not be clearly elucidated. Overall, the tested chitosans showed minimal effect against MNV-1. Thus, caution must be used in interpreting the data based solely on chitosan’s effects against FCV-F9 alone for the use of chitosan as a natural antiviral agent to control foodborne viral infections.
Ganapathy, Radha, "In vitro time and temperature dependence effects of three molecular weight (53, 421 and approximately 1150 kilodaton) chitosans against human noroviral surrogates. " Master's Thesis, University of Tennessee, 2013.