Human norovirus infects humans through the consumption of contaminated food, contact with the excrement or vomit of an infected person, and through airborne droplets that scatter the virus through the air. Being highly infectious and highly viable in the environment, inactivation of the norovirus requires a highly effective inactivating agent. In this study, we have discovered the thermal denaturing capacity of a lysozyme with known antimicrobial activity against gram-positive bacteria, as well as its inactivating effect on murine norovirus. This study is the first report on the norovirus-inactivating effects of a thermally denatured lysozyme. We observed that lysozymes heat-treated for 40 min at 100 °C caused a 4.5 log reduction in infectivity of norovirus. Transmission electron microscope analysis showed that virus particles exposed to thermally denatured lysozymes were expanded, compared to the virus before exposure. The amino acid sequence of the lysozyme was divided into three sections and the peptides of each artificially synthesised, in order to determine the region responsible for the inactivating effect. These results suggest that thermal denaturation of the lysozyme changes the protein structure, activating the region responsible for imparting an inactivating effect against the virus.
A 16S rRNA next-generation sequencing technique was applied
to
investigate the microbial diversity and liquid chromatography–tandem
mass spectrometry was used to identify glutamyl peptide profiles of
10 Thai fermented freshwater fish (Pla-ra) samples. A total of 12
genera of bacteria were able to be detected, with Tetragenococcus spp., Staphylococcus spp., and Lactobacillus spp. dominating. Of the 18 glutamyl
peptides analyzed, 17 were found, even though the amounts detected
were lower than the taste threshold. Despite this, an increase in
mouthfulness sensation, reflecting kokumi activity, was clearly identified
in most of the samples, which might be because of a synergistic effect
of different sub-threshold compounds present in the samples. In principle
component analysis, the relationship between microorganisms and glutamyl
peptide generation was observed, especially between Tetragenococcus spp. and Lentibacillus spp. and the generation of γ-Glu-Val-Gly. Correlations between
microbial diversity and the generation of taste enhancers were identified
in this study.
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