Antifungal activity of silver ions exchanged in mordenite

Abstract

We investigated the action of silver-exchanged mordenite (Ag–mordenite) against the growth of six fungi that are problematic in the food industry. The mould species studied were Rhizopus oryzae, Mucor circinelloides, Geotrichum candidum, and the yeasts were Saccharomyces cerevisiae, Debaryomyces hansenii and Zygosaccharomyces rouxii. Several instrumental methods (EPMA, XRD, XPS, TPR, AAS) were used for the characterization of Ag–mordenite in order to explain its antifungal activity. Results show that Ag–mordenite exerted an effective antifungal action due to a release of silver ions from the zeolite matrix, which acted directly on the walls of the microorganisms, being more effective than the free silver ions in solution. The yeasts were more sensitive than filamentous fungi, S. cerevisiae being the most susceptible specie whereas G. candidum was the more resistant.