Effect of ZnO-nanoparticles on Aspergillus flavus and Fusarium proliferatum growth on maize grains under environmental interacting conditions

Abstract

Maize (Zea mays L.) is the second most important cereal crop worldwide, after wheat, used in human and animal diets as well as raw material for food and pharmaceutical industries. In Argentina, around 60% of maize is exported and the remaining is used as feedstuff. Aspergillus flavus and Fusarium proliferatum are two mycotoxigenic species that frequently contaminate maize and produce aflatoxins and fumonisins, respectively. Since ZnO is a non toxic compound used as an efficient antimicrobial agent, ZnO nanoparticles (ZnO-NPs) could be a strategy of low cost and low environmental impact to reduce mycotoxin accumulation in stored maize. The aim of the present study was: -to evaluate the effect of ZnO-NPs (0, 5, 10 and 25 mM) on growth of two A. flavus strains (RCAF016 and RCAF018) and two F. proliferatum strains (ITEM 15699 and ITEM 15670) under interacting conditions of water activity (0.96, 0.97 and 0.98 for A. flavus, and 0.97, 0.98 and 0.995 for F. proliferatum) on irradiated maize grains. A concentration of 10 mM zinc acetate was included to compare their effect with the same concentration of ZnO-NPs. ZnO-NPs were synthesized according to the drop by drop mixing method and characterized by SEM. Growth rate (mm/day) was obtained by linear regression during the lineal phase of growth. It was observed that growth rates of A. flavus and F. proliferatum decreased significantly as water activity (aW) decreased and ZnO-NPs concentration increased (p≤0.05). The percentages of growth reduction under ZnO-NPs treatments were the highest at 25 mM of ZnO-NPs. This concentration brought 39% and 40% of growth reduction at 0.97 aW for A. flavus RCAF016 and RCAF018, respectively. However, higher growth reduction percentages were observed for F. proliferatum ITEM 15699 (74 %) and ITEM 15670 (100%). Zinc acetate at 10 mM was less efficient that the same concentration of ZnO-NPs in reducing growth of both A. flavus and F. proliferatum showing the relevance of using ZnO-NPs.