Biocontrol of Aspergillus flavus growth and aflatoxin production by kefir-derived microorganisms under simulated storage conditions

Abstract The kefir granules are a microbial consortium with numerous properties, among which their antifungal action has been reported. This study characterize the antifungal activity against Aspergillus flavus of water kefir granules and two microorganisms isolated from them, identified as Saccharomyces cerevisiae and Geotrichum candidum. The study was carried out under minisilo conditions designed to simulate the aerobic phase of commercial corn storage. In dual culture plate assays, A. flavus was inhibited in close contact with both isolates, and mycelial weakening with lower conidia production was observed. Soluble metabolites of microorganisms inhibited conidial germination by 92% (G. candidum) and 65% (S. cerevisiae), while volatile organic compounds (VOCs) reduced mycelial growth by 29.09% and 37.87%, respectively. Kefir granules offers a dual advantage: multi-mechanistic antifungal action and GRAS (Generally Recognized as Safe) status, positioning it as a safe and sustainable alternative. Also in corn minisilo trials water kefir granules and both microorganisms demonstrated strong antifungal activity by day 4, with qPCR of A. flavus DNA and aflatoxin analyses revealing near complete inhibition. The stability and antifungal properties of the selected kefir microorganisms in minisilos highlight their importance as potential large-scale postharvest protection agents.