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Contamination by Aspergillus sp. and the accumulation of its mycotoxins in food and beverages have a high impact on human health and food safety. This investigation inquires the ability of brewer’s yeasts discarded after fermentation (brewing fermentation residue, BFR) to synthesize bioactive compounds and to biocontrol Aspergillus sp. BFRs of Saccharomyces cerevisiae MBELGA62 and Pichia kudriavzevii MBELGA61 proved to have bacteriostatic properties and to be efficient in fungal growth reduction, decreasing the growth rate of Aspergillus flavus and Aspergillus parasiticus up to 37.8% and 42.5%, respectively. Fungal mycelium degradation along with absentia of conidia was detected near the yeast inoculum. Moreover, the yeasts synthesize volatile bioactive compounds that extend Aspergillus sp. lag phase above 100% and decrease fungal growth rates from 20% towards 44%, along with the complete inhibition of conidia synthesis. These results indicate the potential of this residue to be used in biocontrol applications in the food industry.

The capacity of microorganisms from water kefir (WK) to control Aspergillus flavus growth during the aerobic phase of ensiled sorghum grains was determined. Sorghum inoculated with A. flavus was treated with filter-sterilized and non-sterilized water kefir, ensiled, and incubated 7 days at 25 °C. A. flavus growth was quantified by qPCR after incubation. Mold growth was inhibited in the presence of water kefir while no inhibition was observed when filter-sterilized water kefir was applied, demonstrating the relevant role of the microorganisms in the kefir water in the biocontrol process. Fungal and bacterial diversity in treated sorghum mini-silos was analyzed by high-throughput sequencing. Firmicutes was the predominant bacterial phyla and Lactobacillus represented the most abundant genus, while Ascomycota was the predominant fungal phyla with Saccharomyces and Pichia as the major genera. Bacterial and yeast counts before and after incubation indicated that the microbial community obtained from WK was able to grow in the sorghum mini-silos in the presence of A. flavus. Results of the present work indicate that the use of a mixed inoculum of microorganisms present in WK may represent an alternative management practice to avoid the growth of A. flavus in ensiled sorghum grains and the concomitant contamination with aflatoxins.