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.

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Food losses, defined as a reduction in the quantity and quality of food during production and storage, impact food safety and security. Losses caused by plant pathogens are among the most significant. Chemical pesticides have been extensively used to prevent microbial diseases. Their toxicity and reduced efficacy, however, have encouraged investigators to develop alternatives. Alternatives based on microbial biopesticides tend to be safer and more environmentally benign than conventional pesticides. In recent years, formulations based on biopesticides have progressively increased in number and diversity and have attracted commercial interest. Understanding the mechanisms by which biopesticides control the disease is fundamental to achieving optimal disease control. Biocontrol mechanisms can be divided into two main categories: those related to the ability to inhibit pathogens or their virulence factors, and those that enhance host plant fitness and induce disease resistance. Here, the first type of strategy is reviewed, which is directly mediated by physical contact between biocontrol agents and pathogens or indirectly by exposure of a pathogen to antimicrobial or microbial-inhibiting compounds produced by the microbial antagonist. Mechanisms involving physical contact include mycophagy, destruction of pathogenic bacteria by bacteriophages or predation, and disease inhibition by topical applications of specific dsRNA. Indirect mechanisms that do not involve direct contact with a pathogen include the production of antimicrobial compounds, competition, and virulence factor suppression by quorum quenching. These topics are reviewed and discussed.

Limited shelf life of bakery products, caused by microbial deterioration, is a concern for industries due to economic losses. Fungal spoilage of sponge cakes industrially produced in Montevideo was caused mainly by Penicillium species, in particular by Penicillium crustosum. The combination of different hurdles was studied to inhibit P. crustosum growth in sponge cakes. A full factorial design was performed to study the effect of the concentration of potassium sorbate, pH, packaging atmosphere and storage time. The results showed that packaging atmosphere and storage time were the significant factors in the ranges tested. No growth was detected in cakes stored in modified atmosphere packaging (MAP) (N 2 :CO 2 50:50) at room temperature (25°C) for 15 days. The effect of MAP on P. crustosum growth in cakes at room temperature was compared with the effect of air-packaging and storage at low temperature (4°C) for 30 days. P. crustosum growth was not detected in cakes packaged in MAP, whereas it was detected after 20 days in cakes packaged in air and stored at 4°C. This growth was quantified by a specific real time PCR developed in this work. Specific primers were designed using the sequence of b-tubulin gene of P. crustosum as a target and PCR conditions were adjusted to ensure specificity. PCR efficiency was 107%, with a detection limit of 0.0014 ng of DNA. The qPCR method presented here, resulted specific and sensitive enough to detect the growth of P. crustosum even before biodeterioration signs were visible.

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