Biocontrol of Aspergillus flavus in ensiled sorghum by water kefir microorganisms

Authors: GONDA, MARIANA - Universidad De La República; GARMENDIA, GABRIELA - Universidad De La República; RUFO, CATERINA - Universidad De La República; PELANEZ, ANGELA - Universidad De La República; Wisniewski, Michael; DROBY, SAMIR - Volcani Center (ARO); VERO, SILVANA - Universidad De La República

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2019
Publication Date: 8/10/2019
Citation: Gonda, M., Garmendia, G., Rufo, C., Pelanez, A.L., Wisniewski, M.E., Droby, S., Vero, S. 2019. Biocontrol of Aspergillus flavus in ensiled sorghum by water kefir microorganisms. Microorganisms. https://doi.org/10.3390/microorganisms7080253.
DOI: https://doi.org/10.3390/microorganisms7080253

Interpretive Summary: Preserving food after it is harvested is recognized to be an essential aspect of addressing the need to increase food production for a rapidly-expanding global population. There is a need to develop safe and effective methods that do not lie on the use of potentially hazardous synthetic chemicals. There is also a need to prevent food spoilage and contamination by organisms that produce substances, such as aflatoxins, that are harmful to human health. The use of microbiome studies and the development of microbial consortia as biocontrol agents is also being recognized as an important strategy. In the present study, the use of a microbial consortium derived from kefir, a commonly available non-alcoholic, fermented drink that was examined for its potential to prevent contamination of ensiled sorghum with the fungal pathogen, Aspergillus flavus, was investigated. Contamination of ensiled sorghum with Aspergillus severely decreases its value as an animal feed and may also result in the production of toxic levels of aflatoxin. Results indicated that the microbial consortium consisting mainly of species of Lactobacillus bacteria and yeast, was extremely effective in preventing Aspergillus growth in ensiled sorghum. The use of the kefir-derived, microbial consortium for preventing postharvest diseases of fruits and vegetables is being explored.

Technical Abstract: 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 WK, ensiled, and incubated seven days at 25 °C. A. flavus growth was quantified by qPCR after incubation. Mold growth was inhibited in the presence of WK, while no inhibition was observed when filter-sterilized WK 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 highthroughput 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 minisilos 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.