Controlling aflatoxin contamination and propagation of Aspergillus flavus by a soy-fermenting Aspergillus oryzae strain

Abstract

Aflatoxins (AFs) are a group of carcinogenic and immunosuppressive mycotoxins that threaten global food safety. Globally, over 4.5 billion people are exposed to unmonitored levels of AFs. Aspergillus flavus is the major source of AF contamination in agricultural crops. One approach to reduce levels of AFs in agricultural commodities is to apply a non-aflatoxigenic competitor, e.g., Afla-Guard, to crop fields. In this study, we demonstrate that the food fermenting Aspergillus oryzae M2040 strain, isolated from Korean Meju (a brick of dry-fermented soybeans), can inhibit aflatoxin B1 (AFB1) production and proliferation of toxigenic A. flavus in lab culture conditions and peanuts. In peanuts, 1% inoculation level of A. oryzae M2040 could effectively displace the toxigenic A. flavus and inhibit AFB1 production. Moreover, cell-free culture filtrate of A. oryzae M2040 effectively inhibited AFB1 production and A. flavus growth, suggesting A. oryzae M2040 secretes inhibitory compounds. Whole genome-based comparative analyses indicate that the A. oryzae M2040 and Afla-Guard genomes are 37.9 and 36.4 Mbp, respectively, with each genome containing ~100 lineage specific genes. Our study establishes the idea of using A. oryzae and/or its cell-free culture fermentate as a potent biocontrol agent to control A. flavus propagation and AF contamination.

A Liquid Chromatographic Method for Rapid and Sensitive Analysis of Aflatoxins in Laboratory Fungal Cultures

“…Representative chromatograms of A. oryzae NRRL 3483 grown in slant cultivation medium are shown in Figure 4E,F. In addition, A. oryzae M2040 and A. oryzae NRRL RIB40 were unable to produce any types of AFs when grown in different culture medium, as shown in previous studies [28,29]. In summary, in this work, we report a HPLC method coupled with DAD and FLD detectors that would be the first and only validated tool for simultaneous quantitation of AFB1, AFB2, AFG1, and AFG2 in three different laboratory culture conditions.…”

“…Representative chromatograms of A. oryzae NRRL 3483 grown in slant cultivation medium are shown in Figure 4E,F. In addition, A. oryzae M2040 and A. oryzae NRRL RIB40 were unable to produce any types of AFs when grown in different culture medium, as shown in previous studies [28,29]. Figure 4C,D), respectively.…”

“…Aspergillus flavus NRRL 21,882 (Afla-Guard), in which the entire AF biosynthetic gene cluster was deleted, was used as a non-aflatoxigenic strain [28,31] for the recovery experiments. The food-grade Aspergillus oryzae RIB40 [29], A. oryzae M2040 [28], and A. oryzae NRRL 3483 were used as non-aflatoxigenic strains. The aflatoxigenic strain A. flavus NRRL 3357 was used as a positive control, as it is a well-known AFB1 and AFB2 producer in lab and fields [3].…”

A Brief Discussion on Curdling Technology, Microbiological Risks and Contaminants of Fermented Milk Named Biisim Missiga

“…These toxins can cause several disorders at the consumer manifested by many syndromes such as hepatotoxic, neurotoxic, mutagenic, teratogenic, carcinogenic and immunosuppressive effects (Alshannaq et al, 2018;Ezekiel et al, 2018). These effects can be manifested by gastroenteritis, haemorrhage, convulsions, paralysis, oestrogen, kidney and liver damage leading to cancer (Okpala and Ifeoma, 2019;Gauthier, 2016).…”

Control of Aflatoxigenic Molds by Antagonistic Microorganisms: Inhibitory Behaviors, Bioactive Compounds, Related Mechanisms, and Influencing Factors

“…A. oryzae, the nontoxigenic domesticated ecotype of A. flavus, is used as a "Generally Recognized As Safe (GRAS)" microorganism for food fermentation [76,77]. Alshannaq et al demonstrated that co-inoculation with A. oryzae and A. flavus on peanuts with a ratio of 1:100 could effectively inhibit AFB 1 production [41]. The species of A. clavatus could secrete ribonuclease [78], while Skouri-Gargouri and Gargouri revealed that A. clavatus could inhibit the growth of several plant pathogens such as Fusariuym oxysporum and Aspergillus niger due to the secretion of an antifungal peptide [42].…”