Effects of Zinc Chelators on Aflatoxin Production in Aspergillus parasiticus

Three Ecological Models to Evaluate the Effectiveness of Trichoderma spp. for Suppressing Aflatoxigenic Aspergillus flavus and Aspergillus parasiticus

Chemical pesticides help reduce crop loss during production and storage. However, the carbon footprints and ecological costs associated with this strategy are unsustainable. Here, we used three in vitro models to characterize how different Trichoderma species interact with two aflatoxin producers, Aspergillus flavus and Aspergillus parasiticus, to help develop a climate-resilient biological control strategy against aflatoxigenic Aspergillus species. The growth rate of Trichoderma species is a critical factor in suppressing aflatoxigenic strains via physical interactions. The dual plate assay suggests that Trichoderma mainly suppresses A. flavus via antibiosis, whereas the suppression of A. parasiticus occurs through mycoparasitism. Volatile organic compounds (VOCs) produced by Trichoderma inhibited the growth of A. parasiticus (34.6 ± 3.3%) and A. flavus (20.9 ± 1.6%). The VOCs released by T. asperellum BTU and T. harzianum OSK-34 were most effective in suppressing A. flavus growth. Metabolites secreted by T. asperellum OSK-38, T. asperellum BTU, T. virens OSK-13, and T. virens OSK-36 reduced the growth of both aflatoxigenic species. Overall, T. asperellum BTU was the most effective at suppressing the growth and aflatoxin B1 production of both species across all models. This work will guide efforts to screen for effective biological control agents to mitigate aflatoxin accumulation.

Multi-Mycotoxin Contamination, Mold Incidence and Risk Assessment of Aflatoxin in Maize Kernels Originating from Nepal

Occurrence of mycotoxins in staple foods is a major threat to attaining food safety in developing countries. The study investigated multi-mycotoxin contamination for the first time in Nepalese maize along with the incidence of molds in 45 samples of maize used as human food from 45 districts of Nepal. The samples were analyzed quantitatively for the presence of five different mycotoxins (total aflatoxins (AF), total fumonisins (FUM), ochratoxin (OT), zearalenone (ZEA) and (DON) deoxynivalenol) using the competitive direct ELISA technique. The most frequent occurrences were for DON (100%) and AF (78%) followed by FUM and ZEA (both 76%) and OT (62%). Interestingly, all the samples contained at least two mycotoxins while at least three or more mycotoxins were found in 87% of the samples. The most commonly reported binary, ternary and quaternary combinations were DON+AF, AF+FUM+DON and AF+FUM+ZEA+DON, respectively. The mean percentage kernel mold infection was 35.33% with Fusarium, Aspergillus, Rhizopus and Penicillium genera being the predominant molds. Six different species of Aspergillus and a single species of Fusarium were identified. The estimated daily intake, margin of exposure and risk of liver cancer from consuming maize were 30.46 ng/kg bw/day and 5.58 and 0.38 cancer cases/year/100,000 population, respectively. Since maize is the second-most consumed cereal in Nepal, the contamination levels of various mycotoxins and the incidence of molds identified in the study suggests that stricter control is needed to safeguard the health of the substantial population consuming maize as a staple diet.

Aflatoxin Biosynthesis, Genetic Regulation, Toxicity, and Control Strategies: A Review

Aflatoxins (AFs) are highly toxic and cancer-causing compounds, predominantly synthesized by the Aspergillus species. AFs biosynthesis is a lengthy process that requires as minimum as 30 genes grouped inside 75 kilobytes (kB) of gene clusters, which are regulated by specific transcription factors, including aflR, aflS, and some general transcription factors. This paper summarizes the status of research on characterizing structural and regulatory genes associated with AF production and their roles in aflatoxigenic fungi, particularly Aspergillus flavus and A. parasiticus, and enhances the current understanding of AFs that adversely affect humans and animals with a great emphasis on toxicity and preventive methods.

Metabolites Identified during Varied Doses of Aspergillus Species in Zea mays Grains, and Their Correlation with Aflatoxin Levels

Aflatoxin contamination is associated with the development of aflatoxigenic fungi such as Aspergillus flavus and A. parasiticus on food grains. This study was aimed at investigating metabolites produced during fungal development on maize and their correlation with aflatoxin levels. Maize cobs were harvested at R3 (milk), R4 (dough), and R5 (dent) stages of maturity. Individual kernels were inoculated in petri dishes with four doses of fungal spores. Fungal colonisation, metabolite profile, and aflatoxin levels were examined. Grain colonisation decreased with kernel maturity: milk-, dough-, and dent-stage kernels by approximately 100%, 60%, and 30% respectively. Aflatoxin levels increased with dose at dough and dent stages. Polar metabolites including alanine, proline, serine, valine, inositol, iso-leucine, sucrose, fructose, trehalose, turanose, mannitol, glycerol, arabitol, inositol, myo-inositol, and some intermediates of the tricarboxylic acid cycle (TCA—also known as citric acid or Krebs cycle) were important for dose classification. Important non-polar metabolites included arachidic, palmitic, stearic, 3,4-xylylic, and margaric acids. Aflatoxin levels correlated with levels of several polar metabolites. The strongest positive and negative correlations were with arabitol (R = 0.48) and turanose and (R = −0.53), respectively. Several metabolites were interconnected with the TCA; interconnections of the metabolites with the TCA cycle varied depending upon the grain maturity.

A Structure Identification and Toxicity Assessment of the Degradation Products of Aflatoxin B₁ in Peanut Oil under UV Irradiation

Aflatoxins, a group of extremely hazardous compounds because of their genotoxicity and carcinogenicity to human and animals, are commonly found in many tropical and subtropical regions. Ultraviolet (UV) irradiation is proven to be an effective method to reduce or detoxify aflatoxins. However, the degradation products of aflatoxins under UV irradiation and their safety or toxicity have not been clear in practical production such as edible oil industry. In this study, the degradation products of aflatoxin B₁ (AFB₁) in peanut oil were analyzed by Ultra Performance Liquid Chromatograph-Thermo Quadrupole Exactive Focus mass spectrometry/mass spectrometry (UPLC-TQEF-MS/MS). The high-resolution mass spectra reflected that two main products were formed after the modification of a double bond in the terminal furan ring and the fracture of the lactone ring, while the small molecules especially nitrogen-containing compound may have participated in the photochemical reaction. According to the above results, the possible photodegradation pathway of AFB₁ in peanut oil is proposed. Moreover, the human embryo hepatocytes viability assay indicated that the cell toxicity of degradation products after UV irradiation was much lower than that of AFB₁, which could be attributed to the breakage of toxicological sites. These findings can provide new information for metabolic pathways and the hazard assessment of AFB₁ using UV detoxification.