Changing climate, shifting mycotoxins: A comprehensive review of climate change impact on mycotoxin contamination

Climate change (CC) is a complex phenomenon that has the potential to significantly alter marine, terrestrial, and freshwater ecosystems worldwide. Global warming of 2°C is expected to be exceeded during the 21st century, and the frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades, differently affecting areas of the world. How CC may impact multiple food safety hazards is increasingly evident, with mycotoxin contamination in particular gaining in prominence. Research focusing on CC effects on mycotoxin contamination in edible crops has developed considerably throughout the years. Therefore, we conducted a comprehensive literature search to collect available studies in the scientific literature published between 2000 and 2023. The selected papers highlighted how warmer temperatures are enabling the migration, introduction, and mounting abundance of thermophilic and thermotolerant fungal species, including those producing mycotoxins. Certain mycotoxigenic fungal species, such as Aspergillus flavus and Fusarium graminearum, are expected to readily acclimatize to new conditions and could become more aggressive pathogens. Furthermore, abiotic stress factors resulting from CC are expected to weaken the resistance of host crops, rendering them more vulnerable to fungal disease outbreaks. Changed interactions of mycotoxigenic fungi are likewise expected, with the effect of influencing the prevalence and co-occurrence of mycotoxins in the future. Looking ahead, future research should focus on improving predictive modeling, expanding research into different pathosystems, and facilitating the application of effective strategies to mitigate the impact of CC.

May phytophenolics alleviate aflatoxins-induced health challenges? A holistic insight on current landscape and future prospects

The future GCC-connected environmental risk factors expedited the progression of nCDs. Indeed, the emergence of AFs is becoming a global food security concern. AFs are lethal carcinogenic mycotoxins, causing damage to the liver, kidney, and gastrointestinal organs. Long-term exposure to AFs leads to liver cancer. Almost a variety of food commodities, crops, spices, herbaceous materials, nuts, and processed foods can be contaminated with AFs. In this regard, the primary sections of this review aim to cover influencing factors in the occurrence of AFs, the role of AFs in progression of nCDs, links between GCC/nCDs and exposure to AFs, frequency of AFs-based academic investigations, and world distribution of AFs. Next, the current trends in the application of PPs to alleviate AFs toxicity are discussed. Nearly, more than 20,000 published records indexed in scientific databases have been screened to find recent trends on AFs and application of PPs in AFs therapy. Accordingly, shifts in world climate, improper infrastructures for production/storage of food commodities, inconsistency of global polices on AFs permissible concentration in food/feed, and lack of the public awareness are accounting for a considerable proportion of AFs damages. AFs exhibited their toxic effects by triggering the progression of inflammation and oxidative/nitrosative stress, in turn, leading to the onset of nCDs. PPs could decrease AFs-associated oxidative stress, genotoxic, mutagenic, and carcinogenic effects by improving cellular antioxidant balance, regulation of signaling pathways, alleviating inflammatory responses, and modification of gene expression profile in a dose/time-reliant fashion. The administration of PPs alone displayed lower biological properties compared to co-treatment of these metabolites with AFs. This issue might highlight the therapeutic application of PPs than their preventative content. Flavonoids such as quercetin and oxidized tea phenolics, curcumin and resveratrol were the most studied anti-AFs PPs. Our literature review clearly disclosed that considering PPs in antioxidant therapies to alleviate complications of AFs requires improvement in their bioavailability, pharmacokinetics, tissue clearance, and off-target mode of action. Due to the emergencies in the elimination of AFs in food/feedstuffs, further large-scale clinical assessment of PPs to decrease the consequences of AFs is highly required.

Aspergillus derived mycotoxins in food and the environment: Prevalence, detection, and toxicity

Aspergillus species are the paramount ubiquitous fungi that contaminate various food substrates and produce biochemicals known as mycotoxins. Aflatoxins (AFTs), ochratoxin A (OTA), patulin (PAT), citrinin (CIT), aflatrem (AT), secalonic acids (SA), cyclopiazonic acid (CPA), terrein (TR), sterigmatocystin (ST) and gliotoxin (GT), and other toxins produced by species of Aspergillus plays a major role in food and human health. Mycotoxins exhibited wide range of toxicity to the humans and animal models even at nanomolar (nM) concentration. Consumption of detrimental mycotoxins adulterated foodstuffs affects human and animal health even trace amounts. Bioaerosols consisting of spores and hyphal fragments are active elicitors of bronchial irritation and allergy, and challenging to the public health. Aspergillus is the furthermost predominant environmental contaminant unswervingly defile lives with a 40-90 % mortality risk in patients with conceded immunity. Genomics, proteomics, transcriptomics, and metabolomics approaches useful for mycotoxins' detection which are expensive. Antibody based detection of toxins chemotypes may result in cross-reactivity and uncertainty. Aptamers (APT) are single stranded DNA (ssDNA/RNA), are specifically binds to the target molecules can be generated by systematic evolution of ligands through exponential enrichment (SELEX). APT are fast, sensitive, simple, in-expensive, and field-deployable rapid point of care (POC) detection of toxins, and a better alternative to antibodies.

Predicted Aflatoxin B1 Increase in Europe Due to Climate Change: Actions and Reactions at Global Level

Climate change (CC) is predicted to increase the risk of aflatoxin (AF) contamination in maize, as highlighted by a project supported by EFSA in 2009. We performed a comprehensive literature search using the Scopus search engine to extract peer-reviewed studies citing this study. A total of 224 papers were identified after step I filtering (187 + 37), while step II filtering identified 25 of these papers for quantitative analysis. The unselected papers (199) were categorized as “actions” because they provided a sounding board for the expected impact of CC on AFB₁ contamination, without adding new data on the topic. The remaining papers were considered as “reactions” of the scientific community because they went a step further in their data and ideas. Interesting statements taken from the “reactions” could be summarized with the following keywords: Chain and multi-actor approach, intersectoral and multidisciplinary, resilience, human and animal health, and global vision. In addition, fields meriting increased research efforts were summarized as the improvement of predictive modeling; extension to different crops and geographic areas; and the impact of CC on fungi and mycotoxin co-occurrence, both in crops and their value chains, up to consumers.

Brazilian Coffee Production and the Future Microbiome and Mycotoxin Profile Considering the Climate Change Scenario

Brazil holds a series of favorable climatic conditions for agricultural production including the hours and intensity of sunlight, the availability of agricultural land and water resources, as well as diverse climates, soils and biomes. Amidst such diversity, Brazilian coffee producers have obtained various standards of qualities and aromas, between the arabica and robusta species, which each present a wide variety of lineages. However, temperatures in coffee producing municipalities in Brazil have increased by about 0.25 °C per decade and annual precipitation has decreased. Therefore, the agricultural sector may face serious challenges in the upcoming decades due to crop sensitivity to water shortages and thermal stress. Furthermore, higher temperatures may reduce the quality of the culture and increase pressure from pests and diseases, reducing worldwide agricultural production. The impacts of climate change directly affect the coffee microbiota. Within the climate change scenario, aflatoxins, which are more toxic than OTA, may become dominant, promoting greater food insecurity surrounding coffee production. Thus, closer attention on the part of authorities is fundamental to stimulate replacement of areas that are apt for coffee production, in line with changes in climate zoning, in order to avoid scarcity of coffee in the world market.

Practical considerations will ensure the continued success of pre-harvest biocontrol using non-aflatoxigenic Aspergillus flavus strains

There is an important reason for the accelerated use of non-aflatoxigenic Aspergillus flavus to mitigate pre-harvest aflatoxin contamination… it effectively addresses the imperative need for safer food and feed. Now that we have decades of proof of the effectiveness of A. flavus as biocontrol, it is time to improve several aspects of this strategy. If we are to continue relying heavily on this form of aflatoxin mitigation, there are considerations we must acknowledge, and actions we must take, to ensure that we are best wielding this strategy to our advantage. These include its: (1) potential to produce other mycotoxins, (2) persistence in the field in light of several ecological factors, (3) its reproductive and genetic stability, (4) the mechanism(s) employed that allow it to elicit control over aflatoxigenic strains and species of agricultural importance and (5) supplemental alternatives that increase its effectiveness. There is a need to be consistent, practical and thoughtful when it comes to implementing this method of mycotoxin mitigation since these fungi are living organisms that have been adapting, evolving and surviving on this planet for tens-of-millions of years. This document will serve as a critical review of the literature regarding pre-harvest A. flavus biocontrol and will discuss opportunities for improvements.

Transcriptional responses of toxigenic and atoxigenic isolates of Aspergillus flavus to oxidative stress in aflatoxin-conducive and non-conducive media

Aflatoxin production by isolates of Aspergillus flavus varies, ranging from highly toxigenic to completely atoxigenic. Several mechanisms have been identified which regulate aflatoxin production including medium carbon source and oxidative stress. In recent studies, aflatoxin production has been implicated in partially ameliorating oxidative stress in A. flavus. To better understand the role of aflatoxin production in oxidative stress responses, a selection of toxigenic and atoxigenic isolates of A. flavus with moderate to high oxidative stress tolerance were exposed to increasing concentrations of H2O2 in both aflatoxin-conducive and non-conducive media. Mycelial mats were collected for global transcriptome sequencing followed by differential expression, functional prediction, and weighted co-expression analyses. Oxidative stress and medium carbon source had a significant effect on the expression of several secondary metabolite gene clusters including those for aflatoxin, aflatrem, aflavarin, cyclopiazonic acid, and kojic acid. Atoxigenic biological control isolates showed less differential expression under stress than other atoxigenic isolates suggesting expression profiles may be useful in screening. Increasing stress also resulted in regulation of SakA/Hog1 and MpkA MAP kinase signalling pathways pointing to their potential roles in regulating oxidative stress responses. Their expression was also influenced by medium carbon source. These results suggest that aflatoxin production along with that of other mycotoxins may occur as part of a concerted coping mechanism for oxidative stress and its effects in the environment. This mechanism is also regulated by availability of simple sugars and glycolytic compounds for their biosynthesis.

Transcriptional responses of toxigenic and atoxigenic isolates of Aspergillus flavus to oxidative stress in aflatoxin-conducive and non-conducive media

Aflatoxin production by isolates of Aspergillus flavus varies, ranging from highly toxigenic to completely atoxigenic. Several mechanisms have been identified which regulate aflatoxin production including medium carbon source and oxidative stress. In recent studies, aflatoxin production has been implicated in partially ameliorating oxidative stress in A. flavus. To better understand the role of aflatoxin production in oxidative stress responses, a selection of toxigenic and atoxigenic isolates of A. flavus with moderate to high oxidative stress tolerance were exposed to increasing concentrations of H2O2 in both aflatoxin-conducive and non-conducive media. Mycelial mats were collected for global transcriptome sequencing followed by differential expression, functional prediction, and weighted co-expression analyses. Oxidative stress and medium carbon source had a significant effect on the expression of several secondary metabolite gene clusters including those for aflatoxin, aflatrem, aflavarin, cyclopiazonic acid, and kojic acid. Atoxigenic biological control isolates showed less differential expression under stress than other atoxigenic isolates suggesting expression profiles may be useful in screening. Increasing stress also resulted in regulation of SakA/Hog1 and MpkA MAP kinase signalling pathways pointing to their potential roles in regulating oxidative stress responses. Their expression was also influenced by medium carbon source. These results suggest that aflatoxin production along with that of other mycotoxins may occur as part of a concerted coping mechanism for oxidative stress and its effects in the environment. This mechanism is also regulated by availability of simple sugars and glycolytic compounds for their biosynthesis.

Environment Changes, Aflatoxins, and Health Issues, a Review

Crops contaminated by aflatoxins (AFs), the toxic and carcinogenic mycotoxins produced namely by Aspergillus flavus and Aspergillus parasiticus, have severe impacts on human health. Changes in temperature and water availability related to actual climate changes (increased temperature, heavy rainfalls, and droughts) are modulating factors of mould growth and production of mycotoxins. To protect human and animal health from the harmful effects caused by AFs, the development of a safe and effective multifaceted approach in combating food and feed contamination with AFs is necessary. This review aims to collect and analyze the available information regarding AF presence in food and feed to reinforce AF management and to prevent health issues related to the AF exposure in the light of actual climate changes.

Modulation of aflatoxin B1 cytotoxicity and aflatoxin M1 synthesis by natural antioxidants in a bovine mammary epithelial cell line

Aflatoxin (AF) B1, a widespread food and feed contaminant, is bioactivated by drug metabolizing enzymes (DME) to cytotoxic and carcinogenic metabolites like AFB1-epoxide and AFM1, a dairy milk contaminant. A number of natural antioxidants have been reported to afford a certain degree of protection against AFB1 (cyto)toxicity. As the mammary gland potentially participates in the generation of AFB1 metabolites, we evaluated the role of selected natural antioxidants (i.e. curcumin, quercetin and resveratrol) in the modulation of AFB1 toxicity and metabolism using a bovine mammary epithelial cell line (BME-UV1). Quercetin and, to a lesser extent, resveratrol and curcumin from Curcuma longa (all at 5 μM) significantly counteracted the AFB1-mediated impairment of cell viability (concentration range: 96-750 nM). Moreover, quercetin was able to significantly reduce the synthesis of AFM1. The quantitative PCR analysis on genes encoding for DME (phase I and II) and antioxidant enzymes showed that AFB1 caused an overall downregulation of the detoxifying systems, and mainly of GSTA1, which mediates the GSH conjugation of the AFB1-epoxide. The negative modulation of GSTA1 was efficiently reversed in the presence of quercetin, which significantly increased GSH levels as well. It is suggested that quercetin exerts its beneficial effects by depressing the bio-transformation of AFB1 and counterbalancing its pro-oxidant effects.

Current Status and Future Opportunities of Omics Tools in Mycotoxin Research

Mycotoxins are toxic secondary metabolites of low molecular weight produced by filamentous fungi, such as Aspergillus, Fusarium, and Penicillium spp. Mycotoxins are natural contaminants of agricultural commodities and their prevalence may increase due to global warming. Dangerous mycotoxins cause a variety of health problems not only for humans, but also for animals. For instance, they possess carcinogenic, immunosuppressive, hepatotoxic, nephrotoxic, and neurotoxic effects. Hence, various approaches have been used to assess and control mycotoxin contamination. Significant challenges still exist because of the complex heterogeneous nature of food composition. The potential of combined omics approaches such as metabolomics, genomics, transcriptomics, and proteomics would contribute to our understanding about pathogen fungal crosstalk as well as strengthen our ability to identify, isolate, and characterise mycotoxins pre and post-harvest. Multi-omics approaches along with advanced analytical tools and chemometrics provide a complete annotation of such metabolites produced before/during the contamination of crops. We have assessed the merits of these individual and combined omics approaches and their promising applications to mitigate the issue of mycotoxin contamination. The data included in this review focus on aflatoxin, ochratoxin, and patulin and would be useful as benchmark information for future research.

RNA interference-based silencing of the alpha-amylase (amy1) gene in Aspergillus flavus decreases fungal growth and aflatoxin production in maize kernels

Expressing an RNAi construct in maize kernels that targets the gene for alpha-amylase in Aspergillus flavus resulted in suppression of alpha-amylase (amy1) gene expression and decreased fungal growth during in situ infection resulting in decreased aflatoxin production. Aspergillus flavus is a saprophytic fungus and pathogen to several important food and feed crops, including maize. Once the fungus colonizes lipid-rich seed tissues, it has the potential to produce toxic secondary metabolites, the most dangerous of which is aflatoxin. The pre-harvest control of A. flavus contamination and aflatoxin production is an area of intense research, which includes breeding strategies, biological control, and the use of genetically-modified crops. Host-induced gene silencing, whereby the host crop produces siRNA molecules targeting crucial genes in the invading fungus and targeting the gene for degradation, has shown to be promising in its ability to inhibit fungal growth and decrease aflatoxin contamination. Here, we demonstrate that maize inbred B104 expressing an RNAi construct targeting the A. flavus alpha-amylase gene amy1 effectively reduces amy1 gene expression resulting in decreased fungal colonization and aflatoxin accumulation in kernels. This work contributes to the development of a promising technology for reducing the negative economic and health impacts of A. flavus growth and aflatoxin contamination in food and feed crops.

Morphological changes and induction of antifungal resistance in Aspergillus fumigatus due to different CO2 levels

Background and Purpose

Aspergillosis is one of the most common opportunistic fungal infections in immunocompromised and neutropenic patients. Aspergillus fumigatus (A. fumigatus) is the most common causative agent of this infection. Due to variable CO₂ concentrations that pathogens are exposed to during the infection process and to understand the role of CO₂, we examined the effects of various CO₂ concentrations as one of the environmental factors on morphological changes and induction of antifungal resistance in A. fumigatus.

Materials and Methods

A. fumigatus strains were cultured and incubated under 1%, 3%, 5%, and 12% CO₂ atmospheres, each time for one, two, and four weeks. The control culture was maintained for one week without CO₂ atmosphere. Morphological changes were investigated and antifungal susceptibility test was performed according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI) M38-A2 document. The results of different CO₂ atmospheres were compared with that of the control sample.

Results

We found that 1%, 3%, 5%, and 12% CO₂ atmospheres were associated with morphological colony changes. Macroscopically, the colonies were shallow dark green, smooth, crisp to powdery with reduced growth; microscopic examination revealed the absence of conidiation. The induction of antifungal resistance in the susceptible strains to itraconazole, voriconazole, and amphotericin B increased after exposure to 12% CO₂ atmosphere and four weeks of incubation. The MIC values for itraconazole, voriconazole, and amphotericin B were 16 g/ml, 1 g/ml, and 16 g/ml, respectively. These values for the control group were 0.125 g/ml, 0.125 g/ml, and 2 g/ml, respectively.

Conclusion

Exposure to different CO₂ atmospheres induced morphological changes in A. fumigatus, it seems to increase the MIC values, as well. In parallel, resistance to both itraconazole and voriconazole was also observed.

Occurrence of aflatoxin B1 in Triticum species inoculated with Aspergillus flavus

Effects of climate change, global trade and technological changes in processing industries cause higher occurrence of Aspergillus flavus and aflatoxin B1 (AFB1) in cereal crops. Four Triticum species: common wheat (Triticum aestivum L.), spelt (T. aestivum ssp. spelta L.), Khorasan wheat (Triticum turgidum ssp. turanicum Jakubz.) and hybrid wheat (T. aestivum L.– F1) were examined for their response to A. flavus infection and production of AFB1. The grains were obtained from control and artificially field inoculated wheat with A. flavus isolates (No. 1 and No. 2) in the 2016 vegetation season in the region of Vojvodina (Northern province of Serbia). Spelt wheat showed the strongest response to the infection in comparison to other analysed wheat species due to specific physico-chemical characteristics of the hull. The weakest response to A. flavus infections was noted in Khorasan wheat. The highest AFB1 level (256 μg/kg) was observed in the dehulled spelt grains, in comparison to other species where the AFB1 in dehulled grains was not detected. The levels of AFB1 in spelt were about three times higher in hulls (648 and 97.3 μg/kg, respectively) in comparison to grains (256 and 30.7 μg/kg, respectively) in two inoculation treatments (A. flavus No. 1 and No. 2, respectively). In order to investigate the impact of wheat hulls on development of A. flavus, including the biosynthesis of toxic fungal metabolites, physico-chemical and structural properties of different Triticum spp. hulls were characterised. The highest value of the water absorption index and total dietary fibre were observed in spelt hulls in comparison to other wheat species. Additionally, the height value distribution of the fossilized stomatal apparatus of hulls indicates the diversity of spelt wheat compared to other wheat species.

Aspergillus flavus Secondary Metabolites: More than Just Aflatoxins

Aspergillus flavus is best known for producing the family of potent carcinogenic secondary metabolites known as aflatoxins. However, this opportunistic plant and animal pathogen also produces numerous other secondary metabolites, many of which have also been shown to be toxic. While about forty of these secondary metabolites have been identified from A. flavus cultures, analysis of the genome has predicted the existence of at least 56 secondary metabolite gene clusters. Many of these gene clusters are not expressed during growth of the fungus on standard laboratory media. This presents researchers with a major challenge of devising novel strategies to manipulate the fungus and its genome so as to activate secondary metabolite gene expression and allow identification of associated cluster metabolites. In this review, we discuss the genetic, biochemical and bioinformatic methods that are being used to identify previously uncharacterized secondary metabolite gene clusters and their associated metabolites. It is important to identify as many of these compounds as possible to determine their bioactivity with respect to fungal development, survival, virulence and especially with respect to any potential synergistic toxic effects with aflatoxin.

Carbon Dioxide Mediates the Response to Temperature and Water Activity Levels in Aspergillus flavus during Infection of Maize Kernels

Aspergillus flavus is a saprophytic fungus that may colonize several important crops, including cotton, maize, peanuts and tree nuts. Concomitant with A. flavus colonization is its potential to secrete mycotoxins, of which the most prominent is aflatoxin. Temperature, water activity (aw) and carbon dioxide (CO₂) are three environmental factors shown to influence the fungus-plant interaction, which are predicted to undergo significant changes in the next century. In this study, we used RNA sequencing to better understand the transcriptomic response of the fungus to aw, temperature, and elevated CO₂ levels. We demonstrate that aflatoxin (AFB₁) production on maize grain was altered by water availability, temperature and CO₂. RNA-Sequencing data indicated that several genes, and in particular those involved in the biosynthesis of secondary metabolites, exhibit different responses to water availability or temperature stress depending on the atmospheric CO₂ content. Other gene categories affected by CO₂ levels alone (350 ppm vs. 1000 ppm at 30 °C/0.99 aw), included amino acid metabolism and folate biosynthesis. Finally, we identified two gene networks significantly influenced by changes in CO₂ levels that contain several genes related to cellular replication and transcription. These results demonstrate that changes in atmospheric CO₂ under climate change scenarios greatly influences the response of A. flavus to water and temperature when colonizing maize grain.

Aflatoxins contamination of maize in Serbia: the impact of weather conditions in 2015

In recent years climate changes recorded in temperate regions of Europe have led to aflatoxin (AF) contamination of maize. Thus, the aim of this study was to investigate the influence of weather conditions on levels of aflatoxin B₁ (AFB1), aflatoxin B₂ (AFB2), aflatoxin G₁ (AFG1) and aflatoxin G₂ (AFG2) in 180 maize samples collected from the main maize-growing regions (Western Bačka, North Banat, South Banat and Central Serbia) in Serbia after harvest in 2015. The concentrations of AFs were determined by a validated HPLC method with post-column derivatisation and fluorescence detection (HPLC-FLD). The presence of AFB1, AFB2, AFG1 and AFG2 was detected in 57.2%, 13.9%, 5.6% and 2.8% of maize samples in the concentration ranges of 1.3-88.8 µg kg^-1, 0.60-2.8 µg kg^-1, 1.8-28.5 µg kg^-1 and 2.1-7.5 µg kg^-1 respectively. The recorded smaller amount of precipitation and especially higher air temperatures during the summer of 2015 were favourable for AF production, which resulted in 32.2% and 21.1% of samples being unsuitable for human consumption, since AFB1 and the sum of AFs concentrations were above 5.0 and 10.0 µg kg^-1 respectively. Furthermore, the findings in this study indicate that the microclimate conditions in the investigated regions had a great influence on the contamination frequency of maize with AFs. The highest percentage of samples unsuitable for human consumption, considering both AFB1 and total AFs content were 72.5% and 51.5% respectively from Central Serbia, whilst the lowest percentages of 15.6% and 6.2% respectively were found in Western Bačka. These findings confirmed that maize should be continuously monitored in order to protect human and animal health from the harmful effects caused by AFs contamination.