Production of the mycotoxins fusaproliferin and beauvericin by South African isolates in the Fusarium section Liseola

Fusarium Cyclodepsipeptide Mycotoxins: Chemistry, Biosynthesis, and Occurrence

Most of the fungi from the Fusarium genus are pathogenic to cereals, vegetables, and fruits and the products of their secondary metabolism mycotoxins may accumulate in foods and feeds. Non-ribosomal cyclodepsipeptides are one of the main mycotoxin groups and include beauvericins (BEAs), enniatins (ENNs), and beauvenniatins (BEAEs). When ingested, even small amounts of these metabolites significantly affect human and animal health. On the other hand, in view of their antimicrobial activities and cytotoxicity, they may be used as components in drug discovery and processing and are considered as suitable candidates for anti-cancer drugs. Therefore, it is crucial to expand the existing knowledge about cyclodepsipeptides and to search for new analogues of these compounds. The present manuscript aimed to highlight the extensive variability of cyclodepsipeptides by describing chemistry, biosynthesis, and occurrence of BEAs, ENNs, and BEAEs in foods and feeds. Moreover, the co-occurrence of Fusarium species was compared to the amounts of toxins in crops, vegetables, and fruits from different regions of the world.

Fusarium, an Entomopathogen-A Myth or Reality?

The Fusarium species has diverse ecological functions ranging from saprophytes, endophytes, and animal and plant pathogens. Occasionally, they are isolated from dead and alive insects. However, research on fusaria-insect associations is very limited as fusaria are generalized as opportunistic insect-pathogens. Additionally, their phytopathogenicity raises concerns in their use as commercial biopesticides. Insect biocontrol potential of Fusarium is favored by their excellent soil survivability as saprophytes, and sometimes, insect-pathogenic strains do not exhibit phytopathogenicity. In addition, a small group of fusaria, those belonging to the Fusarium solani species complex, act as insect mutualists assisting in host growth and fecundity. In this review, we summarize mutualism and pathogenicity among fusaria and insects. Furthermore, we assert on Fusarium entomopathogenicity by analyzing previous studies clearly demonstrating their natural insect-pathogenicity in fields, and their presence in soils. We also review the presence and/or production of a well-known insecticidal metabolite beauvericin by different Fusarium species. Lastly, some proof-of-concept studies are also summarized, which demonstrate the histological as well as immunological changes that a larva undergoes during Fusarium oxysporum pathogenesis. These reports highlight the insecticidal properties of some Fusarium spp., and emphasize the need of robust techniques, which can distinguish phytopathogenic, mutualistic and entomopathogenic fusaria.

In vitro mechanisms of Beauvericin toxicity: A review

Beauvericin (BEA) is a mycotoxin produced by many species of fungus Fusarium and by Beauveria bassiana; BEA is a natural contaminant of cereals and cereals based products and possesses a wide variety of biological properties. The mechanism of action seems to be related to its ionophoric activity, that increases ion permeability in biological membranes. As a consequence, BEA causes cytotoxicity in several cell lines and is capable to produce oxidative stress at molecular level. Moreover, BEA is genotoxic (produces DNA fragmentation, chromosomal aberrations and micronucleus) and causes apoptosis with the involvement of mitochondrial pathway. However, several antioxidant mechanisms protect cells against oxidative stress produced by BEA. Despite its strong cytotoxicity, no risk assessment have been still carried out by authorities due to a lack of toxicity data, so research on BEA toxicological impact is still going on. This review reports information available regarding BEA mechanistic toxicology with the aim of updating information regarding last researches on this mycotoxin.

Occurrence, toxicity, bioaccessibility and mitigation strategies of beauvericin, a minor Fusarium mycotoxin

Emerging Fusarium mycotoxins include the toxic secondary metabolites fusaproliferin, enniatins, beauvericin (BEA), and moniliform. BEA is produced by some entomo- and phytopathogenic Fusarium species and occurs naturally on corn and corn-based foods and feeds infected by Fusarium spp. BEA has shown various biological activities (antibacterial, antifungal, and insecticidal) and possesses toxic activity, including the induction of apoptosis, increase cytoplasmic calcium concentration and lead to DNA fragmentation in mammalian cell lines. Cereals food processing has an important effect on mycotoxin stability, leading to less-contaminated food compared to the raw materials. Different industrial processes have shown to be effective practices to reduce BEA contents due to thermal food processing applied, such as cooking, boiling, baking, frying, roasting and pasteurization. Some studies demonstrated the capacity of lactic acid bacteria to reduce the presence of the BEA in model solution and in food chain through fermentation processes, modifying this mycotoxin in a less toxic derivate. Prebiotic and probiotic ingredient can modulate the bioaccessibility of BEA reducing the risk of intake of this minor Fusarium mycotoxin. This review summarizes the existing data on occurrence, toxicity and especially on BEA reduction strategies in food and feed such as chemical reduction, biocontrol and food processing.

Mycological analysis and multimycotoxins in maize from rural subsistence farmers in the former Transkei, South Africa

Maize harvested in the Centane region of the former Transkei, Eastern Cape Province, South Africa, by subsistence farmers has been shown over many seasons to be contaminated with fumonisin mycotoxins. However, there are limited data on the presence of other mycotoxins. Two multimycotoxin LC-MS/MS methods were applied to good and moldy maize samples, as separated by the farmers themselves from the 2011 harvest. One method involved extract cleanup on multitoxin immunoaffinity columns before LC-MS/MS analysis for aflatoxins, fumonisins, deoxynivalenol (DON), zearalenone (ZEN), and T-2 and HT-2 toxins. The other method was based on a "dilute-and-shoot" approach for the above mycotoxins and a wide range of other fungal secondary metabolites. Both methods showed high incidences of fumonisins B1 and B2 (FB1 and FB2) in good maize (100% for both by the first method, means were 2083 and 927 μg/kg for the two analogues; 93% for both by the second method, positive means of 2764 and 1050 μg/kg, respectively). All samples of moldy maize were contaminated (mean FB1 of 27.64 and 35.98 mg/kg, respectively; mean FB2 of 10.58 and 14.14 mg/kg, respectively). Comparison of the two methods for FB1 and FB2 over the entire range of samples gave R(2) values 0.9144 and 0.8859, respectively. Low levels of DON were found by both methods (positive means of 12 and 4.7 μg/kg in good maize, respectively, and of 14 and 5.8 μg/kg in moldy maize, respectively). ZEN was determined with positive means of 108 and 25 μg/kg in good maize, respectively, and of 111 and 135 μg/kg in moldy maize, respectively. No aflatoxins, OTA, or T-2 or HT-2 toxins were detected. A wide range of other Fusarium , Aspergillus , Alternaria , and Penicillium mycotoxins and secondary metabolites were determined.

Fusaproliferin, beauvericin and enniatins: occurrence in food – a review

The present review summarises data on the prevalence and concentration of fusaproliferin, beauvericin and enniatins in small grains, maize and processed grain-based foods. These fungal secondary metabolites possess interesting biological activities and are presently often referred to as 'emerging mycotoxins'. They have been considered as less important since they are likely not of acute toxicity. However, their high prevalence in foodstuffs, occasionally in higher mg/kg concentrations, warrants an assessment of their true importance for food (and feed) safety. Thorough surveys that determine the contamination of raw and processed foods with fusaproliferin, beauvericin and enniatins are still scarce and are generally limited to Northern Europe and the Mediterranean. The reported data suggest a connection between the observed concentrations and climate. The data further suggest that humans might be exposed continuously to low levels of enniatins as these compounds were of particularly high prevalence in the surveys. The highest concentrations of enniatins were reported from Spain and Northern Africa (maximum concentration of enniatin A1 814 mg/kg in rice from the Spanish market), while concentrations were significantly lower in Northern Europe (maximum concentration of enniatin B 18.3 mg/kg in wheat from Finland). Beauvericin appears to be of low significance in grains from cooler climates while it has been reported to occur at concentrations of tens of mg/ kg in Southern Europe and Morocco (maximum concentration 59 mg/kg in maize from Morocco). Fusaproliferin has been least investigated. Several reports from the Mediterranean show its occasional occurrence up to 19.6 mg/ kg in rice from Morocco, while its natural occurrence in cooler climates seems to be more rare.

Mycotoxicological research in South Africa 1910-2011

The British mycologist, I.B. Pole-Evans, was appointed as the first South African government mycologist in 1905 following the Anglo-Boer War (1899-1902). The Onderstepoort Veterinary Research Institute was founded in 1908 with the Swiss veterinarian, Arnold Theiler, as the first director. Thus, the stage was set for the commencement of mycotoxicological research when the Union of South Africa came into being in 1910. The first accounts of this pioneering research appeared in the 'Seventh and eight reports of the Director of Veterinary Research, Union of South Africa. 1918' in which D.T. Mitchell reported on the experimental reproduction of the neurotoxic syndrome, diplodiosis, in cattle with pure cultures of Stenocarpella maydis (= Diplodia zea) isolated by P.A. Van der Bijl and grown on sterile maize kernels. This is the first report of the experimental reproduction of a veterinary mycotoxicosis with a pure culture of a fungus in South Africa and possibly in the world. This seminal research was followed by a great deal of multidisciplinary research on veterinary mycotoxicoses as well as human syndromes in which fungal toxins are suspected to be involved, taxonomy of mycotoxigenic fungi and chemistry of mycotoxins in South Africa. The mycotoxicoses studied in South Africa include the following (more or less in chronological order): diplodiosis, Paspalum staggers, aflatoxicosis, human hepatocellular carcinoma, ochratoxicosis, lupinosis, facial eczema, tremorgenic mycotoxicosis, hyperoestrogenism, stachybotryotoxicosis, ergotism, leukoencephalomalacia and human oesophageal cancer. A major breakthrough in mycotoxicological research was made in South Africa in 1988 with the isolation and chemical characterisation of the carcinogenic fumonisins produced by Fusarium verticillioides in maize. Current research at the PROMEC Unit of the South African Medical Research Council on the risk assessment of fumonisins and intervention methods to reduce fumonisin intake by rural populations on a maize staple diet is highlighted. This paper concludes with a selected list of mycotoxicological publications by South African mycologists/plant pathologists, veterinarians and chemists/biochemists.

Determination of the LOQ in real-time PCR by receiver operating characteristic curve analysis: application to qPCR assays for Fusarium verticillioides and F. proliferatum

Real-time PCR (qPCR) is the principal technique for the quantification of pathogen biomass in host tissue, yet no generic methods exist for the determination of the limit of quantification (LOQ) and the limit of detection (LOD) in qPCR. We suggest using the Youden index in the context of the receiver operating characteristic (ROC) curve analysis for this purpose. The LOQ was defined as the amount of target DNA that maximizes the sum of sensitivity and specificity. The LOD was defined as the lowest amount of target DNA that was amplified with a false-negative rate below a given threshold. We applied this concept to qPCR assays for Fusarium verticillioides and Fusarium proliferatum DNA in maize kernels. Spiked matrix and field samples characterized by melting curve analysis of PCR products were used as the source of true positives and true negatives. On the basis of the analysis of sensitivity and specificity of the assays, we estimated the LOQ values as 0.11 pg of DNA for spiked matrix and 0.62 pg of DNA for field samples for F. verticillioides. The LOQ values for F. proliferatum were 0.03 pg for spiked matrix and 0.24 pg for field samples. The mean LOQ values correspond to approximately eight genomes for F. verticillioides and three genomes for F. proliferatum. We demonstrated that the ROC analysis concept, developed for qualitative diagnostics, can be used for the determination of performance parameters of quantitative PCR.

Interaction between western corn rootworm (Coleoptera: Chrysomelidae) larvae and root-infecting Fusarium verticillioides

A greenhouse experiment was conducted to evaluate the effect of soil-dwelling larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, on infection of maize roots by the mycotoxin-producing plant-pathogenic fungus, Fusarium verticillioides (Saccardo) Nirenberg (synonym=Fusarium moniliforme Sheldon). The time and order of application of F. verticillioides and western corn rootworm were varied in three different treatments to investigate the influence of timing on root colonization of F. verticillioides and western corn rootworm larval development. Root feeding by western corn rootworm larvae increased root colonization by F. verticillioides (as determined by real-time polymerase chain reaction) up to 50-fold when a high inoculum (10(7) spores/plant) of F. verticillioides was applied before western corn rootworm eggs were added. This effect was stronger the earlier F. verticillioides was applied relative to the time of western corn rootworm egg application but was only significant for the high F. verticillioides inoculum density treatment; F. verticillioides colonization was not increased when a low F. verticillioides inoculum density (10(6) spores/plant) was applied. F. verticillioides slightly suppressed larval development in that the ratio of second- to third-instar larvae was higher in treatments with F. verticillioides than without F. verticillioides. F. verticillioides reduced western corn rootworm head capsule width when applied before or simultaneously with western corn rootworm. The results of this study are discussed focusing on conditions that favor root colonization by F. verticillioides and its influence on western corn rootworm larval development.

Overview of analytical methods for beauvericin and fusaproliferin in food matrices

In recent years consumers and the scientific community have become increasingly interested in food safety, making it a major focus among the objectives of the international institutions responsible for food safety monitoring, e.g. the European Union or the EFSA. Aspects attracting much attention are the colonization of food by microscopic fungi which, under aerobic conditions, produce toxic secondary metabolites known as mycotoxins, and the accumulation of these toxins in the food chain. Numerous studies of surveillance, detoxification, prevention, and toxicological aspects reported in the literature mostly concentrate on major mycotoxins such as aflatoxins, ochratoxin A, trichothecenes, and fumonisins; studies on toxic secondary metabolites of mycotoxins are less common or are only just beginning. Among the molecules of interest, the family of beauvericin and fusaproliferin is certainly the most interesting. The objective of this review is to summarize reported data and the methods used to extract and quantify beauvericin and fusaproliferin in food matrices.

What about the 'other' Fusarium mycotoxins?

Most Fusarium species are capable of producing mycotoxins that may cause adverse effects on human or animal health. The most commonly studied Fusarium mycotoxins include trichothecenes, zearalenone and fumonisins. However, it seems that nearly all of the most prevalent Fusarium species infecting grains are also capable of producing other toxic metabolites. The existing studies, although exiguous, have clearly demonstrated that other toxic metabolites of Fusarium spp. are also present in our foods and feeds, occasionally at very high levels. It is apparent that since mycotoxins, including these 'other' metabolites, are natural toxins, they cannot be completely eliminated from food and feed chains. However, scientific studies are needed to determine their true significance. Thus, the mechanism and level of toxicity as well as presence and concentration levels will have to be fully clarified. In this paper, we briefly review the prevalence of the dominant Fusarium species contaminating maize and small-grain cereals worldwide, and the current knowledge on the biological activity as well as the natural occurrence of their selected less-known toxic metabolites. Additionally, the significance of these 'other' Fusarium mycotoxins is discussed.

A gas chromatography-flame ionization detection method for detection of fusaproliferin in corn

A sensitive and accurate detection method is of great importance in monitoring fusaproliferin levels in foods and animal feeds and evaluating its potential hazard to human and animal health. Several methods have been developed to detect fusaproliferin in cereals and cereal-related products, including thin-layer chromatography, high-performance liquid chromatography, enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry (MS), gas chromatography (GC), and GC-MS. However, these detection methods either suffer from low sensitivity, need expensive instruments, or are susceptible to interfering substances in the sample matrix. The GC-flame ionization detector method developed herein is sensitive, reliable, and easy to use for detecting fusaproliferin in corn and corn-based samples. Its detection limits were 0.04 ng for standard trimethylsilyl-fusaproliferin and about 5 ppb for fusaproliferin in corn samples. The limits of quantitation of this method were 0.15 ng fusaproliferin/injection and 20 ppb of fusaproliferin in corn samples. The recovery rates of fusaproliferin from corn samples spiked with 200, 1000, and 5000 ppb standard fusaproliferin were 109, 85.7, and 98.9% on average. The repeatability of the method was acceptable when evaluated by the Horwitz equation. Of the tested corn samples, three out of five sweet corn and the three yellow corn samples were found to have low levels of fusaproliferin (9.4-45.3 ppb). A moldy corn sample had a fusaproliferin content of 297 ppb.

Fusaproliferin, beauvericin and fumonisin production by different mating populations among the Gibberella fujikuroi complex isolated from maize

The production of fumonisins, fusaproliferin and beauvericin by Gibberella fujikuroi different mating populations isolated from maize in Argentina was evaluated. From 203 strains of Fusarium verticillioides (G. fujikuroi mating population A), 193 were fumonisin producers. Among members of mating population A, female fertile strains produced 20% more toxin than female sterile ones. Among 78 Fusarium proliferatum strains (G. fujikuroi mating population D) 65 produced fumonisins. The percentage of strains that were high, intermediate and low level toxin producers varied according to the species evaluated and the area from which the strains were isolated. Fusarium subglutinans (G. fujikuroi mating population E) strains produced low levels or were no fumonisin producers. Strains from both G. fujikuroi mating populations D and E were able to produce fusaproliferin and beauvericin. Among the members of F. subglutinans (G. fujikuroi mating population E) the fusaproliferin production was more constant. Co-production of fumonisin, fusaproliferin and beauvericin among the strains belonging to G. fujikuroi D and E was also observed. The co-production of fumonisin, beauvericin and fusaproliferin in maize need to be considered, since from the toxicological point of view interactions between these toxins could occur. The toxigenic ability of the strains evaluated prompt us that is necessary to determine the natural occurrence of fusaproliferin and beauvericin in Argentinean maize.

Analysis of the Fusarium mycotoxins fusaproliferin and trichothecenes in grains using gas chromatography-mass spectrometry

A method is described using gas chromatography-mass spectrometry (GC-MS) for the simultaneous detection of the Fusarium mycotoxins fusaproliferin and seven trichothecenes from grains. Sample purification of the raw extract was carried out with commercial solid phase extraction columns, and the recovery of the more polar analytes was increased by rinsing the column with acetonitrile. A significant matrix effect was found for the analysis of fusaproliferin and trichothecenes; thus, the calibrants should be prepared in a blank matrix. The response was linear in the range used. The mean recovery for fusaproliferin was 60.4 or 62.9%, depending on the spiking level. With respect to the trichothecenes, the recovery was generally higher (70.2-125.3%). The method proved to be repeatable for the analysis of fusaproliferin and trichothecenes. The limit of detection for fusaproliferin in the blank matrix mixture was 50 microg/kg, and that for trichothecenes was 5-15 microg/kg. Thirty-eight Finnish grain samples were analyzed for fusaproliferin and trichothecenes with the method developed. Fusaproliferin was not detected in any of the samples. The mean levels of deoxynivalenol, 3-acetyldeoxynivalenol, nivalenol, HT-2 toxin, and T-2 toxin in Finnish grain samples were 272, 17, 150, 40, and <20 microg/kg, respectively.

Purification of fusaproliferin from cultures of Fusarium subglutinans by preparative high-performance liquid chromatography

Thirty-six Fusarium strains were grown on cracked yellow corn and evaluated for optimum fusaproliferin production, with Fusarium subglutinans E-1583 producing the highest levels (1600 microg/g). Three solvent systems were tested for extracting fusaproliferin from the cultures of F. subglutinans E-1583. Methanol gave the highest fusaproliferin recovery, followed by methanol/1% aqueous NaCl (55:45, v/v) and acetonitrile/methanol/H(2)O (16:3:1, v/v/v). Hexane partitioning was effective in removing many impurities from the crude fusaproliferin extracts prior to the liquid chromatography step. Fusaproliferin samples were further purified by high-performance liquid chromatography (HPLC) with a C18 preparatory column using a mobile phase of acetonitrile/H(2)O (80:20, v/v). The purity of the fusaproliferin was verified by analytical HPLC, GC/MS, (1)H NMR spectroscopy, and electrospray ionization (ESI) MS. The isolated fusaproliferin was shown to be free of impurities and can be used as a standard for routine analysis. Fusaproliferin was shown to be temperature-sensitive when samples were stored at room temperature (20-24 degrees C) for more than several days. After 30 days at 4 degrees C, approximately 8% of the fusaproliferin had been transformed to deacetyl-fusaproliferin; however, samples stored at -20 degrees C for 1 year contained only trace amounts of the deacetylated form.

Production of beauvericin, moniliformin, fusaproliferin, and fumonisins b(1), b(2), and b(3) by fifteen ex-type strains of fusarium species

Fifteen Fusarium species were analyzed by high-performance liquid chromatography for the production of six mycotoxins in corn grits cultures. Production of mycotoxins ranged from 66 to 2,500 micro g/kg for fumonisin B(1), 0.6 to 1,500 micro g/g for moniliformin, 2.2 to 720 micro g/g for beauvericin, and 12 to 130 micro g/g for fusaproliferin. Fumonisin B(2) (360 micro g/kg) was produced by two species, fumonisin B(3) was not detected in any of the 15 species examined, and Fusarium bulbicola produced none of the six mycotoxins that we analyzed.