Geovana D. Savi

Effect of zinc compounds on Fusarium verticillioides growth, hyphae alterations, conidia, and fumonisin production

BACKGROUND Several strategies are used to eliminate toxigenic fungi that produce fumonisins in grains. Fusarium verticillioides can be controlled by the application of synthetic fungicides in the field or during storage. However, there may also be residuals, which may remain in the foods. Inorganic compounds such as zinc are cheap, stable and could present strong antifungal activity. Some Zn compounds can be utilized as dietary supplements and are authorized for the fortification of foods. Knowing the advantages and that low concentrations of Zn can have antimicrobial activity, our objective was to evaluate the effects of Zn compounds on the growth of F. verticillioides and the production of fumonisin and conidia. In addition, we aimed to verify that Zn compounds cause morphological alterations of the hyphae, mortality and production of reactive oxygen species. RESULTS Zn compounds efficiently reduced fungal growth and fumonisin production. Treatment using zinc perchlorate gave the best results. All treatments inhibited conidia production and caused morphological alterations of the hyphae. It was possible to observe cell death and production of reactive oxygen species. CONCLUSION Zn compounds have advantages compared to other antifungal compounds. In particular, they are non-toxic for the organism in appropriate amounts. They could be studied further as potential fungicides in agriculture.

Fungi and the natural occurrence of deoxynivalenol and fumonisins in malting barley (Hordeum vulgare L.).

The industrial use of barley grain has experienced continuous growth, mainly due to its economic importance for malt production. From a technological perspective, fungal persistence can reduce product marketability and cause economic losses. In this sense, the aim of the present study was to determine the presence and identification of mycoflora and the occurrence of deoxynivalenol (DON) and fumonisins (FBs) in malting barley. The samples presented a low count of fungal colonies, with values ranging from 10.5 to 0.5 × 10(1)CFU g(-1) and the species most found were Fusarium graminearum and Fusarium verticillioides with 26% and 12% of incidence, respectively. In the samples analyzed for mycotoxins occurrence, DON and FBs were present in 18% and 12%, respectively. The high concentrations of toxins found in the malting samples may be strongly influenced by agricultural practices and the weather conditions during critical phases of plant growth.

Effects of Ozone Gas Exposure on Toxigenic Fungi Species from Fusarium, Aspergillus, and Penicillium Genera

The antifungal properties of ozone (O3) gas exposure towards toxigenic fungi were evaluated in laboratory-scale treatments trials. O3 gas was utilized at a concentration of 60 μmol/mol at different times of exposure, which efficiently inhibited the fungi colonies growth, especially F. graminearum and P. citrinum. At the concentration applied, O3 gas exposure was able to inhibit conidia germination, caused hyphae morphological alterations that led to hyphae death and ROS production of all fungi tested. O3 action can be related to cell metabolism alterations, leading to apoptosis and oxidative stress, showing to be effective on controlling toxigenic fungal development which is one of the main problems regarding food contamination.

Fumonisins in corn (Zea mays L.) from Southern Brazil

A total of 232 samples of corn commercialised in Santa Catarina state, Southern Brazil (temperate zone climate), were evaluated from 2007 to 2012 for fumonisins (FBs: FB1 and FB2). Before performing this study, a FBs method with liquid chromatography and fluorescence detection (ex. 335; em. 440 nm) was validated first. FBs were detected in 46.6% (108 samples), with values ranging from 66 to 7832 µg kg−1 for FB1 and 110 to 1201 µg kg−1 for FB2. The number of contaminated corn samples for FB1 and FB2 varied and often presented contamination of FB1 only. Per year of analysis, the numbers were: n = 22/8(FB1/FB2), 44/5(FB1/FB2), 25/12(FB1/FB2), 4(FB1), 6(FB1) and 7(FB1) in 2007, 2008, 2009, 2010, 2011 and 2012, respectively. The contamination percentage was 42.3/15.4, 59.5/6.8, 43.8/21.1, 36.4, 35.3 and 33.3%, respectively, during these years. Consumers can be exposed to these mycotoxins and their health can be at risk through the consumption of contaminated corn.

Inhibition of growth and aflatoxin production of Aspergillus parasiticus by guaraná (Paullinia cupana Kunth) and jucá (Libidibia ferrea Mart) extracts

In the present study, fruits extracts (Paullinia cupana K. & Libidibia ferrea M. - guarana & juca, respectively) of the Amazon Region were tested for antifungal and antimycotoxigenic activities against Aspergillus parasiticus using the agar dilution method. The treatments utilized were at three different concentrations (1.08, 1.62 and 3.24%). The effect on both extracts on growth diameter of fungal colony was time and concentration dependent. No treatment completely inhibited fungi growth, however A. parasiticus was significantly reduced by the treatments when compared to the control group. The production of AFB1, AFB2, AFG1 and AFG2 by A. parasiticus grown on guarana and juca extracts treatment was significantly smaller when compared to controls. A. parasiticus strain produced aflatoxins in all concentrations when grown on guarana extracts medium treated and different of that observed when on juca’s treated extracts.

Mycoflora and deoxynivalenol in whole wheat grains (Triticum aestivum L.) from Southern Brazil

The fungal species Fusarium graminearum is related to deoxynivalenol (DON) formation. The aim of this study was to evaluate mycoflora and DON occurrence in 53 whole wheat grain samples collected in Southern Brazil during the 2012 crop. Wheat grains showed adequate values of water activity ranging from 0.48 to 0.72, within the required limits of moisture content, ranging from 9.1% to 13.9%. In addition, low counts of fungal colonies, ranging from 10 to 8.2 × 102, were found. For Fusarium genera, there was predominance of Fusarium verticillioides (34%) and F graminearum (30.2%). For Aspergillus species, 37.7% of Aspergillus flavus was determined. Regarding the Penicillium species, Penicillium digitatum (49%) was the most found species. DON was detected in 47.2% (25 out of 53) of the samples analysed, with levels ranging from 243.7 to 2281.3 µg kg−1 (mean: 641.9 µg kg−1).

Biological Activity of Gold Nanoparticles towards Filamentous Pathogenic Fungi

Gold nanoparticles (GNP) were synthesized, characterized and their antifungal activities investigated against three pathogenic fungi of different genera and species (Fusarium verticillioides, Penicillium citrinum and Aspergillus flavus). The anti-fungi treatments efficiency of the GNP (concentrations: 0, 0.05, 0.1 and 0.2 mg L-1 in PDA media) were evaluated at 2, 4, 6 and 8 days after incubation by measuring the diameter of fungal colonies and investigating fungi structure alterations by scanning electron microscopy (SEM). It was observed that the GNP concentration increased, fungal colony growth diameter reduced. However, the highest GNP concentration applied in the experiment was not able to completely inhibit fungal growth. The SEM analysis of the fungi structure Au treated showed damaged hyphae and unusual bulges that were not observed in fungi that growth on medium without treatment (Control). Although up to the highest concentration of GNP media applied did not completely inhibited fungi growth, the hyphae modifications led growth reduction which could influence the toxins production by these fungi.

Degradation of bifenthrin and pirimiphos-methyl residues in stored wheat grains (Triticum aestivum L.) by ozonation

Pesticide insecticides are used on wheat grains in storage units but their efficiency is hindered by persistent residues in the grains. Therefore, this study aims to evaluate the effectiveness of ozone (O3) gas treatment on the degradation of residual bifenthrin and pirimiphos-methyl insecticides commonly used in storage wheat grains, as well as to evaluate degradation of their by-products. The residues of bifenthrin decreased after 180 min of exposure in a concentration of 60 μmol/mol (a 37.5 ± 7.4% reduction) with 20% moisture content and 0.9 water activity. On the other hand, under the same experimental conditions, the pirimiphos-methyl residues significantly decreased in the wheat grains (71.1 ± 8.6%) after 30 min of exposure. After O3 gas treatment, three by-products of pirimiphos-methyl (m/z=306.1) containing different molecular mass to charge ratios (m/z=278.1, 301.1 and 319.2) were identified by LC-MS. O3 is a strong oxidizer that has shown the potential to reduce pesticide residues in stored grain in order to ensure food quality and safety.

Efficacy of zinc compounds in controlling Fusarium head blight and deoxynivalenol formation in wheat (Triticum aestivum L.).

The efficiency of zinc compounds (zinc sulfate, ZnSO4 and zinc oxide, ZnO in regular and nanosize, respectively) on wheat plants was evaluated against growth of Fusarium graminearum and DON formation. In addition, any possible effects on the grain microstructures were observed by scanning electron microscopy (SEM), and the remaining residue of Zn on wheat plants was analyzed. The plants were inoculated with F. graminearum and treated with Zn compounds (100mM) onto spikelets at the anthesis stage. When wheat plants reached maturation, grains were harvested and evaluated for Fusarium (number of colonies, CFU/g), DON formation, and SEM observation, followed by determination of possible remaining Zn residue. The groups treated with ZnSO4 and ZnO-NP showed a reduction in number of CFU of F. graminearum when compared to the control. Similarly for DON formation, i.e. the toxin was reduced to non-detected levels in the treated group. ZnO-NP efficiently reduced F. graminearum and DON formation in the grains at low concentration. Zn remained within the international recommended level for consumption and the treatment did not cause any damage to wheat grains. New strategies of control using Zn compounds in addition to conventional treatments could increase the efficiency against FBH and DON formation.

Fumonisins B1 and B2 in the corn-milling process and corn-based products, and evaluation of estimated daily intake.

ABSTRACT The distribution of fumonisins (FBs: FB1 and FB2) in the corn-milling process and in corn-based products, as well as daily intake estimates for the Brazilian population were evaluated. Among corn fractions samples, corn meal had the highest mean concentration of FB1 (1305 µg kg−1) and FB2 (651 µg kg−1) and a distribution factors of 452% and 256% in relation to corn grain, respectively. On the other hand, the distribution factor of FB1 and FB2 in corn flour was found to be 144% and 88% respectively, which demonstrates that fumonisins in this fraction were reduced compared with corn grain. As a result, almost half the corn meal samples (47%) would be non-compliant with future Brazilian regulation (2017) for fumonisins. However, corn-based products, such as corn flakes and popcorn, were in compliance with the regulation. The average probable daily intake and maximum probable daily intake of fumonisins estimated for the Santa Catarina state (Brazil) population were below the provisional maximum tolerable daily intake of 2 µg kg−1 body weight day−1 for all corn samples. Despite this, the adoption of practices to control the occurrence of fumonisins should be applied to the corn-milling fractions that may contain a higher concentration of this toxin, such as corn meal, often used for animal feed in Brazil.