RESUMO
The objective of the work reported here was to study the antifungal capability of cell-free supernatants obtained from whey permeates after fermentation by the kefir grains CIDCA AGK1 against Fusarium graminearum growth and zearalenone (ZEA) production. The assays were performed in order to study the conidial germination inhibition -in liquid media- and the effect on fungal growth rate and the Latency phase -in solid media. We observed that fermented supernatants of pH 3·5 produced the highest percentages of inhibition of conidial germination. The dilution and, particularly, alkalinisation of them led to the gradual loss of antifungal activity. In the fungal inhibition assays on plates we found that only the highest proportion of supernatant within solid medium had significant antifungal activity, which was determined as fungicidal. There was no ZEA biosynthesis in the medium with the highest proportion of supernatant, whereas at lower concentrations, the mycotoxin production was strain-dependent. From the results obtained we concluded that kefir supernatants had antifungal activity on the F. graminearum strains investigated and inhibited mycotoxin production as well, but in a strain-dependent fashion. The present work constitutes the first report of the effect of the products obtained from the kefir-grain fermentation of whey permeates - a readily available by-product of the dairy industry - on F. graminearum germination, growth, and toxin production.
Assuntos
Antifúngicos , Fermentação , Fusarium , Kefir/microbiologia , Proteínas do Soro do Leite/metabolismo , Animais , Argentina , Queijo/análise , Indústria de Laticínios , Fusarium/efeitos dos fármacos , Fusarium/metabolismo , Resíduos Industriais , Lactose/análise , Probióticos , Soro do Leite/química , Soro do Leite/metabolismo , Proteínas do Soro do Leite/análise , Zearalenona/biossínteseRESUMO
AIMS: To select lactic acid bacteria with potential silage inoculant properties. The bio-control activity against mycotoxicogenic fungi and the presence of antibiotics resistance gene were also evaluated. METHODS AND RESULTS: Lactobacillus rhamnosus RC007 and Lactobacillus plantarum RC009 were selected on the basis of growth rate and efficacy in reducing the pH of maize extract medium; therefore, they were evaluated for their bio-control ability against Fusarium graminearum and Aspergillus parasiticus. Studies on lag phase, growth rate and aflatoxin B1 (AFB1) and zearalenone (ZEA) production were carried out in vitro under different regimes of aw (0·95 and 0·99); pH (4 and 6); temperature (25 and 37°C); and oxygen availability (normal and reduced). Lactobacillus rhamnosus RC007 was able to completely inhibit the F. graminearum growth at all assayed conditions, while Lact. plantarum RC009 only did it at pH 4. Both Lactobacillus strains were able to significantly reduce the A. parasiticus growth rate mainly at 0·99 aw . A decrease in ZEA production was observed as result of Lactobacillus strains -F. graminearum interaction; however, the A. parasiticus- Lact. plantarum interaction resulted in an increased AFB1 production. Lactobacillus rhamnosus RC007 proved to have no genes for resistance to the tested antibiotics. CONCLUSIONS: The ability of Lact. rhamnosus RC007 to rapidly drop the pH and to inhibit fungal growth and mycotoxin production and the absence of antibiotic resistance genes shows the potential of its application as inoculant and bio-control agent in animal feed. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated the importance of selecting bacteria for silage inoculants not only for the improvement of silage fermentation but also for their effects on mycotoxicogenic fungi and the resulting mycotoxin production due to the risk that they may involve.
Assuntos
Aspergillus/crescimento & desenvolvimento , Agentes de Controle Biológico , Fusarium/crescimento & desenvolvimento , Lactobacillus plantarum/fisiologia , Lactobacillus/fisiologia , Micotoxinas/biossíntese , Silagem/microbiologia , Aflatoxina B1/biossíntese , Fermentação , Lactobacillus/efeitos dos fármacos , Lactobacillus/crescimento & desenvolvimento , Lactobacillus plantarum/crescimento & desenvolvimento , Zearalenona/biossínteseRESUMO
The effect of Saccharomyces cerevisiae RC008 and RC016 strains, previously selected based on their aflatoxin B1 mycotoxin binding ability and beneficial properties, against Aspergillus carbonarius and Fusarium graminearum under different interacting environmental conditions was evaluated. In vitro studies on the lag phase, growth rate and ochratoxin A/zearalenone and DON production were carried out under different regimens of a(w) (0.95 and 0.99); pH (4 and 6); temperature (25 and 37 °C) and oxygen availability (normal and reduced). Both yeast strains showed antagonistic activity and decreasing growth rate compared to the control. In general, the RC016 strain showed the greatest inhibitory activity. Except at the interacting condition 0.95 a(W), normal oxygen availability and 37 °C, at both pH values, A. carbonarius and F. graminearum were able to produce large amounts of mycotoxins in vitro. In general, a significant decrease in levels of mycotoxins in comparison with the control was observed. S. cerevisiae RC008 and RC016 could be considered as effective agents to reduce growth and OTA, ZEA and DON production at different interacting environmental conditions, related to those found in stored feedstuff. The beneficial and biocontrol properties of these strains are important in their use as novel additives for the control of mycotoxigenic fungi in stored feedstuffs.
Assuntos
Antibiose , Aspergillus/metabolismo , Fusarium/metabolismo , Micotoxinas/biossíntese , Saccharomyces cerevisiae/crescimento & desenvolvimento , Aflatoxina B1/metabolismo , Aflatoxina B1/farmacologia , Aspergillus/crescimento & desenvolvimento , Fusarium/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Ocratoxinas/biossíntese , Oxigênio/metabolismo , Temperatura , Tricotecenos/biossíntese , Água/metabolismo , Zearalenona/biossínteseRESUMO
Fusarium equiseti and Fusarium semitectum represent the most abundant species in the Fusarium complex isolated from flowers, soybean pods and seeds in Argentina. The aim of the present study was to assess the production of major type A and type B trichothecenes (diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin, nivalenol, deoxynivalenol) and zearalenone by 40 F. equiseti and 22 F. semitectum isolates on rice culture. Mycotoxins were determined by HPLC with fluorescence detection after derivatisation with 1-anthronylnitrile for type A trichothecenes (i.e. diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin), by HPLC with UV detection for type B trichothecenes (i.e. nivalenol and deoxynivalenol), and by TLC for zearalenone. A total of 22 of 40 F. equiseti isolates produced diacetoxyscirpenol, nivalenol and ZEA alone or in combination, whereas only two of 20 F. semitectum isolates were nivalenol and ZEA producers. Both Fusarium species did not produce any deoxynivalenol, neosolaniol, T-2 toxin and HT-2 toxin. The variable retention in toxigenicity displayed by both fungal species suggests that these species have a saprophytic lifestyle in the soybean agroecosystem in Argentina.
Assuntos
Fusarium/metabolismo , Glycine max/microbiologia , Tricotecenos/biossíntese , Zearalenona/biossíntese , Argentina , Cromatografia Líquida de Alta Pressão , Fusarium/classificação , Especificidade da Espécie , Espectrometria de FluorescênciaRESUMO
The intake of mycotoxin-contaminated feeds can lead to nutrient losses and may have adverse effects on animal health and on productivity. The aims of this study were (1) to determine the mycobiota present in poultry feed samples, and (2) to evaluate the natural occurrence of aflatoxin B(1), fumonisin B(1) and zearalenone. Fungal counts were similar between all culture media tested (10(3 )CFU g(-1)). The most frequent genus isolated was Penicillium spp. (41.26%) followed by Aspergillus spp. (33.33%) and Fusarium spp. (20.63%). High precision liquid chromatography was applied to quantify aflatoxin B(1) and fumonisin B(1). Thin layer chromatography was used to determine zearalenone levels. Aflatoxin B(1 )values ranged between 1.2 and 17.5 microg kg(-1). Fumonisin B(1) levels ranged between 1.5 and 5.5 microg g(-1). Zearalenone levels ranged between 0.1 and 7 microg g(-1). The present study shows the simultaneous occurrence of two carcinogenic mycotoxins, aflatoxin B(1) and fumonisin B(1), together with another Fusarium mycotoxin (zearalenone) in feed intended for poultry consumption. Many samples contained AFB(1 )levels near the permissible maximum and it could affect young animals. A synergistic toxic response is possible in animals under simultaneous exposure.
Assuntos
Aflatoxina B1/análise , Contaminação de Alimentos , Microbiologia de Alimentos , Fumonisinas/análise , Aves Domésticas , Zearalenona/análise , Aflatoxina B1/biossíntese , Criação de Animais Domésticos , Animais , Aspergillus/isolamento & purificação , Aspergillus/metabolismo , Brasil , Cromatografia Líquida , Contagem de Colônia Microbiana , Fumonisinas/metabolismo , Fusarium/isolamento & purificação , Fusarium/metabolismo , Penicillium/isolamento & purificação , Penicillium/metabolismo , Estações do Ano , Zearalenona/biossínteseRESUMO
The galactose oxidase-producing fungus Dactylium dendroides was re-identified as a Fusarium species. Fungi of this genus are well known for the production of mycotoxins. Verification of growth of this fungus on rice, corn and liquid medium described for the production of galactose oxidase is provided to determine whether the fungus could produce Fusarium toxins, namely, moniliformin, fusaric acid, fumonisin, zearalenone and the trichothecenes, deoxynivalenol, 3-acetyldeoxynivalenol, fusarenone, nivalenol, diacetoxyscirpenol, neosolaniol, and toxin T-2. Under the culture conditions used, deoxynivalenol, 3-acetyldeoxynivalenol and zearalenone were detected in the fungal culture medium. The finding is consistent with the hypothesis that the fungus is in fact a Fusarium species.
Assuntos
Fusarium/metabolismo , Galactose Oxidase/biossíntese , Micotoxinas/biossíntese , Animais , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Fina , Fusarium/enzimologia , Fusarium/isolamento & purificação , Cromatografia Gasosa-Espectrometria de Massas , Masculino , Micotoxinas/análise , Micotoxinas/toxicidade , Ratos , Ratos Wistar , Pele/efeitos dos fármacos , Testes de Irritação da Pele , Tricotecenos/análise , Tricotecenos/biossíntese , Tricotecenos/toxicidade , Zearalenona/análise , Zearalenona/biossíntese , Zearalenona/toxicidadeRESUMO
The influence of water activity (a(w)) on the kinetics of aflatoxin and zearalenone production in amaranth grains at 25 degrees C was studied. Minimum a(w) for aflatoxin production in this substrate was 0.825. Accumulation of the four aflatoxins (B1, B2, G1 and G2) was similar at a(w) 0.825 (maximum 81.2 microg/kg after 42 days) and 0.868 (maximum 109.6 microg/kg after 49 days). Maximum accumulation of total aflatoxins at a(w) 0.902 (260.4 microg/kg) was detected after 21 days, with an appreciable increment in the concentration of aflatoxins B1 and G1. These quantities were lower than those reported for aflatoxin production on other cereals and legumes, indicating that amaranth is not a good substrate for aflatoxin production. Zearalenone was not detected at a(w) 0.902. Maximum accumulation of zearalenone was 1.5 microg/g after 35 days at a(w) 0.925 and 11.1 microg/g after 49 days at a(w) 0.950.
Assuntos
Aflatoxinas/biossíntese , Aspergillus/metabolismo , Fusarium/metabolismo , Magnoliopsida/microbiologia , Água/química , Zearalenona/biossíntese , Aspergillus/crescimento & desenvolvimento , Fusarium/crescimento & desenvolvimento , Fatores de TempoRESUMO
Fusarium cultures (27 isolates of Fusarium graminearum, 5 of F. sporotrichioides, 5 of F. semitectum, 2 of F. solani, and one isolate of F. equiseti, F. heterosporum and F. oxysporum respectively, from maize ears) were screened to determine their ability to produce different trichothecenes and zearalenone. Twenty of 27 F. graminearum isolates produced deoxynivalenol (384-5745 micrograms/kg), 7/27 produced 3-acetyl-deoxynivalenol (322-1840 micrograms/kg), 3/27 produced neosolaniol (199-898 micrograms/kg), 5/27 produced diacetoxyscirpenol (205-3095 micrograms/kg), 4/27 produced HT-2 toxin (278-1377 micrograms/kg) and 13/27 produced zearalenone (200-35045 micrograms/kg). No isolate of F. graminearum produced either nivalenol, 15-acetyl-deoxynivalenol, T-2 tosin, T-2 triol or T-2 tetraol. Only chemotype IA (deoxynivalenol and 3-acetyl-deoxynivalenol) was observed. F. sporotrichioides isolates produced deoxynivalenol (5/5), T-2 triol and T-2 tetraol (1/5) and zearalenone (1/5). One F. semitectum isolate produced diacetoxyscirpenol and F. equiseti and F. oxysporum isolates produced only deoxynivalenol. Thus, three of the toxins studied, deoxynivalenol, zearalenone and 3-acetyl-deoxynivalenol are most likely to appear as contaminants in freshly harvested maize.
Assuntos
Microbiologia de Alimentos , Fusarium/metabolismo , Tricotecenos/biossíntese , Zea mays , Zearalenona/biossíntese , Argentina , Cromatografia Gasosa , Cromatografia em Camada FinaRESUMO
To evaluate the potential for mycotoxin production by molds in amaranth grains, the mycoflora was determined both before and after surface disinfection on dichloran-chloramphenicol-peptone agar (DCPA) and dichloran-18% glycerol agar (DG18). On both media Aspergillus, Penicillium, Fusarium and Alternaria were the predominant genera. A flaus and A. parasiticus were the Aspergillus species most frequently isolated. P. chrysogenum was the species most common among the penicillia. F. equiseti was the predominant Fusarium species. Isolates of Aspergillus, Penicillium and Fusarium were screened for mycotoxin production on sterile rice substrate and also using a simple screening method. Toxinogenic strains of A. flavus and A. parasiticus (aflatoxins), A. versicolor (sterigmatocystin), P. citrinum (citrinin), P. viridicatum (penicillic acid), F. moniliforme, F. equiseti and F. semitectum (zearalenone), were encountered. The simple screening method for toxinogenic molds showed good performance for the detection of molds producing aflatoxins and zearalenone compared with mycotoxins production on the natural substrate.
Assuntos
Fungos/isolamento & purificação , Magnoliopsida/microbiologia , Micotoxinas/biossíntese , Aflatoxinas/biossíntese , Argentina , Contagem de Colônia Microbiana , Fungos/crescimento & desenvolvimento , Fungos/metabolismo , Sementes/microbiologia , Zearalenona/biossínteseRESUMO
Zearalenone production by Fusarium graminearum and Fusarium oxysporum was studied under two temperature conditions. Incubation at 25 degrees C for 4 weeks enhanced zearalenone synthesis, improving detection of zearalenone-producing strains of Fusarium oxysporum. Zearalenone production was either totally or partially inhibited when temperature was lowered to 12-14 degrees C during the last 2 weeks of incubation.