Aspergillus flavus is a very important toxigenic fungus that produces aflatoxins, a group of extremely toxic substances to man and animals. Toxigenic fungi can grow in feed cropsAflatoxins constitute a group of low molecular weight compounds known to be extremely toxic to animals and man (Bennett & Klich 2003). They are secondary metabolites produced mainly by Aspergillus flavus and A. parasiticus, which are ubiquitous and cosmopolitan fungi able to grow on a wide variety of substrates. However, not all members of each species are toxigenic (Thapar 1988) and, even within potentially toxigenic strains, growth is not necessarily accompanied by toxin production, which depends on favorable environmental conditions such as temperature and humidity (Correa 2000). The economic losses due to fungal contamination and the high costs of control measures are enormous (Bennett & Keller 1997) and add up to billions of dollars worldwide (Pozzi 2000). For this reason, efforts on scientific research have been towards prevention rather than remedial action (Bennett & Keller 1997).The key action for preventing mycotoxins is to block the growth of toxigenic fungi (Fonseca et al. 1974, Bennett & Keller 1997. But this is not an easy task, since these microorganisms are widely spread through several ecosystems, covering vast geographical areas. Furthermore, they can be easily disseminated by wind and may contaminate food crops at different stages, including harvest, post-harvest, processing, transportation, and even at storage conditions in supermarkets.Several approaches can be adopted to prevent or minimize food contamination by aflatoxins, such as controlling potential toxigenic-fungi carriers (e.g., insects and rodents), reducing the storage period and controlling humidity and temperature (Correa 2000). The use of antifungal compounds and insecticides, in turn, has been increasingly criticized from the standpoint of environmental concerns, as well as being costly. The production of resistant-plant varieties, although not having yielded strong positive results, is considered to be a promising alternative (Trail et al. 1995) to prevent both A. flavus substrate colonization and aflatoxin production upon fungal proliferation. However, it is important to bear in mind that the host-parasite co-evolution frequently leads to an "arms race" (Ridley 2001), and it is thus unlikely that fungi remain stable with respect to their invasive or toxigenic potential, as they continuously adapt.The use of non-toxigenic strains for the biological control of toxigenic ones has already been suggested by Egel and collaborators (1994). The non-toxigenic varieties would be artificially disseminated in nature (Egel et al. 1994, Trail et al. 1995 to compete with the toxigenic strains, driving them out of their ecological niches (Trail et al. 1995). In experiments with plants artificially infected with non-toxigenic fugal strains, a reduction by up to 90% in the aflatoxin contamination was observed (Cotty 1989 apud Tran-Dinh et al. 1999). Yet promising, this ...

Probiotic microorganisms (Saccharomyces cerevisiae var. boulardii, S. cerevisiae UFMG 905, and Lactobacillus delbrueckii UFV H2b20) were evaluated as biological control agents to reduce aflatoxin and spore production by Aspergillus parasiticus IMI 242695 in peanut. Suspensions containing the probiotics alone or in combinations were tested by sprinkling on the grains followed by incubation for seven days at 25°C. All probiotic microorganisms, in live and inactivated forms, significantly reduced A. parasiticus sporulation, but the best results were obtained with live cells. The presence of probiotics also altered the color of A. parasiticus colonies but not the spore morphology. Reduction in aflatoxin production of 72.8 and 65.8% was observed for S. boulardii and S. cerevisiae, respectively, when inoculated alone. When inoculated in pairs, all probiotic combinations reduced significantly aflatoxin production, and the best reduction was obtained with S. boulardii plus L. delbrueckii (96.1%) followed by S. boulardii plus S. cerevisiae and L. delbrueckii plus S. cerevisiae (71.1 and 66.7%, resp.). All probiotics remained viable in high numbers on the grains even after 300 days. The results of the present study suggest a different use of probiotics as an alternative treatment to prevent aflatoxin production in peanut grains.

Aflatoxin B(1) is a toxigenic and carcinogenic compound produced by Aspergillus flavus and Aspergillus parasiticus. To inhibit aflatoxin contamination of peanuts, seeds of two peanut breeds, IAC Caiapó and IAC Runner 886, were inoculated with A. parasiticus (1.0 × 10(6) spores per ml) and the yeast Saccharomyces cerevisiae (3.2 × 10(7) cells per ml) and incubated at 25°C for 7 and 15 days. Two experiments were conducted for each incubation period separately. The treatments were completely randomized, with three replications per treatment. Treatments included the two cultivars and three types of inoculation (pathogen alone, yeast and pathogen, and yeast 3 h before pathogen). Aflatoxin B(1) was quantified with a densitometer at 366 nm after thin layer chromatography. Aflatoxin B(1) contamination in peanuts was reduced after the addition of S. cerevisiae. The concentration of aflatoxin B(1) decreased by 74.4 and 55.9% after 7 and 15 days, respectively. The greatest aflatoxin reduction was observed when S. cerevisiae was inoculated 3 h before the pathogen in IAC Caiapó seeds and incubated for 7 days at 25°C. The use of S. cerevisiae is a promising strategy for biological control of aflatoxin contamination in peanuts.

, Valbert Nascimento Cardoso 4 RESUMOFoi verificado o efeito da irradiação gama ( 60 Co) na capacidade de destruir a microbiota fúngica, em amendoim em grão, cultivar Tatu Vermelho, da safra 2003 (segundo semestre). Os grãos de amendoim, após a irradiação, foram mantidos à temperatura ambiente em embalagem plástica comercial, durante 180 dias. Para a determinação da porcentagem fúngica foi utilizada a técnica do plaqueamento direto utilizando o meio Ágar Dicloran Rosa de Bengala Cloranfenicol (DRBC), desinfetando ou não os grãos com solução de hipoclorito de sódio. Em grãos de amendoim irradiados e desinfetados externamente, observou-se redução da infecção fúngica a 5 kGy e destruição total de fungos a 10 kGy, após 180 dias de armazenamento à temperatura ambiente. Em grãos irradiados e não desinfetados externamente foram verificados, em função do tempo de armazenamento, aumento da população de fungos com a dose de 1 kGy, redução com a dose de 5 kGy e eliminação total com a aplicação de 10 kGy. A irradiação gama, na dose de 10 kGy ou superior, demonstrou ser um processo eficaz na redução da microbiota fúngica de amendoim em grão, cultivar Tatu Vermelho.Termos para indexação: Irradiação gama; aflatoxina B 1 ; amendoim, Arachis hypogaea. ABSTRACTGamma-irradiation effect was verified on the capability of destroying the mycoflora of peanuts grain, Tatu Vermelho cultivar, 2003 crop (second semester). The peanuts grains, after irradiation, were kept at room temperature in plastic bags during 180 days. To determine the percentage of fungi, the direct plating technique was used and the grains were plated out on mycological media dicholoran rose bengal chloranphenicol (DRBC), being desinfected or not with sodium hypochlorite solution. Irradiated and desinfected peanuts was observed a reduction of fungi infection at 5 kGy and total fungi destruction at 10 kGy, after 180 days in storage at room temperature. Irradiated and non desinfected grains showed a increase of fungi population with 1 kGy dose, reduction with 5 kGy dose and total destruction with 10 kGy dose. Gamma-irradiation in 10 kGy dose or higher, showed to be an efficient process to reduce the mycoflora of peanuts, Tatu Vermelho cultivar.

Aspergillus flavus is a very important toxigenic fungus that produces aflatoxins, a group of extremely toxic substances to man and animals. Toxigenic fungi can grow in feed cropsAflatoxins constitute a group of low molecular weight compounds known to be extremely toxic to animals and man (Bennett & Klich 2003). They are secondary metabolites produced mainly by Aspergillus flavus and A. parasiticus, which are ubiquitous and cosmopolitan fungi able to grow on a wide variety of substrates. However, not all members of each species are toxigenic (Thapar 1988) and, even within potentially toxigenic strains, growth is not necessarily accompanied by toxin production, which depends on favorable environmental conditions such as temperature and humidity (Correa 2000). The economic losses due to fungal contamination and the high costs of control measures are enormous (Bennett & Keller 1997) and add up to billions of dollars worldwide (Pozzi 2000). For this reason, efforts on scientific research have been towards prevention rather than remedial action (Bennett & Keller 1997).The key action for preventing mycotoxins is to block the growth of toxigenic fungi (Fonseca et al. 1974, Bennett & Keller 1997. But this is not an easy task, since these microorganisms are widely spread through several ecosystems, covering vast geographical areas. Furthermore, they can be easily disseminated by wind and may contaminate food crops at different stages, including harvest, post-harvest, processing, transportation, and even at storage conditions in supermarkets.Several approaches can be adopted to prevent or minimize food contamination by aflatoxins, such as controlling potential toxigenic-fungi carriers (e.g., insects and rodents), reducing the storage period and controlling humidity and temperature (Correa 2000). The use of antifungal compounds and insecticides, in turn, has been increasingly criticized from the standpoint of environmental concerns, as well as being costly. The production of resistant-plant varieties, although not having yielded strong positive results, is considered to be a promising alternative (Trail et al. 1995) to prevent both A. flavus substrate colonization and aflatoxin production upon fungal proliferation. However, it is important to bear in mind that the host-parasite co-evolution frequently leads to an "arms race" (Ridley 2001), and it is thus unlikely that fungi remain stable with respect to their invasive or toxigenic potential, as they continuously adapt.The use of non-toxigenic strains for the biological control of toxigenic ones has already been suggested by Egel and collaborators (1994). The non-toxigenic varieties would be artificially disseminated in nature (Egel et al. 1994, Trail et al. 1995 to compete with the toxigenic strains, driving them out of their ecological niches (Trail et al. 1995). In experiments with plants artificially infected with non-toxigenic fugal strains, a reduction by up to 90% in the aflatoxin contamination was observed (Cotty 1989 apud Tran-Dinh et al. 1999). Yet promising, this ...