My research focuses on the development of a novel method for the fast detection of aflatoxin-producing fungi from the volatile organic compounds that they produce. Aflatoxins have received great attention because of their demonstrated potent carcinogenic effect in susceptible laboratory animals and their acute toxicological effects in humans. Traditional detection and quantification techniques are considered time-consuming, high cost, and require technical professionals. The `odor' or so called volatile metabolites released by a fungus is the key for fast detection. Several researchers have reported that diverse fungi species have unique volatile metabolite patterns. This study focuses on answering several questions: Is it possible to discriminate aflatoxins-producing fungi from other fungi based on volatile metabolites? What are the key discriminating biomarkers related to each fungus? Does the growth environment have an effect on the production of volatile metabolites? What chemicals are consistently emitted by a fungus under varied conditions? To answer these questions, one toxigenic and one nontoxigenic A. flavus isolate were studied to evaluate the microbial volatile organic compound (MVOC) profiles. The results described in chapter two of this dissertation indicate that MVOC production is time-dependent and that aflatoxigenic and non-aflatoxigenic strains have different MVOC expression patterns. Chapter three describes the effects of experimental parameters on fungal volatile metabolites. The identity and quantity of MVOCs can be affected by many factors including SPME fiber type, fungal growth media, and growth temperature. A CAR/PDMS coated fiber performed better than the other SPME fibers by collecting a larger variety and quantity of MVOCs. Fungi grown on the chemical defined liquid media produced much larger quantities of MVOCs compared to the other media. The highest MVOC production results were found at 30 degrees Celsius. The fungi discrimination study was extended in chapter four by including 3 toxigenic and 3 non-toxigenic isolates using multivariate analysis. The results indicate that volatile patterns vary even at the fungal isolate level and that discrimination of aflatoxin-producing fungi from non-toxigenic fungi is possible.

Aspergillus flavus exemplifies a pathogenic fungus that remains a significant contributor to the loss of corn (Zea mays) crops. The production of carcinogenic aflatoxins renders the crop hazardous for consumption and causes significant loss to farmers. Therefore, the prevention of A. flavus contamination continues to persist as a topic for research intervention. Host resistance to this pathogen provides a promising source of defense for the corn plant. Corn inbred line Mp313E was previously identified to exhibit significant resistance against the A. flavus fungal infection and aflatoxin contamination. Quantitative trait loci (QTL) mapping has previously established four major QTL locations associated with aflatoxin resistance in the corn inbred line Mp313E. Near-isogenic lines were developed containing these previously identified QTLs from backcrossing of inbred lines Mp313E (resistant donor parent) and Va35 (susceptible recurrent parent). Quantitative RT-PCR (qRT-PCR) was used to study gene expression patterns of 17 genes selected from plant-pathogen interaction pathways. Furthermore, genomic primer analysis was used for establishment of 15 candidate genes for marker- assisted breeding.

Aflatoxin is a carcinogen produced by the fungus Aspergillus flavus that causes millions of dollars in agriculture losses in the southeastern US. This thesis examines the dispersal of A. flavus on two corn inbred lines, resistant (Mp313E) and susceptible (B73), which differ in total aflatoxin accumulation after infection with A. flavus. After inoculating corn kernels with the fungus an RNA analysis was used to determine the location (number of kernels away from inoculation site) and abundance of A. flavus at weekly intervals. A. flavus started its spread at 7 days after inoculation (DAI) on both corn lines. The B73 corn line showed a constant spread of 3.4mm per day until the entire ear was infected at 21 DAI. The spread on Mp313E did not proceed beyond 3 kernels away from the inoculation site following 7 DAI. The results are significant because they show a faster rate of spread than previously reported and they help quantify the ability of Mp313E to mitigate infection.

No description available.

La contamination des aliments par les mycotoxines est une source très importante de gaspillage de nourriture. Depuis des années, la stratégie classique pour lutter contre ces contaminants est l’utilisation de pesticides. Cependant, il a été montré que ces produits pouvaient avoir des effets nocifs sur la biodiversité et la santé humaine et animale. Il est donc nécessaire de développer de nouvelles stratégies, plus écologiques, pour lutter contre les mycotoxines. L’utilisation de produits naturels pourrait représenter une alternative intéressante et plus respectueuse de l’environnement. En effet, certains produits naturels sont capables d’inhiber la production de mycotoxines. Cependant, le mécanisme d’action mis en jeu est souvent mal compris. Un des objectifs principaux de ce travail a consisté à identifier des produits naturels capables d’inhiber la production de mycotoxines et d’élucider leur mécanisme d’action moléculaire. Pour ce faire, un outil moléculaire a été conçu pour comprendre les mécanismes permettant à des produits naturels d’inhiber la production d’Aflatoxine B1 (AFB1) chez Aspergillus flavus. L’étude de cette mycotoxine est importante puisque c’est un cancérigène puissant chez l’homme et les animaux. Un outil moléculaire permettant l’analyse simultanée de l’expression de 60 des principaux gènes impliqués dans la synthèse de l’aflatoxine B1 par q-*-PCR a été développé. Il permet d’étudier l’ensemble des gènes du cluster d’AFB1 mais également 33 autres gènes codant pour des facteurs de régulation liés à l’environnement dans lequel se trouve la moisissure. Par cette approche, le mécanisme d'action moléculaire de l’eugénol et la pipérine, ainsi que celui de 3 extraits naturels de plantes a été identifié et l'impact de ces composés sur les gènes impliqués dans la production d'AFB1 a été élucidé. L'un des principaux résultats de cette étude a été de montrer que les différents produits naturels modulent systématiquement plusieurs gènes au cours de l'inhibition de la production d’AFB1. Notre étude montre que les produits naturels représentent une alternative possible pour limiter la contamination des aliments par l’AFB1. L'élucidation du mécanisme d'action des produits naturels ouvre de nouvelles perspectives sur les méthodes à employer pour inhiber la production de la toxine. / Mycotoxin’s contamination represents an important source of food spoilage that has to be taken in consideration. For years pesticides, have been used as a common strategy to combat mycotoxin contamination. However, such products were also demonstrated to be harmful to humans and animals’ health. Therefore, it is necessary to find new strategies in order to avoid mycotoxin contamination and the use of natural products could be a promising alternative. Indeed, these compounds may be eco-friendly and several of them are demonstrated aseffective agents against toxin production. Nevertheless, their precise mechanism of action is poorly documented. One of the principal aim of this work consisted in the identification of natural sources capable to inhibit mycotoxin production and in the elucidation of their molecular mechanism of action. For that, we developed a molecular tool aiming the analysis of the impact of natural extracts on the expression of several genes related to Aflatoxin B1 synthesis in Aspergillus flavus. The study of this mycotoxin is an important issue since it is one of the most dangerous compounds inducing cancer in humans and animals. Taking advantage of the well-studied genome of Aspergillus flavus and considering that AFB1 production involves a great number of genetic elements, a q-PCR approach including 60 of the principal genes involved in toxin biosynthesis was developed. This tool simultaneously studies the entire AFB1 gene cluster but also 33 regulatory factors coding for external stimuli to which fungus is exposed. Using this molecular approach, the study of already known but also, new sources of anti-aflatoxigenic compounds was performed. The molecular mechanism of action of 2 isolated molecules and 3 whole plant extracts were determined and the impact of these compounds on the genes involved in AFB1 production was analysed. One of the innovative findings consisted in the demonstration that natural products systematically modulate several genes within AFB1’s inhibition. Taken together, our approach demonstrated that the use of natural products against mycotoxin production can represent an alternative strategy to inhibit food contamination. The elucidation of the mechanism of action of natural products allowed a better understanding of the fungal machinery through which toxin can be inhibited.

Orientador: Ely Nahas / Banca: José da Cruz Machado / Banca: Antônio Carlos Monteiro / Resumo: O conhecimento da atividade das enzimas hidrolíticas é essencial para compreender as transformações dos nutrientes no solo. O milho é uma das principais culturas sob o ponto de vista econômico. O objetivo deste estudo foi avaliar a influência do crescimento dos fungos em dois tipos de solos, na presença e ausência de glicose, no desenvolvimento das plântulas de milho, no padrão isoenzimático dos coleóptilos, nos teores de carboidratos totais residuais, nas atividades da desidrogenase e amilase. Utilizou-se delineamento inteiramente casualizado com esquema fatorial. A adição de glicose no meio de cultura aumentou a velocidade de crescimento de A. flavus e Penicillium sp., mas não de F. verticillioides. Na presença de glicose, a produção de esporos aumentou de 1,2 (F. verticillioides) e 8,2 vezes (A. flavus), e reduzido de 3,5 vezes com Penicillium sp. A redução dos teores de carboidratos totais ajustou-se significativamente às equações de 1º e 2º grau. A.flavus e Penicillium sp., apresentaram maior consumo de carboidratos totais que o solo sem inoculação ou inoculado com F. verticillioides. A adição de glicose no solo favoreceu o consumo de carboidratos residuais, provavelmente devido ao estímulo do crescimento dos fungos. Exceto com F. verticillioides, a atividade da desidrogenase aumentou em média de 1,5 a 1,8 vez (p<0,05) nos solos com glicose em relação aos solos sem glicose. À atividade da amilase, aumentou 1,3 a 1,5 vez por efeito da adição de glicose no solo. Maior atividade da amilase foi observada no solo Latossolo Vermelho distrófico (LVd) com glicose e inoculado com A.flavus e Penicillium sp. em relação ao controle. As dimensões das plântulas como altura dos coleóptilos, comprimento das raízes e massa seca das plântulas de milho dos solos adicionados de glicose e/ou inoculados com os fungos foram diminuídas. A expressão genética... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The knowledge about hydrolytic enzymes activity is essential to understand the nutrients transformations in soil. Corn is one of the main crops from the economic view in the whole world. The objective of this study was evaluate the fungi growth in two soil types, in the presence and absence of glucose, coleoptiles development, roots and weight of corn seedlings, coleoptiles isoenzyme pattern, content of total residual carbohydrates, enzymes dehydrogenase and amylase activity. Was used a completely randomized design with factorial arrangement. The glucose addition in culture medium increased the growth rate of A. flavus and Penicillium sp., but not F. verticillioides. In the presence of glucose, the spores number was increased from 1.2 (F. verticillioides) and 8.2 times (A. flavus), but was reduced 3.5 times with Penicillium sp. Reducing the levels of total carbohydrates, significantly adjusted to the equations of 1st and 2nd grade. A.flavus and Penicillium sp., showed higher carbohydrates consumption that the soil control or inoculated with F. verticillioides. The glucose addition in soil, favored the use of residual carbohydrates, probably due fungi growth stimulation. Except F. verticillioides, dehydrogenase activity increased in the range 1.5 to 1.8 times (p<0.05) in soils with glucose compared to glucose free soil. Amylase activity increased 1.3 to 1.5 times by glucose addition effect in soil. Increased amylase activity was observed in the Distrophic Red Latosol (DRL) with glucose and inoculated with A.flavus and Penicillium sp., compared to control. The seedlings dimensions as coleoptiles height, root length and dry weight of maize seedlings of the soils added with glucose and inoculated with fungi were decreased. Gene expression of maize seed was changed due probable by fungi inoculated infection in soil. The coleoptiles isoenzymes pattern was amended as early as 5 incubation... (Complete abstract click electronic access below) / Mestre

Orientadores: José Luiz Pereira, Marta Hiromi Taniwaki / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-19T08:18:04Z (GMT). No. of bitstreams: 1 Calderari_ThaianeOrtolan_M.pdf: 6842829 bytes, checksum: 4d9030fc65c6d69a678e084cd772b7ed (MD5) Previous issue date: 2011 / Resumo: A castanha do Brasil (Bertholletia excelsa) é uma das mais importantes espécies de exploração extrativista da floresta Amazônica, sendo exportada para diversos países devido ao seu alto valor nutritivo. No entanto, os baixos níveis tecnológicos característicos de sua cadeia produtiva, considerada ainda extrativista e as condições inadequadas de manejo da matéria prima, favorecem o aparecimento de contaminação por fungos produtores de aflatoxinas, compostos tóxicos considerados cancerígenos para humanos. Este problema é um entrave para a comercialização do produto, principalmente no mercado externo, dado ao rigoroso controle de países europeus e Estados Unidos em relação aos níveis de toxinas presentes nos alimentos. Nestas condições, o presente trabalho teve por objetivo investigar a incidência de fungos em castanhas do Brasil e avaliar o potencial toxigênico dos isolados Aspergillus section flavi para a produção de aflatoxinas, bem como analisar a presença de aflatoxinas nesta matriz. Um total de 143 amostras provenientes dos Estados do Pará, Amazonas e São Paulo em diferentes etapas da cadeia produtiva da castanha foi analisado. A técnica utilizada para análise da infecção fúngica foi o plaqueamento direto em meio Dicloran 18% Glicerol. Os resultados foram expressos em porcentagem de infecção fúngica. Os isolados suspeitos foram purificados em meio Czapek extrato de levedura ágar e incubados a 25ºC/7 dias em diferentes temperaturas para a identificação das espécies. Para a análise do potencial toxigênico de cada isolado da seção flavi foi utilizada a técnica do ágar plug. Para a análise de aflatoxinas foi utilizada coluna de imunoafinidade para extração e limpeza das amostras e Cromatografia Líquida de Alta Eficiência e detector de fluorescência acoplado ao sistema de derivatização Kobracell para detecção e quantificação das aflatoxinas. Dentre o total de amostras coletadas, aquelas provenientes das florestas foram as que apresentaram maior valor médio de atividade de água, assim como maior porcentagem de infecção fúngica quantificada e biodiversidade de espécies. Considerando todas as amostras avaliadas, foram no total 13.421 isolados de fungos filamentosos, sendo que as espécies mais incidentes foram Aspergillus flavus, Aspergillus nomius, Penicillium citrinum, Aspergillus tamarii, Syncephalastrum racemosum e Penicillium sp. Dentre as espécies encontradas, 450 isolados de Aspergillus nomius e 9 de Aspergillus parasiticus foram identificados e 100% apresentaram capacidade de produção de aflatoxinas AFB1, AFB2, AFG1, AFG2. Dos de 703 isolados de Aspergillus flavus, 63,5% apresentaram a capacidade de produzir aflatoxinas AFB1 e AFB2. A média de contaminação por aflatoxinas totais obtida foi de 7,17 µg/kg (ND-104,2 µg/kg), 1,13µg/kg (ND-7,44µg/kg) e 0,47 µg/kg (ND-0,2 µg/kg) para as amostras dos Estados do Pará, Amazonas e de São Paulo, respectivamente. Das 143 amostras coletadas, apenas 5 amostras excederam o limite máximo de aflatoxinas totais estabelecido pela União Européia e pela ANVISA (10,0ug/kg para castanhas do Brasil sem casca destinadas ao consumo direto para humanos) / Abstract: The Brazil nut (Bertholletia excelsa) is one of the most important species extracted from the Amazon forest, and is exported to several countries due to its high nutritional value. However, the low technological level of its productive chain and inadequate raw material handling favour contamination points for aflatoxin fungi producers aflatoxins. The presence of aflatoxins in Brazil nuts has been a barrier for its marketing, mainly for the export market, due to rigorous control of European countries and the United States. Therefore, the present work had the objective of investigating the incidence of fungi in Brazil nuts and evaluate the toxigenic potential of Aspergillus section flavi isolates to produce aflatoxins, as well as analyzing the presence of aflatoxins in this product. A total of 143 samples from three different states, at different stages of the Brazil nut chain was analyzed. The technique used for fungi infection analized was direct plating in DG18. The results were expressed in percentage of fungal infection. The suspected isolates were purified on Czapek yeast extract agar (CYA) and incubated at different temperature for species identification. For toxin production analysis of each isolatec Aspergillus section flavi the agar plug technique was used. For aflatoxin analysis an immunoafinity column was used for extraction and cleaning of the sample, high performance liquid for aflatoxin detection and quantification in Brazil nuts, chromatography (HPLC) with a fluorescence detector was used, coupled with the Kobracell derivatization system. Among the analyzed samples, the ones collected directly from the forests had the highest water activity, the highest fungal infection and greatest biodiversity of species. A total of 13,421 filamentous fungi were quantificated from all the samples with the most common isolated species were: Aspergillus flavus, Aspergillus nomius, Penicillium citrinum, Aspergillus tamarii, Syncephalastrum racemosum e Penicillium spp. All the 450 strains of Aspergillus nomius and 9 strains of Aspergillus parasiticus, showed 100% capacity of aflatoxin B1, B2, G1, G2 production. Out of 703 species of Aspergillus flavus isolated, 63.5% showed capacity of aflatoxin B1 e B2 production. The average of total aflatoxin contamination was: 7.17µg/kg (ND-104.2 µg/kg), 1.13µg/kg (ND-7.44µg/kg) and 0.47 µg/kg (ND-0.2 µg/kg) for samples from Pará, Amazon and São Paulo, respectively. Out of 143 analyzed samples, only 5 samples exceded the maximum level for total aflatoxins established by the European Union and ANVISA of 10 µg/kg for shelled Brazil nuts intended for direct human consumption / Mestrado / Ciência de Alimentos / Mestre em Ciência de Alimentos

Os grãos de milho são expostos, no campo e no armazenamento, à ação de fatores físicos, químicos e biológicos, que interagem entre si, favorecendo a contaminação fúngica, principalmente pelos gêneros Aspergillus, Fusarium e Penicilllium, considerados os mais importantes do ponto de vista toxigênico. O presente trabalho teve como principal objetivo investigar a eficácia do agente de biocontrole Afla-guard® no controle de fungos e de micotoxinas em grãos de milho, no campo, em diferentes estágios de maturidade da planta cultivada no município de Cássia dos Coqueiros, Estado de São Paulo. Visou, também, como objetivos adicionais, a determinação da atividade de água das amostras de milho, a pesquisa de fungos do ar, do solo e do milho, e a influência dos fatores climatológicos (temperatura e precipitação pluvial), no crescimento fúngico e na produção de micotoxinas. A micobiota do milho foi determinada pela técnica da semeadura direta utilizando meio de Ágar Dicloran Rosa Bengala Cloranfenicol (DRBC) e a determinação de micotoxinas por Cromatografia Líquida de Alta Eficiência. A identificação dos fungos foi realizada utilizando metodologia clássica (morfológica) e molecular (sequenciamento do DNA ribossomal). Nas amostras de milho, constatou-se a predominância de Fusarium verticillioides, em todas as coletas. Entretanto, a presença de Aspergillus flavus foi detectada, nas áreas tratadas com produto, a partir da 4ª coleta. No ar atmosférico, os fungos mais frequentes foram: Cladosporium spp., Trichoderma spp. e Fusarium solani. A. flavus foi isolado, principalmente, na 3ª coleta, do tratamento. No solo, os gêneros Penicillium, Trichoderma e Rhizopus foram os mais isolados em todas as coletas. A. flavus foi isolado a partir da 3ª coleta, somente nas áreas tratadas. Das amostras analisadas, a presença de fumonisinas foi detectada em 33,3 % das amostras tratadas com o agente de biocontrole e em 66,6% das amostras do grupo controle (não tratadas). Em relação às aflatoxinas, a presença da toxina foi detectada em apenas 2 amostras (1 tratamento e 1 controle) na 4ª coleta. Quanto à análise do potencial aflatoxigênico determinado, encontramos em 4 dos 13 isolados de A. flavus, aflatoxinas B1 e B2. Os demais isolados não foram potencialmente produtores, podendo ser, portanto, oriundos do Afla-guard®. Já em relação à temperatura, 26 °C foi a média encontrada e 6,3 mm foi a média detectada em relação à precipitação pluvial. Embora não tenha apresentado resultados estatisticamente significativos, o emprego do agente de biocontrole foi relevante no que diz respeito a diminuição da contaminação por Fusarium verticillioides e fumonisinas. Entretanto, outros estudos são necessários para uma melhor avaliação do produto / Maize grains are exposed, in the field and in storage, the action of physical, chemical and biological agents that interact with each other, encouraging fungal contamination, mainly by Aspergillus, Fusarium and Penicillium, considered the most important from the point of view toxigenic. This study aimed to investigate the effectiveness of Afla-guard® biocontrol agent in control of fungi and mycotoxins in corn grain in the field, at different stages of maturity of the plant cultivated in the city of Cassia dos Coqueiros, state São Paulo. Aimed also as additional objectives, determining the water activity of the maize samples, the research air fungi, soil and maize, and the influence of climatic factors (temperature and rainfall) in fungal growth and mycotoxin production. The mycobiota maize was determined by the technique of direct seeding using means of Dichloran Rose Bengal Chloramphenicol Agar (DRBC) and the determination of mycotoxins by high-performance liquid chromatography. The identification of fungi was carried out using classical methods (morphological) and molecular (sequencing of ribosomal DNA). In samples of maize, there was a predominance of Fusarium verticillioides in all samplings. However, the presence of Aspergillus flavus was detected in the areas treated with product samplings from the 4th. In atmospheric air, the most common molds were Cladosporium spp, Trichoderma spp.. Fusarium solani and. A. flavus was isolated mainly in 3rd samplings, treatment. On the ground, Penicillium, Trichoderma and Rhizopus were the most isolated in all samples. A. flavus was isolated from the 3rd collects only in the treated areas. Of the samples tested, the presence of fumonisin was detected in 33.3% of the samples treated with the biocontrol agent and 66.6% of the control group samples (untreated). Regarding the aflatoxins, the presence of the toxin was detected in just 2 samples (1 treatment and 1 control) in 4th collect. The analysis of the potential aflatoxigenic, found in 4 of 13 isolates of A. flavus, aflatoxins B1 and B2. The remaining isolates were not potentially producers and can therefore be derived from the Afla-guard®. Regarding the temperature 26 ° C was found to average 6.3 mm and the average was detected in relation to rainfall. Although not shown statistically significant results, the use of biocontrol agent is relevant as regards the reduction of contamination by Fusarium verticillioides and fumonisins. However, other studies are needed to better evaluate the product

Os grãos de milho são expostos, no campo e no armazenamento, à ação de fatores físicos, químicos e biológicos, que interagem entre si, favorecendo a contaminação fúngica, principalmente pelos gêneros Aspergillus, Fusarium e Penicilllium, considerados os mais importantes do ponto de vista toxigênico. O presente trabalho teve como principal objetivo investigar a eficácia do agente de biocontrole Afla-guard® no controle de fungos e de micotoxinas em grãos de milho, no campo, em diferentes estágios de maturidade da planta cultivada no município de Cássia dos Coqueiros, Estado de São Paulo. Visou, também, como objetivos adicionais, a determinação da atividade de água das amostras de milho, a pesquisa de fungos do ar, do solo e do milho, e a influência dos fatores climatológicos (temperatura e precipitação pluvial), no crescimento fúngico e na produção de micotoxinas. A micobiota do milho foi determinada pela técnica da semeadura direta utilizando meio de Ágar Dicloran Rosa Bengala Cloranfenicol (DRBC) e a determinação de micotoxinas por Cromatografia Líquida de Alta Eficiência. A identificação dos fungos foi realizada utilizando metodologia clássica (morfológica) e molecular (sequenciamento do DNA ribossomal). Nas amostras de milho, constatou-se a predominância de Fusarium verticillioides, em todas as coletas. Entretanto, a presença de Aspergillus flavus foi detectada, nas áreas tratadas com produto, a partir da 4ª coleta. No ar atmosférico, os fungos mais frequentes foram: Cladosporium spp., Trichoderma spp. e Fusarium solani. A. flavus foi isolado, principalmente, na 3ª coleta, do tratamento. No solo, os gêneros Penicillium, Trichoderma e Rhizopus foram os mais isolados em todas as coletas. A. flavus foi isolado a partir da 3ª coleta, somente nas áreas tratadas. Das amostras analisadas, a presença de fumonisinas foi detectada em 33,3 % das amostras tratadas com o agente de biocontrole e em 66,6% das amostras do grupo controle (não tratadas). Em relação às aflatoxinas, a presença da toxina foi detectada em apenas 2 amostras (1 tratamento e 1 controle) na 4ª coleta. Quanto à análise do potencial aflatoxigênico determinado, encontramos em 4 dos 13 isolados de A. flavus, aflatoxinas B1 e B2. Os demais isolados não foram potencialmente produtores, podendo ser, portanto, oriundos do Afla-guard®. Já em relação à temperatura, 26 °C foi a média encontrada e 6,3 mm foi a média detectada em relação à precipitação pluvial. Embora não tenha apresentado resultados estatisticamente significativos, o emprego do agente de biocontrole foi relevante no que diz respeito a diminuição da contaminação por Fusarium verticillioides e fumonisinas. Entretanto, outros estudos são necessários para uma melhor avaliação do produto / Maize grains are exposed, in the field and in storage, the action of physical, chemical and biological agents that interact with each other, encouraging fungal contamination, mainly by Aspergillus, Fusarium and Penicillium, considered the most important from the point of view toxigenic. This study aimed to investigate the effectiveness of Afla-guard® biocontrol agent in control of fungi and mycotoxins in corn grain in the field, at different stages of maturity of the plant cultivated in the city of Cassia dos Coqueiros, state São Paulo. Aimed also as additional objectives, determining the water activity of the maize samples, the research air fungi, soil and maize, and the influence of climatic factors (temperature and rainfall) in fungal growth and mycotoxin production. The mycobiota maize was determined by the technique of direct seeding using means of Dichloran Rose Bengal Chloramphenicol Agar (DRBC) and the determination of mycotoxins by high-performance liquid chromatography. The identification of fungi was carried out using classical methods (morphological) and molecular (sequencing of ribosomal DNA). In samples of maize, there was a predominance of Fusarium verticillioides in all samplings. However, the presence of Aspergillus flavus was detected in the areas treated with product samplings from the 4th. In atmospheric air, the most common molds were Cladosporium spp, Trichoderma spp.. Fusarium solani and. A. flavus was isolated mainly in 3rd samplings, treatment. On the ground, Penicillium, Trichoderma and Rhizopus were the most isolated in all samples. A. flavus was isolated from the 3rd collects only in the treated areas. Of the samples tested, the presence of fumonisin was detected in 33.3% of the samples treated with the biocontrol agent and 66.6% of the control group samples (untreated). Regarding the aflatoxins, the presence of the toxin was detected in just 2 samples (1 treatment and 1 control) in 4th collect. The analysis of the potential aflatoxigenic, found in 4 of 13 isolates of A. flavus, aflatoxins B1 and B2. The remaining isolates were not potentially producers and can therefore be derived from the Afla-guard®. Regarding the temperature 26 ° C was found to average 6.3 mm and the average was detected in relation to rainfall. Although not shown statistically significant results, the use of biocontrol agent is relevant as regards the reduction of contamination by Fusarium verticillioides and fumonisins. However, other studies are needed to better evaluate the product

Made available in DSpace on 2015-05-14T12:59:24Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 819195 bytes, checksum: 00bb6e156c9bc61f631332e47253375e (MD5) Previous issue date: 2011-06-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Due increase of incidence of fungal infections for Candida albicans and Aspergillus spp. in immunocompromised patients, and emerging resistant strains to conventional antifungals, it is accentuated the need for new antifungal. Essential oils have been tested for antimycotic activity and possess potential as antifungal agents. This work investigated the activity of essential oil of Cymbopogon winterianus against Candida albicans, Aspergillus flavus and A. fumigatus, by MIC and MFC; time-kill methods and morphological changes in the C. albicans, inhibition of the fungal mycelial growth and analysis of conidia germination of Aspergillus flavus and A. fumigatus when exposed to several concentrations of oil and by cellular leakage and assessed the bind of essential oil with ergosterol. The results shown that essential oil had concentrationdependent antifungal activity, alters the morphology in C. albicans, inhibits conidia germination and the radial mycelia growth of Aspergillus flavus and Aspergillus fumigatus, causes cellular leakage of all strains of fungal species tested and binds to ergosterol. These results make essential oil of Cymbopogon winterianus a potential agent in controlling fungi growth that cause infections, like hospital-acquired infections. / Devido ao aumento na incidência de infecções fúngicas por Candida albicans e Aspergillus spp. em pacientes imunocomprometidos, e ao surgimento de cepas resistentes aos antifúngicos convencionais, é crescente a necessidade de novos antifúngicos. Óleos essenciais têm sido testados contra fungos, e possuem potencial como agentes antifúngicos. Este trabalho investigou a atividade do óleo essencial de Cymbopogon winterianus contra Candida albicans, Aspergillus flavus e A. fumigatus, através da Concentração Inibitória Mímima (CIM), da Concentração Fungicida Mínima (CFM), do tempo de morte e de mudanças morfológicas em C. albicans; da inibição do crescimento radial fúngico e da análise da germinação dos conídios de Aspergillus flavus e A. fumigatus quando expostos a várias concentrações do óleo e através da lise celular e da ligação do óleo essencial com o ergosterol. Os resultados mostraram que o óleo essencial tem atividade antifúngica dependente da concentração, altera a morfologia de C. albicans, inibe a germinação de conídios e o crescimento micelial radial de Aspergillus flavus e Aspergillus fumigatus, causa lise celular de todas as cepas dos fungos testados e se liga ao ergosterol. Estes resultados fazem do óleo essencial de Cymbopogon winterianus um potencial agente no controle do crescimento de fungos que podem causar infecções, como aquelas que acontecem no ambiente hospitalar.