Muitos equipamentos utilizados para quantificar substâncias, como toxinas em alimentos, freqüentemente apresentam deficiências para quantificar quantidades baixas. Em tais casos, geralmente indicam a ausência da substância quando esta existe, mas está abaixo de um valor pequeno \'ksi\' predeterminado, produzindo valores iguais a zero não necessariamente verdadeiros. Em outros casos, detectam a presença da substância, mas são incapazes de quantificá-la quando a quantidade da substância está entre \'ksai\' e um valor limiar \'tau\', conhecidos. Por outro lado, quantidades acima desse valor limiar são quantificadas de forma contínua, dando origem a uma variável aleatória contínua X cujo domínio pode ser escrito como a união dos intervalos, [ómicron, \"ksai\'), [\"ksai\', \'tau\' ] e (\'tau\', ?), sendo comum o excesso de valores iguais a zero. Neste trabalho, são propostos modelos que possibilitam discriminar a probabilidade de zeros verdadeiros, como o modelo de mistura com dois componentes, sendo um degenerado em zero e outro com distribuição contínua, sendo aqui consideradas as distribuições: exponencial, de Weibull e gama. Em seguida, para cada modelo, foram observadas suas características, propostos procedimentos para estimação de seus parâmetros e avaliados seus potenciais de ajuste por meio de métodos de simulação. Finalmente, a metodologia desenvolvida foi ilustrada por meio da modelagem de medidas de contaminação com aflatoxina B1, observadas em grãos de milho, de três subamostras de um lote de milho, analisados no Laboratório de Micotoxinas do Departamento de Agroindústria, Alimentos e Nutrição da ESALQ/USP. Como conclusões, na maioria dos casos, as simulações indicaram eficiência dos métodos propostos para as estimações dos parâmetros dos modelos, principalmente para a estimativa do parâmetro \'delta\' e do valor esperado, \'Epsilon\' (Y). A modelagem das medidas de aflatoxina, por sua vez, mostrou que os modelos propostos são adequados aos dados reais, sendo que o modelo de mistura com distribuição de Weibull, entretanto, ajustou-se melhor aos dados. / Much equipment used to quantify substances, such as toxins in foods, is unable to measure low amounts. In cases where the substance exists, but in an amount below a small fixed value \'ksi\' , the equipment usually indicates that the substance is not present, producing values equal to zero. In cases where the quantity is between \'\'ksi\' and a known threshold value \'tau\', it detects the presence of the substance but is unable to measure the amount. When the substance exists in amounts above the threshold value ?, it is measure continuously, giving rise to a continuous random variable X whose domain can be written as the union of intervals, [ómicron, \"ksai\'), [\"ksai\', \'tau\' ] and (\'tau\', ?), This random variable commonly has an excess of zero values. In this work we propose models that can detect the probability of true zero, such as the mixture model with two components, one being degenerate at zero and the other with continuous distribution, where we considered the distributions: exponential, Weibull and gamma. Then, for each model, its characteristics were observed, procedures for estimating its parameters were proposed and its potential for adjustment by simulation methods was evaluated. Finally, the methodology was illustrated by modeling measures of contamination with aflatoxin B1, detected in grains of corn from three sub-samples of a batch of corn analyzed at the laboratory of of Mycotoxins, Department of Agribusiness, Food and Nutrition ESALQ/USP. In conclusion, in the majority of cases the simulations indicated that the proposed methods are efficient in estimating the parameters of the models, in particular for estimating the parameter ? and the expected value, E(Y). The modeling of measures of aflatoxin, in turn, showed that the proposed models are appropriate for the actual data, however the mixture model with a Weibull distribution fits the data best.

O trabalho avaliou micobiota, contaminação por aflatoxinas (AFB), ácido ciclopiazônico (ACP) e fitoalexina (trans-resveratrol) nas variedades de amendoim Runner IAC 886 e IAC-Caiapó, no campo e armazenamento. Nas amostras de campo, na IAC 886 predominou Fusarium spp. nos grãos e cascas, contaminação por AFB em 30% dos grãos, ACP em 70% e trans-resveratrol em 5%. Na IAC-Caiapó prevaleceu Fusarium spp., em todas as amostras, AFB em 25% dos grãos, ACP em 55% e trans-resveratrol em 15%. Nas folhas, trans-reveratrol estava presente em 70%, nas variedades. No armazenamento, observou-se maior freqüência de A. flavus, A. parasiticus. Na IAC 886 AFB foi detectada em 20% nos grãos e 23% nas cascas e ACP em 80% dos grãos. Na IAC-Caiapó, AFB foi encontrada em 13% tanto nas amostras de grãos, como nas cascas e ACP em 70% dos grãos. Os resultados do potencial toxigênico de A. flavus revelaram 81% produtores de aflatoxinas, 95% de ACP e 75% de ambas. Todos A. flavus produtores de esclerócios pertenciam ao grupo L. / This study had assessed mycobiota, contamination by aflatoxins (AFB), cyclopiazonic acid (CPA) and phytoalexin (trans-resveratrol) in the peanuts varieties Runner IAC 886 and IAC-Caiapó, in the field and storage. In the Field samples, in IAC 886 it was predominated Fusarium spp. in grains and shells, contamination by AFB in 30% of the grains, CPA in 70% and trans-resveratrol in 5%. In IAC-Caiapó, it was prevailed Fusarium spp. in all samples, AFB in 25% of the grains, CPA in 55% and trans-resveratrol in 15%. In the leaves, trans-resveratrol was present in 70% in the varieties. In the storage, it was observed a higher frequency of A. flavus, A. parasiticus. In IAC 886, it was detected AFB in 20% of the grains and 23% in the shells, and CPA in 80% of the grains. In IAC-Caiapó, it was found AFB in 13% both in grains as in the shells samples, and CPA in 70% of the grains. The toxigenic potential results of A. flavus revealed 81% aflatoxins producers, 95% CPA producers and 75% both producers. All strains of A. flavus sclerotia producers belonged to the L group.

Les travaux présentés dans ce manuscrit concernent le développement d‘une approche originale permettant la détermination de plusieurs composés (principalement aflatoxines et pesticides organophosphorés), à l‘aide de biocapteurs électrochimiques basés sur l‘inhibition de l‘acétylcholinestérase. Dans un premier temps, un nouveau biocapteur potentiométrique utilisant des transistors à effet de champ sensibles au pH (pH-FETs) comme transducteurs a été développé pour la détermination de l‘aflatoxine B1 (AFB1) et différent paramètres d‘élaboration et de fonctionnement du biocapteur ont été optimisés. Le biocapteur proposé est caractérisé par une stabilité opérationnelle élevée and bonne reproductibilité du signal en cours d‘utilisation et de stockage. Le biocapteur a ensuite été évalué pour l‘analyse d‘échantillons réels (blé, sésame, noix et pois) et une simulation mathématique de la réponse du biocapteur potentiométrique à l‘AFB1 a été proposée pour la première fois et validée. Dans un deuxième temps, un biocapteur conductimétrique utilisant des microélectrodes interdigitées en or a été développé. La sensibilité de ce biocapteur aux aflatoxines ainsi qu‘à d‘autres classes de substances toxiques, tels que les pesticides organophosphorés, les métaux lourds, les glycoalkaloïdes, et les surfactants, a été déterminée. Une nouvelle procédure originale, permettant la détermination sélective de toxines multiclasses par application successive de solutions de réactivation visant spécifiquement des inhibiteurs irréversibles ou réversibles, a été finalement proposée. En utilisant cette méthode, il a été montré que les biocapteurs enzymatiques pouvaient être appliqués à l‘analyse des aflatoxines et des pesticides organophosphorés, ainsi qu‘à la détermination de la toxicité globale des échantillons / Investigations reported in this manuscript are focused on the development of an original approach for the detection of several toxic compounds, mainly aflatoxins and organophosphorus pesticides, using acetylcholinesterase (AChE)-based inhibitory electrochemical biosensors. In a first step, a new potentiometric biosensor using pH Sensitive Field-Effect Transistors (pH-FETs) as transducers was investigated for aflatoxin B1 (AFB1) determination and different elaboration and working parameters were optimized. The proposed biosensor was characterized by high operational stability and reproducibility of the signal during the work as well as during the storage. The biosensor was further evaluated for real samples analysis (wheat, sesame, walnuts and peas) and a mathematical simulation of the potentiometric biosensor response to aflatoxin B1 was proposed for the first time and validated. In a second step, a conductometric biosensor using interdigitated gold microelectrodes was developed. The sensitivity of the biosensor to aflatoxins and other classes of toxic substances, such as organophosphorus pesticides, heavy metals ions, glycoalkaloids, and surfactants, was determined. A new and original procedure, enabling the selective determination of multiclass toxins by applying successive reactivation solutions targeting either irreversible or reversible inhibitors, was finally proposed. Using this method, the electrochemical enzyme inhibitory biosensors could be applied to the analysis of aflatoxins and organophosphorus pesticides, as well as for the determination of total toxicity of the samples

A contaminação do amendoim com aflatoxinas é objeto de estudo de vários trabalhos de pesquisa. Entretanto, não consta em trabalhos publicados no país, o estudo da distribuição da contaminação com aflatoxinas entre embalagens de produtos processados que apresentam grãos inteiros e grãos triturados, assim como a estimativa da ingestão de aflatoxinas oriundas do consumo de produtos de amendoim. O objetivo deste trabalho foi investigar a ocorrência e a distribuição da contaminação com aflatoxinas entre embalagens de produtos de amendoim comercializados em estabelecimentos da cidade de Piracicaba – SP, além de caracterizar as amostras quanto a dados qualitativos e quantitativos e condições do ambiente no local da amostragem, assim como estimar a ingestão de aflatoxinas através de produtos de amendoim. A análise qualitativa visual das embalagens não constata esta como fonte de favorecimento da contaminação por aflatoxinas. Quantitativamente, a análise das faixas dos pesos líquidos dos produtos corresponderam aos pesos declarados nas embalagens dos produtos. A atividade de água, mostraram valores normalmente não altos o suficiente para permitirem crescimento fúngico e somente em alguns produtos específicos, os valores poderiam proporcionar o crescimento fúngico. Quanto aos parâmetros temperatura e umidade relativa, observou-se que a temperatura em vários locais amostrados poderia favorecer o crescimento fúngico, enquanto que a umidade relativa não demonstrou valores favoráveis. Os dados de contaminação com aflatoxina mostraram que os produtos comercializados, em alguns casos, ainda apresentam contaminação acima do permitido pela legislação brasileira e que estabelecimentos de diferentes portes apresentaram mesma freqüência e nível de contaminação. O estudo da distribuição da contaminação mostrou que pode ocorrer uma distribuição bastante diferente entre embalagens do mesmo lote, também no produto processado a partir de amendoim triturado, e a detecção da contaminação com aflatoxinas nesses produtos, mostra ser de mais fácil detecção, do que em produtos processados que utilizam amendoim inteiro ou parcialmente inteiro. A avaliação do consumo de produtos de amendoim mostrou níveis de consumo diferentes dos obtidos através de dados de literatura, ressaltando a importância de se trabalhar com dados realísticos de consumo para estimar a ingestão diária provável de aflatoxina AFB1. A estimativa da ingestão diária provável (IDP) de aflatoxina AFB1, mostrou ser inferior a ingestão diária aceitável (IDA) proposta na literatura, ressaltando que as (IDP) relatadas neste estudo foram somente devido ao consumo de produtos de amendoim e não em relação a dieta completa da população. / The peanut contamination with aflatoxins has already been objective of several researches. However there is no published article dealing with the aflatoxin contamination distribution among packages of processed peanut products, containing hole or smashed grains of peanut, neither with the estimate of ingestion of aflatoxins related to peanut products. The objective of this research study was to investigate the occurrence and the widespread-distribution of contamination with aflatoxins in packages of processed peanut products available on the market in Piracicaba city – state of São Paulo and to characterize the samples in terms of: the aspect of the package by visual inspection, the actual weight in comparison to the weight printed on the labels, the water activity of the peanut products and the ambient conditions (temperature and relative humidity) in the sampled stores, as well as to estimate the ingestion of aflatoxin AFB1 through peanut products. In general, based on the visual inspection of the aspect of the peanut products sampled in this study, the packages were not considered a potential source of contamination with aflatoxins. Also, the check of the actual net weight of the products in comparison to the declared weight on the product labels didn’ t show harmfull weight variations to the consumers. The analytical results for water activity showed that in general the values of aw of the products were not high enough to allow the fungic growth-development and the values of water activity could allow the fungic growth. With respect to the temperature and relative humidity it was observed that the temperature of many stores could favor the fungic growth while that relative humidity wasn‘t show values favorable to the fungic growth. The results of contamination with aflatoxins showed that there were some cases which showed contamination with aflatoxin above accepted levels by the Brazilian legislation and that establishment of different size showed one same frequency and level of contamination by aflatoxin. The research of the distribuition of contamination showed that can occur on distribuition enough different among packages of the same lot, also in processed product from peanut products that presented grains crushed, and detection of contamination with aflatoxin in these products, showed to be the more easy detection that in processed products that used grains not crushed or entire grains. The evaluation the consumption the peanut products showed levels differents the levels obtained across the literature datas, to stand up an importance the if to work with real datas of consumption for estimated the probable diary ingestion the aflatoxin AFB1. The estimated of probable diary ingestion (IDP) the aflatoxin AFB1, showed be lower than acceptable diary ingestion (IDA) to proposal by literature, to stand up that as (IDP) reported in this reasearch were only due the consumption the peanut products and not in the statement the completed diet of population.

<p>We followed up with about 2,000 smallholder households in Senegal, two years after these households participated in a randomized controlled trial (RCT) aimed at reducing levels of aflatoxins in smallholders’ stored maize. In the initial intervention, treated households were provided with training on proper post-harvest practices, low-cost moisture meters for testing if maize was sufficiently dry to store, plastic tarps for drying maize of the ground, and hermetic (airtight) storage bags to mitigate aflatoxin development in stored maize. Using cross-sectional follow up data on aflatoxins levels and drying and storage practices from 2019 along with baseline demographic data from 2016, we estimate both the longer-term intention-to-treat (ITT) effects and the treatment on the treated (TOT) effects that the four inputs provided on households’ aflatoxins levels in stored maize. The ITT analyses estimate the intervention’s average effect by treatment group, but this may underestimate the true impact for households who complied with recommended post-harvest practices and adopted the recommended technologies. The TOT analyses estimate the local average treatment effects (LATE) of the intervention, that is its impacts on those who were driven by the intervention to follow best practices or use a given technology. Since the decision to follow these practices or adopt a technology was not random, we instrumented the usage decision with the exogenous, random treatment group assignment to get an unbiased estimate. Outside of our main models, we conducted a heterogeneity analysis to test if households with different characteristics benefit differently from the intervention. We interacted each treatment assignment with various household characteristics, including the woman’s level of involvement in the intervention. Additionally, we estimate the cost-effectiveness of providing training and a tarp, according to WHO guidelines for public health interventions. </p>

Text in English / Fungal species and their mycotoxins are the most predorminant contaminants of dried agricultural products in sub-Saharan Africa (SSA) and the main species of fungi that can synthesize mycotoxins are Aspergillus, Fusarium and Penicillium. In Africa, aflatoxin is labelled as a great threat to human and animal health due to its high contamination levels reported of aflatoxins in foods. The aim of this study was to survey fungi and aflatoxin contamination of small-scale processed foodstuffs sold at informal retail outlets in the Johannesburg metropolis, South Africa. A total of 270 food samples (10 starch and legume based foods, 11 meat and fish based foods, 22 spices and local condiments, 14 dried fruits and vegetables) were collected from retailers; and analysed four (4) times in different seasons of spring, summer, autumn and winter. Out of the 270 samples analysed, only 27.8% were contaminated with fungal. Of all the six categories of foods analysed, roots and tubers (60.0%), nuts and seeds (40.0%), dried vegetables (37.1%), and the Meat and Insect foods (33.3%) respectively, had the most contaminated samples with fungal respectively. The least contaminated food groups were the fish foods (10.0%) and spices and local condiments (16.7%) respectively. Twenty percent of the 270 dried food analysed were contaminated by Aspergillus species out of which 61.1% of the contaminated samples had fungal counts above 103 cfu/g. Aspergillus niger was the most predominant Aspergillus species identified in all the categories of food samples analysed. Fruits and vegetables (24.4%) and the nuts and seeds (20.0%) food groups had the highest number of samples contaminated with aflatoxin. Peanut flour and Cardamom had the most incidence of aflatoxin. AFB1, AFB2 & AFG1 were the most prominent aflatoxin types recovered from the food samples. Almost all the food samples in which aflatoxin were identified had aflatoxin values above 10μg/ml. / Life and Consumer Sciences / M.Sc. (Life Science)

Aquest estudi s’ha realitzat en el marc del projecte titulat: “Ecotoxicidad, micotoxinas y degradación de nonilfenoles en lodos de depuradora y suelos tratados” finançat pel Ministeri d’educació i ciència amb número de referència: CTM2006-14163-C02-02, en col•laboració amb el Centre de Recerca i Aplicacions Forestals. La present Tesi Doctoral aborda els aspectes de determinació analítica de la presència de micotoxines en compost i l’evolució del nonilfenol en sòls. En concret, s’ha estudiat la presència de les aflatoxines G2, G1, B2, B1 i l’ocratoxina A, en tres mostres de compost produït en dues EDAR de Catalunya. Per això s’ha desenvolupat un mètode per a l’anàlisi simultània de les aflatoxines G2, G1, B2, B1 i l’ocratoxina A en compost. En primer lloc s’ha adaptat per aquestes mostres un procediment per HPLC-MS desenvolupat anteriorment en el nostre equip per a la determinació de les aflatoxines G2, G1, B2 i B1 aplicat en matrius de tipus alimentari, que s’ha estès a la determinació conjunta de les quatre aflatoxines i l’ocratoxina A. Aquest procediment ha mostrat problemes pel que fa a la recuperació i precisió dels resultats. Vistes les dificultats, s’ha desenvolupat un nou procediment per UHPLC-Fluorescència que permet una preparació de mostra més ràpida i simple, així com una millor sensibilitat. Aquest nou mètode ha estat validat i permet millorar el temps d’anàlisi i aconseguint eliminar l’etapa de purificació de mostra amb cartutxos de reblert polimèric, utilitzats en el mètode emprat com a punt de partida. Els dos procediment han permès demostrar que, en les mostres de compost estudiades no hi ha quantitats significatives de cap de les cinc micotoxines estudiades. Pel que fa al nonilfenol, s’ha estudiat la seva evolució temporal, durant 32 setmanes, en mostres de sòl, mescles de sòl amb torba i mescles de sòl amb compost, a les que s’ha addicionat nonilfenol a dos nivells de concentració. De la mateixa manera, s’ha estudiat la concentració de nonilfenol en els lixiviats de les mostres de sòl i de les mescles de sòl amb torba. Per això, s’ha posat al punt un procediment analític per HRGC-MS tant per a les mostres de sòls com per a les mostres aquoses dels lixiviats. S’ha posat de manifest la ràpida eliminació del nonilfenol en les tres mostres estudiades i que el nivell de pèrdua per lixiviació és molt baix. En els mateixos lixiviats s’ha determinat la matèria orgànica total i la seva toxicitat a través de l’assaig de Microtox. Les dues determinacions mostren que aquests lixiviats no presenten problemes ja que, complirien les exigències per poder ser abocats a les xarxes públiques de clavegueram. Finalment, es pot afirmar que l’ús del compost en agricultura és una pràctica segura, tant pel que fa a l’absència de les micotoxines, com per la ràpida degradació del nonilfenol en el sòl. / Este estudio se llevó a cabo en el marco del proyecto titulado, "Ecotoxicidad, micotoxinas y degradación de nonilfenoles en lodos de depuradora y suelos tratados" financiado por el Ministerio de educación y ciencia con número de referencia: CTM2006-14163-C02-01, en colaboración con el “Centre de Recerca i Aplicacions Forestals”. La presente Tesis Doctoral aborda los aspectos de determinación analítica de la presencia de micotoxinas en compost y la evolución del nonilfenol en suelos. En concreto, se ha estudiado la presencia de las aflatoxinas B1, B2, G1, G2 y la ocratoxina A en tres muestras de compost producido en dos EDAR de Catalunya. Por lo tanto, se ha desarrollado un método de análisis simultáneos de aflatoxinas B1, B2, G1, G2 y la ocratoxina A en compost. En primer lugar se ha adaptado a estas muestras un procedimiento por HPLC-MS desarrollado previamente en nuestro equipo para la determinación de aflatoxinas B1, B2, G1 y G2 aplicado a matrices alimentarias y se ha extendido a la determinación conjunta de las cuatro aflatoxinas y la ocratoxina A. Este procedimiento ha revelado problemas relativos a la recuperación y la precisión de los resultados. Vistas las dificultades, se ha desarrollado un nuevo procedimiento por UHPLC-fluorescencia que permite una rápida y simple preparación de muestra, así como una mejor sensibilidad. Este nuevo método ha sido validado y puede mejorar el tiempo de análisis y eliminar la etapa con cartuchos de purificación de muestra con cartuchos poliméricos, utilizados en el método de partida. Ambos procedimientos han permitido mostrar que, en las muestras del compost estudiado no hay cantidades significativas de ninguna de las cinco micotoxinas estudiadas. En cuanto a nonilfenol, se ha estudiado su evolución temporal, durante 32 semanas, en muestras de suelo, mezclas de suelo con turba y mezclas de suelo con compost, donde se ha adicionado nonilfenol en dos niveles de concentración. Asimismo, se ha estudiado la concentración del nonilfenol en las muestras de lixiviados de los suelos y mezclas de suelo con turba. Por lo tanto, se ha puesto a punto un procedimiento analítico por HRGC-MS tanto para muestras de suelo como para muestras de lixiviados acuosa. Se ha demostrado la rápida eliminación del nonilfenol en las tres muestras estudiadas y que el nivel de pérdidas por lixiviación es muy baja. Finalmente, en los mismos lixiviados se ha determinado la materia orgánica total y su toxicidad mediante el ensayo de Microtox. Ambas determinaciones muestran que estos lixiviados no presentan problemas ya que cumplen las exigencias para poder ser enviados a las redes de alcantarillado público. Se puede afirmar que el uso de compost en la agricultura es una práctica segura, tanto en cuanto a la ausencia de micotoxinas, como la degradación rápida de nonilfenol en el suelo. / This work was carried out in the framework of the project: “Ecotoxicidad, micotoxinas y degradación de nonilfenoles en lodos de depuradora y suelos tratados". This project was performed in collaboration with "Centre de Recerca i Aplicacions Forestals" and it was supported by “Ministerio de Educación y Ciencia” (contract number CTM2006-14163-C02-01). The present work is referred to the analytical determination of mycotoxins and the degradation of the nonylphenol in soils. Aflatoxins B1, B2, G1, G2 and ochratoxin A in three different samples of compost, produced in two sewage wastewater in Catalonia, has been studied. Also, a method for simultaneous determination of aflatoxins B1, B2, G1, G2 and ochratoxin A in compost has been developed. An analytical method using HPLC-MS has been developed to determinate aflatoxins B1, B2, G1, G2 and ochratoxin A in compost matrices. This method is based on a previous work performed in the Chromatographic Methods Lab at IQS to determinate aflatoxins B1, B2, G1, and G2 in food matrices. It is important to mention that the HPLC-MS method showed low recovery factors and precision problems in the compost samples analyzed. In a second set of experiments a new method using UHPLC-fluorescence has been designed to analyze aflatoxins B1, B2, G1, G2 and ochratoxin A in compost samples. UHPLC-fluorescence allowed quick and simple sample preparation, high sensitivity, short analysis time and the elimination of the purification step using polymeric cartridges. Finally, this method using UHPLC-fluorescence was validated for aflatoxins B1, B2, G1, G2 and ochratoxin A in compost matrices. It is important to mention that HPLC-MS and UHPLC-fluorescence methods verify the absence of mycotoxins in all compost samples analyzed. In a third set of experiments the temporal evolution of nonylphenol has been studied in soil samples, mixtures of soil with peat and soil with compost. The experiments were performed during 32 weeks in which nonylphenol was added at two levels of concentration in the samples at the beginning of the assay. Also, the concentration of nonylphenol in samples of leachates from soil and mixtures of soils with peat has been studied. An analytical method to analyze nonylphenol using HRGC-MS for soil samples and leachates has been designed. Rapid nonylphenol degradation in the three samples analyzed (soil, soil + compost and soil + peat) has been observed and very low nonylphenol levels in samples of leachates from soil and mixtures of soils have been obtained. Finally, Total Organic Carbon (TOC) of the leachates has been measured and also toxicity assays by Microtox test have been performed. Both techniques showed that the leachates analyzed can be dumped in the public sewerage networks because it’s low TOC and toxicity levels. To summarize, it can be assured that the use of compost in agriculture is a safe practice because the absence of mycotoxins and the rapid degradation of nonylphenol in soil.

Le aflatossine sono potenti sostanze cancerogene presenti in natura. L'aflatossina b1 viene poco degradata nel rumine ed è escreta nel latte come aflatossina M1 con un carry over del 1-3%. Nel presente lavoro è stata studiata l'apparizione delle aflatossine nel sangue conseguente all'ingestione orale di un bolo contaminato per verificare come queste tossine sono assorbite nel tratto digestivo delle vacche da latte. La comparsa nel plasma e nel latte attraverso una mucosa tipicamente non di assorbimento per determinare il possibile meccanismo che regola l'assorbimento delle aflatossine è stato un ulteriore oggetto di studio. Un'altra prova è stata effettuata con vacche da latte per studiare il carry-over dell'aflatossina B1 nel latte in relazione al livello produttivo e alle cellule somatiche, come indicatore di processi infiammatori nella mammella. La capacità sequestrante di diversi tipi di adsorbenti è stata comparata in prove in vitro condotte in differenti condizioni sperimentali. Anche il comportamento del complesso aflattosina-adsorbente nel tratto digestivo di vacche in lattazione è stato studiato in vivo per mezzo della misurazione della presenza di aflatossina M1 nel latte. Una prova in vivo è stata effettuata per verificare l'effetto che la pellettatura o la semplice miscelazione di adsorbenti nei mangimi può avere nel migliorare l'efficienza di sequestro. / Aflatoxins are the most potent natural carcinogenic compound present in nature. Aflatoxin B1 is poorly degraded in the rumen and is excreted in milk as aflatoxin M1 with a carry-over rate of 1-3%. The present work investigated rate and schedule of aflatoxins plasma appearance following an oral contaminated bolus to verify how these toxins are absorbed in the gastro-intestinal tract of dairy cows. Aflatoxins plasma and milk appearances were also investigated using a non-absorbing mucosa to understand the possible aflatoxins absorption mechanism through mucous membranes. A trial was carried out in lactating dairy cows to study the carry over of ingested aflatoxin B1 in milk as aflatoxin M1 in relation to milk yield and somatic cells count, the latter as indicator of udder inflammatory processes. sequestering capacity of different kinds of mycotoxins sequestering agents were compared in vitro trial carried out at different experimental conditions. The behaviour of the aflatoxins-adsorbents complexes through digestive tract of lactating dairy cows were also investigated in vivo by measuring appearance of aflatoxin M1 into milk. An in vivo trial was conducted to verify if effect of pelletizing or simply mixing processes is useful to improve mycotoxins sequestering agents efficacy in dairy cow nutrition.

Peanuts contribute significantly to food security in western Kenya due to their high nutritional value and cash crop potential. However, the crop is highly susceptible to aflatoxin contamination. Yet little information is available on the extent of contamination in the region. This study explores the level and extent of contamination of peanuts by aflatoxins, Aspergillus section Flavi, Rhizopus and Penicillium spp. in western Kenya. A survey of 769 households was carried out in the Busia and Homa bay districts of Kenya. Information on peanut pre- and post-harvest practices was collected through person-to-person interviews. Aflatoxin levels of samples collected from each household were determined by indirect competitive ELISA method. Isolation of Aspergillus section Flavi, Penicillium and Rhizopus spp. was done on Modified Dichloran Rose Bengal (MDRB) agar, while identification of specific fungal species was done on Czapek yeast extract agar (CYA). Screening isolates of A. flavus and A. parasiticus for aflatoxin production was done in high sucrose yeast extract (YES) liquid medium, and the aflatoxin types identified on TLC plates, using analytical grades of aflatoxin B1, B2, G1 and G2 as reference standards. Common household preparation techniques (roasting, making peanut paste and boiling peanuts) were evaluated for effectiveness in reducing aflatoxin levels in peanuts. The boiling procedure was modified to test the effect of magadi (locally available salt used mainly to soften legumes, vegetables or maize while cooking), ammonium persulphate and sodium hypochlorite during soaking. Magadi, sodium bicarbonate and locally prepared ash was subsequently used to boil the nuts after soaking. Aflatoxin levels ranged from zero to 7525 ìg/kg. Most samples were safe to consume, based on the European Union and Kenya Bureau of Standards tolerance levels, with 63.7 per cent of all samples having undetectable levels, and only 7.54 per cent being contaminated based on KEBS standards. Peanuts from the Busia district, which has more of Lower Midland 1 (mean annual rainfall of 1600-1800 mm) and Lower Midland 2 (mean annual rainfall of 1300-1700 mm) agro-ecological zones had significantly (÷2=14.172; P=0.0002) higher levels of aflatoxin compared to the Homa bay district, that has more of the drier Lower Midland 3 agroecological zone (mean annual rainfall of 900-1500mm). Improved cultivars had significantly (÷2=9.748; P=0.0018) lower levels of aflatoxin compared to local cultivars. Over 60 per cent of all samples had A. flavus S-strain, A. flavus L-strain and A. niger. A. flavus S-strain was positively correlated with aflatoxin levels. As expected, grading of peanuts post-harvest significantly reduced the incidence of A. flavus S- and L-strains, while peanuts collected from farmers who belonged to producer marketing groups had a significantly lower incidence of A. flavus S- and L-strains, A. niger and Rhizopus spp. The incidence of A. flavus L-strain, A. niger and Rhizopus spp. was significantly higher in local landraces compared to the improved cultivars. Over 60 per cent of isolates produced Aflatoxin B1. Intermediate processes such as sorting and dehusking led to a significant decline in levels of aflatoxin. Soaking peanuts in water, magadi, NaOCl and ammonium persulphate significantly reduced aflatoxin levels by 27.7, 18.4, 18.3 and 1.6 per cent respectively; while boiling the peanuts in magadi, local ash, baking powder and water reduced aflatoxin levels by 43.8, 41.8, 28.9 and 11.7 per cent respectively. Using magadi during boiling increased the acceptability of the boiled peanuts while reducing the aflatoxin levels. The impact of aflatoxin levels in peanuts studied in this research is within safe limits except a few samples, and therefore aflatoxin contamination of peanuts at household level is not a serious threat. Contamination by aflatoxin and post-harvest fungi can be reduced by focusing on improved control strategies for wetter and more humid zones such as planting improved peanut cultivars and controlling pre-harvest pest damage. Conventional household peanut preparation techniques should be explored as possible aflatoxin management strategies in Kenya. The aflatoxin binding properties of locally available salts such as magadi and locally prepared ash should be further investigated. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Les mycotoxines sont des molécules toxiques produites par de nombreuses espèces fongiques. Les seules mycotoxines avérées aujourd’hui cancérigènes pour l’homme sont les aflatoxines. Elles sont produites par le genre Aspergillus principalement et sont retrouvées tout au long de la chaine alimentaire (champs, stockage, transformation, etc.). A cause du réchauffement climatique, la France devient de plus en plus exposée à la présence de ces mycotoxines. Afin de limiter l’exposition des consommateurs, de nombreuses stratégies de prévention ou de décontamination sont développées. Dans ce contexte, nous avons recherché à mettre au point un système de lutte biologique permettant de prévenir la production d’aflatoxines sur le maïs au champ. Pour cela, nous avons choisi des bactéries issues du sol et déjà connues pour être commercialisées pour la lutte biologique, les actinomycètes. Nous avons étudié l’interaction in vitro sur boites de Pétri entre Aspergillus flavus, principal producteur d’aflatoxines, et certains actinomycètes. Nous avons démontré que l’interaction peut réduire la concentration en aflatoxines mesurée par HPLC. De plus, certains isolats bactériens sont aussi capables de réduire, en culture pure, la concentration d’aflatoxine B1 dans le milieu. Des premiers tests d’adsorption ont été réalisés pour comprendre la nature de ce mécanisme. Par ailleurs, une étude approfondie via RT-qPCR sur 6 souches bactériennes du genre Streptomyces sp. A montré que celles-ci étaient capables d’impacter l’expression de différents gènes impliqués dans la voie de biosynthèse chez A. flavus et A. parasiticus. Enfin, nous avons complété les données déjà existantes sur l’impact de facteurs environnementaux (température, disponibilité en eau et du temps d’incubation) sur la production d’aflatoxines. / Mycotoxins are toxic contaminants of foodstuffs produced by a wide range of fungal species. Aflatoxins are the only mycotoxins carcinogenic for humans. They are mainly produced by the Aspergillus genus and can be found at each step of the agrofood chain (e.g. field, storage, process). Due to climate changes, France is starting to be exposed to aflatoxins. In order to limit the consumer exposure, many prevention or decontamination techniques have been developed. To this aim, we started the development of a biocontrol against aflatoxins accumulation for maize field application. Actinomycetes, are soil-borne bacteria that has already been commercialized as biocontrol. In Petri dishes, we studied the in vitro interaction between some actinomycetes and Aspergillus flavus, the main aflatoxins producer. We revealed that the interaction reduced the aflatoxins content (monitored by HPLC). Moreover, some bacterial isolates were able to reduce pure-aflatoxin B1 added in the medium. To understand this mechanism, adsorption tests has been conducted. Otherwise, RT-qPCR methodology was used to study the impact of Streptomyces-Aspergillus sp. on aflatoxin gene expression. Finally, the current knowledge of the impact of environmental factors (temperature, water activity and incubation time) on aflatoxins production was supplemented.