The diploma thesis "Determination of aflatoxin in selected products" deals mainly with aflatoxin, its occurrence in raw materials of plant origin and methods of decontamination. The studied toxin is produced by fibrous micromycetes primarily from genus Aspergillus is their secondary metabolites. It is very widespread and is a frequent cause of retention of raw materials at the border. Factors that affect production of aflatoxin are, among other things, water activity and pH and are also determined in samples and mentioned in theoretical part. A total of 30 samples were tested for aflatoxin B1, including batch of apricot jam, two batches of Svatojánské ořechy and two batches of Jarní hustopečské mandle. A heterogeneous competitive enzyme immunoassay (ELISA) was used for the analysis. Detectable amounts of AFB1 in the range of 1,26 - 1,66 μg∙kg-1 showed 26,67 % of samples. These values were determined in samples of Svatojánské ořechy and Jarní hustopečské mandle, the apricot jam did not contain measurable amount of AFB1.

Bentonite clays have long been used as additives in animal feed, aiming to improve pellet quality and prevent caking. Certain bentonites are also capable of deactivating aflatoxin B_(1) (AfB_(1)) in feed by adsorption, therefore, detoxifying the feed. However, a 10–fold difference in adsorption capacity has been observed among selected bentonites. The major mineralogical and chemical properties of smectites in determining their adsorption capacities for AfB_(1) are still poorly understood. Improved knowledge of the key controlling factors of aflatoxin adsorption to bentonite clays is needed to guide the selection, modification, and application of the clays as aflatoxin binders. The objective of this study was to test a hypothesis that a smectite's selectivity and adsorption capacity for aflatoxin was mainly determined by the size matching requirement on interlayer surface domains and the aflatoxin molecules. Three approaches were used to vary the size of nanometer-scaled nonpolar domains in the interlayer of smectites: 1) exchanging interlayer cations, 2) selecting natural bentonites with different cation exchange capacities (CEC), and 3) reducing charge density of a high CEC smectite. Six bentonites were fractionated, with their major mineralogical and chemical properties determined. Clay suspensions saturated with different cations were tested for aflatoxin adsorption. Some aflatoxin-smectite complexes were prepared and analyzed with FTIR and XRD. AfB_(1) adsorption isotherms were fitted with Langmuir, modified Langmuir with adsorption dependent affinity, and exponential Langmuir models. Divalent exchange cations with low hydration energy in general resulted in a much higher adsorption capacity and affinity for all six natural bentonite clays. Cations with smaller hydration radii tended to further enhance the adsorption process for aflatoxin on smectites. Charge density of smectite had shown significant effects on the adsorption capacity, affinity, and the isotherm shape. Aflatoxin adsorption isotherms on the six natural smectites and the CEC-reduced 5OK samples by Hofmann and Klemen effects suggested that there is an optimal CEC range between 80~110 cmol(+)/kg for the best aflatoxin binding smectites. When the smectite has a CEC within this range, the mineral has the highest affinity and adsorption capacity for AfB_(1). The aflatoxin adsorption results after cation exchange treatment, selection of different CEC smectites, and the CEC reduction on 5OK confirmed the importance of size and polarity matching on the nanometer scale in smectites’ adsorption for AfB_(1). All clay samples tested in this study were capable of adsorbing aflatoxin into interlayers, and the charge density seemed to have no effect on bonding strength.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 107-130).

This diploma thesis deals with the problem of aflatoxin in selected organs of fallow game, roe deer and for comparation of petty game with hare. The aim was to evaluate the free and preserve breeds at a sufficient amount of samples and to assess the suitability of a feeding.There were assessed the parenchymal tissues and kidneys and liver. It evaluated 176 collected biological tissues, including 118 from free places and 58 samples from specialized preserve.After the screening method RIA complemented by gas chromatography, were evaluated concentrations of aflatoxin B1. Diferences of feeding, which were assessed on based of results of evaluation in preserves.Subsequently the problem of submitting feeds was solved, and it was made a manual for submission of a feed.

No description available.

Smectite clay has been shown in studies over the past 20 years to sorb aflatoxin B1 (AfB1) in animal feed and thereby reduce its toxic influence on animals. In this study, 20 smectite samples were selected from industrial products or reference minerals. In the initial steps, it was shown that AfB1 entered the interlayer galleries of smectites and a 10-fold range in sorption ability was observed in a set of 20 smectite samples. Yet, it was not clear which clay properties (CEC, pH, base saturation) influenced this variation. In an effort to further explore properties that might influence the sorption of AfB1, three good sorbent samples were chosen from our set of 20 samples along with one sample of low sorption capacity. Those samples were fractionated into sand, silt, coarse clay (CC), and fine clay (FC) fractions. From all sample fractions, sorption isotherms and X-ray diffraction patterns were obtained. Additionally, a vermiculite and a palygorskite were examined with regard to sorption capacity. Concentration of smectite and their adsorption test suggest that differences in smectite composition are responsible for difference in sorption, not so much their relative abundance or other mineral phases. Initial infrared analysis indicates that weathered aluminous smectites, which have no octahedral iron or magnesium, belong to the poor AfB1 sorbents. Palygorskite and vermiculite are not effective sorbents. Based on the findings in this study, tentative quality criteria of sorbent selection for their use in animal feed were established. These criteria are: pH between 6.5 and 8.5, CEC > 75cmolc/kg, organic carbon < 2.5 g/kg, expression of XRD smectite peak and AlFeOHbending in FTIR and Langmuir adsorption capacity for AfB1 > 0.40 mol/kg.

The principal objective of this investigation was to evaluate the effects of mycotoxin contaminated diets (deoxynivalenol (DON)), aflatoxin B1 (AFB1), and fumonisin (FUM)), with or without the use of a commercially available deactivating compound (DC), in young pullets and replacement laying hens on performance, reproductive, serological, and histopathological parameters. In trial 1, experimental treatments consisted of control, low toxin (1 µg DON/g + 1 µg AFB1/g), and high toxin (2 µg DON/g + 2 µg AFB1/g) diets. Pullets fed the high toxin diet had reduced (P<0.05) body weights compared to control and low toxin diets at d 14, 35, 49, 56, and 63. At d 21 and 28, there was a significant interaction observed between mycotoxin and DC inclusion in body weights. Following necropsies (d 35 and 65), relative liver weights and histopathological liver tissue damage were increased (P<0.05) in pullets fed high toxin diets when compared to control and low toxin diets. Relative kidney weights were increased (P<0.05) due to high toxin diet at d 65. Expected negative effects of toxin administration on titer development were not observed. The only interaction observed between mycotoxin administration and DC inclusion in trial 1 was on body weights. In trial 2, experimental treatments consisted of control, DON (9 µg/g) challenge, AFB1 (2 µg/g) + FUM (54 µg/g) challenge, and a mixed challenge (6 µg DON/g, 1 µg AFB1/g, and 27 µg FUM/g). All mycotoxin diets fed to hens negatively influenced (P<0.05) feed efficiency for the trial period spanning weeks 6 through 10 when compared to control diets. Egg production was not affected (P>0.05) by all mycotoxin diets weeks 6 through 10. Relative weights of the liver and kidney were increased (P<0.05) by AFB1+FUM challenge weeks 4 and 9 compared to control diet. The data reported in this study demonstrate that dietary DON and / or AFB1+FUM influence some performance, reproductive, histopathological, and egg quality traits, but by and large, replacement layer pullets seem to be relatively resistant to the mycotoxins evaluated in this trial at the described levels of administration.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 83-96).

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 64-83).

A avaliação da capacidade produtora de micotoxinas vem sendo utilizada como uma importante ferramenta na identificação de espécies conhecidamente toxigênicas. Poucos são os métodos rápidos e alternativos disponíveis para a determinação do potencial toxigênico de espécies do gênero Aspergillus. Neste contexto, o objetivo deste trabalho foi avaliar a capacidade produtora de aflatoxina B1, em diferentes condições de cultivo, por três isolados de Aspergillus flavus, produtores de aflatoxina B1. O delineamento experimental baseou-se em um planejamento 2³ completo, tendo como variáveis independentes a temperatura (20-40°C), o tempo de incubação (7-21 dias) e o pH (2,0-6,0) nos meio sintéticos (YES, CYA e Sabouraud). As melhores condições encontradas foram aplicadas em testes com meio natural (arroz) e isolados a principio não-aflatoxigênicos. Aflatoxina B1 foi extraída diretamente dos meios sintéticos com clorofórmio e do arroz com metanol. A identificação e quantificação do composto foi realizada por Cromatografia em Camada Delgada e Fotometria Fotográfica. O meio YES se mostrou o melhor para detecção do potencial toxigênico, seguidos de melhor pH 4,0 e 5,2, e temperatura de 20º e 25ºC e tempo de incubação de 11 e 14 dias. O isolado A43, em temperatura de 25º, pH 5,2 e tempo de incubação de 11 dias, mostrou a maior produção de aflatoxina B1, com 206,05 ng. No arroz, os isolados revelaram produção de aflatoxina, apenas a partir do 14ºdia. Dos 30 isolados a princípio não-aflatoxigênicos testados inicialmente em agar coco, 12 apresentaram resultado positivo nos meios e condições aqui apresentados. / Mycotoxins producing capacity evaluation has being used as an important tool, in the identification of toxigenic species. A few of them are available as alternative rapid methods for the determination of the toxigenic potential of species Aspergillus. The objective of this work was to evaluate the aflatoxin B1 producing capacity in different conditions of culture by three Aspergillus flavus. The experimental delineation was based on a 2³ factorial design. To test the effect of three independent variables, the temperature (20-40°C), the incubation time (7-21 days) and pH (2,0 -6,0) in the synthetic medium (YES, CYA and Sabouraud) were applied in the program STATISCA 7.0. The best joined conditions had been applied in tests with natural medium (rice) and isolated tested as nonaflatoxigenics. Aflatoxin B1 was extracted directly from sintetic mediuns by chloroform and from rice by methanol. Thin-layer chromatography (TLC) and Photometric Photography were the methods utilized for the identification and quantification of aflatoxin B1. YES was the best medium for the detention of toxigenic potential, at pH 4,0 and 5,2, temperature of 20º and 25ºC and incubation time of 11 and 14 days. The isolated A43, at temperature of 25ºC, pH 5,2 and incubation time of 11 days showed the biggest aflatoxin B1 production (206,05 ng). Aflatoxin production in rice occurred only after 14 days. 12 of the 30 non aflatoxigenic isolates showed aflatoxin production in the media and conditions tested.