This thesis deals with the issue of mycotoxins, which are important pathogens of many agricultural crops and may pose a high health risk to humans and livestock. It contains an overview of the most important mycotoxins their producers and mycotoxicoses. The main focus of this thesis is the occurrence of mycotoxins in cereals and the effect of processing it on their content. The experimental part focuses on monitoring the content and the penetration of deoxynivalenol and zearalenone in winter wheat from grain to bread. We examined a total of 10 samples of treated and 10 samples of untreated variants of winter wheat. For each sample grain, flour and bread were examined for DON and ZEA content and all tested samples were positive for DON and ZEA. None of the examined samples exceeded or even approached the legislative limits.

Alpha zearalenol is a derivative of the mycotoxin zearalenone, which is commonly found in agricultural crops and commercial feed. It is a secondary metabolite of filamentous fungi of the genus Fusarium. The alpha zearalenol is the result of a biotransformation of zearalenone in the liver and intestinal tissue. When the zearalenone is metobolised this way, it is able to compete for the binding sites of estrogen receptors because the structure is very similar to 17 beta estradiol. Toxicity of alpha zearalenol therefore lies in an estrogenic stimulation, which induces morphological and functional changes in the reproductive organs and gametes. Toxicity is manifested on the male gamete by reducing viability, motility and the portion of sperms capable of undergoing acrosome reaction. The aim of this study was to evaluate the effect of alpha zearalenol on the hyperactivation and acrosome reaction of boar sperm depending on the concentration and duration of exposure to mycotoxins. For the purposes of this study we used two methodologies and the short term chilled commercial insemination doses which were kept in a box with the temperature of 17 degrees of Celsius. The two methodologies had a different count of used concentrations of alpha zearalenol and exposure time. Acrosome reaction of sperms was assessed in both methodologies, while the share of hyperactive sperm was assessed only in the second methodology. The first methodology did not prove any effect of alpha zearalenol on acrosome reaction, but the second methodology has proven a positive effect of concentrations 5, 10 and 20 uM alpha zearalenol on acrosome reaction of boar sperm. Individual values of parameters from CASA analysis (VCL, ALH, LIN and WOB), which were used for evaluation of hyperactivation of boar sperm, were not affected by any used concentrations of alpha zearalenol.

This diploma thesis is focused on current problematics of monitoring of selected mycotoxins, DON and ZEA, in feeds in Czech Republic. The objective of my thesis was to elaborate a literature search from available books, electronic and periodical sources and service materials. Literature search is aimed at overall overview of mycotoxins, describes their characteristics, biological effects, methods of detection as well as summarizes recent legislation requirements concerning occurrence of these substances in feeds for animals. The aim of experimental part was a determination of selected mycotoxins in feed (DON and ZEA) by ELISA method and their evaluation according to the maximum limits. The diploma thesis was prepared in diagnostic laboratory SEVARON, s. r. o. in Brno.

Universiẗat, Diss., 2007--Giessen.

Zugl.: Berlin, Freie Univ., Diss., 2007

A number of chemicals may have a negative impact on the environment and wildlife. Endocrine disruptors (EDs), which can mimic estrogen, interfere with natural hormones in organism and can have a negative effect on the reproductive system. Such substances include zearalenone (ZEA) - mycotoxin, produced by the fungi Fusarium. Despite the non-steriodal structure of its molecule, ZEA and its derivates possess potent estrogenic activity. The influence of ZEA on reproductive parameters and changes in expression of selected genes were tested in the outbred line of mice. This study showed significant effects of ZEA on number of reproductive performances. This effect was observed at lower examined dose, to which are humans normally exposed, and at higher doses, both showed changes in the tested parameters.

Mycotoxins are secondary metabolites of moulds, which attack cereals, for example barley, from which mycotoxins then get to beer. This submitted work is focused on ochratoxin A, deoxynivalenol and zearalenone, which can occur in beer. The first part of this master’s thesis consists of literary research, which describes mycotoxins in general, points out their occurrence, prevention of their formation and delivers information about their physical and chemical properties and toxicity. Furthermore, the research contains basis of malt and beer technology, the occurrence of mycotoxins in beer and raw materials for its production. The research describes changes in concentration of mycotoxins across malt and beer production. The next part deals with possibilities of determination of mycotoxins in barley, malt and beer, compares individual methods of their determination and points out many difficulties of some analyses. The experimental part of this work pursues determination of ochratoxin A, deoxynivalenol and zearalenone in different types of beer with the help of UPLC-FLR, HPLC-MS and ELISA. Instrumental techniques are validated and gathered results are compared with the results in literature. The goal of this master’s thesis is to assess the stability of ochratoxin A and deoxynivalenol in beer over time. The gained results show that there are changes in the concentration of ochratoxin A over time, nevertheless those changes show no pattern. Overall, there was a decrease in concentration in 47 % of the samples and an increase in 28 % of them. In the rest of the samples the concentration did not change. The concentration of deoxynivalenol does not change over time. One of the other goals of this thesis is monitoring of selected mycotoxins in beer. The average concentration of ochratoxin A in the samples was 39 ng/l and deoxynivalenol 9,9 g/l. Zearalenone did not occur in any of the samples when determined by liquid chromatography. All results agree with literature. Next, the thesis compares different analytical methods for determination of ochratoxin A, deoxynivalenol and zearalenone. The screening method ELISA is compared to UPLC-FLR and HPLC-MS. The determination of ochratoxin A by ELISA has shown to be time consuming, nevertheless the results responded to instrumental technique. ELISA overestimated the results of determination of deoxynivalenol in beer by 363–697 % and with zearalenone there were found false positive results.

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