Production of the mycotoxin patulin in nature.

A study was made of the factors governing the production of the mycotoxin patulin in nature, including biological and physiological factors. The objective of the research described in this thesis was to study the ability of the indigenous fungi of fruits and the apple rot fungus, Penicillium expansum, to grow and to produce patulin in different substrates, both natural (apples, sugar beet, wheat straw) and laboratory media. The effect of carbon and nitrogen sources and the relationship between the production of the toxin and nitrification and its action with the natural isolated bacteria and fungi was also investigated. Common members of the genus Penicillium were found to represent a high percentage of the indigenous fungal flora isolated from both apples and sugar beet. Most of these isolates were able to produce patulin in Czapek Dox liquid medium. Although both apple fruit and sugar beet were naturally highly contaminated with moulds, only apples were contaminated with patulin (7598 gg kg"). Confirmatory tests showed patulin production of 8.3% and 50% (after 7 days) to 99.2% (after 30 days) by the indigenous fungi in apple and sugar beet, respectively. The indigenous fungal flora of wheat straw failed to produce patulin when growing naturally. Patulin was produced only by Penicillium expansum alone and not when growing in association with the white rot fungus Phanerochaete chrysosporium. The accumulation of ammonium and nitrate during urea hydrolysis and ammonium nitrification by Penicillium sp (1), Penicillium sp (3) and Penicillim expansum was achieved with varying degree of efficiency. Urea hydrolysis, but not ammonium nitrification was associated with patulin production. Growth of P. expansum and Penicillium species (1 and 3) occurred under oligotrophic conditions. Both carbon and nitrogen are required for patulin production but it is the depletion of nitrogen which is important for production of the toxin

Molecular characterization of ochratoxigenic fungi associated with poultry feedstuffs in Saudi Arabia

Fungal and mycotoxins contamination of food and poultry feeds can occur at each step along the chain from grain production, storage, and processing. A total of 200 samples comprising of mixed poultry feedstuffs (n = 100) and their ingredients (n = 100) were collected from Riyadh, Alhassa, Qassium, and Jeddah cities in Saudi Arabia. These samples were screened for contamination by fungi. Penicillium chrysogenum was the predominant species taking into its account and frequency, respectively, in both mixed poultry feedstuff and barley samples (4,561.9 and 687 fungal colony-forming units (CFU)/g) and (66% and 17%). Moisture content was an important indicator for the count of fungi and ochratoxin A. Ochratoxin analysis of plate cultures was performed by a HPLC technique. Sample of mixed poultry feedstuff which was collected from Jeddah displayed the highest level of ochratoxin (14.8 µg/kg) and moisture content (11.5%). Corn grains samples were highly contaminated by ochratoxin A (450 and 423 µg/kg) and recorded the highest moisture contents (14.1 and 14.5%). Ochratoxin A production in fungal species isolated from mixed poultry feedstuff samples were high with P. verrucosum (5.5 μg/kg) and A. niger (1.1 μg/kg). In sorghum and corn grains, the highest ochratoxins producing species were P. viridicatum (5.9 μg/kg) and A. niger (1.3 μg/kg), respectively. Sixty-three isolates of A. niger were ochratoxigenic, and all of them showed the presence of pks genes using PKS15C-MeT and PKS15KS primer pairs. The detection technique of A. niger in poultry feedstuff samples described in the present study was successfully used as a rapid and specific protocol for early detection of A. niger without cultivation on specific media

Polyphasic taxonomy of Aspergillus section Aspergillus (formerly Eurotium ), and its occurrence in indoor environments and food

Aspergillus section Aspergillus (formerly the genus Eurotium) includes xerophilic species with uniseriate conidiophores, globose to subglobose vesicles, green conidia and yellow, thin walled eurotium-like ascomata with hyaline, lenticular ascospores. In the present study, a polyphasic approach using morphological characters, extrolites, physiological characters and phylogeny was applied to investigate the taxonomy of this section. Over 500 strains from various culture collections and new isolates obtained from indoor environments and a wide range of substrates all over the world were identified using calmodulin gene sequencing. Of these, 163 isolates were subjected to molecular phylogenetic analyses using sequences of ITS rDNA, partial β-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) genes. Colony characteristics were documented on eight cultivation media, growth parameters at three incubation temperatures were recorded and micromorphology was examined using light microscopy as well as scanning electron microscopy to illustrate and characterise each species. Many specific extrolites were extracted and identified from cultures, including echinulins, epiheveadrides, auroglaucins and anthraquinone bisanthrons, and to be consistent in strains of nearly all species. Other extrolites are species-specific, and thus valuable for identification. Several extrolites show antioxidant effects, which may be nutritionally beneficial in food and beverages. Important mycotoxins in the strict sense, such as sterigmatocystin, aflatoxins, ochratoxins, citrinin were not detected despite previous reports on their production in this section. Adopting a polyphasic approach, 31 species are recognised, including nine new species. ITS is highly conserved in this section and does not distinguish species. All species can be differentiated using CaM or RPB2 sequences. For BenA, Aspergillus brunneus and A. niveoglaucus share identical sequences. Ascospores and conidia morphologyw, growth rates at different temperatures are most useful characters for phenotypic species identification