Fusarium and Aspergillus mycotoxins contaminating wheat silage for dairy cattle feeding in Uruguay

Abstract Wheat is one of the most important cultivated cereals in Uruguay for human consumption; however, when harvest yields are low, wheat is usually used in ensiling for animal feeding. Ensiling is a forage preservation method that allows for storage during extended periods of time while maintaining nutritional values comparable to fresh pastures. Silage is vulnerable to contamination by spoilage molds and mycotoxins because ensilage materials are excellent substrates for fungal growth. The aim of the study was to identify the mycobiota composition and occurrence of aflatoxins and DON from wheat silage. A total of 220 samples of wheat were collected from four farms in the southwest region of Uruguay were silage practices are developed. The main fungi isolated were Fusarium (43%) and Aspergillus (36%), with Fusarium graminearum sensu lato and Aspergillus section Flavi being the most prevalent species. Aflatoxin concentrations in silo bags ranged from 6.1 to 23.3 µg/kg, whereas DON levels ranged between 3000 µg/kg and 12,400 µg/kg. When evaluating aflatoxigenic capacity, 27.5% of Aspergillus section Flavi strains produced AFB1, 5% AFB2, 10% AFG1 and 17.5% AFG2. All isolates of F. graminearum sensu lato produced DON and 15-AcDON. The results from this study contribute to the knowledge of mycobiota and mycotoxins present in wheat silage.

Penicillium species present in Uruguayan salami / Especies de Penicillium presentes en salamines uruguayos

The surface coverage of certain dry fermented sausages such as Italian salami by some species of Penicillium provides their characteristic flavor and other beneficial properties. One of them is the protective effect by means of a uniform film of white mold against undesirable microorganisms. The aim of this work was to identify and to isolate the fungal species present in mature Italian type of salami and to evaluate if it is possible to obtain some of them as starters. In addition, the effects of temperature (14 °C and 25 °C), water activity (a w) (0.90, 0.95 and 0.995) and 2.5 % sodium chloride (NaCl) on fungal growth were determined. Similarly, the proteolytic and lipolytic activity and the ability to produce toxic secondary metabolites were evaluated in order to characterize some possible starter strain. All species found belong to the genus Penicillium, including a performing starter as Penicillium nalgiovense and some potentially toxicogenic species. All the strains showed a higher growth rate at 25 °C. The production of extracellular proteases and lipases was significantly higher at 25 °C than at 14 °C with and without sodium chloride. Only Penicillium expansum produced patulin. On the other hand, Penicillium griseofulvum was the only species that produced ciclopiazonic acid but none of the strains produced penicillin. The species present on salami, Penicillium nalgiovense, Penicillium minioluteum, Penicillium brevicompactum and Penicillium puberulum were unable to produce any of the evaluated toxins. These findings suggest that some fungal isolates from the surface of salami such as P. nalgiovense are potentially useful as starters in sausage manufacture.

La cobertura de la superficie de los embutidos fermentados secos -como el salamín tipo italiano- por algunas especies de Penicillium les proporciona un sabor característico y otras propiedades beneficiosas. Una de ellas es el efecto de protección contra microorganismos indeseables, al formarse una película blanca uniforme de mohos. El objetivo de este trabajo fue aislar e identificar los hongos filamentosos encontrados en la superficie de salamines tipo italiano y evaluar la posibilidad de obtener especies para utilizarse como cultivos iniciadores. Se determinó el efecto de la temperatura, la actividad de agua y del cloruro de sodio sobre el crecimiento fúngico. La actividad proteolítica y lipolítica y la capacidad de producir metabolitos secundarios tóxicos fueron evaluadas con el fin de caracterizar algunos posibles cultivos iniciadores. Todas las cepas fúngicas aisladas e identificadas correspondieron a especies del género Penicillium, algunas benéficas, como Penicillium nalgiovense, y otras potencialmente toxicogénicas. Estas cepas tuvieron diferentes tasas de crecimiento en respuesta a las diferentes condiciones de cultivo. Todas las cepas mostraron mayor crecimiento a 25 °C. La producción de proteasas y lipasas extracelulares fue significativamente mayor a 25 °C que a 14 °C. Penicillium expansum fue la única especie que produjo patulina y Penicillium griseofulvum fue la única que produjo ácido ciclopiazónico. Ninguna de las especies produjo penicilina. Penicillium nalgiovense, Penicillium minioluteum, Penicillium brevicompactum y Penicillium puberulum no produjeron ninguna de las toxinas evaluadas. Estos resultados sugieren que algunos aislamientos fúngicos, como P. nalgiovense, son potencialmente útiles como cultivos iniciadores en la fabricación de estos productos.

Fungi and nematodes occurring in different composts used in Uruguayan agriculture.

Forty three thermophilic, thermotolerant and mesophilic fungal species and nematodes from five trophic groups were found in four compost types. Aspergillus fumigatus and A. niger were the most frequent species. Plant pathogenic fungi viz. Fusarium oxysporum, F. acuminatum, F. nygamai and F. solani were found in some of the composts in low frequency. The most abundant species of nematode corresponded to bacterivores. Tylenchus, a phytophagous nematode was scarcely found.