Ochratoxigenic fungi associated with green coffee beans (Coffea arabica L. ) in conventional and organic cultivation in Brazil.

The genera Aspergillus comprises species that produce mycotoxins such as aflatoxins, ochratoxins and patulin. These are cosmopolitan species, natural contaminants of agricultural products. In coffee grains, the most important Aspergillus species in terms of the risk of presenting mycotoxins belong to the genera Aspergillus Section Circumdati and Section Nigri. The purpose of this study was to assess the occurrence of isolated ochratoxigenic fungi of coffee grains from organic and conventional cultivation from the South of Minas Gerais, Brazil, as well as to evaluate which farming system presents higher contamination risk by ochratoxin A (OTA) produced by fungi. Thirty samples of coffee grains (Coffea arabica L.) were analysed, being 20 of them of conventional coffee grains and 10 of them organic. The microbiological analysis was done with the Direct Plating Technique in a Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media. The identification was done based on the macro and micro morphological characteristics and on the toxigenic potential with the Plug Agar technique. From the 30 samples analysed, 480 filamentous fungi of the genera Aspergillus of the Circumdati and Nigri Sections were isolated. The ochratoxigenic species identified were: Aspergillus auricoumus, A. ochraceus, A. ostianus, A. niger and A. niger Aggregate. The most frequent species which produces ochratoxin A among the isolated ones was A. ochraceus, corresponding to 89.55%. There was no significant difference regarding the presence of ochratoxigenic A. ochreceus between the conventional and organic cultivation systems, which suggests that the contamination risk is similar for both cultivation systems.(AU)

Obtenção de protoplastos do fungo filamentoso Aspergillus ochraceus / Production of protoplasts from the filamentous fungus Aspergillus ochraceus

A obtenção de protoplastos é uma ferramenta importante para a transformação genética de fungos. Neste trabalho foi estudada a influência de fatores como idade micelial, tipo e concentração de enzimas e estabilizadores osmóticos na produção de protoplastos de Aspergillus ochraceus. Os melhores resultados de produção de protoplastos foram obtidos utilizando-se NH4Cl 0,8mol L-1 como estabilizador osmótico, micélio com 24h de crescimento e a combinação de Lysing Enzymes e Meicelase ambas, a 20mg mL-1. Entretanto, bons resultados foram também obtidos com a utilização apenas de Lysing Enzymes.(AU)

Production of protoplasts is an important tool for genetic transformation of fungi. A protocol for protoplasts production in Aspergillus ochraceus was developed, evaluating culture aging of mycelium, different commercial enzymes and osmotic stabilizers. The best results were obtained with NH4Cl 0.8mol L-1 as osmotic stabilizer, mycelial age of 24 hours and Lysing Enzymes (20mg mL-1) plus Meicelase (20mg mL-1) as lytic enzymes. Good results were also obtained with Lysing Enzymes alone.(AU)

Growth of Aspergillus ochraceus, A. carbonarius and A. niger on culture media at different water activities and temperatures

The objective of this paper was to determine the influence of three culture media with different water activities, times of incubation and temperatures on the growth of A. ochraceus, A. carbonarius and A. niger. Spores of A. ochraceus, A. carbonarius and A. niger were inoculated onto three culture media: Czapeck Yeast extract Agar (CYA), Dichloran 18% Glycerol Agar (DG18) and Malt Yeast extract 40% Glucose Agar (MY40G). The plates were incubated at five different temperatures (8, 25, 30, 35 and 41ºC). The growth of fungi was evaluated every 24h, measuring the colony diameter (mm). None of the species grew at 8ºC in any culture media. For A. carbonarius, 30ºC was the best temperature for growth while for A. niger temperatures above 30ºC were better in all culture media. A. ochraceus presented good growth at 25 and 30ºC in all culture media, while at 35ºC, growth was slower, especially on CYA. At 41ºC, A. ochraceus did not grow in any culture media and A. carbonarius was significantly inhibited. A. niger grew at 41ºC and was shown to be the most xerophilic fungi when compared to A. carbonarius and A. ochraceus.

Esporos de A. ochraceus, A. carbonarius e A. niger foram inoculados em três meios de cultura: Agar extrato de levedura Czapeck (CYA), Agar Glicerol 18% com dicloran (DG18), Agar Extrato de levedura e malte com 40% de glicose (MY40G). As placas foram incubadas em 5 temperaturas diferentes: 8, 25, 30, 35 e 41ºC. O crescimento dos fungos foi avaliado medindo o diâmetro da colônia a cada 24h. O objetivo deste trabalho foi determinar a influência de três meios de cultura com atividade de água diferente tempo de incubação e temperaturas, sobre o crescimento de A. ochraceus, A. carbonarius and A. niger. Nenhuma das espécies cresceu à 8ºC em nenhum dos meios de cultura. Para A. carbonarius, 30ºC foi a melhor temperatura para o seu crescimento enquanto para A. niger temperaturas acima de 30ºC foram melhores em todos os meios de cultura. A. ochraceus apresentou bom crescimento a 25 e 30ºC em todos os meios de cultura, enquanto seu crescimento à 35ºC foi mais lento, especialmente no meio CYA. A 41ºC, A. ochraceus não cresceu em nenhum dos meios de cultura estudados e A. carbonarius foi significantemente inibido. A. niger cresceu à temperatura de 41ºC e apresentou-se como o fungo mais xerofílico, comparado com A. carbonarius e A. ochraceus.