Marcelo Elias Fraga

Potential ochratoxin A producers from wine grapes in Argentina and Brazil

The aim was to identify the normal mycoflora in wine grapes from Argentina and Brazil. We collected 50 grapes samples from Malbec and Chardonnay varieties in each country during the 1997–98 harvest. Yeasts were a major component of the fungal population, and the most frequent genera of filamentous fungi isolated were: Aspergillus, Penicillium and Botrytis. Other genera identified (in decreasing order) were: Phythophthora, Moniliella, Alternaria and Cladosporium. From grapes, the mean frequency of filamentous fungi ranged from 1.3 × 104 to 5.4 × 106 CFUg-1. We isolated 48 Aspergillus niger strains from Argentinian grape, of which eight could produce ochratoxin A. Sixteen of 53 A. niger strains from Brazilian grapes produced ochratoxin A. The results indicate that similar mycobiota were isolated from Argentinian and Brazilian wine grapes and there could be ochratoxin A production in this substrate.

Occurrence of ochratoxin A in wine and grape juice marketed in Rio de Janeiro, Brazil

Ochratoxin A (OA) is receiving attention world-wide because of the hazard it poses to human health. The aim was to test the distribution of OA in grape juice, pulps of frozen grapes, and national and imported table wine obtained from markets in Rio de Janeiro, Brazil. Analytical methodology using immunoaffinity column for OA extraction and clean-up with a final separation on a reversed-phase (C18) column and fluorescence detection in high-performance liquid chromatography showed a detection limit of 21 ng l−1. The mean recovery was 91% for red wines and 82% for white wines; while the mean recoveries for juices and pulps of frozen grapes were 91.6 and 88%, respectively. Of 64 samples of grape juice and frozen pulps, 25% were positive for OA, being the mean content of 37 ng l−1 with a maximum concentration of 100 ng l−1. In wines, the mean concentration detected in 80 samples analysed was 34.4 ng l−1 with 28.75% of positive samples. Red wines showed the highest percentages and levels of contaminated samples: 38% and 37 ng l−1, respectively. The white wine contained levels above 26 ng l−1 in 17.75% of the analysed samples. The levels of contamination detected in red wine sold in Río de Janeiro were not enough to surpass the virtually safe dose established as 5 n g kg−1 body weight of daily intake.

Potential aflatoxin and ochratoxin a production by Aspergillus species in poultry feed processing.

Poultry feeds are prone to fungal growth and mycotoxin production during processing. The identification of biota with the ability to produce mycotoxins is essential. The aims of this study were (1) to monitor the mycobiota counts at different stages of poultry feed processing; (2) to determine the occurrence of Aspergillus species; (3) to evaluate the natural incidence of aflatoxins and ochratoxin A. The ability of Aspergillus spp. and its teleomorphs isolated here to produce these toxins was also investigated. Samples (144) were collected at random from a factory in Brazil. The occurrence of Aspergillus and Eurotium species was demonstrated on DRBC and DG18 media and the production of aflatoxins and ochratoxin A and their natural incidence were determined by TLC and HPLC methods. A. flavus and E. chevalieri were the most prevalent species isolated. Fungal contamination was not found after the pelleting process, though Aspergillus and Eurotium species were recovered from trough samples. High levels of aflatoxin and ochratoxin A producers were found at all stages of poultry feed processing. Also, high natural contamination with aflatoxins and ochratoxin A was found in the samples. Contact of feed with remainder poultry feed could lead to fungal contamination, so the risk of aflatoxin and/or ochratoxin A contamination of feed must be taken into account.

Fourier transform infrared as a powerful technique for the identification and characterization of filamentous fungi and yeasts

Fourier transform infrared is considered a powerful technique for characterizing chemical compositions of complex probes such as microorganisms. It has successfully been applied to fungal identification. In this paper, the current state of identification and characterization of filamentous fungi and yeasts by Fourier transform infrared is reviewed.

Influence of water activity, temperature and time on mycotoxins production on barley rootlets

Aims:  The objective of this study was to determine the ochratoxin (OT) and aflatoxin (AF) production by three strains of Aspergillus spp. under different water activities, temperature and incubation time on barley rootlets (BR).

Mycological survey for potential aflatoxin and ochratoxin producers and their toxicological properties in harvested Brazilian black pepper

A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis.

Characterization of Aspergillus species based on fatty acid profiles

Cellular fatty acid (FA) composition was utilized as a taxonomic tool to discriminate between different Aspergillus species. Several of the tested species had the same FA composition and different relative FA concentrations. The most important FAs were palmitic acid (C16:0), estearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2), which represented 95% of Aspergillus FAs. Multivariate data analysis demonstrated that FA analysis is a useful tool for differentiating species belonging to genus Aspergillus. All the species analyzed showed significantly FA acid profiles (p < 0.001). Furthermore, it will be possible to distinguish among Aspergillus spp. in the Flavi Section. FA composition can serve as a useful tool for the identification of filamentous fungi.

Seleção de isolados de "Metarhizium anisopliae" e "Beauveria bassiana" patogênicos a soldados de "Atta bisphaerica" e "Atta sexdens rubropilosa" em condições de laboratório

As formigas do genero Atta sao pragas importantes de diversas culturas agricolas, pastagens e reflorestamentos. Os fungos entomopatogenicos estao entre os fatores naturais de mortalidade dessas formigas e por isso apresentam potencial para serem usados no controle biologico dessa praga. O presente trabalho teve como objetivo selecionar isolados de Metarhizium anisopliae e Beauveria bassiana patogenicos a soldados de Atta bisphaerica e Atta sexdens rubropilosa em condicoes de laboratorio. Para a avaliacao da patogenicidade, foram utilizados oito isolados de M. anisopliae e seis de B. bassiana. O experimento foi conduzido em DIC, sendo a parcela composta por um grupo de 10 soldados por especie de formiga, sendo utilizadas tres repeticoes por tratamento. Para cada isolado, tres grupos de soldados foram pulverizados com suspensao de 1,0 x 108 conidios ml-1 e mantidos em câmara umida (25±1°C, 80±1% de UR e no escuro) sem alimentacao, sendo a mortalidade verificada diariamente. Dos 14 isolados testados, quatro de M. anisopliae e quatro de B. bassiana foram patogenicos aos soldados de ambas as especies de formigas. A virulencia foi avaliada para os isolados que causaram mortalidade igual ou maior a 50%. Para cada isolado, suspensoes contendo 1,0 x 106 a 1,0 x 1011 conidios ml-1 foram pulverizadas sobre tres grupos de 10 soldados e igualmente acondicionados como no teste de patogenicidade. A porcentagem de mortalidade foi calculada a cada 24 horas para determinacao do TL50. O isolado ENA04 de M. anisopliae foi mais patogenico, causando mais de 80% de mortalidade nos primeiros tres dias apos a inoculacao, apresentou maior capacidade de esporular nos cadaveres dos soldados e foi o mais virulento para os soldados de A. bisphaerica, com um TL50 de 1,15 dias. Todos os isolados patogenicos aos soldados de A. sexdens rubropilosa foram igualmente virulentos.

Selection of cellulolytic fungi isolated from diverse substrates

The aim of the present work was to select filamento us fungi isolated from diverse substrates to obtain the strains with potential to produce the hydrolytic enzymes. F rom a total of 215 strains, seven strains from the soils, six from the plants and one from sugarcane bagasse were sele cted and identified as belonging to the Trichoderma, Penicillium and Aspergillus genera. The best hydrolytic activities obtained by semi-solid fermentation using these strains were approximately: 35; 1; 160; 170 and 120 U/gdm (CMCase, FPase, β-glucosidase, xylanase and polygalacturonase, respectively), demonstrating the ir potential to synthesize the enzymes compared wit h the results reported in the literature.

Chemical, Technological and Sensory Properties of Wheat Grains (Triticum aestivum L) as Affected by Gaseous Ozonation

Gaseous ozonation, an emerging technology, is applied to microbiological decontamination and to the degradation of residues and contaminants in wheat grains. However, due to its high oxidizing capacity, ozone may cause undesirable effects on the quality of grains or in their derivatives. This study aimed to evaluate the influence of ozone gas on wheat grain quality when exposed to different levels of ozone concentration, exposure time, and grain mass, using a full 23 factorial design. After the milling of ozonized grains, two fractions were evaluated: flour (A) and bran plus germ (B). In fraction A, the quality of the wheat flour was analyzed by both alveography and farinography. The flour extraction rate, falling number and gluten contents were also measured. The chemical and mineral profiles were determined in both fractions. A sensory evaluation, using the difference-from-control test, was applied to investigate the possible differences in aroma or in overall appearance of the flour obtained from the ozonized grains. The results showed that ozone concentration (60 mg/L) positively affected (p < 0.05) the toughness and the falling number of the flour. The other parameters of alveography, as well as farinography, gluten content, chemical composition, mineral, and sensory profiles were not affected (p > 0.05) by ozonation. This study demonstrated that gaseous ozonation, when applied under the conditions of 10 to 60 mg/L, from 2 to 5 h of exposure, grain mass from 2 to 5 kg, does not cause any negative impact on the wheat quality.