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ABSTRACT: Ergosterol has been suggested as a paramoter for studying the content and evolution of fungal infestation in different products. Important differences in this parameter have been described for different genera and species. A study of the relationship between ergosterol content and dry mass in a strain of Aspergillus ochraceus, which is able to produce an antifungal agent, has therefore been carried out in order to use this parameter to accurately evaluate the fungal mass of this strain. We report herein our research work to determine the ergosterol content of the mycelial mass of our mould and how it changes with the fungal age.
Letters in Applied Microbiology 06/2008; 15(1):20 - 22. · 1.62 Impact Factor
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ABSTRACT: Geostatistical analysis was applied to the incidence of Aspergillus Section Nigri and A. carbonarius in Southern Europe and Israel for the 3-year period 2001-2003 to facilitate identification of regions of high risk from contamination with these fungi and production of ochratoxin. The highest incidence of black aspergilli was normally observed at harvesting. At this grape growth stage, spatial variability of black aspergilli was significantly related to latitude and longitude, showing a positive West-East and North-South gradient. Predictive maps of infected berries incidence were drawn and showed the same trend in the 3 years, but incidence was highest in 2003, followed by 2001 and 2002. The highest incidence was always observed in Israel, Greece and Southern France, associated with the highest incidence of A. carbonarius. Southern Spain and Southern Italy also had relevant incidence of black aspergilli. The thermo-wetness maps for the 3 years showed a trend similar to the incidence of black aspergilli. The coldest and wettest year was 2002, while 2003 was the hottest and driest, particularly during August, with Israel being the hottest and driest country, followed by Greece and Southern Italy. This indicates that meteorological conditions can contribute to explain spatial distribution variation of black aspergilli within the Mediterranean basin.
International Journal of Food Microbiology 10/2006; 111 Suppl 1:S72-82. · 3.33 Impact Factor
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ABSTRACT: A scanning electron microscopy (SEM) study of the effect of water activity (a(w)), temperature and fungal interactions on the very early phases of Aspergillus ochraceus, Alternaria alternata and Fusarium verticillioides development on maize grains was carried out. Germination and growth of individual fungal strains were assayed at 0.92, 0.95 and 0.98 a(w), and 20 and 30 degrees C. Hyphal lengths were measured on micrographs taken by SEM at different periods of incubation. A. alternata had the highest linear growth at 0.98 a(w), and was the only species able to grow under all conditions tested, whereas A. ochraceus was not able to germinate at 0.92 a(w) at any temperature assayed. F. verticillioides demonstrated a different behaviour depending on growth temperature. Fungal interactions were studied at 0.95a(w) and 30 degrees C. A. ochraceus germination was inhibited when it was co-inoculated with one or two of the other species. A. alternata showed an increased growth rate when growing together with the other fungi, whereas growth of F. verticillioides was significantly inhibited when paired with A. ochraceus.
International Journal of Food Microbiology 04/2003; 81(3):185-93. · 3.33 Impact Factor
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ABSTRACT: The effect of water activity (0.98, 0.95, 0.93) and temperature (15, 25 degrees C) on fungal growth and toxin production from interactions between isolates of Fusarium moniliforme and F. proliferatum producing fumonisin, and an isolate of F. graminearum producing zearalenone, incubated at the same time on irradiated maize grains were determined in vitro. Populations (CFUs) of F. moniliforme and F. proliferatum were reduced to a greater or lesser extent by the presence of F. graminearum under all conditions tested, while that the presence of F. moniliforme or F. proliferatum had a minor inhibitory effect on fungal populations of F. graminearum. Fumonisin B, production by F. proliferatum was inhibited under all conditions tested, while fumonisin B1 production by F. moniliforme was inhibited at 15 degrees C and enhanced at 25 degrees C in the presence of F. graminearum. The level of zearalenone was not significantly modified in the presence of F. moniliforme and F. proliferatum under the conditions tested.
International Journal of Food Microbiology 08/2000; 59(1-2):59-66. · 3.33 Impact Factor
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ABSTRACT: Six 100 ppm fumonisin B(1) (FB(1)) solutions were prepared by dissolving pure standard in six different solvents containing SO(2). Two of the solvents contained 0.2 or 0.4% SO(2) in distilled water. The other four solvents were obtained by steeping corn kernels at 60 degrees C in a 0.2% SO(2) aqueous solution for 6, 12, 24, or 48 h. After the addition of FB(1), all solutions were maintained at 60 degrees C for 7 days. Fumonisin B(1) content in each solution was determined in triplicate by HPLC. Steeping corn kernels in 0.2% solution at 60 degrees C for 6 h seems to be the most effective treatment to decrease the amount of FB(1).
Journal of Agricultural and Food Chemistry 02/1999; 47(1):276-8. · 2.82 Impact Factor
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ABSTRACT: The effect of different water availabilities (water activity, aw; 0.98-0.93) and time (up to 15 days) on the production of seven hydrolytic enzymes by strains of F. moniliforme and F. proliferatum during early colonisation of gamma-irradiated living maize grain were examined in this study. Both the total activity (micromol 4-nitrophenol min(-1) g(-1) maize) and specific activity (nmol 4-nitrophenol min(-1) microg(-1) protein) were quantified using chromogenic p-nitrophenyl substrates. The dominant three enzymes produced by the fungi on whole colonised maize kernels were alpha-D-galactosidase, beta-D-glucosidase, and N-acetyl-beta-D-glucosaminidase. The other four enzymes were all produced in much lower total amounts and in terms of specific activity (beta-D-fucosidase, alpha-D-mannosidase, beta-D-xylosidase and N-acetyl-alpha-D-glucosaminidase), similar to that in uncolonised control maize grain. There were significant increases in the total production of the three predominant enzymes between 3-15 days colonisation, and between 3-6 days in terms of specific activity when compared to untreated controls. The total and specific activity of the alpha-D-galactosidase, beta-D-glucosidase and N-acetyl-beta-D-glucosaminidase, were maximum at 0.98 aw with significantly less being produced at 0.95 and 0.93 aw, with the exception of the total activity of alpha-D-galactosidase which was similar at both 0.95 and 0.93 aw. Single factors (time, aw, and inoculation treatment), two- and three- way interactions were all statistically significant for the three dominant enzymes produced except for specific activity of beta-D-glucosidase (two and three-way interactions) and for total activity of alpha-D-galactosidase in the time x aw treatment. This study suggests that these hydrolytic enzymes may play an important role in enabling these important fumonisin-producing Fusarium spp. to rapidly infect living maize grain over a wide aw range.
International Journal of Food Microbiology 08/1998; 42(3):185-94. · 3.33 Impact Factor
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ABSTRACT: Corn kernels naturally contaminated with fumonisins B1 and B2 were steeped by dipping the whole kernels in either water or a 0.3% solution of sodium bisulphite (pH = 5.7) for 6, 12, 24, 36 and 48 h. The toxin content of both the solid and the liquid were analysed for each time period. A different rate of interchange between the solid matrix and the water solution was found for FB1 and FB2 and some differences were found in the fate of both fumonisins between the two steeping systems studied. In addition, a preliminary study of the distribution of FB1 and FB2 between the germ and the remaining part of the kernel was carried out.
Food Additives and Contaminants 08/1996; 13(5):511-7. · 2.13 Impact Factor
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ABSTRACT: Contamination studies by ochratoxin A on pork kidney and chicken liver has been carried out in Catalonia (Spain). 73% of the pork kidney samples analyzed did not contain an amount of ochratoxin A over our detection limit (0.5 ng/g) whereas only 7% had contamination higher than 1 ng/g. None of the chicken samples analyzed were contaminated by this toxin above the detection limit. All contamination levels found are below the maximum levels accepted by several countries for this kind of material. A confirmative test is necessary before discarding false positive samples.
Mycopathologia 02/1994; 125(1):29-32. · 1.65 Impact Factor
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ABSTRACT: A simple and economical method has been developed for the determination of patulin in apple juice. The sample is extracted with ethyl acetate in a diphasic dialysis system, and the extract is cleaned up by elution from a Sep-Pak cartridge. Patulin is detected and determined by reversed-phase high-performance liquid chromatography using a Novapak C18 column and an ultraviolet detector. The lower detection limit is 1 microgram l-1 and the recovery is 85% at the 20 micrograms l-1 level.
The Analyst 03/1993; 118(2):171-3. · 4.23 Impact Factor
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ABSTRACT: Patulin production by Penicillium griseofulvum was monitored with Sep-Pak cartridges and high-pressure liquid chromatography. Determination and quantification of this metabolite proved to be very simple, and our method saved time and a large amount of organic solvents.
Applied and Environmental Microbiology 02/1986; 51(1):209-10. · 3.83 Impact Factor
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ABSTRACT: The effect of water activity (aw, 0-995-0-85) and temperature (15, 25 °C) on the in vitro inter- and intra-specific interactions between thirteen fungi commonly isolated from maize grain were investigated. The fungi were paired and their interactions given a numerical score to obtain an Index of Dominance (ID) for each species. Aspergillus niger had the highest overall ID in most of the conditions tested, while the Aspergillus species tested were also quite dominant. Fusarium species appeared to be dominant only at high water availability (0-995 aw), while Eurotium species dominated at the lower aws (0-85-0-90). The relative growth rates of each fungus were also calculated under the same range of environmental conditions. In general, Aspergillus, Fusarium and Trichoderma species grew most rapidly under the combination of aw and temperature conditions in which they were able to grow, while Penicillium species had the slowest growth rates. There was a positive correlation between growth rate and ID for Trichoderma viride and three Fusarium spp. but not for Aspergillus and Penicillium and Eurotium spp. The different possible strategies in fungal competition for grain are discussed in relation to these in vitro findings.
Mycological Research.
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ABSTRACT: The effect of different water availabilities (water activity, aw; 0.98–0.93) and time (up to 15 days) on the production of seven hydrolytic enzymes by strains of F. moniliforme and F. proliferatum during early colonisation of gamma-irradiated living maize grain were examined in this study. Both the total activity (μmol 4-nitrophenol min−1 g−1 maize) and specific activity (nmol 4-nitrophenol min−1 μg−1 protein) were quantified using chromogenic p-nitrophenyl substrates. The dominant three enzymes produced by the fungi on whole colonised maize kernels were α-d-galactosidase, β-d-glucosidase, and N-acetyl-β-d-glucosaminidase. The other four enzymes were all produced in much lower total amounts and in terms of specific activity (β-d-fucosidase, α-d-mannosidase, β-d-xylosidase and N-acetyl-α-d-glucosaminidase), similar to that in uncolonised control maize grain. There were significant increases in the total production of the three predominant enzymes between 3–15 days colonisation, and between 3–6 days in terms of specific activity when compared to untreated controls. The total and specific activity of the α-d-galactosidase, β-d-glucosidase and N-acetyl-β-d-glucosaminidase, were maximum at 0.98 aw with significantly less being produced at 0.95 and 0.93 aw, with the exception of the total activity of α-d-galactosidase which was similar at both 0.95 and 0.93 aw. Single factors (time, aw, and inoculation treatment), two- and three- way interactions were all statistically significant for the three dominant enzymes produced except for specific activity of β-d-glucosidase (two and three-way interactions) and for total activity of α-d-galactosidase in the time ×aw treatment. This study suggests that these hydrolytic enzymes may play an important role in enabling these important fumonisin-producing Fusarium spp. to rapidly infect living maize grain over a wide aw range.
International Journal of Food Microbiology.
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ABSTRACT: The effect of a commercial mixture of propionates at two different doses (0.05% and 0.1%) on fungal spoilage of natural maize stored at 0.85, 0.90 and 0.95 water activity (aw) was investigated. Parallel treatments with added inoculum of Fusarium Liseola section isolates (Fusarium moniliforme and F. proliferatum) were carried out in order to determine the effect of fungal interactions on the development of fumonisin-producers on maize in relation to preservative efficacy. Fungal colonisation of grain was measured as fungal counts (CFUs g−1 maize). In general, no differences were found between inoculated and uninoculated samples. Besides the selective effect of aw on maize mycoflora, it was demonstrated that most genera which colonise maize remained unaffected by the preservative concentrations applied. However, Penicillium populations (CFUs g−1 maize) counts decreased significantly. As they represent a major component of the total fungal counts, an overall control of total mycoflora was observed. Furthermore, there was a significant statistical interaction between preservative and aw levels, with the preservative activity enhanced at low aw. The concentrations of fumonisin B1 were unaffected by treatment with no significant differences in concentrations found. This suggests that the natural mycoflora of maize may act as an inhibitor of Fusarium development, and consequently of fumonisin biosynthesis.
Journal of Stored Products Research.
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ABSTRACT: The effect of water activity (0.98, 0.95, 0.93) and temperature (15, 25°C) on fungal growth and toxin production from interactions between isolates of Fusarium moniliforme and F. proliferatum producing fumonisin, and an isolate of F. graminearum producing zearalenone, incubated at the same time on irradiated maize grains were determined in vitro. Populations (CFUs) of F. moniliforme and F. proliferatum were reduced to a greater or lesser extent by the presence of F. graminearum under all conditions tested, while that the presence of F. moniliforme or F. proliferatum had a minor inhibitory effect on fungal populations of F. graminearum. Fumonisin B1 production by F. proliferatum was inhibited under all conditions tested, while fumonisin B1 production by F. moniliforme was inhibited at 15°C and enhanced at 25°C in the presence of F. graminearum. The level of zearalenone was not significantly modified in the presence of F. moniliforme and F. proliferatum under the conditions tested.
International Journal of Food Microbiology.
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ABSTRACT: Growth of A. ochraceus at 30°C was significantly influenced by changes in both solute (NaCl, glycerol) and matric potential (PEG 8000). Optimum growth rates were at approx. – 10.0 MPa with the non-ionic solute, and between – 3.5 (= 0.975 aw) and 14.0 MPa (= 0.90 aw) with the ionic solute in a sucrose-based minimal salts medium. The optimum matric potential for growth was at – 7.0 MPa (= 0.95 aw). Growth rates were influenced by whether colonies were grown directly on the agar medium or on cellophane overlays. Sclerotia were profusely formed on media > – 1.5 MPa (= 0.99 aw), only initials at – 3.5 MPa, and none under optimum conditions for growth (- 7.70 to – 10.0 MPa). The contents of low and high mol. wt polyols (glycerol, erythritol, arabitol and mannitol) and sugars (glucose and trehalose) were quantified in whole colonies and conidia grown under different osmotic and matric potential conditions for the first time. There was a higher total amount of polyols (μg mg−1 D.W.) in conidia than in whole colonies. In glycerol-amended osmotic media maximum total polyols were present at – 4.5 (= 0.965 aw) and – 17.0 MPa (= 0.88 aw) in mycelial colonies and conidia respectively, with glycerol and mannitol being predominant in both, with small amounts of erythritol also present in conidia. By contrast, in matrically-modified media, the high mol. wt mannitol was the major component (> 75% of the total) with small amounts of arabitol and the low mol. wt erythritol and glycerol, regardless of matric potential. For sugars, trehalose was predominant in conidia (> 90%) from osmotically-modified media with low levels of glucose present in both conidia and mycelial colonies at all potentials tested. By contrast, in matric media trehalose was the predominant sugar in both conidia and whole colonies. This study suggests that xerophilic fungi may use different mechanisms for overcoming osmotic and matric stress.
Mycological Research.
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ABSTRACT: The effects of different steady-state water activity levels (aw, 0.93, 0.95 and 0.98) and temperature (15 and 25°C) on colonisation patterns of Aspergillus and Penicillium spp., when colonising irradiated maize grain in the presence of Fusarium moniliforme and Fusarium proliferatum were assayed in terms of populations (colony forming units, CFUs g grain−1), seed infection and colonisation rates. The activity of F. moniliforme and F. proliferatum in grain reduced the presence of Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus to some extent, particularly at 15°C and higher water availabilities (0.95–0.98 aw). In contrast, colonisation patterns of Penicillium implicatum on maize grain were unaffected by either Fusarium spp. in terms of CFUs or seed infection. Correlations were made between CFUs, seed infection, growth rates and niche overlap indices and hyphal interactions to try and link key indicators of competitiveness and dominance by an individual species.
International Journal of Food Microbiology.
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ABSTRACT: A scanning electron microscopy (SEM) study of the effect of water activity (aw), temperature and fungal interactions on the very early phases of Aspergillus ochraceus, Alternaria alternata and Fusarium verticillioides development on maize grains was carried out. Germination and growth of individual fungal strains were assayed at 0.92, 0.95 and 0.98 aw, and 20 and 30 °C. Hyphal lengths were measured on micrographs taken by SEM at different periods of incubation. A. alternata had the highest linear growth at 0.98 aw, and was the only species able to grow under all conditions tested, whereas A. ochraceus was not able to germinate at 0.92 aw at any temperature assayed. F. verticillioides demonstrated a different behaviour depending on growth temperature. Fungal interactions were studied at 0.95aw and 30 °C. A. ochraceus germination was inhibited when it was co-inoculated with one or two of the other species. A. alternata showed an increased growth rate when growing together with the other fungi, whereas growth of F. verticillioides was significantly inhibited when paired with A. ochraceus.
International Journal of Food Microbiology.
