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ABSTRACT: Aflatoxin (highly toxic and carcinogenic secondary metabolites produced by fungi) contamination is a serious problem worldwide. Modern agriculture and animal production systems need to use high-quality and mycotoxin-free feedstuffs. The use of microorganisms to preserve food has gained importance in recent years due to the demand for reduced use of chemical preservatives by consumers. Lactic acid bacteria are known to produce various antimicrobial compounds that are considered to be important in the biopreservation of food and feed. Lactobacillus rhamnosus L60 and Lactobacillus fermentum L23 are producers of secondary metabolites, such as organic acids, bacteriocins and, in the case of L60, hydrogen peroxide. The antifungal activity of lactobacilli strains was determined by coculture with Aspergillus section Flavi strains by two qualitative and one quantitative methods. Both L23 and L60 completely inhibited the fungal growth of all aflatoxicogenic strains assayed. Aflatoxin B (1) production was reduced 95.7-99.8% with L60 and 27.5-100% with L23. Statistical analysis of the data revealed the influence of L60 and L23 on growth parameters and aflatoxin B (1) production. These results are important given that these aflatoxicogenic fungi are natural contaminants of feed used for animal production, and could be effectively controlled by Lactobacillus L60 and L23 strains with probiotic properties.
FEMS Microbiology Letters 04/2012; 332(1):27-33. · 2.04 Impact Factor
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ABSTRACT: The efficacy of two strains of Kluyveromyces thermotolerans in preventing the growth and ochratoxin A (OTA) accumulation of ochratoxigenic fungi both "in vitro" and "in situ" was evaluated. The data from this study showed that both yeast strains were able to control Aspergillus carbonarius and A. niger aggregate species growth and ochratoxin A accumulation. The inhibitory effects were dependent on the ochratoxigenic species, yeast strains, a(w) and temperature evaluated and their interactions. Over all conditions assayed, ochratoxin A accumulation was reduced from 3% to 100% and the growth rate from 11% to 82.5%, depending on conditions. These results are promising for future development of a bio-pesticide.
International journal of food microbiology 08/2011; 151(1):70-7. · 3.01 Impact Factor
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ABSTRACT: In this study, ochratoxin A (OTA) occurrence in Argentinean musts, wines and dried vine fruits was evaluated, alongside with the performance of OchraStar(TM) columns for OTA extraction. In all the three matrices analyzed, the OchraStar(TM) columns showed good performance. The analysis of natural occurrence of OTA in the red must and the red wine samples showed low incidence with low levels of mean OTA contamination (0.12 ng/mL and 0.37 ng/mL, respectively), while 60% of the dried vine fruit samples were contaminated with OTA, in levels ranging from 0.26 to 20.28 ng/g.
Toxins. 08/2010; 2(8):1984-96.
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ABSTRACT: This study was carried out to determine the efficacy of the phenolic antioxidant propyl paraben (PP) under different interacting water activity (a(W)) and temperature regimes on lag phase, growth rate and Ochratoxin A production by Aspergillus section Nigri strains. In this experiment six Aspergillus section Nigri strains were used. Peanut meal extract agar (PMEA) was prepared at 2%. The a(W) of the medium was adjusted to 0.995, 0.980 and 0.930, PP levels of 1, 5, 10 and 20 mmol/L were added to the basic medium. Plates were inoculated and incubated for 30 days at 18 and 25 degrees C. Lag phase (h) and radial growth rates (mm/day) were calculated. In control treatments, the lag phase increased and the growth rate decreased as a(W) reduced in all assayed strains. At all a(W) levels, when antioxidant concentrations increased the growth rate decreased. At 5, 10 and 20 mmol/L of PP the strains were not able to reach the exponential phase and completely inhibited fungal growth and OTA production regardless of a(W) used in all the evaluated strains.
International journal of food microbiology 09/2009; 136(1):133-6. · 3.01 Impact Factor
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ABSTRACT: Ochratoxin A (OTA) is one of the most important mycotoxins of worldwide concern for human health. The aims of this study were to evaluate the effects of water activity, temperature, incubation time and their interactions on growth, lag phase and OTA production by two strains belonging to A. niger aggregate in irradiated corn grains. This study shows that OTA production on corn grains occurs within a more restricted range of water activity and temperature than fungal growth. This point is important in order to maintain the appropriate conditions in stored corn that prevent toxigenic fungal growth and thus OTA production. Irradiated corn grains were re-hydrated to 0.910-0.995 of a(W) with sterile distillate water. The temperatures assayed were 15, 25 and 30 degrees C. Growth assessment was made every day during the incubation period (21 days) to calculate the growth rate, lag phase and the OTA production at 7, 14 and 21 days. Both strains showed optimum growth at 30 degrees C at 0.951 a(W). Ochratoxin A production occurred over a range of temperatures (15-30 degrees C) with optimum production at 25 degrees C depending on a(W) assayed. Maximum OTA production was obtained for both strains at 0.973 a(W). The results obtained suggest that the storage of corn grains at water activities lower than 0.951 and 15 degrees C should prevent these fungal species growth and OTA production during 21 days approximately.
International journal of food microbiology 12/2008; 129(2):174-9. · 3.01 Impact Factor
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ABSTRACT: The objectives of this study were to determine the effect of water activity, temperature, and their interactions on a) mycelial growth rate and b) the lag phase prior to grow of seven isolates of Aspergillus section Nigri isolated from peanuts, maize kernels, dried grapes and coffee cherries from Argentina. Three Aspergillus niger, three A. awamori and one A. carbonarius isolates examined showed optimum a(W) level for growth at 0.97 with optimal temperature of 30 degrees C. for most of the isolates and 25 degrees C for only one (A. awamori RCP176). Minimal a(W) for growth was 0.85 at the highest temperature tested. Overall growth was reduced up to 50% at 0.93 a(W). Growth was also to a large extend inhibited at 0.85 a(W) for most isolates even after 21 days of incubation at temperatures lower than 30 degrees C. The analysis of variance of the effect of single (isolate, a(W) and temperature), two- and three-way interaction showed that all factors alone and all interactions were statistically significant (P<0.001) in relation to growth rates and lag phase for A. niger, A. awamori and A. carbonarius isolates. These data are relevant since these species are isolated in high frequency on numerous substrates for human and animal consumption in Argentina.
International Journal of Food Microbiology 12/2007; 119(3):314-8. · 3.33 Impact Factor
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ABSTRACT: The evolution of contamination with Aspergillus section Nigri and ochratoxin A occurrence was evaluated in four vineyards located at Mendoza province, Argentina during 2003-2004. The survey included two grape varieties, one of late maturation (Bonarda) and the other of early maturation (Tempranillo). The vineyards were set under non-organic and organic cropping systems. Bunches of grapes at different growth stages were collected, and berries (50 by sample) were plated on Petri dishes containing Dichloran 18% Glycerol Agar (DG18) and Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media. After an incubation period of 7 days at 25 degrees C+/-1 degrees C, the mycoflora belonging to Aspergillus section Nigri was identified. The ability to produce ochratoxin A (OTA) by the potential ochratoxigenic species was evaluated on YES (2% yeast extract, 15% sucrose) medium. The cultures were incubated at 30 degrees C+/-1 degrees C for 10 days in darkness. The OTA content of the grapes was determined by HPLC. Through the different growth stages, from setting to harvest, grape contamination by the Aspergillus species, section Nigri increased. The main species isolated belonged to the A. niger aggregate. From 246 strains evaluated 24% was ochratoxigenic. OTA was not detected in grapes during the survey.
International Journal of Food Microbiology 04/2007; 114(2):131-5. · 3.33 Impact Factor
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ABSTRACT: Since there is no available information about the natural occurrence of ochratoxin-producing fungi and ochratoxin A (OTA) in peanut seeds in Argentina, the aims of this work were to isolate and identify Aspergillus section Nigri and to evaluate the natural occurrence of OTA in stored peanut seeds. Likewise, the capacity to produce OTA by Aspergillus section Nigri was studied. Forty-seven samples of peanut seeds were obtained from a storage plant in the south of Córdoba Province, Argentina. Each sample of 100 seeds was surface-disinfected and plated onto a dichloran 18% glycerol agar (DG18). OTA was detected by HPLC. The production of OTA in strains belonging to section Nigri was tested in YES medium (2% yeast extract, 15% sucrose). Aspergillus spp., the most frequent mould, occurred in 100% of samples, followed by Penicillium spp. (87%) and Eurotium spp. (6.4%). A. flavus was isolated in 100% of the samples, followed by A. niger var. niger, A. niger var. awamori and A. carbonarius at a lower frequency, 89%, 68% and 4%, respectively. OTA was found in 32% of the peanut seed samples, with mean levels ranging from 0.5 to 170 ng g−1. The mean recovery of the method used was 85 ± 2%. Forty-three isolates (27%) of Aspergillus section Nigri, were found to be OTA producing strains. The highest percentage of ochratoxigenic strains (57%) was found within the A. carbonarius ssp. These results indicate a human exposure to OTA in Argentina through the ingestion of peanut seeds and peanut products. Copyright © 2006 Society of Chemical Industry
Journal of the Science of Food and Agriculture 09/2006; 86(14):2369 - 2373. · 1.44 Impact Factor
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ABSTRACT: Alternaria alternata is isolated in high frequency in sunflower seeds both in the field and storage. This species produces several toxic metabolites among them alternariol, alternariol monomethyl ether and tenuazonic acid. The accumulation of mycotoxins is regulated by physical, chemical and biological factors and for their production in many commodities nothing is known with regards to these conditions. In sunflower seeds the optimal conditions of temperature and water activity for tenuazonic acid production are unknown. The aim of this work was to investigate the effect of temperature and water activity on tenuazonic acid production byAlternaria alternata ITEM 539 in sunflower seeds. The temperature conditions evaluated were: 20, 25, and 30 C and the water activities were 0.97, 0.90, 0.87, 0.80. The tenuazonic acid determinations were carried out during the incubation period at intervals of 7 days. Under conditions of constant temperature 25 C) and variable water activities, 0.90 was the optimal value for tenuazonic acid production. At this water activity of the optimal temperature for tenuazonic acid production was 25 C.
Mycopathologia 05/1994; 126(3):179-182. · 1.65 Impact Factor
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ABSTRACT: This study was carried out to determine the efficacy of phenolic antioxidant butylated hydroxyanisole (BHA) under different interacting water activity (aW) and temperature regimes on the lag phase and growth rate by Aspergillus section Nigri strains. In this experiment four A. section Nigri strains were used. Peanut meal extract agar (PMEA) was prepared at 2%. The aW of the medium was adjusted to 0.995, 0.980 and 0.930, BHA at 1, 5, 10 and 20 mmol l−1 was added to the basic medium. The plates were inoculated and incubated for 30 days at 18 and 25 °C. Radial growth rates (mm d−1) and lag phase (h) were calculated. In control treatments, the growth rate decreased as water activity reduced in all strains assayed. At all aW levels tested, BHA at 20 mmol l−1 completely inhibited growth. In general, at 10 mmol l−1 and 0.995 and 0.980aW level, a significant reduction respect to control was observed. This antioxidant completely inhibited OTA production, at concentrations of 20 mmol l−1, regardless of aW used by all the strains evaluated.
Food Control.
