Effect of pH on ochratoxin A production by A. niger aggregate species

Grup de Micologia Veterinària, Departament de Sanitat i d'Anatomia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
Food Additives and Contaminants (Impact Factor: 2.13). 07/2006; 23(6):616-22. DOI: 10.1080/02652030600599124
Source: PubMed


The effect of pH (2-10) on growth and ochratoxin A (OTA) production by 12 Aspergillus niger aggregate strains was studied in two culture media: Czapek yeast autolysate agar (CYA) and yeast extract sucrose agar (YES), over 30 days. The strains were selected to include different sources, different reported abilities to produce OTA and different ITS-5.8S rDNA RFLP patterns. YES was a better culture medium than CYA for OTA production. In this medium, OTA was produced from pH 2 or 3 to 10 depending on the strain. The results show the ability of A. niger aggregate strains not only to grow, but also to produce OTA over a wide pH range. The results will lead to a better understanding of the role of A. niger aggregate strains in the OTA contamination of several food commodities.

Download full-text


Available from: F. Javier Cabañes, Oct 05, 2015
53 Reads
  • Source
    • "Recently (Esteban et al., 2006) in an attempt to understand the relative significance of OTA producing fungi showed that A. niger aggregate not only flourishes but also produces OTA over a wide pH range. It may be that the significance of A. niger as an OTA producer has been previously underestimated. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Fifty individual figs which had been rejected as potentially contaminated by sorting under UV light were separately analysed to identify the presence of fungi and their mycotoxins. Aflatoxin B-1 was found in 49 samples with levels ranging from 0.7 to 222 ng g(-1), with 40 individual figs containing more than 2 ng g(-1), indicating the efficacy of the UV screening process in identifying contaminated fruit. Ochratoxin A (OTA) was found in 32 of the figs at levels from 0.4 to 1710 ng g(-1), with 50% of the samples containing levels above 1 ng g(-1). There was no evident correlation between levels of aflatoxin B-1 and levels of OTA. Twenty fungal species were isolated from the outer and inner surfaces of the figs, some of which were subsequently cultured on YES and PDB and the media analysed for the presence of aflatoxin B-1 and OTA to establish their toxigenicity.
    World Mycotoxin Journal 02/2008; 1(1):79-86. DOI:10.3920/WMJ2008.x009 · 2.16 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to determine the effects of water activity (a(w)) (0.92-0.98), temperature (5-45 °C) and incubation time (5-60 days) on growth and ochratoxin A (OTA) production by Aspergillus niger and Aspergillus carbonarius on maize kernels using a simple method. Colony diameters of both strains at 0.92 a(w) were significantly lower than those at 0.96 and 0.98 a(w) levels. The optimum growth temperature range for A. niger was 25-40 °C and for A. carbonarius 20-35 °C. A. niger produced OTA from 15 to 40 °C, and the highest OTA level was recorded at 15 °C. The concentration of OTA produced at 0.92 a(w) was significantly lower than those at 0.96 and 0.98 a(w). A. carbonarius produced OTA from 15 to 35 °C and the maximum concentration was achieved at 15 °C, although not differing statistically from the concentration detected at 20 °C. At 0.98 a(w) the OTA concentration was significantly higher than at 0.96 and 0.92 a(w). Our results show that maize supports both growth and OTA production by A. niger and A. carbonarius. The studied strains were able to produce OTA in maize kernels from the fifth day of incubation over a wide range of temperatures and water availabilities. Although the limit of quantification of our method was higher than that required for the analysis of OTA in food commodities, it has proved to be a useful and rapid way to detect OTA production by fungi inoculated onto natural substrates, in a similar way as for pure culture. Both species could be a source of OTA in this cereal in temperate and tropical zones of the world.
    International journal of food microbiology 03/2011; 147(1):53-7. DOI:10.1016/j.ijfoodmicro.2011.03.005 · 3.08 Impact Factor
Show more