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Effect of pH on ochratoxin A production by Aspergillus niger aggregate species
A Esteban1, M L Abarca, M R Bragulat
1Grup de Micologia Veterinària, Departament de Sanitat i d'Anatomia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
Abstract:
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.
Insights
This study shows that Aspergillus niger aggregate strains can grow and produce ochratoxin A (OTA) across a wide pH range (2-10). Yeast extract sucrose agar (YES) medium was more effective for OTA production by these fungal strains.
Area of Science:
- Food microbiology
- Mycology
- Food safety
Background:
- Aspergillus niger aggregate species are known contaminants of food commodities.
- Ochratoxin A (OTA) is a mycotoxin with potential health risks.
- Understanding the environmental factors influencing OTA production is crucial for risk assessment.
Purpose of the Study:
- To investigate the impact of pH on the growth and ochratoxin A (OTA) production of Aspergillus niger aggregate strains.
- To compare the efficacy of two different culture media for OTA production.
- To assess the adaptability of A. niger aggregate strains to various pH conditions.
Main Methods:
- Twelve Aspergillus niger aggregate strains with diverse origins and OTA-producing capabilities were cultured.
- Growth and OTA production were monitored over 30 days in Czapek yeast autolysate agar (CYA) and yeast extract sucrose agar (YES) media.
- Experiments were conducted across a pH range of 2 to 10.
Main Results:
- Yeast extract sucrose agar (YES) supported higher OTA production compared to CYA.
- Aspergillus niger aggregate strains exhibited growth and OTA production across a broad pH range (pH 2-10), varying by strain.
- Specific pH thresholds for OTA production were observed, with some strains producing OTA from pH 2 or 3 up to pH 10 in YES medium.
Conclusions:
- Aspergillus niger aggregate strains demonstrate significant adaptability to a wide spectrum of pH conditions for both growth and ochratoxin A (OTA) synthesis.
- The findings highlight the potential for widespread OTA contamination in food commodities due to the resilience of these fungal strains.
- This research contributes to a better understanding of the ecological factors governing A. niger-associated OTA contamination in food products.
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