Assessment of the ochratoxin A production ability of Aspergillus tubingensis

Abstract

Aspergillus tubingensis is a black Aspergillus frequently isolated from different agricultural products, including grapes. Conflicting results have been published in recent years about its ability to produce ochratoxin A (OTA), a potent nephrotoxic and carcinogenic mycotoxin. This study re-examined six A. tubingensis strains deposited in international culture collections for OTA production. OTA could not be detected in any A. tubingensis extract using HPLC coupled with a fluorescence detector (FLD), whereas it was easily detected in ochratoxigenic A. niger extracts used as positive control. The same outcome was obtained using LC-MS. The presence of other metabolites with retention times similar to the OTA signal in the A. tubingensis extracts or background noise of the growth media may be reasons for the misinterpretation of the chromatograms obtained by HPLC-FLD.

Keywords:

• black aspergilli
• grapes
• secondary metabolite
• mycotoxin

Acknowledgements

This work was funded by the Autonomous Province of Trento, Project ENVIROCHANGE, Call for Proposal Major Projects 2006. The authors thank Francesca G. Dennert for valuable assistance in microbiological work; and Björn Studer from the Institut für Terrestrische Ökosysteme, ETHZ, for valuable technical assistance in HPLC analysis.