Study on the presence of ochratoxin α in cultures of ochratoxigenic and non- ochratoxigenic strains of Aspergillus carbonarius

Ochratoxin A (OTA) is a potent nephrotoxin and carcinogen which is found in a wide variety of common foods and beverages and it is produced by several species of Aspergillus and Penicillium. Ochratoxin α (OTα), a major metabolite of OTA, has also been reported to occur in cultures of OTA-producing species. However there is some controversial about the participation of OTα in the biosynthesis of OTA, mainly because its biosynthesis pathway has not yet been completely characterized. Aspergillus carbonarius is the main responsible source of ochratoxin A (OTA) in food commodities such as wine, grapes or dried vine fruits from main viticultural regions worldwide. However, little is known about the presence of OTα in isolates of A. carbonarius. In this study we evaluated the effects of temperature and incubation time on OTα production by both OTA and non-OTA-producing strains of A. carbonarius. OTA and OTα were detected on the basis of HPLC fluorometric response compared with that of their standards and confirmed by HPLC-MS in selected samples. The non-OTA-producing strains did produce neither OTA nor OTα at any of the conditions tested. The OTA-producing strains studied were able to produce both OTA and OTα in most of the conditions tested. In general, higher amounts of OTA than OTα were produced, but a positive correlation in the production of these two metabolites was detected. The lack of production of both OTA and OTα in the non-OTA-producing strains could be caused by the presence of silent genes or by mutations in functional or regulatory genes involved in OTA production.