Aureobasidium pullulans strains degrade Ochratoxin A in vitro and protect wine grape from ochratoxigenic Aspergillus carbonarius.

Ochratoxin A (OTA) is a possibly carcinogenic mycotoxin produced by Aspergillus and Penicillium spp. It is a contaminant of different foodstuffs and beverages such as wine. Wine contamination is mainly due to the attack by Aspergillus carbonarius on wine-grape. In this study, we assessed the ability of 4 Aureobasidium pullulans strains (LS30, AU14-3-1, AU34-2, AU18-3B) to degrade OTA in vitro and, in lab-scale experiments, their activity as biocontrol agents (BCAs) against A. carbonarius on wine grape and their influence on the level OTA accumulation in berries. All the four strains determined significant decreases of OTA recovery from their growth medium. The less toxic Ochratoxin a (OTa) was the major degradation product, putatively derived from carboxy-peptidase activity of the A. pullulans strains. In biocontrol activity assays, the 4 strains significantly lowered the levels of infections by A. carbonarius. Analyses of wine grape treated with the BCAs and inoculated with A. carbonarius showed significant decreases of berries contamination with OTA, as compared to untreated control. OTA contamination in samples treated with strains AU14-3-1 and AU18-3B was comparable to Switchtm–treated berries, although the fungicide treatment showed no visible symptoms of fungal infection. This datum suggests a possible active role of AU14-3-1 and AU18-3B in lowering OTA contamination in wine grape berries. Our results encourage further assessments of microbial biocontrol for reducing both fungicide applications and mycotoxin contamination.