ASaccharomyces cerevisiaewine strain inhibits growth and decreases ochratoxin a biosynthesis byAspergillus carbonariusandAspergillus ochraceus

The aim of this study was to select wine yeast strains as biocontrol agents against fungal contaminants responsible for the accumulation of ochratoxin A (OTA) in grape and wine and to dissect the mechanism of OTA detoxification by aSaccharomyces cerevisiaestrain (DISAABA1182), which had previously been reported to reduce OTA in a synthetic must. All of the yeast strains tested displayed an ability to inhibit the growth of Aspergillus carbonarius bothin vivoandin vitroand addition of culture filtrates from the tested isolates led to complete inhibition of OTA production.S. cerevisiaeDISAABA1182 was selected and further tested for its capacity to inhibit OTA production and pks (polyketide synthase) transcription inA. carbonariusandAspergillus ochraceus in vitro. In order to dissect the mechanism of OTA detoxification, each of these two fungi was co-cultured with living yeast cells exposed to yeast crude or to autoclaved supernatant:S. cerevisiaeDISAABA1182 was found to inhibit mycelial growth and OTA production in bothAspergilliwhen co-cultured in the OTA-inducing YES medium. Moreover, a decrease inpkstranscription was observed in the presence of living cells ofS. cerevisiaeDISAABA1182 or its supernatant, while no effects were observed on transcription of either of the constitutively expressed calmodulin and β-tubulin genes. This suggests that transcriptional regulation of OTA biosynthetic genes takes place during the interaction between DISAABA1182 and OTA-producingAspergilli.