Cubaiu, Loredana (2009) Prevention and biocontrol of ochratoxin a in wine. Doctoral Thesis.
This PhD thesis dealt with the study of yeast species involved in wine fermentation and with a potential for biocontrol of Aspergillus ochraceus and Aspergillus carbonarius, the main fungal species responsible for the accumulation of ochratoxin A (OTA) in grape and wine. Yeast isolates were tested and those showing an antagonistic activity against OTA producing fungi were selected. Yeast isolates were characterised by using a nutritional competition assay in YES and CYA agar media. Some of the isolates analysed caused a significant growth reduction in A. carbonarius and A. ochraceus. All yeasts strains reduced significantly A. carbonarius colonisation on artificially inoculated grape berries. Most yeast strains were able to significantly reduce OTA content in the culture filtrates when co-cultivated with ochratoxigenic strains. The effects of the best antagonistic strain of Saccaromyces cerevisae has been tested on OTA production and pks gene expression in A. carbonarius and A. ochraceus. The S.cerevisiae strain was able to inhibit growth and OTA production when co-cultured in YES. Quantitative RT-PCR confirmed the down-regulation of the pks gene in both mould suggesting that S.cerevisiae is able to inhibit OTA production at trascriptional level. The results indicate that yeasts, which are naturally present on grapes, must and wine are promising “eco-friendly” biocontrol tools, which should not interfere with the equilibrium of the natural environment.
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