Selection of Saccharomyces cerevisiae strains with high ability to adsorb ochratoxin A during fermentation

Ochratoxin A (OTA) exerts several toxic effects, mainly involving kidney and liver. Itsoccurrence in wines, mainly in the red ones, has been widely reported (Zimmerli andDick, 1996). Recent studies prove the possibility to decontaminate grape musts withselected yeasts able to remove OTA during winemaking (Bejaoui et al., 2004; Caridiet al., 2006); this ability seems related to the adsorption on the outermost layer of theyeast celi wall and has been associated to the parietal mannoproteins, whosecontent in S. cerevisiae depends on the specific yeast strain (Caridi, 2006). In thisstudy, 120 strains of S. cerevisiae coming from three Italian collections [Portici(Naples), Reggio Calabria and Reggio Emilia] previously characterized for theirphysiological, technologieal and genetic features were tested in vitro for OTA removalcapacity in synthetic rnust. Pre-cultures were prepared in YPD at 28'C for 48 h. Testswere performed in triplicate on 10 mi of synthetie must artificially contaminated wilh 5ppb of OT A. After inoculums with 0.2 mi of YPD pre-culture, tubes were incubated at25\ub0C for 21 days. Residual OTA in wines was determined by HPLC as alreadydeseribed by Caridi et al. (2006), analyzing three aliquots of each tesi tube. In aglobal view of results oblained it seams that S. cerevisiae strains are able to removeabout 45% of OTA during fermentalion (the mean value of the 120 wines was45.75% \ub1 6.29). By contrast, analyzing in detail the results it is evident a highvariability: some strains were able to remove less Ihan 30% of OTA, others reachedremoval levels of 55-60%. The occurrence of strains showing an OTA removal majorthan 55%, and with a low standard deviation, were very low: a} two strains out 38 ofthe Portici colleclion (% of OTA removal: 58.83 \ub1 1.12 and 57.13 \ub1 4.42,respectively); b) one strain out 18 of the Reggio Emilia colleclion (% of OTA removal:61.08 \ub1 1.09); c) three strain out 64 of the Reggio Calabria colleetion (% of OTAremoval: 57.96 \ub1 2.68, 57.35 \ub1 1.99, and 57.19 \ub1 3.88, respectively). ReferencesCaridi et al. (2006). Enzyme and Microbial Technology 40, 122-126. Caridi (2006).Antonie van Leeuwenhoek 89, 417-422. Bejaoui et al. (2004). Journal of AppliedMicrobiology 97, 1038-1044. Zimmerli and Dick (1996). Food Additives andContaminants 13, 655-68