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. Its occurrence in wines, mainly in the red ones, has been widely reported (Zimmerli and Dick, 1996). Recent studies prove the possibility to decontaminate grape musts with selected yeasts able to remove OTA during winemaking (Bejaoui et al., 2004; Caridi et al., 2006); this ability seems related to the adsorption on the outermost layer of the yeast cell wall and has been associated to the parietal mannoproteins, whose content in S. cerevisiae depends on the specific yeast strain (Caridi, 2006). In this study, 120 strains of S. cerevisiae coming from three Italian collections [Portici (Naples), Reggio Calabria and Reggio Emilia] previously characterized for their physiological, technological and genetic features were tested in vitro for OTA removal capacity in synthetic must. Pre-cultures were prepared in YPD at 28°C for 48 h. Tests were performed in triplicate on 10 ml of synthetic must artificially contaminated with 5 ppb of OTA. After inoculums with 0.2 ml of YPD pre-culture, tubes were incubated at 25°C for 21 days. Residual OTA in wines was determined by HPLC as already described by Caridi et al. (2006), analyzing three aliquots of each test tube. In a global view of results obtained it seams that S. cerevisiae strains are able to remove about 45% of OTA during fermentation (the mean value of the 120 wines was 45.75% ± 6.29). By contrast, analyzing in detail the results it is evident a high variability: some strains were able to remove less than 30% of OTA, others reached removal levels of 55-60%. The occurrence of strains showing an OTA removal major than 55%, and with a low standard deviation, were very low: a) two strains out 38 of the Portici collection (% of OTA removal: 58.83 ± 1.12 and 57.13 ± 4.42, respectively); b) one strain out 18 of the Reggio Emilia collection (% of OTA removal: 61.08 ± 1.09); c) three strain out 64 of the Reggio Calabria collection (% of OTA removal: 57.96 ± 2.68, 57.35 ± 1.99, and 57.19 ± 3.88, respectively). References Caridi et al. (2006). Enzyme and Microbial Technology 40, 122–126. Caridi (2006). Antonie van Leeuwenhoek 89, 417-422. Bejaoui et al. (2004). Journal of Applied Microbiology 97, 1038-1044. Zimmerli and Dick (1996). Food Additives and Contaminants 13, 655–68.