Removal of Ochratoxin A in Saccharomyces cerevisiae Liquid Cultures
AbstractThe capacity for removal of ochratoxin A (OTA) during alcoholic fermentation was evaluated in batch systems with
one commercial strain and one wild strain of Saccharomyces cerevisiae. Batch alcoholic fermentations were carried
out in yeast extract-malt extract broth (YM) medium, with 18.0% glucose and OTA added to final concentrations
of 3.48 and 4.95 ng/mL respectively. The removal capacity of each yeast strain was examined after completion of
fermentation in batch culture and after extended contact with yeast biomass. The removal capacity of the yeast
strains was also examined in stationary phase cultures. Stationary phase yeasts were studied with biomass harvested
from the stationary phase of anaerobic fermentation, by incubation in phosphate buffer, with the addition of 5.00 ng/
mL of OTA. Removal studies with stationary phase cells were performed with viable and non-viable cells inactivated
with Na-azide. The study showed that in growing phase cultures, OTA removal was significant only after extended
contact with yeast biomass; up to 29.7% and 25.4% for wild yeast ZIM 1927 and commercial yeast Lalvin EC-1118
respectively, but not during alcoholic fermentation. In stationary phase cultures, viable and non-viable cells were
not significantly different in OTA removal from the medium. This demonstrated that OTA was not metabolised, but
possibly adsorbed by the yeast cells. The presence of OTA in synthetic media influenced yeast metabolism, causing
the production of higher volatile acidity by 0.08 and 0.13 g/L for Lalvin EC-1118 and ZIM 1927 respectively, and
lower concentrations of reducing sugar, by 0.32 g/L, but only for ZIM 1927.
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