Zinc, Copper and Manganese Enrichment in Yeast Saccharomyces cerevisae
Vesna Stehlik-Tomas, Vlatka Gulan Zetić*, Damir Stanzer, Slobodan Grba and Nada Vahčić
Laboratory of Fermentation and Yeast Technology, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, HR-10000 Zagreb, Croatia
Article history:
Received May 14, 2003
Accepted February 16, 2004
Key words:
yeast enriched with microelements, Saccharomyces cerevisiae, alcoholic fermentation, zinc, copper, manganese, metal uptake
Summary:
The aim of the present work was to study the incorporation of some microelements in the yeast Saccharomyces cerevisiae and its impact on the physiological state of the yeast cells during the alcoholic fermentation. The cultivations were performed on molasses medium in anaerobic (thermostat) and semiaerobic (shaker) conditions, with and without the addition of zinc, copper and manganese sulphate (0.1 g/L of each) at 30 °C and different pH values of the medium (3.5–6.0) for 8 h. The addition of the mentioned salts in molasses medium enhanced the yield of the yeast biomass up to 30 % in semiaerobic conditions, but the ethanol yield was changed very little. On the other hand, in anaerobic conditions the yields of the yeast biomass were increased up to 10 % and alcohol yield up to 20 %. After the fermentations were performed, the concentration of metal ions in yeast cells was determined. Different values were achieved depending on the used growth conditions. The highest amount of Zn ions in dry matter (700 µg/g) was incorporated in the yeast biomass under anaerobic conditions. In contrast, the incorporation of Cu and Mn was preferred in semiaerobic conditions and the highest value of Cu2+ ions in dry matter (1100 µg/g) and Mn2+ in dry matter (300 µg/g) in yeast biomass were obtained. Optimal pH for all ion incorporations was between 4 and 5.
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