[Effect of microelements on formation of acids and ethyl alcohol by Saccharomyces carlsbergensis yeasts]

Abstract

The effect of Fe, Zn, Mn, Pb, Al, Cu, and K on the synthesis of pyruvic, alpha-ketoglutaric and total volatile acids and ethanol was studied in the process of fermentation of 6 per cent maltose solution by Saccharomyces carlsbergensis 776. Experiments were conducted using techniques of their mathematical planning. Fe, Pb, and Mn at concentrations of 15.0, 0.5, and 1.5 mg/litre, respectively, had a positive effect on the synthesis of pyruvic acid whose concentration in the medium increased by 3.3 mg per 100 ml to become equal to 43.3 mg per 100 ml. Fe3+ at a concentration of 15 mg/litre had a negative effect on the synthesis of alpha-ketoglutaric acid. The synthesis of volatile acids depended on the presence of Fe, Zn, Pb, Al, and K. Fe and Al at concentrations of 15 mg/litre favoured the synthesis of volatile acids by 2.72 mg/litre. In the presence of Zn (1.5 mg/litre), Pb (0.5 mg/litre), and K (15 mg/litre), the content of volatile acids decreased by 4.48 mg/litre and became equal to 14.94 mg/litre. Zn at a concentration of 1.5 mg/litre inhibited it.