EFFECT OF ETHANOL ON THREE POOLS OF GLYCOGEN IN TOP FLOCCULATING STRAIN OF SACCHAROMYCES CEREVISIAE- 3441M.S. DAKE1 AND N.B. PATIL
Three pools of glycogen present in yeast are soluble cytoplasmic glycogen, cell wall bound insoluble glycogen and cell surface glycogen. Yeast cells can store excess of glycogen when subjected to nutritional stress conditions or when grown in presence of higher sugar concentrations. But study regarding effect on glycogen content in yeast under ethanol stress conditions is equally important. Especially study is significant in both top and bottom fermenting yeast strains which exhibit different fermentation behavior. The present work is intended to study effect of external ethanol on all three pools of glycogen in top fermenting yeast strain Saccharomyce cerevisiae 3300 using alkali digestion process. Cells grown with ethanol concentrations from 2-8 % (v/v) exhibit significant rise in insoluble glycogen and other cell wall carbohydrate content. But depletion of insoluble glycogen was observed at higher ethanol concentrations from 10-12 % (v/v). Such inhibitory effect of ethanol was supported by reduction in total cell count of yeast when grown at ethanol concentrations from 2-16 % (v/v). Data indicates protective role of insoluble glycogen in yeast against ethanol stress by minimizing leakage cause by the action of ethanol on cell wall and cell membrane. Elevated level of cell surface α-glucans of yeast grown with externally added ethanol indicates correlation between ethanol, glycogen and flocculation.
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