Analysis of Key Factors Affecting Ethanol Production by Saccharomyces cerevisiae IFST-072011

Ethanol production by Saccharomyces cerevisiae is affected not only by fermentation conditions (temperature, pH and sugar concentration) but also by the intrinsic factors e.g., culture medium, dissolved O2, immobilization and other micronutrients. In order to investigate the influence of key factors on ethanol production by S. cerevisiae, a laboratory strain S. cerevisiae IFST-072011 was used in this study. Several fermentation runs were carried out varying temperature, pH, sugar concentration, aeration, immobilization and supplementation of metal ions employed. Experimental data on several fermentation runs showed that reducing sugar concentration ranged between 5-6%, temperature of 30°C and pH between 5.0 and 6.0 were optimum for maximum yield of ethanol by S. cerevisiae IFST-072011.The strain produced 86.9 g L-1 ethanol by free cells using the initial reducing sugar concentration 5.50% at 48 h under shaking condition. Maximum yield of ethanol 94.8 g L-1 was produced by immobilized cells using the reducing sugar concentration 5.50% at 48 h. Ethanol production was higher by immobilized cells in shaking conditions than free cells with same culture conditions. Influence of boron, chromium, copper and magnesium was investigated on ethanol production. Only chromium was found to show slight stimulatory effect on ethanol production.