Process Optimization for Ethanol Production from Sweet Sorghum Juice Using Saccharomyces cerevisiae Strain NRRL Y-2034 by Response Surface Methodology

In the present study, ethanol production from sweet sorghum juice of variety, CSV19SS was optimized using response surface methodology with the help of statistical software Statgraphics Centurian XVI.I. To check storage stability, sweet sorghum juice was stored at 0 and −20 °C and was analyzed for reducing sugars, total acidity, pH and total soluble sugars for a period of 75 days. Sweet sorghum juice was found to be stable under refrigeration conditions for about 75 days without any significant changes in the sugar profile and acidity of the juice. For optimization, effect of three factors i.e. inoculums size, agitation rate and temperature on three response variables i.e. ethanol content, total acidity and pH were studied. The surface plots for desirability and overlay plots were generated to determine the optimum response. Sweet sorghum juice inoculated with Saccharomyces cerevisiae NRRL Y-2034 yielded 8.83 % (v/v) ethanol with fermentation efficiency of 87.33 % under optimized conditions of temperature (30 °C), agitation rate (50 rpm) and inoculum size (7.5 % v/v).