Parametric studies on batch alcohol fermentation using Saccharomyces yeast extracted from toddy

The present study deals with the development of a Saccharomyces cerevisiae yeast strain from toddy and the study of important process parameters which will facilitate the fermentation of sugar to alcohol using the developed strain. Evaluation of the yeast strain was performed in a batch fermenter of 1 L capacity under varying pH, temperature, sugar concentration, inoculum time and medium constituents. The optimum pH and temperature were found to be 4.25 and 30degreesC. The present yeast strain was found to be efficient to ferment 200 g/L sugar solution without any difficulty and 90 g/L ethanol was formed with an ethanol yield based on sugar utilized of 0.462. The fermentation time was reduced from 96 to 63 hours by increasing the inoculum time from 12 to 48 hours. From the study of the nutrient composition it was established that beef extract can be substituted for costly yeast extract. A higher concentration and yield of ethanol were obtained using a yeast strain developed from toddy compared to bakers' yeast Saccharomyces cerevisiae.