Fuel Ethanol Production from Molasses by Some Indigenous Yeast Isolates

Abstract

In view of the anticipated shortage of the traditional supplies of fossil fuels there is a great deal of interest in production of ethanol as an alternative biofuel in recent years. The present report describes the search for potential yeast isolates from various ferments capable of producing ethanol. Twenty-one indigenous yeast isolates were recovered from various sources. Thirteen of them were found to produce ethanol belonging to the genera Saccharomyces, Zygosaccharomyces and Kluyveromyces. Comparative studies of the desirable properties of yeast showed that five isolates were promising from the industrial viewpoint, of them S. cerevisiae EP-17 was the most potent isolate for ethanol production. The isolates showed good tolerance of ethanol. Ethanol production by the selected yeasts was highest at pH 4.5 and 30°C in molasses medium with initial sugar concentration of 15%. S. cerevisiae EP-17 produced 7.89% ethanol using an inoculum size of 108 cells/ml. In larger fermentation tank, the yeast isolate produced 6.65% ethanol. After one-step distillation, 210 ml ethanol was obtained from 3 l molasses ferments and the concentration of ethanol was 65.56%. This study further revealed that indigenous yeast isolates could be used to benefit the fuel ethanol, spirit and industrial alcohol industries. Keywords: Biofuel; Ethanol; Indigenous yeasts; Saccharomyces cerevisiaeDOI: http://dx.doi.org/10.3329/bjm.v25i2.4875 Bangladesh J Microbiol, Volume 25, Number 2, December 2008, pp 129-133