Isolation and characterization of thermo, osmotic and ethanol tolerant yeast for ethanol production from molasses-based media

Abstract

Laboratory experiments were carried out to isolate and characterize the thermo tolerant yeast for ethanol production from molasses and to study some environmental condition and physiological parameters. Forty eight yeast stains were isolated from fruits (10 from banana (SB1-SB10), 7 from mango (SM1-SM7), 7 from orange (SO1-SO7), 8 from grape (SG1-SG8), 7 from apple (SA1-SA7) and 10 from date (SD1-SD10)), the fruits were collected from local market, Khartoum, Sudan. From the isolated isolate, two isolates (SD6 and SG3) were selected for further tests based on thermo tolerant, osmo tolerant and ethanol tolerant and identified by morphological and physiological characterization. Molasses was diluted by hot water (1:1). Fermentation was carried out in Erlenmeyer conical flasks. Fermentation media was taken into 500ml Erlenmeyer flasks and then the homogenous suspension of yeast inoculum was inoculated into the media in an aseptic condition. To increase ethanol yield, different amounts of nutrients were added to the molasses. The effectiveness of each supplement was evaluated at pH 6.0and temperature of 40oC in incubation. The molasses contained 83.2% total soluble solids, 17.8% reducing sugars, 32.1% sucrose, 49.9% total sugars, 10.25% ash, 0.54% calcium, 0.28% sodium, 2.89% potassium and it had a pH value of 5.6. sugar concentrations on ethanol production efficiency by strain SD6 and SG3 showed the best result at 40% conc. Keywords: Thermo tolerant yeast, fermentation, molasses, ethanol production.