[01] Iman Mohammed Ali, Food Science and Rural Development Department, Faculty of Agriculture, Omdurman Islamic University, Omdurman, Sudan. [02] Sara El Kheir Mustafa, Nutrition and Food Technology Department, Faculty of Science and Technology, Omdurman Islamic University, Omdurman, Sudan. [03] Fatin Hassan Farahat, Food Science and Rural Development Department, Faculty of Agriculture, Omdurman Islamic University, Omdurman, Sudan. [04] Abdel Mutalab Mohammed Khater, Food Science and Rural Development Department, Faculty of Agriculture, Omdurman Islamic University, Omdurman, Sudan.

A total of Seventy four (74) thermotolerant yeast strains were isolated from 67 food samples taken from different areas in the Sudan. Among the collected yeasts 47 isolates were regarded as thermophilic, 5 isolates regards as extremely thermopilic because they grow at 20°C and 49°C. The yeasts described as extremely thermophilic were identified to the genus and species level according to Lodder and Barnett. Three isolates were assigned to species Saccharomyces cereivisae and two isolates were assigned as Kluyveromyces ssp. The optimum growth temperature ranged between 30°C and 40°C. The extremely thermophilic yeast isolates were used in fermentation tests for the production of ethanol. The isolate identified as Kluyveromces sp gave final ethanol concentrations in the mash of 6% (w/v). This amount represented a yield of 83% of the theory. The other isolates gave ethanol concentrations of 3% to 2.5% (w/v) representing yields of only 50% of the theory. This indicates that these isolates area not suitable for ethanol production. Being thermotolerant they could be of interest for single cell protein production.

Thermotoleant Yeast, Thermophilic Yeast, Saccharomyces cereivisae

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