Isolation of thermotolerant ethanologenic yeasts and use of selected strains in industrial scale fermentation in an Egyptian distillery

An enrichment and isolation program for new ethanol-producing thermotoleran t yeasts as well as a screening program of some known thermotolerant strain s resulted in the selection of several strains capable of growth at 40-43 d egrees C. Among these strains four grew and fermented sugar cane molasses a t 43 degrees C under batch conditions with sugar-conversion efficiencies >9 4% and ethanol concentrations 6.8-8.0% (w/v). The two best-performing strai ns, a Saccharomyces cerevisiae F111 and a Kluyveromyces marxianus WR12 were used in eight 87.5 m(3) fermentation runs (four using each strain) for ind ustrial ethanol production in an Egyptian distillery using sugar cane molas ses. Mean ethanol production was 7.7% and 7.4% (w/v), respectively, with an added advantage of cooling elimination during fermentation and higher etha nol yields compared to the distillery's S. cerevisiae SIIC (ATCC 24855) str ain in use. The isolate S. cerevisiae F111 was subsequently adopted by the distillery for regular production with significant economical gains and wat er conservation. (C) 2000 John Wiley & Sons, Inc.