Fuel alcohol production: optimization of temperature for efficient very-high-gravity fermentation.

The time required to end ferment wheat mash decreased as the temperature was increased from 17 to 33 degrees C, but it increased as the concentration of dissolved solids was raised from 14.0 to 36.5 g/100 ml. Ethanol yield was not appreciably affected. Over the range of fermentation temperatures tested, the addition of urea accelerated the rate of fermentation, decreased the time required to complete fermentation at all dissolved-solid concentrations, and stimulated the production of slightly more ethanol than was produced by the corresponding unsupplemented control mashes. The optimum temperature for maximum ethanol production in urea-supplemented very-high-gravity wheat mash was 27 degrees C. These data are important for the industrial assessment of very-high-gravity fermentation technology.