FERMENTATION OF MOLASSES USING A THERMOTOLERANT YEAST, KLUYVEROMYCES-MARXIANUS IMB3 - SIMPLEX OPTIMIZATION OF MEDIA SUPPLEMENTS

The use of molasses as a substrate for ethanol production by the therm otolerant yeast Kluyveromyces marxianus var. marxianus was investigate d at 45 degrees C. A maximum ethanol concentration of 7.4% (v/v) was p roduced from unsupplemented molasses at a concentration of 23% (v/v). The effect on ethanol production of increasing the sucrose concentrati on in 23% (v/v) molasses was determined. Increased sucrose concentrati on had a similar detrimental effect on the final ethanol produced as t he increase in molasses concentration. This indicated that the effect may be due to increased osmotic activity as opposed to other component s in the molasses. The optimum concentration of the supplements nitrog en, magnesium, potassium and fatty acid for maximum ethanol production rate was determined using the Nelder and Mead (Computer J 7:308-313, 1965) simplex optimisation method. The optimum concentrations of the s upplements were 0.576 gl(-1) magnesium sulphate, 0.288 gl(-1) potassiu m dihydrogen phosphate and 0.36% (v/v) linseed oil. Added nitrogen in the form of ammonium sulphate did not affect the ethanol production ra te.