Production of Fuel Ethanol from Molasses by Thermotolerant Yeast

Abstract

A thermotolerant strain of the yeast Kluyveromyces marxianus,
isolated from Kenana sugar factory in the Sudan, was used for the
production of ethanol from molasses. Fermentations were carried out in a
bioreactor with 10-litre working volume at three temperatures and three
sugar concentrations in batch and at one temperature and three feeding
rates in fed-batch processes. In the batch fermentations, the best results
were obtained at 40°C and 20% sugar, where a maximum of 9.2% (w/v)
ethanol concentration was produced in 30 hours with a yield of 90% of
the theoretical and a maximum ethanol specific productivity of 0.65 g per
gramme yeast and hour. In the fed-batch process at 40°C, the best results
were obtained at 0.5 l/h feeding rate of a substrate with 400 g/l sugar.
Under such conditions, the yeast produced up to 9.34% (w/v) ethanol with
91.6% of the theoretical yield in 14 hours of fermentation and a maximum
specific ethanol productivity of 0.9 g per gramme yeast and hour.