1.1 Significance of the study
The production of pure ethanol apparently begins in the 12-14th century along
with improvements in the art of distillation permitting the condensation of vapors of
lowers boiling liquids. During the middle ages, alcohol was not only mainly used for
the production or as a constituent of medical drugs, but also for the manufacture of
painting pigments and other chemical industries. And it was only in the 19th century
that this trade became an industry with enormous production, due to economic
improvements of the distilling process (Roehr, 2001). Now, ethanol is an important
industrial chemical with emerging potential as a biofuel to replace vanishing fossil
fuels (Alfenore et al., 2002).
Ethanol may be produced commercially by chemical synthesis or biosynthesis.
Chemical synthesis is by hydration of ethylene (C2H4). For the biosynthesis, in the
fermentation process, yeast uses monosaccharides as a carbon source and then
converts to ethanol via glycosis under anaerobic conditions. The overall reaction can
be summarized as follow:
C6H12O6 + 2ADP + 2Pi 2 C2H5OH + 2 CO2 + 2ATP + 2H2