The conventional ethanol fermenting yeast
(S. cerevisiae) or bacterium (Zymomonas mobilis) cannot ferment
xylose and arabinose to ethanol. A number of recombinant microorganisms such asEscherichia coli, Klebsiella oxytoca, Z. mobilis, and
S. cerevisiaehave been developed over the last 25 years with a goal
of fermenting both hexose and pentose sugars to ethanol (Saha,
2003).