Limited research concerning the fermentation of arabinose
and galacturonic acid has been conducted because most
biomass feedstock have limited concentrations of these
sugars [15,16]. Conventional ethanol-fermenting yeasts such
as Saccharomyces cerevisiae can metabolize glucose, fructose
and sucrose [17] but are typically unable to metabolize either
arabinose or galacturonic acid to produce ethanol. The
genetically engineered bacterium Escherichia coli KO11 (E. coli
KO11) can ferment arabinose and galacturonic acid with
relatively high yields and is tolerant to by-products [18].
However, E. coli KO11 has a lower ethanol tolerance
(40e60 g L1) than yeasts, which can typically withstand
ethanol concentrations greater than 130 g L1