Lignocellulosic hydrolysates are desirable feedstocks for bioethanol
production by S. cerevisiae. These hydrolysates contain
not only fermentable sugars but also inhibitors and sugars that are
nonfermentable by this yeast (16, 32, 39). Examples of feedstocks
that contain multiple substrates are sugar beet pulp and citrus peel
hydrolysates (Table 1), which are currently used mostly as animal
feed. Alternatively, they could be hydrolyzed and used as a substrate
for fermentation (10, 14). In contrast to commonly investigated
sources of lignocellulose, such as corn stover, wheat straw,
and switch grass, sugar beet pulp and citrus peel contain less lignin
(14) but instead contain a significant amount of pectin (14, 29).
Pectin is a complex polysaccharide that consists of a backbone of
galacturonic acid residues and can have side chains containing
various neutral sugars (30). In addition, the polymer can be
methylesterified and acetylated