44 Introduction to Renewable Biomaterials
OH
OH OH
OH
HO
HO
HO
O O HO
O
O
O
O
O
O
O
OH
HO
(a)
(b)
(c)
O
OH
HO
O O
HO O O
HO
COOH
O
OH
MeO
O
O
O
OHO
O
CH 3
CH 3
CH 3
OH
OH
HO
HO
HO
HO
H 3 CO
O OH
O
O
O
O O
O
O
O O
O
O O
O
O
O O
O
O
O
O
CH 3
Figure 2.4Various structural representations of xylan. (a) Simple xylan backbone composed of
non-functionalized xylose monomers. (b) Xylan backbone with a pendant 4-O-methylhexenuronic acid
residue at the 2-carbon. (c) Representation of a xylan backbone decorated with pendant acetyl groups.
O
O
O
O-Ac O-Ac
CH 2 OH
CH 2 OH
CH 2
CH 2 OH CH 2 OH CH 2 OH
CH 2 OH
OH
OH OH
OH OH OH OH OH
OH
OH
OH
OH
OH
O
O
O
O O
O
O O
O O
O
O
OH
Figure 2.5Representative structure of the galactoglucomannan heteropolysaccharide. Note that the
glucomannan backbone has several Ac (acetyl) groups decorating it, while it possesses a pendant
galactose residue on the 6 carbon of a mannose residue.
In addition, there are galactoglucomannans, arabinoxylans, and so on. The list is
nearly endless in the natural diversity of heteropolysaccharides that are found.
Figure 2.5 shows the structure, for example, of galactoglucomannan, a typical branched
heteropolysaccharide.
