5).The guluronic acid to mannuronic acid
was found to be 0.43 (33% guluronic acid and 77% mannuronic acid
) while of algal alginate was 0.81 (45% guluronic acid and 55% mannuronic acid
) as shown in Fig.
The mannuronic acid
(M block) forms [beta]-(1 [right arrow] 4) linkages, while the guluronic acid (G block) gives rise to [alpha]-(1 [right arrow] 4) linkages, which serves to introduce a steric hindrance around the carboxyl groups.
This enzyme, isolated from the soil bacterium Azotobacter vinelandii and expressed in Escherichia coli, converts mannuronic acid
residues into guluronic acid residues in the polymer backbone without breaking of the glycosidic bond [87, 115, 116].
Alginate, the biopolymer of b-D- mannuronic acid
its C-5 epimer a-L-guluronic acid, has wide range of industrial and pharmaceutical applications (Butt et al., 2011).
These long cellulose fibers are coated with hemicelluloses which are branched polysaccharides mainly consisting of D-xylose and small amounts of L-arabinose, D-glucose, D-mannose, D-galactose, glucuronic acid, mannuronic acid
and lignin (WYMAN et al., 2005).
Chemically, alginic acid is a block copolymer of anhydro [beta]-D mannuronic acid
and anhydro [alpha]-D glucouronic acid.
Alginates are, in fact, polymers of two uronic acids--guluronic acid (G) and mannuronic acid
(M)--grouped into homopolymeric segments of guluronic (G blocks) and mannuronic acid
(M blocks), respectively, and a block of alternating residues (MG blocks).
These unidentified peaks were not N-acetyl-mannosamine, arabinose, fucose, fructose, galactosamine, galacturonic acid, [TABULAR DATA FOR TABLE III OMITTED] glucosamine, glucuronic acid, mannosamine, mannuronic acid
, rhamnose, or xylose.
Two sugars in variable portions, L-guluronic acid and D- mannuronic acid
constitute alginate which is an acidic linear polysaccharide.
The second stage appears in the range between 231 and 283[degrees]C which could be assigned to degradation of PMA chain  and may be also due to breaking of segments of mannuronic acid
and glucuronic acid of alginate .
The peaks at 819, 886 ve 951 [cm.sup.1] are characteristic for polysaccharide structure, and they confirm the presence of guluronic and mannuronic acid
Alginate derived from brown sea algae is a random anionic linear polymer consisting of varying ratios of [beta]-L guluronic acid (G) and [alpha]-D mannuronic acid
(M) units (4).