Heteropolysaccharides, biosynthesis

Figure 13.9 Mechanism for biosynthesis of microbial heteropolysaccharides. UDP = uridine diphosphate UMP = uridine monophosphate P-P = pyrophosphate P = phosphate. (Adopted from Sutherland 1979.)...

The proposed structure of the complex heterosaccharide is shown in Fig. 9. Fragmentation studies suggest that the carbohydrate monomers are supposed to be arranged in three domains. Glycyl bridges may link (V-acetylglucosamine and uronosyl residues of the different domains [85]. No data on the biosynthesis of the Halococcus cell-wall heteropolysaccharide are available. 

Hemicelluloses are heteropolysaccharides. Their structure and polymeric properties vary depending on the origin, i.e., plant species, industrial processing, isolation and purification procedure. They are a heterogeneous group of polysaccharides. The term was coined at a time when the structures were not well understood and biosynthesis was completely unknown [6]. 

Hemicelluloses are among the world s most abundant biopolymers. They are heteropolysaccharides present in large quantities in wood and the majority of plant tissues. The total global production of lignocellulosic materials in forests is estimated at 140 billion tons per year. The assumption that about 25 % of the lignocellulosic materials are hemicelluloses gives an estimation of the annual hemicellulose biosynthesis of 35 billion metric tons. 

De Vuyst, L., De Vin, F., Vaningelgem, F., Degeest, B. (2(X)1). Recent developments in the biosynthesis and applications of heteropolysaccharides from lactic acid bacteria. International Dairy Journal, 11(9), 687-707. 

Molecules with a long main chain (backbone) and a few short side chains are called linearly branched p. The majority of all p. are formed by biosynthesis in green plants or in fungi and bacteria. Some important p. are synthesized by animals, such as - chitin, hyaluronic acids or glycogen. P. can be hydrolized (->hydrolysis). P. that yield only one monomer are called homopolysaccharides if there are two or more different monomers, they are heteropolysaccharides. 

---