ANALYSIS AND MODIFICATION OF CARRAGEENAN STRUCTURE USING ENZYMES

摘要

Carrageenans represent a class of sulphated galactans that have a wide spectrum of chemical structures. This class of macromolecules, occurring exclusively in the cell walls of red algae, shares a common galactan backbone of alternating 3-linked-p-D-galactopyranoses (G) and 4-linked-d-D-galactopyranoses (D). The disaccharide repetition moieties or carrabiose units are classified according to the number and position of sulphate ester groups (S) and the occurrence of 3,6-anhydro-D-galactose (DA) on the 1,4-linked residue found in gelling carrageenans. For example, the three most widely used carrageenans in industry — kappa- (κ, DA-G4S), iota- (ι, DA2S-G4S) and lambda- (A,, D2S6S-G2S) carrageenans — are differentiated by the presence of one, two and three ester sulphate groups, respectively, on each repeating disaccharide unit (Figure 1). Other derivatives such as methyl (M) or pyruvate (P) groups have been also observed. The number of possible carrabiose structures is therefore very large.