Tissue age as a factor affecting carrageenan quantity and quality in farmed Kappaphycus striatum (Schmitz) Doty ex Silva

Abstract

Carrageenan yield and quality from young and old tissues of Kappaphycus striatum ‘‘sacol’’ green variety were investigated using native and alkali-modified carrageenan extraction procedures. Dried apical (young) and basal (old) segments were pooled to produce 5 g of dried samples of each for carrageenan extraction. Mature tissues yielded greater amounts of carrageenan than young tissues. The latter exhibited higher gel strength, cohesiveness, viscosity properties and lower average-molecular weight than the mature, old tissues. FT-IR and 13C and 1 H NMR analyses showed that both young and old tissues contained mostly the kappa-type repeating disaccharide sequences of 3-linked b-D-galactopyranose 4-sulfate (G4S) and 4-linked 3,6-anhydro-a-D-galactopyranose (DA). Moreover, the study showed that, as the algal thalli aged, the iota carrageenan (G4S-DA2S) and methlylated (G6M) carrageenan units (these were minor substituents in the major kappa-carrageenan repeating disaccharide unit) decreased in quantity. These differences suggest that the timing of galactan biosynthesis may be related to certain physiological and structural functions during the growth of the alga.